Heteroleptic Tin(IV) Aminoalkoxides and Aminofluoroalkoxides as MOCVD Precursors for Undoped and F-Doped SnO2 Thin Films

Article abstract of DOI:10.1021/acs.inorgchem.0c00617

A series of asymmetric and potentially bidentate amino alcohols and amino fluoro alcohols (R_NOH) having a different number of methyl/trifluoromethyl substituents at the α-carbon atom, [HOC(R¹)(R²)CH₂NMe₂] (R¹ = R² = H (dmaeH); R¹ = H, R² = CH₃ (dmapH); R¹ = R² = CH₃ (dmampH); R¹ = H, R² = CF₃ (F-dmapH); R¹ = R² = CF₃ (F-dmampH)) have been used to develop new monomeric and heteroleptic tin(IV) amino(fluoro)alkoxides [Sn(OR)₂(OR_N)₂] (R = Et, Prⁱ, Bu^t). These new complexes, which were thoroughly characterized by spectroscopy (IR and multinuclei NMR (¹H, ¹³C, ¹⁹F, and ¹¹⁹Sn)) as well as single-crystal X-ray studies on representative samples, were investigated for their thermal behavior to determine their suitability as MOCVD precursors for the deposition of metal oxide thin films. The two most suitable compounds, [Sn(OBu^t)₂(dmamp)₂] and [Sn(OBu^t)₂(F-dmamp)₂], were used in a direct liquid injection chemical vapor deposition (DLI-CVD) process to deposit undoped SnO₂ and F-doped SnO₂ thin films, respectively, on silicon and quartz substrates. Film growth rates at different temperatures (from 400 to 700 °C), film thickness, crystalline quality, and surface morphology were investigated. The films deposited on quartz showed high transparency (above 80%) in the visible region and low carbon contamination on the surface (11-13% from XPS), which could easily be removed completely with 2 min of Ar⁺ sputtering.

Full text of DOI:10.1021/acs.inorgchem.0c00617

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Article
Heteroleptic Tin(IV) Aminoalkoxides and Aminofluoroalkoxides as
MOCVD Precursors for Undoped and F‑Doped SnO2 Thin Films
̀
́
Alexandre Verchere, Shashank Mishra,* Erwann Jeanneau, Herve Guillon, Jean-Manuel Decams,
́
and Stephane Daniele*
Cite This: Inorg. Chem. 2020, 59, 7167−7180
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ABSTRACT: A series of asymmetric and potentially bidentate
amino alcohols and amino fluoro alcohols (RNOH) having a
different number of methyl/trifluoromethyl substituents at the α-
carbon atom, [HOC(R1)(R2)CH2NMe2] (R1 = R2 = H (dmaeH);
R1 = H, R2 = CH3 (dmapH); R1 = R2 = CH3 (dmampH); R1 = H,
R2 = CF3 (F-dmapH); R1 = R2 = CF3 (F-dmampH)) have been
used to develop new monomeric and heteroleptic tin(IV)
amino(fluoro)alkoxides [Sn(OR)2(ORN)2] (R = Et, Pri, But).
These new complexes, which were thoroughly characterized by
spectroscopy (IR and multinuclei NMR (1H, 13C, 19F, and 119Sn))
as well as single-crystal X-ray studies on representative samples,
were investigated for their thermal behavior to determine their
suitability as MOCVD precursors for the deposition of metal oxide thin films. The two most suitable compounds,
[Sn(OBut)2(dmamp)2] and [Sn(OBut)2(F-dmamp)2], were used in a direct liquid injection chemical vapor deposition (DLI-
CVD) process to deposit undoped SnO2 and F-doped SnO2 thin films, respectively, on silicon and quartz substrates. Film growth
rates at different temperatures (from 400 to 700 °C), film thickness, crystalline quality, and surface morphology were investigated.
The films deposited on quartz showed high transparency (above 80%) in the visible region and low carbon contamination on the
surface (11−13% from XPS), which could easily be removed completely with 2 min of Ar+ sputtering.
associated processes, which usually allow significant control of
film thickness, tunability through metal−organic precursor
choice, conformal coating, and scalability, are important gas-
phase methods.9 In this bottom-up chemical preparations of
metal oxides, the chemistry of the precursors is very important
because their properties such as volatility, solubility (for DLI-
CVD if the precursors are solid), hydrolytic and thermal
stability, etc. play a crucial role during deposition. However,
there are only a limited number of studies on CVD of SnO2 and
F-doped SnO2 using metal−organic precursors, especially
alkoxide, the vast majority of them being either inorganic or
organometallic compounds such as SnX4 (X = Cl, I), SnR4 (R =
Me, Et, Bu, −(CH2)3NMe2, etc.), BuSnCl3, and Me2SnCl2.10 In
comparison to the above precursors which have limitations in
terms of being too reactive, being highly toxic, or contain halides,
metal−organic complexes are the precursors of choice, as their
INTRODUCTION
■
Economic and environmental reasons ensure an increasing
demand for transparent conductive metal oxides (TCOs) made
entirely of earth-abundant elements.1 Among these, the
undoped and F-doped SnO2 thin films are the most studied
TCO materials and have been commercially exploited in many
areas such as gas sensors, lithium ion batteries, sensitized solar
cells, and photocatalytic systems.2 Undoped SnO2 is a wide-
band-gap n-type semiconductor that contains oxygen vacancies
and tin interstitials in its lattice.2 The two important properties
of tin dioxide, i.e. low electrical resistance and high optical
transparency in the visible range of the electromagnetic
spectrum, can further be modified by fluoride-ion doping, as
demonstrated by the higher figures of merit (σ/R) for F-doped
SnO2 (where σ is the conductivity and R is the visible absorption
coefficient).3
The development of advanced materials for modern
applications requires synthetic manufacturing and processing
techniques that are well controlled, tunable, and scalable. The
synthesis of undoped and F-doped SnO2 materials has
previously been reported by numerous chemical and physical
methods, including microwave,4 hydrolytic5 or nonhydrolytic6
sol−gel methods, various deposition techniques,7 and mecha-
nochemical treatments.8 Chemical vapor deposition (CVD) and
Received: February 26, 2020
Published: April 27, 2020
https://dx.doi.org/10.1021/acs.inorgchem.0c00617
© 2020 American Chemical Society
Inorg. Chem. 2020, 59, 7167−7180
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Article
Scheme 1. Amino Alcohols and Amino Fluoro Alcohols Employed in This Study
30 mL/min of argon or 20 mL/min of nitrogen using a Setaram
TGA92-12 thermal analyzer (thermal ramp 5 °C/min, temperature
range 20−600 °C). Scanning electron microscopy (SEM) measure-
ments were performed on a Hitachi S800 system. We used a Bruker D8
Advance A25 system with Cu Kα1+2 (λ = 0.154184 nm) radiation at 50
kV and 35 mA to measure the X-ray diffraction (XRD) patterns of the
thin films. The thickness measurement was performed at the center of
the substrate with a “Film Sense” ellipsometer on a Model FS-1 Multi-
Wavelength Ellipsometer. An electron spectrometer (Kratos Axis Ultra
DLD) with an Al Kα (1486.6 eV) radiation source was used to perform
the X-ray photoelectron spectroscopy (XPS) analysis of the thin films
on silicon substrates. Corrections to the constant charging of the XPS
spectra were made by the C 1s peak of adventitious carbon (binding
energy of 284.6 eV). XPS analysis of the thin films on quartz substrates
was performed using an ULVAC-PHI Versa Probe II spectrometer
equipped with a microfocused monochromatic Al Kα X-ray beam. The
resistivity of the SnO2 films was measured by a four-point probe method
with 600 μm distance between the points. A PerkinElmer Lambda 1050
UV−visible spectrophotometer with an integrating sphere was used to
measure transmittance spectra of the thin films on quartz.
physicochemical properties can be optimized according to the
ligand design.11
Only a handful of metal−organic complexes of Sn(IV),
typically first-generation precursors containing a classical
alkoxide or carboxylate ligand such as [Sn(OCH-
(CF3)2)4(HNMe2)2], [Bu3Sn(OCH(CF3)2)], [Sn(OBut)4],
[R2Sn(O2CCF3)] (R = Me, Bu), and [Bu3Sn(O2CF2CF3)]
have been used as MOCVD precursors.12 In general, an all-
oxygen-coordinated system is stable under ambient conditions
but requires high process temperatures to decompose and
minimize impurity content.13 On the other hand, an all-
nitrogen-coordinated system is less stable and highly reactive to
air and moisture and therefore is difficult to handle and operate
under ambient conditions.14 With a mixed O/N environment,
metal aminoalkoxides provide a good compromise between the
two extremes above and, therefore, have previously been used as
sol−gel15 or MOCVD16 precursors for several metal oxide
nanomaterials. The introduction of fluorine into the ligand can
influence the volatility, Lewis acidity, and stability of the
resulting metal fluoroaminoalkoxides and provides an intrinsic/
intramolecular source of fluorine for F-doped SnO2.17 Although
Sn(IV) aminoalkoxides are known in the literature,18 they have
not been used as precursors for SnO2 thin films.
In this work, we use a series of asymmetric and potentially
bidentate amino alcohols (RNOH) with different alkyl
substituents at the α-carbon atom, [HOC(R1)(R2)CH2NMe2]
(R1 = R2 = H, dimethylaminoethanol (dmaeH); R1 = H, R2 =
CH3, dimethylaminopropan-2-ol (dmapH); R1 = R2 = CH3, 3-
dimethylamino-2-methylpropan-2-ol (dmampH); R1 = H, R2 =
CF3, 3-dimethylamino-1,1,1-trifluoropropan-2-ol (F-dmapH);
R1 = R2 = CF3, 2-(dimethylamino)methyl-1,1,1,3,3,3-hexafluor-
oproan-2-ol (F-dmampH)) (Scheme 1) to develop new
heteroleptic Sn(IV) aminoalkoxides [Sn(OR)2(ORN)2] (R =
Et, Pri, But). These derivatives have shown great promise as
metal−organic chemical vapor deposition (MOCVD) precur-
sors, and the selected candidates [Sn(OBut)2(dmamp)2] and
[Sn(OBut)2(F-dmamp)2] performed very well in the direct
liquid injection chemical vapor deposition (DLI-CVD) process
for undoped and F-doped SnO2 (FTO) thin films, respectively,
the latter having implications for other studies on the
development of precursors for F-doped metal oxides.
DLI-CVD Processes and Machine. The DLI-CVD processes19
were performed with a MC-050 DLI-RTCVD machine20 from
Annealsys equipped with a Vapbox 1500 DLI vaporizer from
Kemstream. The substrates were installed on a SiC-coated graphite
susceptor holder. The chamber is a horizontal quartz tube with external
infrared halogen lamps that heats the susceptor and the substrate. A
Vapbox DLI vaporizer achieves a fine control of the carrier gas flow and
of the liquid (solution) flow and mixes them prior to injection of the
generated mixture as an aerosol in a vaporization chamber in a pulsed
regime with a chosen/selected injection frequency. The generated
aerosol is vaporized in the heated vaporization chamber of the Vapbox.
