Synthesis and Application of Monomeric Chalcogenolates of 13 Group Elements

Article abstract of DOI:10.1002/asia.201901085

Utilization of the N,C,N-chelating ligand L (L={2,6-(Me₂NCH₂)₂C₆H₃}^?) in the chemistry of 13 group elements provided either N→In coordinated monomeric chalcogenides LIn(μ-E₄) (E=

Full text of DOI:10.1002/asia.201901085

CHEMISTRY
AN ASIAN JOURNAL
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Accepted Article
Title: Synthesis and application of monomeric chalcogenolates of 13
group elements
Authors: Marek Bouška, Tomáš Řičica, Yaraslava Milasheuskaya,
Zdeňka Růžičková, Petr Němec, Pavel Švanda, Zuzana
Olmrová Zmrhalová, and Roman Jambor
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10.1002/asia.201901085
Chemistry - An Asian Journal
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Synthesis and application of monomeric chalcogenolates of 13
group elements
Tomáš Řičica,[b] Yaraslava Milasheuskaya,[b] Zdeňka Růžičková,[b] Petr Němec,[a] Pavel Švanda,[c]
Zuzana Olmrová Zmrhalová,[d] Roman Jambor[b] and Marek Bouška[a]*
Abstract: The utilization of the N,C,N-chelating ligand L (L = {2,6-
(Me2NCH2)2C6H3}-) in the chemistry of 13 group elements provided
either N→In coordinated monomeric chalcogenides LIn(-E4) (E = S,
Se) with unprecedented InE4 inorganic ring or monomeric
chalcogenolates LM(EPh)2 (M = Ga, In). Complex LGa(SePh)2 has
been selected as the most suitable single source precursor (SSP) for
the deposition of amorphous semiconducting GaSe thin film using
spin coating method.
exploited as SSPs for the deposition of III-VI amorphous thin films
by spin coating method.6,7
R
R
R
E
R
R
M
P
Se
M
R´
E
M
N
M
E
R´
M
P
R
Se
R
R
B
A
N
R2P
Te
Te
M
PR2
Introduction
Me2N
Ga
NMe2
S
Te
Te
M
M
Due to their outstanding properties, the applications of
amorphous chalcogenides of III-VI materials cover different fields
such as infrared optics, photonics, development of next
generation computer memories, emerging applications in
medicine or military fields, etc.1 Apart from physical vapor
deposition techniques, recent synthetic approaches of these
materials are based on chemical vapor deposition (CVD) of single
source precursors (SSPs). Suitable SSPs are therefore widely
studied and chalcogenides or chalcogenolates of group 13
elements are the most popular. Gallium and indium
chalcogenides [RM(-E)]4 (M = Ga, In; E = S, Se, Te; R = tBu,
CMe2Et) were successfully applied as the prominent SSPs for III-
VI materials depositions (Scheme 1A).2 Later on, complexes
Ga
NMe
Te
Te
2 S
S
Me2N
R2P
N
PR2
N
Ga
Me2N
NMe2
Te
Te
Te
P
P
R2
R2
D
C
But
NEt2
Ga
S
S
But
Ga
tBu
tBu
Et2N
[Me2M(SePiPr2)2N]3 (Scheme 1B) and {M(μ-Te)[N(iPr2PTe)2]}3
4
(Scheme 1C) were used for the deposition of cubic M2E3 (E = Se,
Te) thin films and the complexes GaCl3·(nBu2E) were applied in
low pressure CVD (LP-CVD) of crystalline Ga2E3.5 Our previous
studies also showed that N→Ga coordinated chalcogenides
[LGa(-S)]3 and [L1Ga(-Se)]2 (L = {2,6-(Me2NCH2)2C6H3}- and
L1= {2-(Et2NCH2)-4,6-tBu2-C6H2}-) (Scheme 1D, E) can be
E
Scheme 1. Examples of gallium and indium chalcogenides.
