Synthesis and characterization of novel zinc precursors for ZnO thin film deposition by atomic layer deposition

Article abstract of DOI:10.1039/c9dt04644e

A novel series of zinc complexes, [EtZn(dab)]₂ (1), [EtZn(damb)]₂ (2), [EtZn(damp)]₂ (3), and [EtZn(dadb)]₂ (4), were prepared via single-step substitution. Further, these were analyzed by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, single crystal X-ray diffraction analysis, and thermogravimetric analysis (TGA). The X-ray crystallography analysis revealed that all complexes exist as dimeric structures with distorted tetrahedral geometry having zinc centers that are interconnected via μ₂-O bonding of the aminoalkoxy oxygen atom. TGA and thermal analysis of the complexes showed high volatilities and stabilities at sublimation temperatures of 70, 95, 90, and 105 °C at 0.5 Torr for the respective compounds. Precursor 3 was successfully used for ZnO thin film deposition by ALD. A growth rate per cycle (GPC) of 0.125 nm per cycle was obtained at 200 °C and XPS analysis confirmed the growth of highly pure ZnO films without carbon and nitrogen impurities, while XRD analysis revealed the deposition of reasonably crystalline films. Additionally, the high transmittance and wide bandgap of the films are suitable for optoelectronic applications.

Full text of DOI:10.1039/c9dt04644e

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PAPER
Synthesis and characterization of novel zinc
precursors for ZnO thin film deposition by atomic
layer deposition†
Cite this: DOI: 10.1039/c9dt04644e
a,b
a,c
a,b
Seong Ho Han,
Bo Keun Park,
Raphael Edem Agbenyeke, Ga Yeon Lee,
a,c
a,c
a,c
b
Chang Gyoun Kim, Young Kuk Lee,
Seung Uk Son
a,c
and Taek-Mo Chung
*
A novel series of zinc complexes, [EtZn(dab)]
2
(1), [EtZn(damb)]
2
(2), [EtZn(damp)]
2
(3), and [EtZn(dadb)]
2
(
4), were prepared via single-step substitution. Further, these were analyzed by nuclear magnetic reso-
nance (NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, single crystal X-ray diffr-
action analysis, and thermogravimetric analysis (TGA). The X-ray crystallography analysis revealed that all
complexes exist as dimeric structures with distorted tetrahedral geometry having zinc centers that are
2
interconnected via μ -O bonding of the aminoalkoxy oxygen atom. TGA and thermal analysis of the com-
plexes showed high volatilities and stabilities at sublimation temperatures of 70, 95, 90, and 105 °C at 0.5
Torr for the respective compounds. Precursor 3 was successfully used for ZnO thin film deposition by
ALD. A growth rate per cycle (GPC) of 0.125 nm per cycle was obtained at 200 °C and XPS analysis
confirmed the growth of highly pure ZnO films without carbon and nitrogen impurities, while XRD ana-
lysis revealed the deposition of reasonably crystalline films. Additionally, the high transmittance and wide
bandgap of the films are suitable for optoelectronic applications.
Received 5th December 2019,
Accepted 5th March 2020
DOI: 10.1039/c9dt04644e
rsc.li/dalton
1
0
cells composed of dye sensitized metal oxides, room temp-
Introduction
1
1
12,13
erature UV laser diodes, light-emitting diodes (LEDs),
1
4–17
Zinc oxide (ZnO) is a potentially useful material with a wide and thin-film transistors (TFTs).
optical band gap (3.37 eV), high n-type conductivity, and rela-
Numerous techniques have been developed for ZnO film
1
8
19
−3
tively low electron concentration (10 –10 cm ) compared to deposition for the applications listed above. The most
2
1
−3
indium tin oxide (ITO, 10 cm ). It is a suitable transparent common methods include chemical vapor deposition (CVD)
conductive oxide (TCO) candidate due to its reduced parasitic and atomic layer deposition (ALD) because of their potential to
free carrier absorption. Furthermore, ZnO is chemically and produce highly conformal coatings. As electronic devices
thermally stable as well as environmentally-friendly. Recently, decrease in size and increase in complexity, film conformality
ZnO has been extensively studied for various applications becomes increasingly important for the deposited films. A pre-
1
2
including in piezoelectric transducers, optical waveguides,
requisite for high quality films growth in ALD is the use of a
3
4,5
sensors, nano-generators, thin film bulk acoustic resonator suitable precursor that should exhibit good volatility, adequate
FBAR) filters, transparent conductive oxide (TCO) layers in thermal stability, and good chemical reactivity resulting in
6
(
7
–9
thin film silicon solar cells,
electrochemical photovoltaic pure film deposition.
Typical precursors for ALD deposition of ZnO thin films
1
8
19
20–23
18
include zinc, alkylzinc, zinc acetate,
zinc chloride,
a
Thin Film Materials Research Center, Korea Research Institute of Chemical
Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon 34114, Republic of Korea.
E-mail: tmchung@krict.re.kr
24
and methylzinc isopropoxide. Generally, alkyl metal precur-
sors are pyrophoric and extremely air-sensitive; further, metal
halide precursors produce corrosive byproducts, etching, and
exhibit low chemical reactivity at low substrate temperatures.
In contrast, zinc acetate precursor requires high substrate
temperatures for proper deposition. Thus, alkyl-metal-ami-
noalkoxide complexes have been proposed as ideal precursors
as these are non-halogenic, non-pyrophoric, and exhibit suit-
able reactivity at reasonable temperatures.
b
Department of Chemistry and Department of Energy Science, Sungkyunkwan
University, 2066 Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do 16419, Republic of
Korea
c
Department of Advanced Materials and Chemical Engineering, University of Science
and Technology (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of
Korea
†
CCDC 1946852 and 1943947–1943949. For crystallographic data in CIF or other
electronic format see DOI: 10.1039/c9dt04644e
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Herein, the synthesis and characterization of novel zinc pre- bonding of the other metal complexes (Mg, Sr, In, Co) contain-
2
5–30
cursors with a combination of ethyl and aminoalkoxide ing aminoalkoxide previously reported.
ligands, 4-dimethylamino-2-butoxide (dab), 4-dimethylamino- In all complexes, each zinc ion was bonded to one terminal
-methyl-2-butoxide (damb), 4-dimethylamino-2-methyl-2- ethyl group and two bridging aminoalkoxide ligands; these
pentoxide (damp), and 4-dimethylamino-2,3-dimethyl-2-butox- ions exhibited tetra-coordinated metal centers and a distorted
ide (dadb), is reported. The complexes, [EtZn(dab)] (1), [EtZn tetrahedral geometry (as shown in Fig. 1–4). In particular, the
damb)] (2), [EtZn(damp)] (3), and [EtZn(dadb)] (4) were pre- aminoalkoxide ligand is bound to zinc as a bidentate ligand
2
2
(
2
2
2
pared via simple substitution reaction using the corresponding and forms a 6-membered ring composed of Zn–N–C–C–C–O.
ligands and diethylzinc. All complexes were characterized via Selected bond lengths and bond angles of the complexes are
NMR, FT-IR, elemental analysis, thermogravimetric analysis listed in Table 2.