When a Vapbox is used, the CVD process performed is more specifically
pulsed DLI-CVD.
Synthesis of Commercially Nonavailable Ligands. Three
commercially nonavailable ligands, i.e. dmampH, F-dmapH, and F-
dmampH (sometimes also abbreviated as amakH in the literature),21
were synthesized by a modified method of ring opening of an
appropriate epoxide using an excess of amine22−24 and characterized
completely by elemental analysis, FT-IR, 1H and 13C NMR, and
thermogravimetric studies (see the Supporting Information for details).
Synthesis of Sn(IV) Derivatives 1−12. [Sn(OBut)2(dmae)2] (1).
In a Schlenk tube containing the dmaeH ligand (0.26 g, 2.96 mmol), a
solution of [Sn(OBut)4] (0.61 g, 1.48 mmol) in n-pentane solution (10
mL) was added dropwise and the reaction mixture was stirred for 1 h at
room temperature. The slightly turbid solution was filtered to obtain a
colorless transparent solution. The volatile materials were removed
under vacuum, and the residues were extracted with n-pentane. Yield:
0.62 g (95%). Colorless crystals suitable for X-ray analysis were
obtained from a concentrated n-pentane solution. Anal. Calcd for
C16H38N2O4Sn (441): C, 43.52; H, 8.61; N, 6.35. Found: C, 43.37; H,
8.51; N, 6.30. FT-IR (Nujol, cm−1): ν 2725 (w), 2690 (w), 1246 (w),
1188 (m), 1094 (m), 1020 (m), 949 (m), 920 (w), 888 (w), 781 (m),
722 (m), 590 (m), 519 (m), 513 (m), 464 (w), 400 (vw). NMR (400
MHz, C6D6, 23 °C, ppm): 1H, δ 1.65 (s, 18 H, CH3 of ButO), 2.14 (s, 12
H, CH3 of dmae), 2.29 (t, 3J = 5.48 Hz, 4 H, NCH2), 3.83 (t, 3J = 5.4 Hz,
4 H, CH2O of dmae); 13C, δ 31.6 (s, CH3 of ButO), 47.1 (s, CH3 of
dmae), 58.6 (s, NCH2), 62.4 (s, CH2O of dmae), 71.1 (s, C (CH3)3 of
ButO); 119Sn, δ −533 ppm.
EXPERIMENTAL SECTION
■
General Procedures. All manipulations were carried out under
argon using Schlenk tubes and vacuum line techniques. [Sn(OBut)4]
(Strem), N,N-dimethylaminoethanol (Sigma-Aldrich), N-methylme-
thanamine (Sigma-Aldrich), 3,3,3-trifluoro-1,2-epoxypropane (abcr
GmbH), and 2,2-dimethyloxirane (abcr GmbH) were purchased and
used as received. FT-IR spectra were recorded as films of either neat
compound (ligands) or Nujol mulls (derivatives 1−12) on KBr pellets
using a Bruker Vector 22 spectrometer. 1H, 13C, 19F, and 119Sn NMR
spectra were recorded on a Bruker AVANCE III 400 MHz
spectrometer using Topspin software. All chemical shifts were
measured in C6D6 as a solvent. 119Sn NMR chemical shifts were
referenced externally to SnMe4. Thermogravimetric analysis (TGA)
data were collected at atmospheric pressure under a neutral gas flow of
Using the same method, complexes 2−5 were also synthesized from
the reactants given below.
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Article
[Sn(OBut)2(dmap)2] (2). dmapH (0.50 g, 4.88 mmol) and [Sn-
(OBut)4] (1.0 g, 2.45 mmol) in n-pentane (20 mL) were reacted to
form compound 2. Yield: 1.1 g (91%). Compound 2, obtained as a
yellow oil, decomposes at 150 °C on attempted distillation at 10−3 mm
Hg. Anal. Calcd for C18H42N2O4Sn (468.9): C, 40.10; H, 8.96; N, 5.97.
Found: C, 39.93; H, 8.85; N, 5.90. FT-IR (Nujol, cm−1): ν 2363 (vw),
1717 (s), 1652 (m), 1459 (s), 1377 (s), 1265 (w), 1145 (w), 1135 (w),
1096 (w), 954 (m), 946 (s), 835 (s), 722 (m), 608 (s), 533 (m). NMR
(400 MHz, C6D6, 23 °C, ppm): 1H, δ 1.20 (s, 18 H, (CH3)2C of ButO),
1.25−1.37 (m, 6 H, (CH3) CH of dmap), 1.61 (s, 12 H, (CH3)2N),
2.28−2.36 (m, 4 H, CH2N), 3.86−4.2 (m, 2 H, CH of dmap); 13C, δ
23.9 (s, CH3CH of dmap), 31.9 (s, CH3 of ButO), 47.5 (s, (CH3)2N),
63.7 (s, NCH2), 71.1 (s, CCH3)3 of ButO), 71.5 (s, CH of dmap); 119Sn,
δ −544 ppm.
[Sn(OEt)2(dmae)2] (7). 1 (0.93 g, 2.10 mmol) was stirred in n-
pentane (10 mL) and ethanol (10 mL) for 2 h to give 7 as a colorless oil
in almost quantitative yield. Attempted distillation at 130 °C/10−2
mmHg led to its decomposition. Anal. Calcd for C12H30N2O4Sn
(384.9): C, 37.41; H, 7.79; N, 7.27. Found: C, 37.23; H, 7.63; N, 7.15.
FT-IR (Nujol, cm−1): ν 2280 (vw), 1653 (w), 1279 (w), 1158 (vw),
1126 (vw), 1043 (s), 948 (s), 884 (s), 780 (s), 662 (m), 516 (s). NMR
(400 MHz, C6D6, 23 °C, ppm): 1H, δ 1.37 (t, 6 H, CH3 of EtO), 2.33 (s,
12 H, CH3 of dmae), 2.42 (s, 4 H, NCH2), 3.85 (s, 4 H, CH2O of
dmae), 4.18 (q, 4 H, CH2 of EtO); 13C, δ 21.5 (s, CH3 of EtO), 46.1 (s,
CH3 of dmae), 58.9 (s, NCH2), 61.3 (s, CH2 of EtO), 63.3 (s, CH2O of
dmae); 119Sn, δ −533 ppm.
[Sn(OPri)2(dmamp)2] (8). 3 (1.13 g, 2.28 mmol) was stirred in n-
pentane (10 mL) and isopropyl alcohol (10 mL) for 2 h to afford 8 as a
yellowish oil in almost quantitative yield. The IR, NMR, and TGA
studies on the initially isolated liquid suggested retention of one
molecule of ButOH in the lattice, which can be eliminated on keeping
the product under vacuum for a longer period of time. Attempted
distillation of 8 at 130 °C/10−2 mmHg led to its decomposition. Anal.
Calcd for C18H42N2O4Sn (468.9): C, 46.06; H, 8.95; N, 5.97. Found: C,
45.89; H, 8.94; N, 5.93. FT-IR (Nujol, cm−1): ν 2361 (vw), 1298 (m),
1168 (m), 1156 (s), 1128 (s), 994 (w), 956 (m), 952 (m), 842 (w), 838
(w), 818 (w), 627 (w), 590 (w). NMR: (400 MHz, C6D6, 23 °C, ppm).
1H, δ 1.34 (s, 12 H, (CH3)2 C of dmamp), 1.42 (s, 12 H, (CH3)2CH of
PriO), 2.30 (s, 4 H, NCH2), 2.40 (s, 12 H, (CH3)2N), 4.68 (sept, 2 H,
CH of PriO).; 13C δ 28.5 (s, CH3 of PriO), 33.5 (s, (CH3)2C of
dmamp), 48.5 (s, (CH3)2N), 65.6 (s, CH of PriO), 67.0 (s, NCH2), 70.5
(s, C of dmamp).; 119Sn, δ −537 ppm.
[Sn(OEt)2(dmamp)2] (9). 3 (0.95 g, 1.91 mmol) was stirred in n-
pentane (10 mL) and ethanol (10 mL) for 2 h to give 9 in almost
quantitative yield. As was the case for compound 8, this compound also
initially retains one molecule of ButOH in the lattice, which can be
eliminated on keeping the product under vacuum for a longer period of
time. Attempt to distill this yellowish oil failed, as it decomposed at 130
°C/10−2 mmHg. Anal. Calcd for C16H38N2O4Sn (440.9): C, 43.55; H,
8.62; N, 6.35. Found: C, 43.35; H, 8.57; N, 6.3. FT-IR (Nujol, cm−1): ν
2711 (m), 2609 (w), 2367 (vw), 2357 (vw), 2149 (vw), 1944 (w), 1607
(s), 1559 (m), 1297 (m), 1216 (m), 1206 (m), 1161 (m), 1099 (m),
1052 (m), 944 (m), 892 (m), 838 (m), 796 (m), 762 (m), 589 (m).
NMR (400 MHz, C6D6, 23 °C, ppm): 1H, δ 1.12 (s, 12 H, (CH3)2C of
dmamp), 1.36 (t, 6H, CH3 of EtO), 2.10 (s, 4 H, NCH2), 2.44 (s, 12 H,
(CH3)2N), 3.37 (quadruplet, 4 H, CH2 of EtO); 13C, δ 19.0 (s, CH3 of
EtO), 31.7 (s, (CH3)2C of dmamp), 48.7 (s, (CH3)2N), 58.1 (s, CH2 of
EtO), 67.6 (s, NCH2), 71.2 (s, C of dmamp); 119Sn, δ −522 ppm.
[Sn(OBut)(OPri)(F-dmamp)2] (10). Reacting 5 (1.75 g, 2.46 mmol)
with 1 equiv of isopropyl alcohol (0.15 g, 2.46 mmol) in n-pentane (10
mL) for 2 h afforded 10 as a white solid in quantitative yield. Colorless
crystals suitable for X-ray analysis were obtained from a concentrated n-
pentane solution at −20 °C. Yield: 1.4 g (82%). Anal. Calcd for
SnC19H32F12N2O4 (699.1): C, 32.61; H, 4.57; N, 4.0. Found: C, 32.55;
H, 4.55; N, 4.10. FT-IR (Nujol, cm−1): ν 2728 (s), 2673 (w), 2359 (w),
2335 (w), 1716 (m), 1452 (s), 1378 (s), 1291 (w), 1232 (w), 1226 (w),
1162 (w), 1013 (w), 985 (m), 889 (w), 840 (w), 740 (w), 725 (s), 685
(m), 594 (w), 561 (w), 557 (w), 536 (w), 503 (w). NMR (400 MHz,
C6D6, 23 °C, ppm): 1H, δ 1.04 (s, 9 H, CH3 of ButO), 1.20 (d, 6 H, J = 6
Hz, CH3 of PriO), 1.64 (s, 12 H, CH3 of F-dmamp), 2.29 (s, 4 H,
NCH2), 4.42 (s, 2 H, J = 6 Hz, CH2 of PriO); 13C, δ 27.8 (s, CH3 of
PriO), 31.6 (s, CH3 of ButO), 46.0 (s, CH3 of F-dmamp), 57.4 (s,
NCH2), 66.2 (s, CH2 of PriO), 66.4 (s, CH2 of ButO); 19F, δ −78.4;
119Sn, δ −574 ppm.