Despite these examples, chalcogenolates of group 13 elements
were also used as suitable SSPs. Studies of Nomura et al. and
Barron et al. demonstrated that dimeric complexes [R2M(ER´)]2
and [RM(ER´)2]2 (E = Ga, In; E = S, Se, Te; R = nBu, iBu, tBu,
CMe2Et; R´= iPr, nPr, tBu, Ph) are useful SSPs for the preparation
of both ME and M2E3 thin films by either low pressure-CVD (LP-
CVD) or CVD.8-13 In addition, the cubic and hexagonal In2Se3 thin
films were deposited onto Si or GaAs substrates from polymeric
In(SePh)3 by metal-organic CVD (MOCVD) or from
In[SeC(SiMe3)3]3 by MOCVD, respectively.14,15 Later on, Dutta16
et al. reported the synthesis of Ga2S3 and In2S3 nanoparticles by
thermally induced destruction of [MeM(SCH2CH2S)]n (M= Ga, In),
that had been shown as suitable SSP despite its polymeric nature.
The above mentioned polymers are also suitable starting
compounds for the synthesis of [(R3P)mCunMe2−xGa(EPh)n+x+1] (R
= Me, Et, iPr, tBu; E = S, Se, Te; x = 0, 1) that were used as SSPs
for the preparation of ternary CuGaE2 semiconductors.17
However, all these studies also revealed that synthesis of
monomeric chalcogenolates of group 13 elements is rather
problematic. The Lewis acidic metal centrum is usually involved
[a]
Dr. M. Bouška, prof. P. Němec
Department of Graphic Art and Photophysics
University of Pardubice
Studentská 95, 532 10 Pardubice (Czech Republic)
E-mail: marek.bouska@upce.cz
[b]
[c]
[d]
Dr. T. Řičica, Y. Milasheuskaya, Dr. Z. Růžičková, prof. R.
Jambor, Department of General and Inorganic Chemistry
University of Pardubice
Studentská 95, 532 10 Pardubice (Czech Republic)
Dr. P. Švanda
Department of Mechanics, Materials and Machine Parts
University of Pardubice
Studentská 95, 532 10 Pardubice (Czech Republic)
Dr. Z. Olmrová Zmrhalová
Center of Materials and Nanotechnologies
University of Pardubice
Studentská 95, 532 10 Pardubice (Czech Republic)
Supporting information for this article is given via a link at the
end of the document.
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NMe2
InCl2
NMe2
Me2N
In
in intermolecular E→M interactions, which provide their polymeric
structures making these compounds low volatile and hardly
soluble in common organic solvents, therefore unfavorable for
SSPs. In 1984, Hofmann18 et al. showed that simple addition of
external Lewis base NMe3 to the polymeric gallium thiolates
Ga(SR)3 (R = CH3, C2H5, nPr, iPr, Ph, CH2Ph) provides the
monomeric complexes Ga(SR)3·NMe3. Later on, the concept of
intramolecular P→Ga interaction stabilized monomeric complex
Me2Ga{(SC6H4-2-PPh2)-2S,P} (Scheme 2A).19 Importantly, the
crucial role of Y→Ga interaction for the stabilization of monomeric
chalcogenolates was also established, since the modification of
donor atom Y yielded As→Ga coordinated dimeric compound
[Me2Ga{(μ2-SC6H4-2-AsPh2)-S}]2 (Scheme 2B).19 Therefore, the
concept and strength of Y→M intermolecular coordination can be
used for the synthesis of monomeric chalcogenolates of 13 group
Te
THF
+
2 Li2Te
2
In
-4 LiCl
Te
NMe2
NMe2
Me2N
1
Scheme 3. Preparation of 1
Single crystals of 1 were obtained upon storage in toluene at room
temperature. The molecular structure of 1 is shown in Figure 1
and selected bond lengths and angles are given in Table 1.
elements.
S
Me2
Ga
GaMe2
P
S
S
Ga
Me2
AsPh2
Ph2As
A
B
Scheme 2. Examples of gallium complexes with different coordination geometry.