(TGA), and X-ray crystallography. The thermal analysis showed
The bond lengths between zinc and ethyl group carbon of
that the newly synthesized complexes are sufficiently thermally the dimer complexes were determined to be 1.979(4) Å (1),
stable and volatile for use in the ALD process. In addition, 1.9927(14) Å (2), 1.992(3) Å (3), and 1.954(5) Å (4), which are
1
1
deposition of ZnO thin films using [EtZn(damp)] and hydro- similar to those of [EtZnL ] (1.985(2) Å) (where L = 1,3-bis(di-
2
2
31
gen peroxide as an oxygen source by ALD was demonstrated.
methylamino)-2-(dimethylaminomethyl)-propan-2-olate) and
2
1
2
1
[
1
EtZnL N ]
,1,3,3-tetramethylguanidine).
bonding distances with aminoalkoxide ligands were 2.212(3),
.1868(12), 2.194(2), and 2.189(3) Å for complexes 1–4, respect-
ively. These Zn–N bond lengths are similar to those of
2
(1.996(3) Å) (where L = neopentyl alkoxide, N =
32
The coordinated Zn–N
Results and discussion
Synthesis
2
Novel zinc complexes were synthesized by controlled substi-
tution reactions as shown in Scheme 1. A hexane solution of
diethylzinc (DEZ) was mixed with 1 equivalent of the amino-
alcohol (dabH, dambH, dampH, and dadbH) at low tempera-
ture. The crude products were subsequently extracted using
methylene dichloride and purified by sublimation with
1
31
3
[
1
EtZnL ]
2
(2.1847(16) Å) and [EtZnL ]
-phenyl-1-((1-phenylethyl)(2-(phenylethylamino)ethyl)amino)
ethanolate). The Zn–O bond lengths with the aminoalkoxide
ligands were determined to be 2.008(2), 1.9966(9), 1.9845(18),
and 1.9883(19) Å for complexes 1–4, respectively; these are
2
(2.17(2) Å) (where L3 =
33
1
31
slightly shorter than those of [EtZnL ] (2.0451(12) Å) and
2
appreciable yields of at least 50%. All complexes, [EtZn(dab)]
1), [EtZn(damb)] (2), [EtZn(damp)] (3), and [EtZn(dadb)] (4)
2
3
33
[
EtZnL ]
noalkoxide ligand on the Zn center are 91.51(10)°, 91.91(4)°,
2.33(8)°, and 90.01(10)° for complexes 1–4, respectively; these
2
(2.02(2) Å). The bite angles subtended by the ami-
(
2
2
2
prepared herein were highly soluble in common organic sol-
vents including hexane, toluene, methylene dichloride, THF,
and diethyl ether. Additionally, the prepared complexes are
9
are smaller than ideal hexagonal angles. The bridging Zn–O–
Zn bond angles in compounds 1–4 are 97.56(10), 97.69(4),
7.42(8), and 97.81(9)°, respectively; these are larger than
quite stable under inert conditions with
atmosphere.
a
nitrogen
9
1
31
[EtZnL ]
2
(94.72(5))° indicating that inner angles of the
6
-membered ring are wider than those of the 5-membered
Crystal structures
ring. Other reported zinc complexes with 7-membered rings
X-ray quality crystals of 1–4 were obtained by slow evaporation exhibited inner angles of 99.1(7)°, which is larger than those
of a saturated methylene chloride solution in a glove box at of the compounds 1–4.33
room temperature. Complexes 1 and 3 crystallized in the tri-
clinic space group while complexes 2 and 4 crystalized in the
monoclinic space group (Table 1). All complexes formed
NMR spectral analysis
dimers with aminoalkoxy oxygen bridging the two metal The NMR spectra of complexes 1–4 were observed using
centers in the complexes via μ
2
-O bonding, similar to the benzene-d
6
as the solvent and reference at room temperature.
Scheme 1 Synthesis of complexes 1–4.
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Table 1 Crystallographic parameters of complexes 1–4
Compound
1
2
3
4
Empirical formula
Formula weight
T/K
C
16
H
38Zn
2
N
O
2 2
C
18
H
42Zn
N O
2 2 2
C
20
H
46Zn
2
N O
2 2
C
20 2 2 2
H46Zn N O
421.22
100(1)
449.28
100(1)
477.32
100(1)
477.32
100(1)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
Triclinic
Monoclinic
P2(1)/n
8.9302(3)
7.9409(2)
16.0244(5)
90
94.905(2)
90
1132.19(6)
4
1.318
2.130
480
0.40 × 0.30 × 0.04
2.52 to 26.00
−11 ≤ h ≤ 10
0 ≤ k ≤ 9
0 ≤ l ≤ 19
2219
Triclinic
Monoclinic
P2(1)/n
8.4368(7)
9.2545(8)
16.2121(14)
90
97.626(4)
90
1254.62(19)
4
1.264
1.926
512
0.40 × 0.30 × 0.20
2.54 to 25.99
−10 ≤ h ≤ 10
0 ≤ k ≤ 11
0 ≤ l ≤ 19
2444
Pˉ1
Pˉ1
9.952(5)
10.298(5)
12.228(6)
72.78(2)
89.89(3)
63.71(2)
1060.9(9)
2
1.319
2.268
448
0.20 × 0.16 × 0.04
2.31 to 26.02
−12 ≤ h ≤ 12
8.7333(5)
9.0204(6)
9.2754(6)
74.598(3)
74.548(3)
62.454(3)
615.72(7)
2
1.287
1.962
256
0.36 × 0.30 × 0.14
2.31 to 27.88
−11 ≤ h ≤ 11
−11 ≤ k ≤ 11
−12 ≤ l ≤ 8
10 730
γ (°)
V (Å )
3
Z
−
3
ρ (g cm
μ (mm
F(000)
)
1
−
)
3
Crystal size (mm )
θ range (°)
Index ranges
−
11 ≤ k ≤ 12
0
≤ l ≤ 15
Reflections collected
Independent reflections
4020
4020
2219
2903
2444
[
R(int) = 0.0000]
[R(int) = 0.0000]
1.048
0.0181
[R(int) = 0.0605]
1.077
0.0435
[R(int) = 0.0000]
1.056
0.0441
2
Goodness-of-fit on F
0.943
0.0430
0.1049
a
R [I > 2σ(I)]
b
wR2
0.0457
0.1234
0.1360
a
b
2
o
2 2
2 2 1/2
o
R = (∑||F | − |F
c
||)/∑|F
o
|. wR2 = [∑w(F
− F
c
) /∑w(F
o
) ]
.