[Sn(OBut)2(dmamp)2] (3). dmampH (0.74 g, 6.30 mmol) and
[Sn(OBut)4] (1.30 g, 3.16 mmol) in n-pentane (20 mL) were reacted to
form compound 3. Yield: 1.53 g (98%). Colorless crystals of 3 suitable
for X-ray analysis were obtained from a concentrated n-pentane
solution at −20 °C. Anal. Calcd for C20H46N2O4Sn (496.9): C, 48.30;
H, 9.26; N, 5.63. Found: C, 48.13; H, 9.17; N, 5.53. FT-IR (Nujol,
cm−1): ν 3563 (w), 2367 (vw), 2247 (vw), 1920 (vw), 1297 (s), 1206
(s), 1156 (s), 993 (s), 985 (s), 946 (s), 913 (s), 839 (s), 798 (s), 770
(s), 625 (s), 551 (m), 465 (s), 424 (m). NMR (400 MHz, C6D6, 23 °C,
1
ppm): H, δ 1.35 (s, 12 H, (CH3)2C of dmamp), 1.63 (s, 18 H,
(CH3)3C of ButO), 2.25 (s, 4 H, NCH2), 2.34 (s, 12 H, (CH3)2N); 13C,
δ 33.6 (s, CH3 of ButO), 34.7 (s, (CH3)2C of dmamp), 49.2 (s,
(CH3)2N), 67.6 (s, C of dmamp), 70.6 (s, NCH2), 72.0 (s, C (CH3)3 of
ButO); 119Sn, δ −561 ppm.
[Sn(OBut)2(F-dmap)2] (4). F-dmapH (1.35 g, 8.60 mmol) and
[Sn(OBut)4] (1.77 g, 4.31 mmol) in n-pentane (25 mL) were reacted to
form compound 4. Yield: 2.41 g (97%). Compound 4, obtained as a
yellowish oil, decomposes at 150 °C on attempted distillation at 10−2
mmHg. Anal. Calcd for C18H36N2F6O4Sn (576.7): C, 37.45; H, 6.24;
N, 4.86. Found: C, 37.13; H, 6.17; N, 4.75. FT-IR (KBr windows,
Nujol, cm−1): ν 3563 (w), 2367 (vw), 2247 (vw), 1920 (vw), 1297 (s),
1257 (w), 1156 (s), 993 (s), 913 (s), 839 (s), 798 (s), 770 (s), 625 (s),
551 (m), 465 (s). NMR (400 MHz, C6D6, 23 °C, ppm): 1H, δ 1.04 (s,
18 H, (CH3)2C of ButO), 1.65 (m, 4 H, (CH2)N), 2.01 (s, 12 H,
(CH3)2N), 3.76 (m, 2 H, CH of F-dmap); 13C, δ 31.9 (s, CH3 of ButO),
45.3 (s, N(CH3)2), 58.3 (s, NCH2), 71.1 (s, C(CH3)3 of ButO); 19F, δ
−78.5; 119Sn, δ −546 ppm.
[Sn(OBut)2(F-dmamp)2] (5). F-dmampH (1.11 g, 4.92 mmol) and
[Sn(OBut)4] (1.01 g, 2.46 mmol) in n-pentane (15 mL) were reacted to
form compound 5. Yield: 1.73 g (97%). Colorless crystals suitable for X-
ray analysis were obtained after crystallization at −20 °C from a
concentrated n-pentane solution. Anal. Calcd for SnC20H32F12N2O4
(711.2): C, 33.74; H, 4.50; N, 3.94. Found: C, 33.61; H, 4.46; N, 3.91.
FT-IR (Nujol, cm−1): ν 2857 (s), 2712 (w), 2379 (w), 2367 (w), 2263
(w), 2135 (w), 1716 (m), 1459 (s), 1378 (s), 985 (m), 898 (m), 782
(m), 776 (m), 726 (m), 695 (m), 648 (w), 558 (m), 476 (m), 463 (m).
1
NMR (400 MHz, C6D6, 23 °C, ppm): H, δ 1.37 (s, 18 H, CH3 of
ButO), 2.30 (s, 12 H, CH3 of F-dmamp), 2.58 (s, 4 H, NCH2); 13C, δ
33.8 (s, CH3 of ButO), 49.1 (s, CH3 of F-dmamp), 57.2 (s, NCH2), 72.9
(s, C of ButO); 19F, δ −76.5; 119Sn, δ −601 ppm.
[Sn(OPri)2(dmae)2] (6). The title complex as a yellowish liquid was
obtained by stirring complex 1 (0.66 g, 1.49 mmol) in n-pentane (10
mL) and isopropyl alcohol (10 mL) for 2 h followed by removal of the
volatiles from the reaction mixture in vacuo. Yield: 0.61 g (99%).
Attempted distillation at 130 °C/10−2 mmHg led to decomposition of
the product. Anal. Calcd for C14H34N2O4Sn (412.9): C, 40.69; H, 8.23;
N, 6.78. Found: C, 40.33; H, 8.10; N, 6.70. FT-IR (Nujol, cm−1): ν
2359 (vw), 2337 (vw), 1280 (m), 1161 (m), 1103 (m), 1087 (m), 960
(m), 951 (s), 886 (s), 835 (w), 779(m), 594 (m), 516 (m). NMR (400
MHz, C6D6, 23 °C, ppm). 1H: δ 1.35 (s, 12 H, CH3 of PriO), 2.27 (s, 12
H, CH3 of dmae), 2.36 (s, 4 H, NCH2), 3.84 (s, 4 H, CH2O of dmae),
4.54 (s, 2 H, CH of PriO); 13C, δ 28.0 (s, CH3 of PriO), 46.7 (s, CH3 of
dmae), 58.8 (s, NCH2), 63.1 (s, CH2O of dmae), 65.4 (s, CH of PriO);
119Sn, δ −541 ppm.
[Sn(OPri)2(F-dmamp)2] (11). Treating 5 (1.01 g, 1.46 mmol) with an
excess of isopropyl alcohol (10 mL) in n-pentane (10 mL) for 2 h gave
11 as a crystalline solid in 75% yield (0.75 g). Anal. Calcd for
SnC18H30F12N2O4 (684.9): C, 31.54; H, 4.38; N, 4.01. Found: C,
31.57; H, 4.39; N, 4.10. FT-IR (Nujol, cm−1): ν 2723 (w), 2669 (vw),
1715 (s), 1459 (s), 1377 (s), 1299 (w), 1170 (w), 1162 (w), 1014 (vw),
748 (vw), 722 (m), 558 (vw). NMR (400 MHz, C6D6, 23 °C, ppm):
1H, 1.21 (d, 12 H, J = 5.96 Hz, CH3 of PriO), 1.65 (s, 12 H, CH3 of F-
dmamp), 2.28 (s, 4 H, NCH2), 4.43 (s, 2 H, J = 6 Hz, CH2 of PriO); 13C,
Using the same method employed for 6, complexes 7−12 were also
synthesized by reacting 1, 3, or 5 with PriOH or EtOH, as given below.
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Table 1. Crystallographic and Refinement Data for 1, 5, and 10
1
5
10
empirical formula
formula wt
cryst syst
space group
a (Å)
b (Å)
c (Å)
V (Å3)
SnC16H38N2O4
441.17
orthorhombic
P212121
9.1619(7)
14.8500(13)
15.1316(17)
2058.7(3)
4
SnC20H34F12N2O4
713.16
orthorhombic
Pbca
16.198(1)
11.949(1)
28.562(3)
5528.3(9)
8
SnC19H32F12N2O4
699.14
orthorhombic
Pbca
16.095(2)
11.966(1)
28.202(3)
5431.4(11)
8
Z
μ (mm−1
)
1.26
1.034
1.049
temp (K)
150
100
150
no. of measd rflns
no. of indep rflns (Rint)
no. of data/restraints/params
goodness of fit
28990
28080
25663
5320 (0.078)
4684/225/288
1.02
6989 (0.053)
5254/153/390
1.03
6788 (0.057)
4424/115/385
1.07
R1 (I > 2(I))
0.05
0.092
0.082
wR2 (all data)
0.117
0.264
0.265
residual electron density (e Å−3
CCDC no.
)
−2.00 to 0.94
1951886
−2.75 to 1.73
1951887
−2.04 to 2.08
1951888
Scheme 2. Synthesis of New Heteroleptic Tin(IV) Aminoalkoxides and Aminofluoroalkoxides
27.8 (s, CH3 of PriO), 46.0 (s, CH3 of F-dmamp), 57.3 (s, NCH2), 66.2
(s, CH2 of PriO); 19F, δ −78.4; 119Sn, δ −552 ppm.
tion, peak integration, and background determination were carried out
with the CrysalisPro software.25 An analytical absorption correction
was applied using the modeled faces of the crystal.26 The resulting sets
of hkl values were used for structure solutions and refinements. The
structures were solved with the ShelXT27 structure solution program
using the intrinsic phasing solution method and by using Olex228 as the
graphical interface. The model was refined with version 2018/3 of
ShelXL29 using least-squares minimization. Some selected crystallo-
graphic and refinement data of 1, 5, and 10 are given in Table 1.
[Sn(OEt)2(F-dmamp)2] (12). Treating 5 (0.99 g, 1.50 mmol) with an
excess of ethanol (10 mL) in n-pentane (10 mL) for 2 h afforded 12 as a
pale yellow oil. Yield: 0.89 g (97%). Anal. Calcd for SnC16H26F12N2O4
(656.9): C, 29.23; H, 3.96; N, 4.26. Found: C, 28.87; H, 3.71; N, 4.08.
FT-IR (Nujol, cm−1): ν 2725 (w), 1927 (m), 1709 (m), 1446 (w), 1384
(w), 1271 (w), 1233(w), 1197 (w), 1058 (w), 1039 (w), 987 (w), 881
(w), 779 (w), 696 (w), 693 (w). NMR (400 MHz, C6D6, 23 °C, ppm):
1H, δ 1.12 (s, 12 H, CH3 of F-dmamp), 1.20 (t, 6 H, J = 4.48 Hz, CH3 of
EtO), 2.61 (s, 4 H, NCH2), 3.99 (s, 4 H, J = 6.6 Hz, CH2 of EtO); 13C, δ
31.6 (s, CH3 of EtOH), 46.1 (s, CH3 of F-dmamp), 57.6 (s, NCH2) and
61.9 (s, CH2 of EtOH); 19F, δ −78.53; 119Sn, δ −532 ppm.