As mentioned above, we have used the concept of N→Ga
coordination and prepared useful SSPs [LGa(-S)]3 and [L1Ga(-
Se)]2 for deposition of GaE thin layers.6,7 Here, we expanded our
studies and showed that the N,C,N-chelating ligand L is useful for
stabilization of either N→In coordinated monomeric
chalcogenides LIn(-E4) (E = S, Se) with unprecedented InE4
inorganic ring or N→M monomeric chalcogenolates LM(EPh)2 (M
= Ga, In). All prepared compounds were characterized by means
of NMR and thermogravimetric analysis (TG). Selected
complexes were studied by X-ray structure analysis. Moreover,
monomeric complex LGa(SePh)2 has been also selected as the
most suitable SSP for the deposition of amorphous
semiconducting GaSe thin film using easy and low cost spin
coating method .
Figure 1. ORTEP plot of the crystal structure of 1 with ellipsoids drawn at 30%
probability level (hydrogen atoms omitted for clarity).
The molecular structure of 1 revealed a dimeric nature with a
central four-membered In2Te2 core. The In1 atom is five
coordinated by N1, N2 and C1 atoms of the L ligand, and by two
tellurium atoms. The coordination geometry can be best
described as a distorted tetragonal-pyramid with τ = 0.09. The C1,
N1, N2 and Te1 atoms form the square base while the Te1a atom
is in apical position. Both In1–N1 (2.597(3) Å) and In1–N2
(2.632(3) Å) bond distances suggest the presence of N→In
coordination in 1 (compare with ∑covSB(N, In) = 2.13 Å)21,22. The
In–Te distances in 1 (the range of 2.7461(4) – 2.7732(3) Ǻ) are
similar with In-Te distances in {In(μ-Te)[N(iPr2PTe)2]}3 (2.744(1)
and 2.8089(9))20 and shorter than those found in tetrameric
[RIn(μ-Te)]4 (R = tBu, Me2EtC), where the range of 2.87 – 2.90 Ǻ
has been obtained.23
Results and Discussion
Synthesis and characterization of N→In coordinated monomeric
chalcogenides
The 1H NMR spectrum of 1 showed non-equivalence of
methylene CH2N groups resonating as the AB spin system at 
2.99 and the singlet resonance at 3.26 ppm. Non-equivalence
of CH2N groups was also observed in 13C NMR spectrum, where
signals at 64.2 and 64.8 ppm were observed.
Our initial studies were focused on the reaction of LInCl2 with Li2E
(E = S, Se) in the aim to prepare N→In coordinated indium
chalcogenides [LIn(-E)2]. However, these reaction provided ill
soluble material only and interestingly, the only isolable product
[LIn-Te)]2 (1) has been obtained from the reaction of LInCl2 with
Li2Te (generated in situ by the reaction of 2 eq. Li[Et3BH] + 1eq.
Te, Scheme 3).
The low solubility, however, defer us to study 1 as a potential SSP
for InTe deposition. The change of the stoichiometry of LInCl2 with
E
yielded monomeric N→In coordinated organoindium
tetrachalcogenides LIn(2-E4) (E= S(2), Se(3)). Thus the reaction
of LInCl2 with one equivalent of Li2E4 (generated in situ by the
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reaction of 2 eq. Li[Et3BH] + 4 eq. E, see Scheme 4) provided well
soluble complexes 2 and 3 in reasonable yields (64% for 2 and
49% for 3).
InSe4 cycle are involved in the Se-Se short contacts with
additional different molecules of 3 providing thus 3D polymeric
arrangement of 3. The Se-Se´ distances are in the range of 3.483
– 3.800 Å being longer than the sum of covalent radii (∑cov(Se,Se)
= 2.32 Å)21,22 but still shorter than sum of the Van der Waals radii
of Se atoms (∑VdW(Se,Se) = 3.80 Å).26 No such short contacts
were found in complex 2.
NMe2
InCl2
NMe2
E
E
E
THF
Li2E4
In
+
-2LiCl
E
NMe2
NMe2
2 (E= S), 3 (E= Se)
Scheme 4. Preparation of 2 and 3
Single crystals suitable for X-ray diffraction analysis of 2 and 3
were obtained from saturated toluene solutions at 4°C. The
molecular structures of 2 and 3 are shown in Figure 2 and
selected bond lengths and angles are given in Table 1.