Fig. 1 Crystal structure of [EtZn(dab)]
2
(1).
2
Fig. 2 Crystal structure of [EtZn(damb)] (2).
1
The H NMR spectra of the N(CH
3
)
2
group methyl of com- with triplets; these values indicated that all proton resonances
plexes 1–4 displayed singlet resonances at 2.02, 2.00, 2.06, and were shifted downfield compared with DEZ.
.04 ppm, respectively. Compared to the corresponding
2
protons in free aminoalcohols, these resonances exhibited a
clear downfield shift. The proton resonances for the alkoxy
Thermogravimetric analysis
3
moiety CH group appeared at 1.20, 1.25, 1.28, and 1.23, TGA was performed for complexes 1–4 from room temperature
1
.07 ppm for complexes 1–4, respectively; these were shifted to 500 °C (Fig. 5). The samples were prepared inside an argon-
downfield compared to the corresponding protons of the free filled glove box and data collection was performed under a
ligand. In addition, the proton resonances of the ethyl group constant flow of nitrogen without air exposure. The TGA plots
were recorded at 0.51 (for 1), 0.45 (for 2 and 3), and 0.36 (for of complexes 1, 2, 3, and 4 showed sharp curves with single
4
) with quartets, and 1.73 (for 1), 1.72 (for 2, 3) 1.63 (for 4) step weight losses of 90%, 94%, 99%, and 99% from 100–295,
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Fig. 5 TGA plot of complexes 1–4. Black (1), red (2), blue (3), pink (4).
2
Fig. 3 Crystal structure of [EtZn(damp)] (3).
istics. Complexes 1–4 were sublimed at 70, 95, 90, and 105 °C,
respectively, under 0.5 Torr with good to excellent yields.
ZnO deposition
Comparing the TG results, compound 3 exhibited the most
suitable characteristics for the ALD process; this was due to
the absence of residue and relatively low sublimation tempera-
ture. The precursor [EtZn(damp)] was used in a thermal ALD
2
with 50% H O as a reactant. The precursor was heated at
2
2
135 °C and added to the reaction chamber with high purity
argon gas at a flow rate of 30 sccm. The H O was maintained
2
2
at room temperature and transported without carrier gas. The
films were grown on bare silicon substrates at 200 °C and the
growth rate per cycle was 0.125 nm per cycle.
2
Fig. 4 Crystal structure of [EtZn(dadb)] (4).
First, while keeping the H O dose time constant at 5 s and
2
2
the Ar purge time at 20 s, the [EtZn(damp)]
00–260, 160–280, and 160–275 °C for compounds 1–4, varied from 0 to 14 s. As evident from Fig. 6a, precursor satur-
respectively. All complexes displayed excellent vaporization ation was obtained after 10 s of dosing. Next, the H O co-reac-
2
dose time was
1
2
2
and thermal characteristics. The residues remaining after TGA tant dose time was varied between 0 and 5 s, with saturation
were 10%, 5%, 0%, and 0% for complexes 1–4, respectively. after 2 s (Fig. 6b).
Sublimation experiments were conducted under reduced
Using the optimized ALD sequence of 10 s – 20 s – 4 s – 20 s,
pressure (0.5 Torr) to better understand the volatile character- the linear increase in film thickness characteristic of ALD was
Table 2 Selected bond lengths (Å) and bond angles (°) for complexes 1–4
Compound 1
Compound 2
Compound 3
Compound 4
Bond lengths (Å)
Zn1–C1
1.979(4)
2.008(2)
1.984(2)
2.212(3)
3.0029(16)
1.9927(14)
1.9966(9)
1.9816(10)
2.1868(12)
2.9954(3)
1.992(3)
1.954(5)
1.9883(19)
1.976(2)
2.189(3)
2.9878(7)
Zn1–O1
Zn1–O1
1.9845(18)
1.9820(17)
2.194(2)
i
Zn1–N1
Zn1⋯Zn1
Bond angles (°)
i
2.9802(5)
C1–Zn1–O1
C1–Zn1–O1
O1–Zn1–O1
126.24(15)
134.39(13)
82.44(10)
111.83(14)
91.51(10)
100.33(10)
97.56(10)
130.28(5)
132.00(5)
82.31(4)
111.01(5)
91.91(4)
99.87(4)
97.69(4)
128.58(11)
131.68(11)
82.59(8)
112.41(10)
92.33(8)
99.91(7)
97.42(8)
133.9(2)
126.0(3)
82.19(9)
115.0(3)
90.01(10)
100.22(11)
97.81(9)
i
i
C1–Zn1–N1
O1–Zn1–N1
i
O1 –Zn1–N1
i
Zn1–O1–Zn1
Data for only one of the two molecules in the asymmetric unit is reported for 1.
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Fig. 6 Variations in growth rate per cycle as a function of (a) [EtZn
(
2 2 2
damp)] dose time and (b) H O dose time at 200 °C.
Fig. 8 (a) Zn 2p and (b) O 1s spectra of ZnO films deposited at 200 °C.
(c) Adventitious C 1s spectrum and (d) N 1s spectrum.
O–H species as the dominant component of the 531.4 eV sub-
peak. The films exhibited good purities, as confirmed by the
absence of carbon or nitrogen (Fig. 8(c) and (d)).
Fig. 7 (a) Linear increase in film thickness with ALD cycle number and
b) temperature-dependent growth characteristics between 180 and
50 °C.
(
2
The plane view morphology of the ZnO film deposited on
SiO substrates was observed using FE-SEM. As depicted in
2
Fig. 9, highly dense and pin-hole free films were obtained with
average grain sizes ranging between 40 and 50 nm.