RESULTS AND DISCUSSION
■
Synthesis and Characterization of New Sn(IV) Amino-
alkoxides and Aminofluoroalkoxides. We have used a
series of asymmetric and potentially bidentate amino alcohols
(RNOH) of the general formula [HOC(R1)(R2)CH2N(CH3)2]
(R1 = R2 = H (dmaeH); R1 = H, R2 = CH3 (dmapH); R1 = R2 =
CH3 (dmampH); R1 = H, R2 = CF3 (F-dmapH); R1 = R2 =
CF3(F-dmampH)) (Scheme 1) to develop new monomeric and
heteroleptic tin(IV) aminoalkoxides and aminofluoroalkoxides
X-ray Crystallography. Suitable crystals of 1, 5, and 10 were
obtained as described in the synthetic procedure. Crystal structures
were measured using Mo radiation (λ = 0.71073 Å) on an Xcalibur
Gemini ultradiffractometer equipped with an Atlas CCD detector.
Intensities were collected at 100 K for compound 5 and 150 K for
compounds 1 and 10 by means of the CrysalisPro software.25 Reflection
indexing, unit-cell parameter refinement, Lorentz−polarization correc-
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[Sn(OR)2(ORN)2] (R = Et, Pri, But) as potential MOCVD
precursors for SnO2 and F-doped SnO2 thin films. The
asymmetric substitution in terms of the different numbers of
methyl groups at the α-carbon atom of these amino alcohols was
aimed to increase the volatility of the metal complexes by
decreasing the intermolecular interactions. For the same reason,
the use of aromatic groups has also been avoided, which could
otherwise decrease the volatility due to the possible
intermolecular π stacking. The use of CF3 group(s) in the F-
dmapH and F-dmampH ligands was intended to further
enhance the volatility of the precursors and to provide intrinsic
fluorine for the elaboration of F-doped SnO2 thin films.17 While
the dmaeH and dmapH ligands are commercially available, the
other three ligands have been synthesized either as colorless
liquids (dmampH and F-dmampH) or a crystalline solid (F-
dmapH) by a modified ring-opening method of an appropriate
epoxide using an excess of amine and thoroughly characterized
X-ray Crystal Structures. Suitable single crystals of the
complexes 1, 5, and 10 were grown from their n-pentane
solutions at −20 °C. These isostructural complexes crystallize in
the orthorhombic space group P212121 (1) or Pbca (5 and 10)
and are monomeric, a favorable characteristic for enhanced
volatility. Table 2 summarizes some selected bond lengths and
Table 2. Selected Bond Lengths and Angles for 1, 5, and 10
1
5
10
Bond Lengths (Å)
Sn1−N1
Sn1−N2
Sn1−O1
Sn1−O2
Sn1−O3
Sn1−O4
2.458(7)
2.364(7)
2.005(6)
2.014(5)
1.994(6)
1.997(5)
2.317(7)
2.299(7)
2.048(5)
2.070(5)
1.974(5)
1.967(6)
2.308(7)
2.280(7)
2.039(5)
2.061(5)
1.978(5)
1.968(5)
Bond Angles (deg)
1
by elemental analysis, FT-IR, H, 13C, and 19F NMR and
N1−Sn1−O1
N2−Sn1−O2
O3−Sn1−O4
O1−Sn1−O2
78.2(3)
77.2(2)
98.0(2)
94.4(3)
74.5(2)
75.4(3)
75.6(2)
91.6(2)
90.0(2)
thermogravimetric analyses (see the Supporting Information for
details).
75.2(2)
91.3(2)
91.3(2)
[Sn(OBut)4] reacted with 2 equiv of five asymmetric amino
alcohols (RNOH) in n-pentane to give the new tin(IV)
aminoalkoxides and aminofluoroalkoxides [Sn(OBut)2(ORN)2]
(ORN = dmae (1), dmap (2), dmamp (3), F-dmap (4), F-
dmamp (5)) in very good yield as potential MOCVD precursors
for undoped and F-doped SnO2 thin films (Scheme 2). The tert-
butoxo group(s) in complexes 1−5 can further be exchanged
with isopropoxo or ethoxo groups by reacting them with an
excess/equivalent amount of EtOH and PriOH (Scheme 2).
The aminoalkoxide/aminofluoroalkoxide moiety in 1−12 acts
as a N,O-chelating ligand and provides an octahedral environ-
ment around the tin(IV) center, as shown by the X-ray crystal
structures for 1, 5, and 10. These air-sensitive derivatives are
solids (1, 3, 5, 10, 11) or liquids (2, 4, 6−9, and 12) and are
soluble in common organic solvents.
bond angles for these complexes. In all of these complexes, the
aminoalkoxide ligands are coordinated to the SnIV center in a
N,O-chelating bidentate manner (Figure 1). The bite angle of
the nonfluoro dmae ligand in 1 (77.2−78.2°) is slightly more
than that of the fluoro F-dmamp ligand in 5 and 10 (74.5−
75.6°). The bite angle of the F-dmamp ligand in metal
complexes has been shown to be quite flexible, varying
considerably according to the coordination constraints of the
metal centers.33 The average Sn−N bond length, 2.34 Å, is
longer than the average Sn−O bond length (2.04 Å). Two
terminal alkoxo groups in cis positions complete a distorted-
octahedral geometry around the metal center. The electron-
withdrawing effect of the fluorinated methyl groups of the F-
dmamp ligand causes electron deficiency at the metal center and
thus promotes the formation of a stronger metal−OR
interaction, as indicated by the slightly shorter Sn−O(alkoxo)
distances (average 1.97 Å) in 5 and 10 in comparison to the
average 1.99 Å in nonfluorinated 1.18 In addition, the larger size
of fluorine in the F-dmamp ligand causes the two alkoxo groups
to be less spaced in 1, as indicated by the angle O3−Sn−O4 in 5
and 10 being considerably smaller (91.3−91.6°) than that found
in 1 (98.0°). However, the presence of the fluorinated ligand F-
dmamp introduces significant intermolecular H bonding in 5
and 10, causing molecules to be more closely packed than in the
nonfluorinated 1 (Figures S3 and S4).
Thermogravimetric Studies. Thermogravimetric analysis
(TGA) of precursors 1−12 was then used to evaluate their
suitability for chemical vapor deposition processes. These
studies were carried out under an inert atmosphere at
temperatures between 20 and 600 °C. For comparison, TGA
data on the starting reagent [Sn(OBut)4] were also collected
under similar conditions (Figure 2). Some selected TGA data
are summarized in Table S1.
Influence of Nature of Aminoalkoxide Ligands. The TGA
curves of the three tin(IV) complexes with a nonfluorinated
asymmetric aminoalkoxide ligand, [Sn(OBut)2(ORN)2] (ORN =
dmae (1), dmap (2), dmamp (3)), show that the introduction of
an aminoalkoxide ligand improves the thermal stability and
volatility of the starting reagent [Sn(OBut)4] (Figure 2a). All of
these precursors exhibit only one significant weight loss between
Spectroscopic Characterization. The salient features of the
IR spectra of 1−12 are (i) the absence of a broad absorption
band characteristic of the OH group in the 3250−3550 cm−1
region, (ii) the presence of strong bands in the regions 2850−
3000 and 1000−1200 cm−1 due to ν(C(sp3)−H) and metal
alkoxo group vibrations ν(Sn−O−C), respectively, therefore
confirming the bonding of OR (R = Et, Pri, But) groups to tin,
and (iii) the appearance of new medium-intensity bands at 400−
600 cm−1 due to Sn−O and Sn−N vibrations. For octahedral
complexes of the type [Sn(η1-OR)2(η2-ORN)2], five diaster-
eoisomers are possible, three of them being present as pairs of
enantiomers.30 However, the 1H NMR spectra of several of the
above tin(IV) aminoalkoxides indicate the presence of a
fluxional process at room temperature. A nondissociative
Ray−Dutt twist mechanism31 would lead to rapid isomerization
of the complex and result in a time-averaged plane of symmetry
through the chelate ligands, which explains the simplicity of the
1
resulting spectra. For example, the H and 13C solution NMR
spectra of [Sn(OPri)2(dmae)2] (6) correspond to the presence
of a single species in solution with five peaks each due to protons
and carbons of the groups OCHMe2, CH2N, OCH2, NMe2, and
OCHMe2, respectively (in the expected region, multiplicity, and
1
integrated intensity ratios for the H NMR spectrum) (Figure
S2). This fluxional process does not cease even at low
temperature. The 119Sn NMR chemical shifts of 1−12 exhibit
only a sharp peak at δ −520 to −600 ppm, which is consistent
with the literature value of a six-coordinated Sn(IV) center.32
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Figure 1. Molecular structures of 1 (a), 5 (b), and 10 (c) with displacement ellipsoids drawn at the 50% probability level. C and F atoms are drawn as
balls and sticks, and H atoms of alkyl groups are omitted for clarity.
Figure 2. TGA curves of [Sn(OR)2(ORN)2] (where ORN = dmae, dmap, dmamp, F-dmap, F-dmamp; R = But, Pri, Et). For comparison, a TGA curve
of the starting reagent [Sn(OBut)4] is also included.
180 and 280 °C with a residual mass lower than the theoretical
amount of SnO2, thus indicating their good volatility even at
atmospheric pressure. The onset values of the volatilization
temperature increase with the increase in the number of methyl
group(s) at the α-carbon atom at the hydroxyl group of the
aminoalkoxide ligand: [Sn(OBut)4] (110 °C) < [Sn-
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(OBut)2(dmae)2] (no methyl at the α-C position, 150 °C) <
[Sn(OBut)2(dmap)2] (one methyl at the α-C position, 200 °C)
< [Sn(OBut)2(dmamp)2] (two methyls at the α-C position, 210
°C). Thus, the Sn(IV) derivative with the heaviest ligand,
dmamp, is the most volatile precursor of the series. The
asymmetric nature of the ligand dmampH, which contains two
methyl groups at the α-C atom, has been exploited previously to
design metal precursors with enhanced volatility due to
decreased intermolecular interactions.34
and the two most volatile precursors, [Sn(OBut)2(dmamp)2]
(3) and [Sn(OBut)2(F-dmamp)2] (5), have been chosen to
deposit undoped SnO2 and F-doped SnO2 thin films,
respectively.