Figure 3 ORTEP plot of the crystal structure with contacts Se-Se of 3 with
ellipsoids drawn at 30% probability level (hydrogen atoms omitted for clarity)
In the 1H and 13C NMR spectra of 2 and 3, one set of signals was
found. The 1H NMR spectra revealed singlets of methyl N(CH3)2
group at δ 2.00 ppm for both compounds and methylene CH2N
group resonate at δ 2.93 ppm for 2 and at δ 3.00 ppm for 3,
respectively. In the 77Se NMR spectrum of 3, only one broad
signal at δ 108.4 ppm was found suggesting fast rotation within
the InSe4 ring in the solution. UV-VIS absorption spectra of 2 and
3 showed absorption maximum at 237 nm (2) and 236 nm (3) due
to the presence of an aromatic region and the absorption at 350
nm of InSe4 ring of 3 was observed as well (for details see SI).
These unique compounds with stoichiometry InE4 were studied as
potential SSPs. Unfortunately, while compound 2 is stable in
propylamine, complex 3 easily eliminates elemental Se which can
be the result of the existence of Se-Se contacts in 3. The TG
analysis of 2 showed the multistep decomposition (Figure S23 in
SI). Due to these facts, both 2 and 3 were not studied as potential
SSP. It is evident, that the presence of N→In coordination may
provide monomeric organoindium chalcogenides with unusual
InE4 inorganic ring, but these compounds are not suitable SSPs
for InE thin layers depositions.
Figure 2. ORTEP plot of the crystal structure of 2 and 3 with ellipsoids drawn at
30% probability level (hydrogen atoms omitted for clarity)
Crystallographic data are summarized in Table S1. In the solid
state, compounds 2 and 3 are monomeric. Both contain InE4 (E =
S, Se) five-membered ring. The In1 atoms are five-coordinated by
two nitrogen and carbon atoms of the ligand L and by two E atoms
of the (2-E4) fragment. The coordination geometry is a distorted
trigonal-bipyramid with the C1, E1, and E4 atoms located in the
equatorial positions, while both N1 and N2 atoms are in axial
positions with N1–In1–N2 bond angle of 149.12(6)° (2) and
148.3(6)° (3), respectively. Nitrogen atoms are involved in N→In
coordination in both compounds as demonstrated by the In–N
bond lengths with the range of 2.470(1) – 2.520(2) Å (see Table
1). The bond distances In1–S1 (2.4583(6) Å) and In1–S4
(2.4535(9) Å) in 2 as well as the In1–Se1 (2.569(3) Å) and In1–
Se4 (2.576(3) Å) in 3 corresponds to typical In–E covalent bonds
(compare with ∑covSB(S, In) = 2.13 Å and ∑covSB(Se, In) = 2.58)21,22
.
Synthesis and characterization of N→M monomeric
chalcogenolates LM(EPh)2
It is evident that the presence of ligand L provided efficient
stabilization of rare inorganic In(2-E4) ring. This five membered
ring has been observed in inorganic indium polyselenides [In2(-
As mentioned above, the chalcogenolates of 13 group elements
are second category of widely studied SSPs. Since it was shown
that the presence of Y→M coordination can be used for the
synthesis of monomeric forms,19 we set out to synthesize
monomeric chalcogenolates by using of ligand L. We have found
-
Se4)4(-Se5)]4 or [In(-Se4)(m-Se)]224 and also in [TmtBu]In(κ2-S4)
(TmtBu = tris(2-mercapto-1-tert-butylimidazolyl)borate)25 as the
closest analogues of 2 and 3. Despite the monomeric nature of
In(2-E4), close inspection in the structure of 3 revealed the
presence of Se-Se´ short contacts (Figure 3). Three Se atoms of
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out an easy concept for the synthesis of desired monomeric
chalcogenolates LM(EPh)2 via two step reaction.
28
Starting from LMCl2 (M = Ga, In),27, the organogallium and
indium amides LM(NEt2)2 (M = Ga(4), In(5)) were prepared as oily
products, by the treating of LMCl2 with 2 eq. of LiNEt2 (Scheme
5). Both compounds were characterized by NMR spectroscopy.