UV-visible spectroscopy was used to determine the optical
properties of the prepared ZnO film. The transmittance and
absorbance spectra of the film were measured from 300 to
investigated. As depicted in Fig. 7a, the thickness increased
linearly with increasing cycle number with no growth delay or
incubation regime. A GPC of 0.125 nm per cycle was estimated
from the slope of the plot, which represents one of the highest
GPCs in ZnO ALD at such moderate temperatures. The
temperature-dependent growth behavior of the films was
investigated within a temperature range of 180–250 °C. The
growth rate increased with deposition temperature from
1
9
800 nm, as shown in Fig. 10(a). A sharp absorption edge was
observed at approximately 410 nm, while a transmittance of
over 80% was obtained in the visible region. Tauc plots, con-
2
sisting of (αhυ) vs. (hυ), were used to estimate the optical
0
2
.088 nm per cycle at 180 °C to around 0.15 nm per cycle at
25 °C. Subsequently, a growth rate was observed between 225
and 250 °C indicating a narrow but clear ALD window
Fig. 7b).
The chemical composition and possible impurities of the
film incorporation were investigated by XPS. An adventitious C
s peak with a binding energy of 284.6 eV was used as the
(
1
reference to calibrate all generated spectra. Fig. 8(a) shows the
Zn 2p3/2 and Zn 2p1/2 spectra centered at 1021 and 1044 eV,
respectively, with a spin orbital splitting of ∼23 eV consistent
3
4
with previously reported values for ZnO. The O 1s spectrum
depicted in Fig. 8(b) was deconvoluted into two sub-peaks cen-
tered at 529.6 and 531.4 eV. The sub-peak at 529.6 eV corres-
ponds to lattice oxide, whereas the peak at 531.4 eV corres-
ponds to O–H species, C–O species, or oxygen vacancies in the
films. No carbon was detected in the films during etching and
their high resistivity further suggested the formation of stoi-
chiometric films with limited oxygen vacancies. This leaves Fig. 9 FE-SEM plan-view image of ZnO thin film deposited at 200 °C.
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The thermogravimetric analyses were conducted using a
Thermo plus EVO II TG8120 series thermogravimetry and
differential thermal analysis instrument under a constant
nitrogen flow. All reactions, except for the ligand preparations,
were performed under inert and dry conditions using standard
Schlenk techniques or in an argon-filled glovebox. The dabH
was synthesized using
method.
a
slightly modified literature
Hexane and diethyl ether were purified using an
Innovative Technology PS-MD-4 solvent purification system
and methylene chloride was distilled from CaH . Diethyl zinc
Fig. 10 (a) UV-vis spectra of ZnO film deposited at 200 °C and (b) Tauc was purchased from DNF and all other chemicals were pur-
3
8,39
2
plot of the same film with a bandgap of 3.2 eV.
chased from Sigma Aldrich and used as-received.
General procedure for the synthesis of aminoalcohols
The substituted ethyl acrylate was added dropwise into an
aqueous dimethylamine solution at 0 °C with constant stir-
ring. After addition, the reaction mixture was allowed to warm
to room temperature and stirred for 3 h. The product was
extracted with ethyl acetate and the organic layer was washed
with brine and dried over anhydrous MgSO . The solvent was
4
removed by evaporation and the desired compound was
obtained as a colorless liquid after distillation. To make
aminoalcohol, a methyllithium solution was added dropwise
into the solution of the obtained compound in THF at −78 °C
2
with constant stirring under N . After the addition, the reac-
tion mixture was slowly warmed to room temperature and
stirred for another 5 h. To complete the reaction, an aqueous
ammonium chloride solution was slowly added to reaction
mixture at 0 °C. The product was extracted with diethyl ether
and the combined organic layer was washed with brine and
2
Fig. 11 GIXRD pattern of ZnO thin film deposited on SiO substrate at
200 °C.
4
dried over anhydrous MgSO . The solvent was removed by
evaporation and product was obtained as a colorless liquid
after distillation.
4-(Dimethylamino)-2-methylbutan-2-ol (dambH). Ethyl acry-
late (3.27 mL, 30 mmol) and dimethylamine (2.03 g, 45 mmol)
bandgap of the films. The transition probability of (n) = 2 was
used since the films showed good crystallinity. Fig. 10(b)
shows an optical bandgap of 3.2 eV that is in good agreement
3
5–37
with previously reported values.
The crystal structure of the ∼40 nm thick film deposited on
SiO substrate was investigated by high resolution GIXRD. As
were used as starting materials. Yield: 2.51 g (64%). B.P. 60 °C/
2
1
0
.5 Torr. H NMR (CDCl
3
, 500 MHz): 1.21 (6H, s, CH
2
COH
shown in the diffraction patterns in Fig. 11, the film displayed
an appreciable degree of crystallinity with diffraction peaks at
(
2
CH ) ), 1.57 (2H, t, CH COH(CH ) ), 2.24 (6H, s, (CH ) NCH ),
3
2
2
3 2
3 2
2
3
1
.55 (2H, t, (CH
3
)
2
NCH
2
), 6.22 (1H, br, CH
2
COH(CH ).
3
)
2
C
3
1.9, 34.4, and 36.4 which are characteristic of the (100), (002),
NMR (CDCl
3
, 125 MHz): 29.8 (CH
2
COH(CH
3
)
2
), 37.7 (CH COH
2
and (102) planes of hexagonal wurtzite ZnO (JPCDS 36-1451).
The peaks positions also indicated the growth of good quality
films without lattice strains.
(
CH ) ), 45.5 ((CH ) NCH ), 56.5 ((CH ) NCH ), 71.2 (CH COH
3
2
3 2
2
3 2
2
2
(
CH
3
)
2
).
4-(Dimethylamino)-2-methylpentan-2-ol (dampH). Ethyl but-
2
4
-enoate (3.73 mL, 30 mmol) and dimethylamine (2.03 g,
5 mmol) were used as starting materials. Yield: 2.65 g (61%).
1
B.P. 60 °C/0.5 Torr. H NMR (CDCl
3
, 500 MHz): 0.88 (3H, d,
Experimental section
(
CH ) NCHCH CH ), 1.17 (3H, s, CH COH(CH ) ), 1.20 (1H, m,
3
2
3
2
2
3 2
Materials
CH
2
COH(CH
COH(CH
Advance NEO 500 MHz spectrometer with CDCl and C D as (CH ) NCHCH ).
3
)
2
), 1.22 (3H, s, CH
2
COH(CH
3
)
2
), 1.68 (1H, m,
), 3.08 (1H, m,
NMR (CDCl3, 125 MHz): 11.4
), 28.7 (CH COH(CH ), 31.8 (CH COH
NCHCH ), 44.3 (CH COH(CH ), 56.4
a 4 mm KBr window or KBr pellets. The KBr pellets were pre- ((CH ) NCHCH ), 70.4 (CH COH(CH ) ).