Deposition of SnO2 and F-Doped SnO2 Thin Films by
DLI-CVD. After determination of the thermal behavior of 1−12
as revealed by TG-DTA studies, the most suitable precursors
[Sn(OBut)2(dmamp)2] (3) and [Sn(OBut)2(F-dmamp)2] (5)
were selected to deposit undoped and F-doped SnO2 thin films,
respectively, on silicon and quartz substrates by the DLI-CVD
process at temperatures ranging from 400 to 700 °C. SnO2 and
F-doped SnO2 thin films were deposited by DLI-CVD under
primary vacuum in a quartz CVD reaction chamber on double-
side-polished Si (100) wafers (Table 3) with the surface being
kept parallel to the gas flow. The substrate was heated by
external infrared lamps.
Influence of Nature of Alkoxy Group. The substitution of
OBut group(s) in [Sn(OBut)2(ORN)2] with sterically less
hindered OPri and OEt groups converts the above solid
derivatives into liquids, which is a favorable characteristic for
constant mass transport during CVD experiments. However, the
volatility seems to be affected significantly for these [Sn-
(OR)2(ORN)2] (R = Pri, Et) precursors. For example, unlike a
major step observed in [Sn(OBut)2(ORN)2], the derivatives
[Sn(OR)2(dmamp)2] (R = Pri, Et) appear to retain one
molecule of ButOH in their lattice (as also confirmed by IR and
NMR studies) and show multiple-step decomposition pattern
(Figure 2c). Thus, the TGA curve of [Sn(OEt)2(dmamp)2] (9)
shows a weight loss of 14.4% in the first step at 50 °C, which
corresponds to the loss of one ButOH (theoretical value 14.4%).
The second and third steps correspond to the loss of the two
dmamp groups (theoretical value 38.5%) and ethoxy groups,
respectively. The residual mass at 400 °C corresponds well to
SnO2 (34.6% experimental weight loss versus 34.3% calculated
weight loss). No particular trend is observed for the thermal
stability of the resulting precursors. While the thermal stability
increases with the increased bulkiness of the alkoxy group in the
series [Sn(OR)2(dmae)2] (R = But, Pri, Et) (Figure 2b), an
opposite trend is observed in the series [Sn(OR)2(dmamp)2] (R
= But, Pri, Et) (Figure 2c).
Table 3. Experimental Conditions Used for the Elaboration
of SnO2 Thin Films on Silicon Substrates by DLI-CVD using
Nonfluorinated [Sn(OBut)2(dmamp)2] (3) and Fluorinated
[Sn(OBut)2(F-dmamp)2] (5)
precursor
[Sn(OBut)2(dmamp)2]
[Sn(OBut)2(F-
dmamp)2] (5)
(3)
substrate temp (°C)
total pressure (Torr)
carrier gas (N2) (sccm)
400−650
1.2
462
600−700
1.05
530 (600 and 650 °C)
462 (675 and 700 °C)
40 (600 and 650 °C)
108 (675 and 700 °C)
7.5 (600 and 650 °C)
19 (675 and 700 °C)
0.024 in toluene
reactive gas (O2) (sccm)
%O2 (O2/(N2 + O2))
solution concn
108
19
0.015 in toluene
Influence of Fluorine Substitution. By introducing fluorine
in the aminoalkoxide ligand, we aimed not only to provide an
intrinsic source of fluorine for F-doped SnO2 but also to improve
the volatility and stability of the obtained precursors, as is usually
the case for metal complexes with fluorinated ligands because of
the weaker van der Waals intermolecular interactions caused by
the electrostatic repulsion of the CF3 groups.17 However, the
TGA curves of the precursors [Sn(OR)2(F-dmamp)2] (R = Et,
Pri, But) and [Sn(OBut)(OPri)(F-dmamp)2] show that they are
less volatile than their nonfluorinated analogues (Figure 2d).
This may be attributed to a significant intermolecular H bonding
in the fluorinated precursors due to the high electronegativity of
the fluorine atom, as indicated by the X-ray structures of 5 and
10. For [Sn(OBut)2(F-dmamp)2] (5), the residue left at the end
is 15.5% (21.1% calculated for SnO2 decomposition), which
suggests that, like precursors with nonfluorinated ligands,
sublimation and decomposition occur simultaneously during
the temperature ramp-up. For 4 and 10−12, however, the
residue left is either equal to or more than that calculated for
decomposition to SnO2, indicating that at atmospheric pressure
these complexes decompose without sublimation. For example,
the precursor [Sn(OPri)2(F-dmamp)2] (11) clearly shows a
two-step decomposition: loss of two F-dmamp ligands in the
first step (66% experimental weight loss versus 65.4% calculated
wieght loss) (150−260 °C), followed by the removal of OPri
groups (260−340 °C). The residual mass at 350 °C corresponds
well to SnO2 (21.8% experimental weight loss versus 22%
calculated weight loss). As we use direct liquid injection
MOCVD at reduced pressures, the absence of very good
volatility at atmospheric pressure is not necessarily a problem
(mol L−1
)
flow of the solution
0.5
0.32
(g min−1
)
precursor flow
0.0086
130
0.0083
140
(mmol min−1
)
Vapbox 1500
evaporation temp
(°C)
Deposition of SnO2 from [Sn(OBut)2(dmamp)2] (3) on
Silicon Substrate. The precursor [Sn(OBut)2(dmamp)2] (3)
was dissolved in toluene with a concentration of 0.015 mol L−1.
For all of the experiments, a solution flow of 0.5 g min−1 was
injected and vaporized in the Vapbox 1500 vaporization
chamber heated at 130 °C. It corresponds to a precursor flow
of 0.0086 mmol min−1. The generated precursor vapors were
transported toward the Si single-crystal substrate using a
nitrogen flow as the carrier gas (462 sccm) mixed with an
oxygen flow as the reaction gas (108 sccm). The substrate
temperature was maintained at 400, 450, 500, 550, 600, and 650
°C during the process. The total pressure in the reaction
chamber was about 1.2 Torr during all of the deposition
processes. Table 4 gives the thicknesses and deposition rates,
while Figure 3 shows the Arrhenius plot for the SnO2 growth
rate (v, nm min−1) as a function of the substrate temperature for
the precursor [Sn(OBut)2(dmamp)2] (3). A thickness measure-
ment was performed at the center of the substrate with a “Film
Sense” ellipsometer (Model FS-1 Multi-Wavelength Ellipsom-
eter). Two regions can be identified in the Arrhenius plot. At low
temperatures between 400 and 600 °C, the growth rate increases
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reaction (i.e., determined by the thermally activated decom-
position process of precursors at the substrate surface). An
activation energy of 32 kJ/mol (∼0.34 eV) was calculated using
the slope of this linear relationship. At high temperatures (from
600 to 650 °C), the growth rate becomes less temperature
dependent, as shown by the red dot, and is limited mainly by the
diffusion of precursor molecules on the substrate surface: i.e., by
the feed rate of the precursor and no longer by the thermal
energy available.
Table 4. Thicknesses and Deposition Rates for SnO2 Films
Obtained on Silicon Substrates at Different Temperatures
Using the Precursor [Sn(OBut)2(dmamp)2] (3)
temp
(°C)
thickness
(nm)
deposition time
(s)
growth rate
grain size
(nm)
(nm s−1
)
400
450
500
550
600
650
55
50
39
52
66
48
5400
3600
1800
1800
1800
1200
0.0102
0.0139
0.0217
0.0289
0.0367
0.0400
14
16
19
23
29
37
3
2
5
3
6
4
The films grown from the precursor 3 in the temperature
range 400−650 °C were well crystallized, as shown by XRD
studies (Figure 4a). These diffractograms showed the presence
of two phases: orthorhombic SnO2 (2θ = 24.5°, red line in
Figure 4a) as a minor phase and cassiterite SnO2 with a rutile
structure as a major phase. The preferential orientation (200) is
observed with an increase in substrate temperature. These
results are in agreement with those reported by Drevet et al. for
pulsed DLI-CVD, who also observed a (200) preferential
orientation.35 These films were studied by XPS spectra to
determine their surface chemical composition. The survey
spectra reveal that these films contain, in addition to tin and
oxygen, a high carbon content (due to incomplete decom-
position of the precursor), which can be reduced by postdeposit
annealing.36 Quantitative analysis of these as-deposited thin
films revealed an O/Sn stoichiometry between 1.63 and 1.84
(Table S2). This oxygen scarcity is common for the SnO2 film
deposited by CVD even at higher deposition temperatures.37 In
the core level spectra of Sn (Figure 4b), the electron binding
energy (BE) value for Sn 3d5/2 lies at 486.6 eV, which is in
agreement with the BE values known for the oxygen-deficient
SnOx (with 2 ≥ x ≥ 1) in the range between 485.5 and 487.0
eV.10f,38
SEM analyses were carried out on selected samples to study
morphological changes occurring as a function of deposition
temperature. Figure 5 shows representative top-view and cross-
sectional SEM images of SnO2 grown on Si substrates at
temperatures between 400 and 600 °C. These images show
compact homogeneous (pore-free) films consisting of nano-
meter-sized grains whose average size varies with deposition
temperature (Table 4). In general, an increase in deposition
Figure 3. Arrhenius plot for the SnO2 growth rate (v, nm min−1) as a
function of the substrate temperature for the precursor [Sn-
(OBut)2(dmamp)2] (3).
linearly with the temperature and we assume that across this
temperature window the growth rate is limited by the surface
Figure 4. XRD patterns (a) and XPS spectra (b) of the SnO2 thin films grown from the precursor [Sn(OBut)2(dmamp)2] (3) at variable temperatures.
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Figure 5. SEM images of SnO2 thin films deposited by DLI-CVD between 400 and 600 °C on Si wafer substrates using the precursor
[Sn(OBut)2(dmamp)2] (3). The cross-sectional images of the representative films are shown in the insets.
temperature resulted in the formation of improved facet features
and increased average grain sizes: e.g., the average grain size
doubles approximately on increasing the deposition temperature
from 400 °C (14 3 nm) to 600 °C (29 6 nm). Cross-
sectional images recorded for some representative samples
confirmed the dense nature of the deposit. The film thickness
measured from these cross-sectional images are also in
agreement with those measured by ellipsometry.
In contrast to the XRD patterns of the films grown from 3, the
XRD studies on the films grown from the fluorinated precursor 5
in the temperature range 600−700 °C showed the presence of
cassiterite SnO2 as the only phase (Figure 6). While fluorine was
Deposition of F-Doped SnO2 Thin Films from [Sn(OBut)2(F-
dmamp)2] (5) on Silicon Substrates. The precursor [Sn-
(OBut)2(F-dmamp)2] (5) was dissolved in toluene with a
concentration of 0.024 mol L−1. For all the experiments a
solution flow of 0.32 g min−1 was injected and vaporized in the
Vapbox vaporization chamber heated at 140 °C. It corresponds
to a precursor flow of 0.0083 mmol min−1. The generated
precursor vapors were transported to the Si monocrystalline
substrate using a nitrogen flow as the carrier gas (530 or 462
sccm) mixed with an oxygen flow as the reaction gas (40 or 108
sccm). The substrate temperature was maintained at 600, 620,
650, 675, and 700 °C during the process. The total pressure in
the reaction chamber was maintained at 1.05 Torr during the
deposition process. Table 5 gives the deposition rates,
thicknesses, and average grain sizes, while Table S3 summarizes
chemical compositions for the SnO2 films obtained at different
temperatures using the precursor 5.