1
Most importantly, the H NMR spectrum showed singlet of the
methylene CH2N groups resonating at δ 3.34 ppm for 4 and at δ
3.23 ppm for 5, respectively, while NEt groups resonated as a
triplet (NCH2CH3) and quartet (NCH2CH3) resonances in
expected ratios. Complexes 4 and 5 were found as suitable
starting materials for the synthesis of monomeric chalcogenolates
LM(EPh)2 via an easy amine elimination reaction. Thus the
treatment of with 4 and 5 with commercial available phenylthiol or
selenol PhEH (E = S, Se) yielded complexes with the formula
LM(EPh)2 6 – 9 (for E = S, M = Ga (6), M = In (7), for E = Se, M
= Ga (8), M = In (9)) along with amine HNEt2 elimination in
excellent yields (up to 93%).
Figure 4 ORTEP plot of the crystal structure of 6 – 9 with ellipsoids drawn at
30% probability level (hydrogen atoms omitted for clarity)
NMe2
NMe2
+
2 LiNEt2
MCl2
M(NEt2)2
NMe2
-4 LiCl
The Ga and In atoms are five-coordinated by two nitrogen and
carbon atoms of the ligand L and by two E atoms (E = S, Se) of
the EPh fragments. The coordination geometries may be best
described as distorted trigonal bipyramid with the C1, E1 and E2
in equatorial plane, while N1 and N2 atoms are in axial positions
with the range of N1–M1–N2 147.3(1) – 153.94(6)°. The M–N
bond distances (the range of 2.294(2) – 2.566(2) Ǻ) suggest the
presence of N→M intramolecular interaction, while M–E bond
distances correlates with the sum of the covalent radii of the
parent atoms (∑covSB(Ga,S) = 2.27 Å∑covSB(Ga,Se) = 2.40 Å,
NMe2
M= Ga (4), In (5)
M= Ga, In
NMe2
NMe2
M
EPh
EPh
M(NEt2)2 +
2 PhEH
-2 HNEt2
NMe2
NMe2
∑
covSB(In,S) = 2.45 Å and ∑covSB(In,Se) = 2.58 Å).21,22 In addition,
M= Ga (4), In (5)
E= S, Se
6 M= Ga, E= S
7 M= In, E= S
8 M= Ga, E= Se
9 M= In, E= Se
the Ga1–S bond lengths (2.2517(5) and 2.2503(4) Ǻ) in 6 are
somewhat shorter that those found in monomeric P→Ga
coordinated organogallium thiolates (the range of 2.268(3) –
2.343(1) Å)19. Similarly, the Ga1-Se bond distances (2.3735(3)
and 2.3880(3) Ǻ) in 8 are shorter than those found in the
monomeric complex [(Mes)2Ga(SeMes)]•(NC5H4-4-Me) (Mes
2,4,6-Me3C6H2) (2.4383(9) Å).29 Monomeric organoindium
chalcogenolates were not reported so far, and the In-E bond
distances found in 7 and 9 (see Table 1) are shorter than those
found in dimeric or polymeric indium chalcogenolates, where the
Scheme 5. The synthetic approach for the synthesis of monomeric
chalcogenolates LM(EPh)2
Complexes 6 – 9 were characterized by the help of NMR
spectroscopy and X-ray structure analysis. Single crystals of 6 –
9 suitable for X-ray diffraction analysis were obtained from
saturated toluene-hexane solutions at 4°C. The molecular
structures of 6 – 9 showed their monomeric nature and they are
depicted in Figure 4, while selected bond lengths and angles are
given in Table 1.
range of 2.5755
– 2.777 Å
was found.10a,30 As stated,
chalcogenolates of 13 group elements easily form polymeric
structures due the additional intermolecular M←E´ coordination.
For example, the structures of [R´2In(ER)]n contain strong
intermolecular interaction In←E´ with In-E´ distances ranging
from 2.6041 to 2.9007 Ǻ.30 No intermolecular contacts were
observed in the 6 – 9 proving strictly monomeric character of
these compounds.