1
13
The H and C NMR spectra were recorded using a Bruker (CH
2
3
)
2
), 2.22 (6H, s, (CH
3
)
2
NCHCH
3
1
3
C
3
6
6
3 2
3
the solvent and standard, respectively. FT-IR spectra were ((CH
obtained using a Nicolet Nexus FT-IR spectrophotometer with (CH
3
)
2
NCHCH
3
CH
2
2
3
)
2
2
3
)
2
), 39.5 ((CH
3
)
2
3
2
3 2
)
3
2
3
2
3 2
pared using a standard pellet technique inside an argon-filled
4-(Dimethylamino)-2,3-dimethylbutan-2-ol (dadbH). Ethyl
glovebox. The elemental analyses were performed using a methacrylate (3.73 mL, 30 mmol) and dimethylamine (2.03 g,
Thermo Scientific FLASH EA-2000 organic elemental analyzer. 45 mmol) were used as starting materials. Yield: 2.48 g (57%).
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1
1
B.P. 60 °C/0.5 Torr. H NMR (CDCl
3
, 500 MHz): 0.75 (3H, d, and 440(m).
H
NMR (C
6
D
6
,
500 MHz): 0.47 (2H, q,
CHCH COH(CH ) ), 1.08 (3H, s, CHCH COH(CH ) ), 1.16 (1H, ZnCH CH ), 1.18 (3H, dd, N(CH ) CH CH CH(CH )), 1.36 (2H,
3
3 2
3
3 2
2
3
3 2
2
2
3
s, CHCH
3
COH(CH
3
)
2
), 1.88 (1H, m, CHCH
3
COH(CH
3
)
2
), br, N(CH
3
)
2
CH
CH
2
CH
CH
2
CH(CH
CH(CH
3
)), 1.69 (3H, t, CH
)), 2.02 (6H, s, N(CH
2
CH
3
), 1.98 (1H,
CH CH CH
2
2
1
.06–2.09 (1H, m, (CH
3
)
2
NCH ), 2.22 (6H, s, (CH
2
3
)
2
NCH
2
), m, N(CH
3
)
2
2
2
3
3
)
2
2
2
1
3
.59 (1H, m, (CH ) NCH ). C NMR (CDCl , 125 MHz): (CH )), 2.43 (1H, m, N(CH ) CH CH CH(CH )), 4.02 (1H, m,
3
2
2
3
3
3 2
2
2
3
1
3
5.1 ((CH
COH(CH
(CH ) NCH ), 64.4((CH ) NCH ), 73.9 (CHCH COH(CH ) ).
3
)
2
NCH
2
CHCH
3
), 23.1 (CHCH
3
COH(CH
3
)
2
), 29.8 N(CH
3
)
2
CH
2
CH
2
CH(CH
3
)). C NMR (C
6
D
6
, 125 MHz): −2.4
(CHCH
3
3
)
2
),
39.4
((CH
3
)
2
NCHCH
3
),
45.7 (CH
2
CH ), 14.6 (CH
3
2
CH
3
), 27.3 (N(CH ) CH CH CH(CH )),
3 2 2 2 3
(
37.1 (N(CH ) CH CH CH(CH )), 47.1 (N(CH ) CH CH CH(CH )),
3
2
2
3 2
2
3
3 2
3 2
2
2
3
3 2
2
2
3
4
-(Dimethylamino)butan-2-ol (dabH). Methylvinylketone 60.4 (N(CH
3
)
2
CH
2
CH
2
CH(CH
3
)), 71.1 (N(CH
3
)
2
2 2 3
CH CH CH(CH )).
38 2 2 2
(0.3 mol, 24.3 mL) was added to a 40 wt% aqueous dimethyl- Anal. Calcd for C16H N O Zn : C, 45.6; H, 9.09; N, 6.65. Found:
amine solution (0.36 mol, 16.2 g) with cerium ammonium C, 44.9; H, 9.80; N, 6.60.
nitride (0.011 mol, 6.12 g) in H O (100 mL) at room tempera- [EtZn(damb)] (2). DEZ (0.618 g, 5 mmol) and dambH
2
2
ture under constant stirring. After addition, the reaction (0.656 g, 5 mmol) were used as starting materials. The product
mixture was stirred continuously for 15 min. The product was was obtained as a white solid and purified by sublimation
extracted with diethyl ether and the organic layer washed with under vacuum (95 °C/0.5 Torr) and recrystallized from methyl-
4
brine then dried over anhydrous MgSO . The solvent was ene chloride. Yield: 0.61 g (52%). M.P. 205 °C. FT-IR (KBr,
−1
removed by evaporation and the desired compound was cm ): 2965(s), 2880(s), 2789(m), 1465(s), 1387(m), 1375(w),
obtained as a colorless liquid after distillation. Sodium boro- 1366(m), 1356(s), 1287(w), 1229(m), 1201(s), 1183(s), 1167(s),
hydride was slowly added to obtained solution of the inter- 1146(m), 1108(w), 1064(w), 1027(m), 1006(s), 982(s), 966(s),
mediate (4-(dimethylamino)butan-2-one) in methanol at 0 °C. 921(w), 872(m), 835(s), 711(w), 597(s), 543(s), 518(s), and 486(s).
1
After addition, the reaction mixture was allowed to warm to
H NMR (C
NCH
6
D
6
, 500 MHz): 0.45 (2H, q, CH
2
CH
3
), 1.25 (6H, s,
NCH CH
room temperature and stirred for another 3 h. To complete the (CH
3
)
2
2
CH C(CH O), 1.41 (2H, br, (CH
2
)
3 2
3
)
2
2
2
C
reaction, cold water was slowly added to the reaction mixture. (CH ) O), 1.72 (3H, t, CH CH ), 2.00 (6H, s, (CH ) NCH CH C
3
2
2
3
3 2
2
2
1
3
The product was extracted with diethyl ether and the com- (CH
bined organic layer was washed with brine then dried over (C
anhydrous MgSO . The solvent was removed by evaporation ((CH ) NCH CH C(CH ) O), 32.0 ((CH ) NCH CH C(CH ) O),
3
)
2
O), 2.19 (2H, br, (CH
3
)
2
NCH
2
CH
2
C(CH
3
)
2
O). C NMR
6
D
6
,
125 MHz): 0.0 (CH
2
CH
3
2
), 14.6 (CH CH ), 23.1
3
4
3 2
2
2
3 2
3 2
2
2
3 2
and the product was obtained as a colorless liquid after distillation 40.1 ((CH
3
)
3
)
2
NCH
NCH
.15 (1H, m, CH CH(OH)CH ), 1.23 (3H, d, CH CH(OH)CH ), 1.42 C, 48.1; H, 9.42; N, 6.23. Found: C, 48.1; H, 9.50; N, 6.23.