Figure 6. XRD patterns of the films grown from the precursor
[Sn(OBut)2(F-dmamp)2] (5) in the temperature range 600−700 °C.
Table 5. Thicknesses and Deposition Rates for SnO2 Films
Obtained on Silicon Substrates at Different Temperatures
Using the Precursor [Sn(OBut)2(F-dmamp)2] (5)
absent in the film deposited at 600 °C, a 0.6−0.8% atomic
content of fluorine was determined by the XPS studies in the
films deposited at higher temperature (625−700 °C). These
spectra show a characteristic F 1s XPS peak at 683.2 eV (Figure
7a).39 Usually, a shift to higher values in Sn 3d and O 1s peaks is
observed in F-doped SnO2 due to the incorporation of doped F
at SnO2 lattice oxygen sites.40 However, we do not observe any
significant shift in Sn 3d (486.3 eV) on F doping (Figure 7b),
temp
thickness
(nm)
deposition time
(s)
growth rate
grain size
(nm)
(°C)
(nm s−1
)
600
625
650
675
700
40
66
55
70
60
2400
2400
1800
1500
1200
0.0166
0.0275
0.0305
0.0466
0.05
27
36
44
50
55
5
6
4
6
3
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Figure 7. XPS spectra of the F-doped SnO2 thin films deposited by DLI-CVD between 600 and 700 °C on Si wafer substrates using the precursor
[Sn(OBut)2(F-dmamp)2] (5).
Figure 8. SEM images of SnO2 thin films deposited by DLI-CVD between 600 and 700 °C on Si wafer substrates using the precursor [Sn(OBut)2(F-
dmamp)2] (5).
probably due to the relatively low fluorine content in these films.
SEM images of SnO2 thin films deposited between 600 and 700
°C on Si wafer substrates using the fluorinated precursor 5 are
shown in Figure 8. In comparison to the undoped SnO2 films
deposited using precursor 3, which are composed of faceted
grains of 10−35 nm size, the films here are rough and contain
irregular grains of 22−58 nm. When the temperature is
increased, larger grains begin to appear on the surface. The
film thicknesses measured from these cross-sectional images
(40−80 nm) are in agreement with those measured by
ellipsometry. Three selected films deposited at 625, 650, and
700 °C and having an insulating Al2O3 layer between the silicon
substrate and F-doped SnO2 layers were studied for conductivity
measurements. These samples showed resistivity values on the
order of 10−3 Ω cm, with the sample SnO2:F deposited at 700 °C
exhibiting the lowest resistivity (8.7 × 10−3 Ω cm). These values
are slightly inferior to the reported 10−4 Ω cm resistivity for
commercial products: i.e., F-doped SnO2 deposited on glass by
chemical vapor deposition or high-vacuum processes at 600
°C.41 As the amount of the doped fluorine strongly influences
the structural, optical, and electrical properties of SnO2 thin
films,42 it is highly likely that the conductive properties of our
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Figure 9. SEM images and XPS C1 spectra of SnO2 thin films deposited on quartz substrates using the precursors [Sn(OBut)2(dmamp)2] (3) and
[Sn(OBut)2(F-dmamp)2] (5) (optical images given in the inset): (a) SEM image of the film deposited at 400 °C using 3; (b) SEM image of the film
deposited at 625 °C using 5; (c) XPS C1 spectra of the film deposited at 500 °C using 3; (d) XPS C1 spectra of the film deposited at 650 °C using 5 ((i)
as-deposited films, (ii) films after 2 min of Ar+ sputtering, and (iii) films after 4 min of Ar+ sputtering).
materials could be improved by optimizing the percent of the F
dopant.
Deposition of SnO2 and F-Doped SnO2 Thin Films from 3
and 5 on Quartz Substrates. After having optimized the
deposition conditions on silicon substrates, which allowed us a
facile structural characterization (XRD, ellipsometry, SEM...),
we deposited thin layers of SnO2 and F-doped SnO2 on quartz
substrates as well, mainly to measure the transmittance of the
deposited films. Under the same deposition conditions
described above, SnO2 thin films were deposited on quartz
substrates at 400, 500, and 600 °C using the nonfluorinated
precursor 3 and at 625, 650, 675, and 690 °C using the
fluorinated precursor 5. The SEM images of these visibly
transparent films were smoother than those deposited on silicon
substrates using the same precursors under identical conditions.
These homogeneous, 40−65 nm thick films were pore free and
dense and consisted of grains of 17−21 nm medium-sized grains
(Figure 9). However, these films were weakly crystallized in
comparison to those deposited on silicon substrates (Figure S5).
Film compositions were also studied by XPS, which showed
nearly pure SnO2 films with only a low amount of carbon
content (11−13%) on the surface (284−288.5 eV). This carbon
content could, however, be easily and completely removed by
Ar+ sputtering (1 KeV, 3 nm min−1) for 2 min (Figure 9). The
optical transmittance spectra were measured on these films and
compared with that of an uncoated quartz substrate (Figure 10).
A high transparency of ∼80% in the visible range (450−850 nm)
was observed for these SnO2 films, in accordance with the
requirements for transparent conducting oxide applications.43,44
As expected, the transmittance decreases in the UV region
Figure 10. Transmittance spectra of SnO2 thin films deposited on
quartz substrates using the precursors 3 (blue line) and 5 (red line) at
400 and 650 °C, respectively. For comparison, the transmittance
spectrum of the uncoated quartz substrate is also included (gray line).
Corresponding Kubelka−Munk plots are shown in the inset.
because of the onset of a fundamental absorption at about 340
nm. The UV−visible spectra were transformed into Kubelka−
Munk plots to measure the direct band gap of these SnO2 films
(Figure 10, inset). The film deposited from the fluorinated
precursor 5 shows a decrease in the band-gap value (3.37 eV) in
comparison to the film deposited from the nonfluorinated
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precursor 3 (3.75 eV), thus clearly demonstrating the influence
of fluorine doping on the optical properties of SnO2 films.
Email: shashank.mishra@ircelyon.univ-lyon1.fr; Fax: (+33)
472445399
́
́
Stephane Daniele − Universite Claude Bernard Lyon 1, C2P2,
CPE Lyon - CNRS, UMR 5265, 69616 Villeurbanne, France;
Email: stephane.daniele@univ-lyon1.fr
CONCLUSIONS
■
In conclusion, a series of asymmetric amino alcohols with
different numbers of methyl or trifluoromethyl substituents at
the α position of the alcohol functionality, [HOC(R1)(R2)-
CH2NMe2] (R1 and R2 = H, CH3, CF3), was synthesized,
characterized, and employed to develop the 12 new heteroleptic
tin(IV) complexes [Sn(OR)2(ORN)2] (R = Et, Pri, But) as
potential MOCVD precursors. Although all of the precursors
have a monomeric structure and favorable characteristics of
good volatility and easy transport, this study shows that small
changes in the nature of the ligands, whether for the OR or ORN
groups, have a strong effect in terms of thermal behavior and
volatility. TGA studies indicated that the most appropriate
precursors for DLI-CVD deposits were those with the heaviest
and bulkiest ligands: i.e., [Sn(OBut)2(dmamp)2] and [Sn-
(OBut)2(F-dmamp)2]. The toluene solutions of these two
precursors were therefore used to deposit thin films of SnO2 and
F-doped SnO2, respectively, on silicon and quartz substrates. A
comparative study of the thin film elaboration using these two
precursors shows that the presence of the fluorine in
[Sn(OBut)2(F-dmamp)2] not only allows in situ F doping but
also has an effect on the reactivity of this precursor in terms of a
higher activation energy (77 instead of 32 kJ mol−1), a
monophasic film (cassiterite instead of a cassiterite/ortho-
rhombic mixture), and a lower growth rate. This systematic
study also proves that a subtle balance between the intra- and
intermolecular interactions must be found in order to get
suitable MOCVD molecular precursors. Future work will be
devoted to strategies to improve the efficiencies of these
precursors and to the deposition process to enhance the fluorine
incorporation.
Authors
̀
́
Alexandre Verchere − Universite Claude Bernard Lyon 1, CNRS,
UMR 5256, Institut de Recherches sur la Catalyse et
l’Environnement de Lyon (IRCELYON), 69626 Villeurbanne,
France
Erwann Jeanneau − Universite Claude Bernard Lyon 1, Centre de
Diffractometrie Henri Longchambon, 69100 Villeurbanne,
́
́
France
́
Herve Guillon − ANNEALSYS, 34000 Montpellier, France
Jean-Manuel Decams − ANNEALSYS, 34000 Montpellier,
France
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.inorgchem.0c00617
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
́
A LABEX iMust grant (ANR-10-LABX-0064) of Universite de
Lyon, within the program “investisements d’Avenir” (ANR-11-
IDEX-0007) operated by the French National Research Agency
(ANR) is acknowledged. The authors also thank L. Burel
(SEM), Y. Aizac (PXRD), and Dr. L. Cardenas and P.-P.
Bargiela (XPS) of IRCELYON, Dr. A. Benayad (XPS) of CEA
̀
Grenoble, Dr. S. Pailhes (conductivity measurements) of ILM,
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.inorgchem.0c00617.
■
́
Prof. C. Vallee (ellipsometeric measurements) of Laboratoire
sı
́
des Technologies de la Microelectronique (LTM) in Grenoble,
and D. Hadwiger (ellipsometric measurements) of Film Sense
Company.
Synthesis and characterization of the synthesized ligands,
1H, 13C, and 119Sn NMR spectra of a representative
complex (6), packing diagrams showing intermolecular
H-bonding among mononuclear entities of fluorinated
[Sn(OBut)2(F-dmamp)2] (5) and [Sn(OBut)(OPri)(F-
dmamp)2] (10), XRD of thin films on quartz, and
selective data on TGA of the precursors and chemical
composition of the SnO2 and F-doped SnO2 thin films
(PDF)
REFERENCES
■
(1) (a) Kumar, A.; Zhou, C. The race to replace tin-doped indium
oxide: which material will win? ACS Nano 2010, 4, 11−14. (b) Ellmer,
K. Past achievements and future challenges in the development of
optically transparent electrodes. Nat. Photonics 2012, 6, 809−817.
(2) (a) Wang, H.; Rogach, A. L. Hierarchical SnO2 Nanostructures:
Recent Advances in Design, Synthesis, and Applications. Chem. Mater.
2014, 26, 123−133. (b) Das, S.; Jayaraman, V. SnO2: A comprehensive
review on structures and gas sensors. Prog. Mater. Sci. 2014, 66, 112−
255. (c) Chen, J. S.; Lou, X. W. SnO2-Based Nanomaterials: Synthesis
and Application in Lithium-Ion Batteries. Small 2013, 9, 1877−1893.