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Table 1 Selected bond lengths (Å) and angles (deg) for 1, 2, 3, 6, 7, 8 and 9
1
2
3
6
7
8
9
M=In, E= Te
2.156(4)
2.597(3)
2.632(3)
2.7461(4)
2.7732(4)
-
80.21(1)
122.01(8)
137.97(8)
-
M=In, E= S
2.115(2)
2.479(2)
2.520(2)
2.4583(6)
-
2.4535(9)
149.12(6)
128.38(6)
-
M=In, E= Se
2.12(3)
2.47(1)
2.50(2)
2.569(3)
-
2.576(3)
148.3(6)
134.1(7)
-
M=Ga, E=S
1.941(2)
2.294(2)
2.556(2)
2.2517(5)
2.2503(4)
-
154.80(5)
129.01(5)
131.94(5)
-
M=In, E=S
2.124(5)
2.555(3)
2.508(2)
2.439(2)
2.446(1)
-
147.3(1)
124.9(1)
123.9(1)
-
M=Ga,E=Se
1.949(2)
2.352(2)
2.547(2)
2.3735(3)
2.3880(3)
-
153.94(6)
135.68(6)
117.38(6)
-
M=In, E=Se
2.130(2)
2.520(2)
2.556(2)
2.5381(3)
2.5533(3)
-
147.48(6)
134.77(6)
118.95(6)
-
M1-C1
M1-N1
M1-N2
M1-E1
M1-E2
M1-E4
N1-M1-N2
C1-M1-E1
C1-M1-E2
C1-M1-E4
C1-M1-N1
E1-M1-E2
131.54(6)
74.80(7)
119.8(7)
74.6(8)
71.72(10)
79.95(6)
98.35(2)
73.0(1)
110.82(5)
77.00(7)
106.89(1)
74.22(7)
106.26(1)
The NMR spectra were consistent with their monomeric structure
and one set of signals was found in the 1H and 13C NMR spectra
of 6 – 9. The 1H NMR spectra showed singlets of methyl N(CH3)2
groups at δ 2.20 (6), 2.10 (7), 2.22 (8) and 2.11 (9) ppm and
singlet resonances of methylene CH2N protons at δ 3.13 (6), 3.04
(7), 3.10 (8) and 3.03 (9) ppm, respectively. In the 77Se NMR
spectra of 8 and 9, the signals at δ 459.5 (8) and 2.5 (9) ppm were
found and fall into the broad range observed for organometallic
selenolates.31 However, the signals of 8 (459.5 ppm) and of 9 (2.5
ppm) are shifted downfield in comparison to related complexes
[tBu2Ga(-SetBu)]2 (156 ppm)10b and Mes2ln(-SeR) (R = Me, Ph,
Mes) (range from -56 to -160 ppm)31,32 having the SeR bridging
groups. This may be the consequence of monomeric nature 8 and
9. UV-VIS absorption spectra of 8 and 9 showed absorption
maximum of aromatic part at 238 nm (8) and 239 nm (9) and
shoulder at 325 nm for 8 (for details see SI).
propylamine solution of 8 (c = 0.5 mol/l) led to the preparation of
GaSe thin films with poor quality by spin coating. Therefore, the
propylamine solution of 8 with c = 0.087 mol.l-1 was used for the
preparation of GaSe thin films by spin coating on silicon substrate
using 1000 and 1500 rpm. Prepared GaSe thin films were
amorphous, as confirmed by XRD (SI Figure 1) and showed
strong influence of thickness on spinning speed (Table S2 in SI).
Although the composition has been similar in both experiments,
the better results were obtained for deposition at 1500 rpm. The
scanning electron microscopy (SEM) (Fig. 5a) and atomic force
microscopy (AFM) (Fig. 5b) images showed that spin-coated films
have higher surface roughness (AFM root mean square
roughness <4 nm within 2m x 2 m scan area) in comparison
with thin amorphous chalcogenide films fabricated by physical
vapor deposition techniques.