2
CH
2
CH
2
C(CH
2
C(CH
3
)
3
)
2
O), 57.6 ((CH
2
O). Anal. Calcd for C18
3
)
2
NCH
2
CH
H
2
C(CH
3
)
2
O),
2
:
1
at 40 °C/0.5 Torr. Yield: 21.6 g (61%). H NMR (C
6
D
6
, 500 MHz): 70.0 ((CH
2
42
N
2
O
2
Zn
1
2
3
2
3
(
1H, m, CH
2
CH(OH)CH
3
), 1.87 (6H, s, N(CH CH
3
)
2
2
), 2.03 (1H, m,
2
[EtZn(damp)] (3). DEZ (0.618 g, 5 mmol) and dampH
N(CH
3
)
2
CH
2
), 2.26 (1H, m, N(CH
3
)
2
CH ), 3.93 (1H, m, (0.726 g, 5 mmol) were used as starting materials. The product
2
CH CH(OH)CH ), 5.39 (1H, br, CH CH(OH)CH .
was obtained as a white solid and purified by sublimation
under vacuum (90 °C/0.5 Torr) and recrystallized from methyl-
ene chloride. Yield: 0.67 g (56%). M.P. 230 °C. FT-IR (KBr,
2
3
2
3
General procedure for the synthesis of the [EtZn
aminoalkoxide)] complexes
(
2
−1
cm ): 2957(s), 2928(s), 2846(s), 2797(m), 1463(s), 1374(s),
A hexane solution (10 mL) of aminoalcohol was added drop- 1354(s), 1304(w), 1241(s), 1220(m), 1196(s), 1176(s), 1120(s),
wise to a DEZ solution in hexane (50 mL) at −78 °C with con- 1030(w), 1019(m), 980(s), 939(s), 886(m), 776(w), 735(m),
1
stant stirring under N condition for 1 h. The reaction mixture 601(s), 559(m), 522(m), and 494(m). H NMR (C D , 500 MHz):
2
6 6
was slowly warmed to room temperature and subsequently 0.45 (2H, q, CH
2
CH
3
), 0.55 (3H, dd, (CH
3
)
2
NCH(CH
3 2
)CH C
stirred for another 15 h. After the reaction was complete, the (CH
3
)
2
O) 1.02 (1H, d, (CH
3
)
2
NCH(CH )CH
3
2
C(CH O), 1.28
3 2
)
volatiles were removed in vacuo and the residue was extracted (6H, s, (CH ) NCH(CH )CH C(CH ) O), 1.65 (1H, br, (CH ) NCH
3
2
3
2
3 2
3 2
into methylene chloride and filtered. The solvent was removed (CH
to obtain the crude product and the pure product was (CH
3
)CH
2
C(CH
3
)
2
O), 1.72 (3H, t, CH
2
CH
3
), 2.06 (6H, s,
3
2
) NCH(CH
3
)CH C(CH ) O) 2.96 (1H, m, (CH ) NCH(CH )
2
3 2 3 2 3
1
3
obtained by sublimation under vacuum and recrystallization CH C(CH ) O). C NMR (C D , 125 MHz): 0.2 (CH CH ),
2
3 2
6
6
2
3
from methylene chloride. X-ray quality crystals were grown by 12.0 (CH
slow evaporation from a saturated methylene chloride solution ((CH NCH(CH
in a glove box at room temperature. (CH ) O), 48.1
EtZn(dab)] (1). DEZ (0.618 g, 5 mmol) and dabH (0.586 g, ((CH NCH(CH )CH
mmol) were used as starting materials. The product was (CH
2
CH
3
), 14.6 ((CH
3
)
2
NCH(CH
3
)CH
2
C(CH
3 2
) O), 30.7
3
)
2
3 2 3 2
)CH C(CH ) O), 35.0 ((CH
3
2
) NCH(CH
3
)CH
57.0
)CH
2
C
((CH ) NCH(CH )CH C(CH ) O),
3
2
3 2
3
2
3 2
[
2
)
3 2
3
2
C(CH
3
)
2
O), 70.1 ((CH
Zn
3
2
) NCH(CH
3
2
C
5
3
)
2
O). Anal. Calcd for C20
H
N O
46 2 2
2
: C, 50.3; H, 9.71; N,
obtained as a white solid and purified by sublimation under 5.87. Found: C, 50.0; H, 9.78; N, 5.84.
vacuum (70 °C/0.5 Torr) and recrystallized from methylene [EtZn(dadb)] (4). DEZ (0.618 g, 5 mmol) and dadbH
chloride. Yield: 0.52 g (50%). M.P. 160 °C. FT-IR (KBr, cm− ): (0.726 g, 5 mmol) were used as starting materials. The product
2
1
2
1
1
9
950(s), 2935(s), 2874(s), 2836(s), 1469(s), 1444(s), 1365(s), was obtained as a white solid and purified by sublimation
341(m), 1317(m), 1278(w), 1256(w), 1233(m), 1174(s), 1141(s), under vacuum (105 °C/0.5 Torr) and recrystallized from
100(m), 1074(s), 1027(m), 1000(w), 970(m), 954(m), 935(s), methylene chloride. Yield: 0.66 g (55%). M.P. 250 °C. FT-IR
−
1
15(m), 902(m), 813(m), 768(m), 590(s), 535(s), 492(s), 470(s), (KBr, cm ): 2963(s), 2922(s), 2880(s), 2844(s), 2795(m),
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1
466(s), 1375(m), 1356(s), 1293(m), 1239(m), 1184(s), 1155(m), X-ray source was used to determine the chemical composition
008(m), 982(s), 967(s), 929(m), 865(w), 835(w), 771(w), 601(w), and check for impurities in the films. As the transparency of
1
and 545(s). H NMR (C
6
D
6
, 500 MHz): 0.36 (2H, q, CH
2 3
CH ), the ZnO films is essential to their application as an ITO, the
0
.62 (3H, dd, (CH
3
)
2
NCH CH(CH )C(CH O) 1.07 (3H, d, transmittance and absorbance of the deposited films on soda-
2
3
3 2
)
(
CH ) NCH CH(CH )C(CH ) O), 1.23 (3H, s, (CH ) NCH CH lime glass substrates was determined using a UV-visible
3
2
2
3
3 2
3 2
2
(CH
3
)C(CH
3
)
2
O), 1.43 (1H, br, (CH O), spectrometer (UV-2550, Shimadzu). In addition, the optical
3
)
2
NCH
2
CH(CH
3
)C(CH
3
)
2
1
.63 (3H, t, CH
2
CH ), 1.76 (1H, br, (CH ) NCH CH(CH )C bandgap of the films was estimated from the corresponding
3
3 2 2 3
(
(
1
CH ) O), 2.04 (6H, t, (CH ) NCH CH(CH )C(CH ) O), 2.67 Tauc plots. Finally, the surface morphologies of the films were
3 2 3 2 2 3 3 2
1
3
1H, m, (CH
3
)
2
NCH
CH
2
CH(CH
3
)C(CH
3
)
2
O).