(d) Batzill, M.; Diebold, U. The surface and materials science of tin
oxide. Prog. Surf. Sci. 2005, 79, 47−154.
Accession Codes
CCDC 1951886−1951888 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: +44 1223 336033.
(3) Gordon, R. G. Criteria for choosing transparent conductors. MRS
Bull. 2000, 25, 52−57.
(4) Cirera, A.; Vila, A.; Cornet, A.; Morante, J. R. Properties of
nanocrystalline SnO2 obtained by means of a microwave process. Mater.
Sci. Eng., C 2001, 15, 203−205.
AUTHOR INFORMATION
■
(5) Lada, W.; Deptula, A.; Olczak, T.; Torbicz, W.; Pijanowska, D.; Di
Bartolomeo, A. Preparation of thin SnO2 layers by inorganic sol-gel
process. J. Sol-Gel Sci. Technol. 1994, 2, 551−554.
Corresponding Authors
́
Shashank Mishra − Universite Claude Bernard Lyon 1, CNRS,
UMR 5256, Institut de Recherches sur la Catalyse et
l’Environnement de Lyon (IRCELYON), 69626 Villeurbanne,
France; orcid.org/0000-0003-2846-4221;
(6) Aboulaich, A.; Boury, B.; Mutin, P. H. Reactive and Organosoluble
SnO2 Nanoparticles by a Surfactant-Free Non-Hydrolytic Sol-Gel
Route. Eur. J. Inorg. Chem. 2011, 2011, 3644−3649.
7178
https://dx.doi.org/10.1021/acs.inorgchem.0c00617
Inorg. Chem. 2020, 59, 7167−7180

Inorganic Chemistry
pubs.acs.org/IC
Article
(7) (a) Reddy, S. R.; Mallik, A. K.; Jawalekar, S. R. Optical and
electrical properties of SnO2 films prepared by chemical vapour
deposition. Bull. Mater. Sci. 1986, 8, 357−363. (b) Inal, O. T.; Bengisu,
M.; Guardian, J. Plasma-assisted chemical vapour deposition of tin
oxide coatings. J. Mater. Sci. 1993, 28, 1155−1160. (c) Parshina, L. S.;
Novodvorsky, O. A.; Khramova, O. D.; Petukhov, I. A.; Mikhalevsky, V.
A.; Lotin, A. A.; Cherebilo, E. A.; Panchenko, V. Ya. Properties of
SnO2:Sb films produced on flexible organic substrates by droplet-free
pulsed laser deposition method. Opt. Quantum Electron. 2016, 48, 316.
(8) Xiang, X.; Zhu, D.; Wang, D. Enhanced formaldehyde gas sensing
properties of La-doped SnO2 nanoparticles prepared by ball-milling
solid chemical reaction method. J. Mater. Sci.: Mater. Electron. 2016, 27,
7425−7432.
(9) Koponen, S. E.; Gordon, P. G.; Barry, S. T. Principles of precursor
design for vapour deposition methods. Polyhedron 2016, 108, 59−66.
(10) (a) Sundqvist, J.; Ottosson, M.; Harsta, A. CVD of Epitaxial SnO2
Films by the SnI4/O2 Precursor Combination. Chem. Vap. Deposition
2004, 10, 77−82. (b) Chae, Y.; Houf, W. G.; McDaniel, A. H.; Troup,
J.; Allendorf, M. D. Stagnation Flow Reactor Investigation of Tin Oxide
CVD from Monobutyltin Trichloride. J. Electrochem. Soc. 2004, 151,
C527−C534. (c) Korotkov, R. Y.; Ricou, P.; Farran, A. Preferred
orientations in polycrystalline SnO2 films grown by atmospheric
pressure chemical vapor deposition. Thin Solid Films 2006, 502, 79−87.
(d) Molloy, K. C. Precursors for the formation of tin(IV) oxide and
related materials. J. Chem. Res. 2008, 2008, 549−554. (e) Chew, C. K.
T.; Salcianu, C.; Bishop, P.; Carmalt, C. J.; Parkin, I. P. Functional thin
film coatings incorporating gold nanoparticles in a transparent
conducting fluorine doped tin oxide matrix. J. Mater. Chem. C 2015,
3, 1118−1125. (f) Zanders, D.; Ciftyurek, E.; Hoppe, C.; Arcos, T. D.
L.; Kostka, A.; Rogalla, D.; Grundmeier, G.; Schierbaum, K. D.; Devi, A.
Validation of a Terminally Amino Functionalized Tetra-Alkyl Sn(IV)
Precursor in Metal-Organic Chemical Vapor Deposition of SnO2 Thin
Films: Study of Film Growth Characteristics, Optical, and Electrical
Properties. Adv. Mater. Interfaces 2019, 6, 1801540.
(11) (a) Powell, M. J.; Carmalt, C. J. Aerosols: A Sustainable Route to
Functional Materials. Chem. - Eur. J. 2017, 23, 15543−15552.
(b) Seisenbaeva, G. A.; Kessler, V. G. Precursor directed synthesis-
“molecular” mechanisms in the Soft Chemistry approaches and their
use for template-free synthesis of metal, metal oxide and metal
chalcogenide nanoparticles and nanostructures. Nanoscale 2014, 6,
6229−6244. (c) Mishra, S.; Daniele, S.; Hubert-Pfalzgraf, L. G. Metal 2-
Ethylhexanoates and Related Compounds as Useful Precursors in
Materials Science. Chem. Soc. Rev. 2007, 36, 1770−1787. (d) Hubert-
Pfalzgraf, L. G. To What Extent Can Design of Molecular Precursors
Control the Preparation of High Tech Oxides? J. Mater. Chem. 2004,
14, 3113−3123. (e) Hubert-Pfalzgraf, L. G. Some Trends in the Design
of Homo- and Heterometallic Molecular Precursors of High-Tech
Oxides. Inorg. Chem. Commun. 2003, 6, 102−120.
ylalkenolate complexes and their properties as PI-MOCVD precursors
for SnO2 deposition. Eur. J. Inorg. Chem. 2018, 2018, 5027−5035.
(13) (a) Jones, A. C. Molecular design of improved precursors for the
MOCVD of electroceramic oxides. J. Mater. Chem. 2002, 12, 2576−
2590. (b) Otway, D. J.; Rees, W. S. Group 2 element β-diketonate
complexes: synthetic and structural investigations. Coord. Chem. Rev.
2000, 210, 279−328. (c) Tiitta, M.; Niinisto, L. Volatile metal β-
diketonates: ALE and CVD precursors for electroluminescent device
thin films. Chem. Vap. Deposition 1997, 3, 167−182.
(14) (a) Soussi, K.; Mishra, S.; Jeanneau, E.; Mantoux, A.; Daniele, S.
Synthesis, characterization and thermal transport properties of
heteroleptic N-alkyl triazenide complexes of titanium(IV) and
niobium(V). Polyhedron 2018, 152, 84−89. (b) Soussi, K.; Mishra,
S.; Jeanneau, E.; Millet, J.-M. M.; Daniele, S. Asymmetrically
substituted triazenes as poor electron donor ligands in the precursor
chemistry of iron(II) for iron-based metallic and intermetallic
nanocrystals. Dalton Trans. 2017, 46, 13055−13064. (c) Barry, S. T.
Amidinates, guanidinates and iminopyrrolidinates: Understanding
precursor thermolysis to design a better ligand. Coord. Chem. Rev.
2013, 257, 3192−3201. (d) Edelmann, F. T. Lanthanide amidinates
and guanidinates: from laboratory curiosities to efficient homogeneous
catalysts and precursors for rare-earth oxide thin films. Chem. Soc. Rev.
2009, 38, 2253−2268.
(15) (a) Mishra, S.; Jeanneau, E.; Rolland, M.; Daniele, S. Structural
isomers of iron(III) N-methyl diethanolaminate as sol-gel precursors
for iron-based oxide nanomaterials. RSC Adv. 2016, 6, 1738−1743.
(b) Mishra, S.; Mendez, V.; Jeanneau, E.; Caps, V.; Daniele, S. A Single
Source Precursor Route to Group 13 Homo- and Heterometallic
Oxides as Highly Active Supports for Gold-Catalyzed Aerobic
Epoxidation of trans-Stilbene. Eur. J. Inorg. Chem. 2013, 2013, 500−
510. (c) Mishra, S.; Jeanneau, E.; Daniele, S.; Mendez, V. Aminoalkoxo-
supported heteroleptic hexanuclear gallium(III) wheel as a synthon for
group 13 heterometallics: A rare sol-gel precursor for mixed Al-Ga
oxide as support for gold catalysts. Dalton Trans. 2010, 39, 7440−7443.
(d) Mishra, S.; Daniele, S.; Petit, E.; Jeanneau, M. Rolland, Homoleptic
gallium(III) and indium(III) aminoalkoxides as precursors for sol-gel
routes to metal oxide nanomaterials. Dalton Trans. 2009, 2569−2577.
(16) Marchand, P.; Carmalt, C. J. Molecular precursor approach to
metal oxide and pnictide thin films. Coord. Chem. Rev. 2013, 257,
3202−3221.
(17) Mishra, S.; Daniele, S. Metal-Organic Derivatives with
Fluorinated Ligands as Precursors for Inorganic Nanomaterials.
Chem. Rev. 2015, 115, 8379−8448.
(18) (a) Han, S. H.; Jung, E. A.; Lee, J. H.; Kim, D. H.; Lee, G. Y.; Park,
B. K.; Kim, C. G.; Son, S. U.; Chung, T.-M. Synthesis and Structure of
Novel Tin Complexes Containing Aminoalkoxide Ligands. Chemistry
Select 2018, 3, 7836−7839. (b) Glowacki, B.; Lutter, M.; Schollmeyer,
D.; Hiller, W.; Jurkscha, K. Novel Stannatrane N-
(CH2CMe2O)2(CMe2CH2O)SnO-t-Bu and Related Oligonuclear
Tin(IV) Oxoclusters. Two Isomers in One Crystal. Inorg. Chem.
2016, 55, 10218−10228. (c) Zoller, T.; Jurkschat, K. Novel
Trialkanolamine Derivatives of Tin of the Type [N-
(CH2CMe2O)2(CH2)nOSnOR]m (m = 1, 2; n = 2, 3; R = t-Bu, 2,6-
Me2C6H3) and Related Tri- and Pentanuclear Tin(IV) Oxoclusters.