Deposition of amorphous chalcogenide thin films by spin coating
method
Monomeric complexes 6 – 9 were further studied as potential
SSPs. TG analyses of 6 and 7 showed two steps decomposition
(see Figures S24 – 25 in SI) starting at 190°C (for 6) and 150° (for
7) and continue until 340°C (for 6) and 315° (for 7). Moreover, the
observed mass losses (69% for 6 and 62% for 7) in comparison
with expected (79% for 6 and 72% for 7) indicate incomplete
decomposition of 6 and 7. In contrast, the TG analysis of 8 and 9
showed one step decompositions (see Figures S26 – 27 in SI)
and continue until 295°C (for 8) and 255°C (for 9). The total
expected (73% for 8 and 69% for 9) and observed (70% for 8 and
66% for 9) mass losses indicate the formation of GaSe and InSe
material after complete decomposition of SSPs. Therefore both
compounds 8 and 9 were tested as suitable SSPs for preparation
of GaSe and InSe thin films by spin coating method. Due to
monomeric nature of 8 and 9, compounds are highly soluble in
propylamine (about 300 mg in 1 ml propylamine) and thus the
concentrations up to 0.5 mol/l may be obtained. In comparison,
amorphous GaSe thin films have been recently obtained from
0.06 mol/l propylamine solution of N→Ga coordinated
organogallium selenides.7 The use of highly concentrated
Figure 5 a) SEM image, b) AFM image of the surface of 1500 rpm spin-coated
GaSe thin film fabricated using of 8 SSP.
Energy-dispersive X-ray spectroscopy (EDX) revealed that the
chemical composition of the resulting thin film is Ga49.6Se50.4 for
1500 rpm. The Ga/Se atoms ratio in 8 is therefore retained in the
prepared GaSe thin films. Optical functions of prepared GaSe
layer as well as their thickness were obtained from the analysis of
variable angle spectroscopic ellipsometry (VASE) data. The
thickness of the as-dried Ga-Se thin film was 83.7±2 nm and the
refractive index was n = 2.28 at λ = 1.5 μm (Figure 6). These
values are little bit lower, but comparable to those found for
amorphous GaSe thin films produced by vacuum evaporation (n
≈ 2.41 at λ = 1.6 μm) noting that the chemical composition of the
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latter was probably richer in selenium content due to the fact that
GaSe9 starting material was used.33 Refractive index data
obtained in this work are in agreement with our previous report (n
= 1.96 - 2.26 at λ = 1.5 μm).7 Finally, compound 9 was used as
SSPs for the preparation of InSe thin films by spin-coating method
on silicon substrate using 1000 and 1500 rpm. Both propylamine
solutions of 9 with c = 0.09 and 0.5 mol.l-1 were tested, but the
resulting thin films, after the annealing, contained 25−35 at.% of
Se according to EDX.
Experimental Section
Supporting Information. Experimental details, NMR spectra for prepared
complexes, crystallographic parameters, (CCDC nos. 1915933-1915939
for 1, 2·0.5C6H6, 3 and 6 – 9, respectively), Variable Angle Spectroscopic
Ellipsometry (VASE), thermogravimetric analyses and UV-VIS
measurements.
Acknowledgements
We are grateful to the Czech Science Foundation (project no. 18-
03823S) for supporting this work.
Keywords: single-source precursor • spin-coating • GaSe
material • amorphous thin films • chalcogenolates
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Chemistry - An Asian Journal
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Entry for the Table of Contents (Please choose one layout)
Layout 2:
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Tomáš Řičica,[b] Yaraslava
Milasheuskaya,[b] Zdeňka Růžičková,[b]
Petr Němec,[a] Pavel Švanda,[c] Zuzana
Olmrová Zmrhalová,[d] Roman Jambor[b]
and Marek Bouška[a]*
Page No. – Page No.
Synthesis of indium chalcogenides with In2Te2, InS4 or InSe4 rings and monomeric
chalcogenolates LM(EPh)2 (L = {2,6-(Me2NCH2)2C6H3}-, M = Ga, In, E = S, Se) is
shown. LGa(SePh)2 compound has been successfully applied for amorphous
GaSe thin film preparation.
Synthesis and application of
monomeric chalcogenolates of 13
group elements
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