C
NMR (C
6
D
6
,
investigated using a field emission scanning electron micro-
25 MHz): 0.0 (CH
2
3
), 14.6 (CH
2
CH
3
), 18.0 ((CH
3
)
2
NCH
2
CH scope (FESEM, LSM 880, Carl Zeiss).
(
CH )C(CH ) O), 25.1 ((CH ) NCH CH(CH )C(CH ) O), 33.3
3 3 2 3 2 2 3 3 2
(
(CH
3
)
2
NCH
O),
2
CH(CH
65.4
3
)C(CH
3
)
2
O), 45.3 ((CH
NCH CH(CH )C(CH
Anal.
3 2
3
)
2
NCH
2
CH(CH
3
)C
(CH
3
)
2
((CH
3
)
2
2
3
3
)
2
O),
72.9 Conclusion
((CH ) NCH CH(CH )C(CH ) O).
Calcd
for
3
2
2
3
In summary, novel zinc complexes containing aminoalkoxides
were successfully synthesized by controlled substitution reac-
tions using DEZ as a starting material. All compounds were
obtained as dimers in their crystal structures. The alkoxy oxygen
of the aminoalkoxide used herein acted as a bridge between the
C
20
H
46
N
2
O
2
2
Zn : C, 50.3; H, 9.71; N, 5.87. Found: C, 50.4; H,
9
.73; N, 5.52.
Crystallography
Single crystals of 1–4 were grown by slow evaporation from a
saturated solution with methylene chloride in a glove box at
room temperature. An obtained specimen of suitable size and
quality was coated with Paratone oil and mounted on a glass
capillary. Reflection data were collected using a Bruker SMART
Apex II-CCD area detector diffractometer with graphite-mono-
chromated Mo Kα radiation (λ = 0.71073 Å). The hemisphere of
the reflection data was collected as ω-scan frames with 0.3° per
frame and an exposure time of 10 s per frame. The cell para-
meters were determined and refined using the SMART
program. The data reduction was performed using SAINT
software. The data were corrected for Lorentz and polariz-
ation effects and an empirical absorption correction was
applied using the SADABS program. The structures of the
prepared compounds were solved by direct methods and all
non-hydrogen atoms were subjected to anisotropic refinement
two zinc metal centers by μ -O bonding. In the prepared com-
2
plexes, the metal center adopted a distorted tetrahedral geome-
try. The TGA curves for complexes 1–4 indicated that <10% non-
volatile residues were present, indicating their possible vaporiza-
tion in ALD. The sublimation studies of complexes 1, 2, 3, and 4
revealed their excellent volatile character at 70, 95, 90, and
1
05 °C, respectively, under 0.5 Torr. Precursor 3 was successfully
used for the deposition of ZnO thin films by ALD. A GPC of
.125 nm per cycle was obtained at 200 °C, while XPS analysis
0
4
0
confirmed the growth of highly pure ZnO films free of both
carbon and nitrogen impurities, while XRD analysis revealed the
deposition of reasonably crystalline films. Additionally, the high
transmittance and wide bandgap of the films make them a good
candidates for optoelectronic applications.
4
1
4
2
2
by full-matrix least-squares method on F using the SHELXTL/
4
3
Conflicts of interest
PC package. Hydrogen atoms were placed at their geometri-
cally calculated positions and refined based on the corres-
ponding carbon atoms with isotropic thermal parameters.
The supplementary crystallographic data for this paper can
be found in CCDC 1946852 (1), 1943947 (2), 1943948 (3), and
There are no conflicts to declare.
Acknowledgements
1
943949 (4).†
This research was supported by a grant for the development of
smart chemical materials for IoT devices project through the
Korea Research Institute of Chemical Technology (KRICT) of
the Republic of Korea (SI1921-20). The authors would like to
thank the Center for Chemical Analysis at the Korea Research
Institute of Chemical Technology (KRICT) for use of their
facilities for solving the molecular structures.
ZnO thin film deposition and characterization
The ZnO thin film ALD test was conducted in a lateral flow-
type thermal ALD reactor (Atomic Classic, CN-1), between
1
2
80–250 °C using [EtZn(damp)] as the metal–organic precur-
sor and H O as a reactant. The precursor was heated at 135 °C
2
2
and delivered to the reaction chamber aided by high purity
argon gas at a flow rate of 30 sccm. The H was maintained
2 2
O
at room temperature and transported without a carrier gas.
The film thickness was measured by spectroscopic ellipsome-
try (SE, Horiba Jobin Yvon UVISEL) at 70° which gave a growth
rate of 0.125 nm per cycle. The film crystallinity was investi-
gated via glancing angle X-ray diffraction (GAXRD, Smart-Lab,
Rigaku). An X-ray photoelectron spectrometer (XPS, K-Alpha,
Thermo Scientific) equipped with a monochromatic Al Kα
Notes and references
1 Y.-C. Hu, T.-H. Lee, P.-Z. Chang and P.-C. Su, Thin Solid
Films, 2015, 584, 112–115.
2 E. J. Ibanga, C. Le Luyer and J. Mugnier, Mater. Chem.
Phys., 2003, 80, 490–495.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2020

View Article Online
Dalton Transactions
Paper
3
4
5
L. Zhu and W. Zeng, Sens. Actuators, A, 2017, 267, 242–261.
Z. L. Wang and J. Song, Science, 2006, 312, 242.
K. Savarimuthu, R. Sankararajan, R. Govindaraj and 25 S. M. George, H.-S. Kim, B. K. Park, C. G. Kim and
S. Narendhiran, Nanoscale, 2018, 10, 16022–16029. T.-M. Chung, Inorg. Chim. Acta, 2015, 436, 118–122.
J.-B. Lee, D.-H. Cho, D.-Y. Kim, C.-K. Park and J.-S. Park, 26 H.-S. Kim, S. M. George, B. K. Park, S. U. Son,
24 K.-S. An, W. Cho, B. K. Lee, S. S. Lee and C. G. Kim,
J. Nanosci. Nanotechnol., 2008, 8, 4856–4859.
6
7
8
9
Thin Solid Films, 2007, 516, 475–480.