Syntheses and Molecular Structures. Inorg. Chem. 2013, 52, 1872−
1882. (d) Iovkova-Berends, L.; Berends, T.; Zoller, T.; Schollmeyer, D.;
Bradtmoller, G.; Jurkschat, K. Trapping Molecular SnBr2(OH)2 by Tin
Alkoxide Coordination: Syntheses and Molecular Structures of
[ M e N ( C H 2 C M e 2 O )2 S n B r 2 ] 2 · S n B r 2 ( O H )2 a n d R N -
(CH2CMe2O)2SnL [R = Me, n-Octyl; L = Lone Pair, Cr(CO)5,
W(CO)5, Fe(CO)4, Br2]. Eur. J. Inorg. Chem. 2012, 2012, 3463−3473.
(e) Zoller, T.; Iovkova-Berends, L.; Dietz, C.; Berends, T.; Jurkschat, K.
On the Reaction of Elemental Tin with Alcohols: A Straightforward
Approach to Tin(II) and Tin(IV) Alkoxides and Related Tinoxo
Clusters. Chem. - Eur. J. 2011, 17, 2361−2364.
(12) (a) Suh, S.; Hoffman, D. M.; Atagi, L. M.; Smith, D. C.; Liu, J.-R.;
Chu, W.-K. Precursor Oxidation State Control of Film Stoichiometry in
the Metal-Organic Chemical Vapor Deposition of Tin Oxide Thin
Films. Chem. Mater. 1997, 9, 730−735. (b) Suh, S.; Zhang, Z.; Chu, W.-
K.; Hoffman, D. M. Atmospheric-Pressure Chemical Vapor Deposition
of Fluorine-Doped Tin Oxide Thin Films. Thin Solid Films 1999, 345,
240−243. (c) Mahon, M. F.; Molloy, K. C.; Stanley, J. E.; Rankin, D. W.
H.; Robertson, H. E.; Johnston, B. F. Atmospheric Pressure Deposition
of Fluorine-Doped SnO2 Thin Films from Organotin Fluorocarbox-
ylate Precursors. Appl. Organomet. Chem. 2005, 19, 658−671.
(d) Molloy, K. C.; Stanley, J. E. Atmospheric Pressure Deposition of
F-Doped SnO2 Thin Films from Organotin Fluoroalkoxide Precursors.
Appl. Organomet. Chem. 2009, 23, 62−67. (e) Drevet, R.; Legros, C.;
́
Berardan, D.; Ribot, P.; Dragoe, D.; Cannizzo, C.; Barthes-Labrousse,
M. G.; Chausse, A.; Andrieux, M. Metal organic precursor effect on the
properties of SnO2 thin films deposited by MOCVD technique for
electrochemical applications. Surf. Coat. Technol. 2015, 271, 234−241.
(f) Podhorsky, J.; Murauskas, T.; Hegemann, C.; Graf, D.; Fischer, T.;
Babiak, M.; Pinkas, J.; Plausinaitiene, V.; Mathur, S.; Abrutis, A.;
Moravec, Z. Preparation of Heteroleptic Tin(IV) N, O-β-heteroar-
(19) Astie, V.; Millon, C.; Decams, J.-M.; Bartasyte, A. Direct Liquid
Injection Chemical Vapor Deposition. In Chemical Vapor Deposition for
Nanotechnology; Mandracci, P., Ed.; IntechOpen: 2019. DOI: 10.5772/
intechopen.80244.
7179
https://dx.doi.org/10.1021/acs.inorgchem.0c00617
Inorg. Chem. 2020, 59, 7167−7180

Inorganic Chemistry
pubs.acs.org/IC
Article
(20) https://www.annealsys.com/products/annealsys-products/dli-
cvd-dli-ald/mc-050.html.
(21) Chou, T.-Y.; Chi, Y.; Huang, S.-F.; Liu, C.-S. Fluorinated
Aminoalkoxide and Ketoiminate Indium Complexes as MOCVD
Precursors for In2O3 Thin Film Deposition. Inorg. Chem. 2003, 42,
6041−6049.
(22) George, S. M.; Park, B. K.; Kim, C. G.; Chung, T. M.; Carty, A. J.;
Scoles, L.; Udachin, K. A. Heteroleptic group 2 metal precursors for
metal oxide thin films. Eur. J. Inorg. Chem. 2014, 2014, 2002−2010.
(23) Katagiri, T.; Fujiwara, Y.; Takahashi, S.; Uneyama, K.
Intermolecular-medium and intramolecular-weak hydrogen bonding
chains in the crystals of chiral trifluoromethylated amino alcohols. J.
Fluorine Chem. 2005, 126, 1134−1139.
(24) Petrov, V. A. Synthesis of Polyfluorinated Tertiary Alcohols
Using Ring Opening Reactions of 2, 2-Bis(trifluoromethyl)oxirane.
Synthesis 2002, 15, 2225−2231.
(25) CrysAlisPro Software System Rigaku Oxford Diffraction: 2018.
(26) Clark, R. C.; Reid, J. S. The Analytical Calculation of Absorption
in Multifaceted Crystals. Acta Crystallogr., Sect. A: Found. Crystallogr.
1995, A51, 887−897.
(27) Sheldrick, G. M. ShelXT-Integrated space-group and crystal-
structure determination. Acta Crystallogr., Sect. A: Found. Adv. 2015,
A71, 3−8.
(37) Lu, Y. M.; Jiang, J.; Becker, M.; Kramm, B.; Chen, L.; Polity, A.;
He, Y. B.; Klar, P. J.; Meyer, B. K. Vacuum 2015, 122, 347.
(38) Choi, W.; Jung, H.; Koh, S. J. Vac. Sci. Technol., A 1996, 14, 359.
(39) Mu, S.; Wu, J.; Shi, Q.; Zhang, F. Electrocatalytic Reduction of
Carbon Dioxide on Nanosized Fluorine Doped Tin Oxide in the
Solution of Extremely Low Supporting Electrolyte Concentration: Low
Reduction Potentials. ACS Appl. Energy Mater. 2018, 1, 1680−1687.
(40) Wang, X.; Wang, X.; Di, Q.; Zhao, H.; Liang, B.; Yang, J. Mutual
Effects of Fluorine Dopant and Oxygen Vacancies on Structural and
Luminescence Characteristics of F Doped SnO2 Nanoparticles.
Materials 2017, 10, 1398.
(41) Pilkington NSG Group Flat Glass Business. NSG TEC. Available
from: https://www.pilkington.com/en-gb/uk/products/product-
categories/solar-energy/nsg-tec.
(42) Benhaoua, A.; Rahal, A.; Benhaoua, B.; Jlassi, M. Effect of fluorine
doping on the structural, optical and electrical properties of SnO2 thin
films prepared by spray ultrasonic. Superlattices Microstruct. 2014, 70,
61−69.
(43) Guillen, C.; Herrero, J. TCO/metal/TCO structures for energy
and flexible electronics. Thin Solid Films 2011, 520, 1−17.
(44) Nadarajah, A.; Carnes, M. E.; Kast, M. G.; Johnson, D. W.;
Boettcher, S. W. Aqueous Solution Processing of F-Doped SnO2
Transparent Conducting Oxide Films Using a Reactive Tin(II)
Hydroxide Nitrate Nanoscale Cluster. Chem. Mater. 2013, 25, 4080−
4087.
(28) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.;
Puschmann, H. Olex2: A complete structure solution, refinement and
analysis program. J. Appl. Crystallogr. 2009, 42, 339−341.
(29) Sheldrick, G. M. Crystal structure refinement with ShelXL. Acta
Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3−8.
(30) North, M. Principles and Applications of Stereochemistry; CRC
Press: Cheltenham, 1998.
(31) Rzepa, H. S.; Cass, M. E. In Search of the Bailar and Ray-Dutt
Twist Mechanisms That Racemize Chiral Trischelates: A Computa-
tional Study of ScIII, TiIV, CoIII, ZnII, GaIII, and GeIV Complexes of a
Ligand Analogue of Acetylacetonate. Inorg. Chem. 2007, 46, 8024−
8031.
(32) (a) Mishra, S.; Jeanneau, E.; Mangematin, S.; Chermette, H.;
Poor Kalhor, M.; Bonnefont, G.; Fantozzi, G.; Le Floch, S.; Pailhese, S.;
Daniele, S. A convenient and quantitative route to Sn(IV)-M [M =
Ti(IV), Nb(V), Ta(V)] heterobimetallic precursors for dense mixed-
metal oxide ceramics. Dalton Trans. 2015, 44, 6848−6862. (b) Mishra,
S.; Jeanneau, E.; Berger, M. H.; Hochepied, J.-F.; Daniele, S. Novel
heteroleptic heterobimetallic alkoxide complexes as facile single source
precursors for Ta5+- doped TiO2-SnO2 nanoparticles. Inorg. Chem.
2010, 49, 11184−11189. (c) Mishra, S.; Goyal, M.; Singh, A. Synthesis
1
and spectroscopic (IR, H, 13C, and 119Sn NMR) characterization of
mono- and diorganotin(IV) complexes containing sterically hindered
N-arylsalicylaldiminate groups. Main Group Met. Chem. 2002, 25, 437−
444.
(33) Somesa̧ n, A.-A.; Roisnel, T.; Dorcet, V.; Silvestru, C.; Sarazin, Y.
Aminofluoroalkoxide amido and boryloxo lead(II) complexes. Dalton
Trans. 2019, 48, 9944−9948.
(34) (a) Han, J. H.; Park, B. K.; Chung, T.-M. Atomic layer deposition
of pure In2O3 films for a temperature range of 200−300 °C using
heteroleptic liquid In(DMAMP)2(OiPr) precursor. Ceram. Int. 2020,
46, 3139−3143. (b) Kim, H.-S.; Jung, E. A.; Han, S. H.; Han, J. H.; Park,
B. K.; Kim, C. G.; Chung, T.-M. Germanium Compounds Containing
Ge = E Double Bonds (E = S, Se, Te) as Single-Source Precursors for
Germanium Chalcogenide Materials. Inorg. Chem. 2017, 56, 4084−
4092. (c) Han, J. H.; Chung, Y. J.; Park, B. K.; Kim, S. K.; Kim, H.-S.;
Kim, C. G.; Chung, T.-M. Growth of p-Type Tin(II) Monoxide Thin
Films by Atomic Layer Deposition from Bis(1-dimethylamino-2-
methyl-2propoxy)tin and H2O. Chem. Mater. 2014, 26, 6088−6091.
(35) Drevet, R.; Legros, C.; Berardan, D.; Ribot, P.; Chausse, A.;
Andrieux, M. Nanocrystallized SnO2 thin films deposited on Si and
LaAlO3 substrates by pulsed-MOCVD technique for electrochemical
applications. Surf. Coat. Technol. 2013, 230, 180−185.
(36) Yang, J.; Liu, W.; Dong, L.; Li, Y.; Li, C.; Zhao, H. Studies on the
structural and electrical properties of F-doped SnO2 film prepared by
APCVD. Appl. Surf. Sci. 2011, 257, 10499−10502.
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https://dx.doi.org/10.1021/acs.inorgchem.0c00617
Inorg. Chem. 2020, 59, 7167−7180