C. G. Kim and T.-M. Chung, Dalton Trans., 2015, 44, 2103–
2109.
27 H.-S. Kim, S. M. George, E. A. Jung, B. K. Park, S. U. Son,
C. G. Kim and T.-M. Chung, Polyhedron, 2015, 101, 185–
190.
S. Faÿ, U. Kroll, C. Bucher, E. Vallat-Sauvain and A. Shah,
Sol. Energy Mater. Sol. Cells, 2005, 86, 385–397.
M. L. Addonizio and L. Fusco, J. Alloys Compd., 2015, 622,
8
51–858.
A. Hultqvist, K. Aitola, K. Sveinbjörnsson, Z. Saki, 28 E. A. Jung, S. M. George, S. H. Han, B. K. Park, J. H. Han,
F. Larsson, T. Törndahl, E. Johansson, G. Boschloo and
M. Edoff, ACS Appl. Mater. Interfaces, 2017, 9, 29707–29716.
S. U. Son, C. G. Kim and T.-M. Chung, Inorg. Chim. Acta,
2016, 446, 1–5.
1
1
0 J.-Y. Liao and K.-C. Ho, Sol. Energy Mater. Sol. Cells, 2005, 29 E. A. Jung, S. M. George, J. H. Han, B. K. Park, S. U. Son,
8
6, 229–241.
1 H. von Wenckstern, H. Schmidt, M. Brandt, A. Lajn,
R. Pickenhain, M. Lorenz, M.
C. G. Kim and T.-M. Chung, J. Organomet. Chem., 2017,
833, 43–49.
Grundmann, 30 S. H. Han, S. M. George, G. Y. Lee, J. H. Han, B. K. Park,
D. M. Hofmann, A. Polity, B. K. Meyer, H. Saal,
M. Binnewies, A. Börger, K. D. Becker, V. A. Tikhomirov
and K. Jug, Prog. Solid State Chem., 2009, 37, 153–172.
2 Y. Zhang, L. Ge, M. Li, M. Yan, S. Ge, J. Yu, X. Song and
B. Cao, Chem. Commun., 2014, 50, 1417–1419.
C. G. Kim, S. U. Son, M. S. Lah and T.-M. Chung, ACS
Omega, 2017, 2, 5486–5493.
31 A. L. Johnson, N. Hollingsworth, G. Kociok-Köhn and
K. C. Molloy, Inorg. Chem., 2008, 47, 12040–12048.
32 S. D. Bunge, J. M. Lance and J. A. Bertke, Organometallics,
2007, 26, 6320–6328.
33 H. Mimoun, J. Y. de Saint Laumer, L. Giannini,
R. Scopelliti and C. Floriani, J. Am. Chem. Soc., 1999, 121,
6158–6166.
1
1
1
1
1
1
1
3 Z. Zang, X. Zeng, J. Du, M. Wang and X. Tang, Opt. Lett.,
2
016, 41, 3463–3466.
4 K. Song, J. Noh, T. Jun, Y. Jung, H.-Y. Kang and J. Moon,
Adv. Mater., 2010, 22, 4308–4312.
5 Y.-Y. Lin, C.-C. Hsu, M.-H. Tseng, J.-J. Shyue and F.-Y. Tsai, 34 R. Al-Gaashani, S. Radiman, A. R. Daud, N. Tabet and Y. Al-
ACS Appl. Mater. Interfaces, 2015, 7, 22610–22617. Douri, Ceram. Int., 2013, 39, 2283–2292.
6 F. B. Oruc, L. E. Aygun, I. Donmez, N. Biyikli, A. K. Okyay 35 R. Javed, M. Usman, B. Yücesan, M. Zia and E. Gürel, Plant
and H. Y. Yu, J. Vac. Sci. Technol., A, 2015, 33, 01A105. Physiol. Biochem., 2017, 110, 94–99.
7 Z. Sisman, S. Bolat and A. K. Okyay, Phys. Status Solidi C, 36 S. Marouf, A. Beniaiche, H. Guessas and A. Azizi, Mater.
017, 14, 1700128. Res., 2017, 20, 88–95.
8 K. Kopalko, A. Wójcik, M. Godlewski, E. Łusakowska, 37 V. Pawar, P. K. Jha, S. K. Panda, P. A. Jha and P. Singh, Phys.
W. Paszkowicz, J. Z. Domagała, M. M. Godlewski, Rev. Appl., 2018, 9, 054001.
A. Szczerbakow, K. Świątek and K. Dybko, Phys. Status 38 R. Varala, N. Sreelatha and S. R. Adapa, Synlett, 2006, 1549–
Solidi C, 2005, 2, 1125–1130. 1553.
9 T. Tynell and M. Karppinen, Semicond. Sci. Technol., 2014, 39 S. Singto, T. Supap, R. Idem, P. Tontiwachwuthikul,
2
1
2
2
9, 043001.
S. Tantayanon, M. J. Al-Marri and A. Benamor, Sep. Purif.
Technol., 2016, 167, 97–107.
40 SMART, version 5.0, Data collection software, Bruker AXS,
Inc., Madison, WI, 1998.
0 M. Tammenmaa, T. Koskinen, L. Hiltunen, L. Niinistö and
M. Leskelä, Thin Solid Films, 1985, 124, 125–128.
2
2
1 K. Kenkichiro and O. Shinji, Chem. Lett., 1997, 26, 511–512.
2 A. Wójcik, M. Godlewski, E. Guziewicz, R. Minikayev and 41 SAINT, version 5.0, Data integration software, Bruker AXS
W. Paszkowicz, J. Cryst. Growth, 2008, 310, 284–289. Inc., Madison, WI, 1998.
3 E. Guziewicz, M. Godlewski, T. Krajewski, Ł. Wachnicki, 42 G. M. Sheldrick, SADABS, Program for absorption correction
2
A. Szczepanik, K. Kopalko, A. Wójcik-Głodowska,
E. Przeździecka, W. Paszkowicz, E. Łusakowska,
with the Bruker SMART system, Universitat Gottingen,
Germany, 1996.
P. Kruszewski, N. Huby, G. Tallarida and S. Ferrari, J. Appl. 43 M. Sheldrick, SHELXL-93: Program for the refinement of
Phys., 2009, 105, 122413. crystal structures, Universitat Göttingen, Germany, 1993.
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