Aerosol assisted chemical vapor deposition (AACVD) of CdS thin films from heterocyclic cadmium(II) complexes

Article abstract of DOI:10.1016/j.ica.2015.05.024

Abstract Cadmium dithiocarbamato complexes of piperidine (1) and tetrahydroquinoline (2) were synthesized and characterized by elemental analysis, FT-IR spectroscopy, NMR and TGA analyses. The X-ray single crystal structure of bis(piperidinedithiocarbamato)cadmium(II) complex (1) was determined. The synthesized compounds were used as single source precursors to deposit CdS films on glass substrates at 350, 400 and 450 °C using the aerosol assisted chemical vapor deposition (AACVD) method. The surface morphology and the size of the CdS films were determined by AFM and SEM analyses; the crystalline phases by p-XRD analyses and the elemental composition by EDX measurements. The particle sizes were found to be in the range between 50-110 nm and 100-220 nm for complex (1) and (2), respectively. The electronic properties of the CdS films were analyzed by UV-Vis and Raman spectroscopic methods. Results revealed that the morphology, size and composition of the films are influenced by the deposition temperature.

Full text of DOI:10.1016/j.ica.2015.05.024

Inorganica Chimica Acta 434 (2015) 181–187
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Aerosol assisted chemical vapor deposition (AACVD) of CdS thin films
from heterocyclic cadmium(II) complexes
a
b
b
c
c
c
Sixberth Mlowe , Linda D. Nyamen , Peter T. Ndifon , M. Azad Malik , James Raftery , Paul O’Brien ,
a,
⇑
Neerish Revaprasadu
a
Department of Chemistry, University of Zululand, Private Bag X1001, Kwa-Dlangezwa 3886, South Africa
Department of Inorganic Chemistry, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon
School of Materials, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Cadmium dithiocarbamato complexes of piperidine (1) and tetrahydroquinoline (2) were synthesized
and characterized by elemental analysis, FT-IR spectroscopy, NMR and TGA analyses. The X-ray single
crystal structure of bis(piperidinedithiocarbamato)cadmium(II) complex (1) was determined. The synthe-
sized compounds were used as single source precursors to deposit CdS films on glass substrates at 350,
Received 19 March 2015
Received in revised form 25 May 2015
Accepted 26 May 2015
Available online 6 June 2015
400 and 450 °C using the aerosol assisted chemical vapor deposition (AACVD) method. The surface mor-
phology and the size of the CdS films were determined by AFM and SEM analyses; the crystalline phases
by p-XRD analyses and the elemental composition by EDX measurements. The particle sizes were found
to be in the range between 50–110 nm and 100–220 nm for complex (1) and (2), respectively. The elec-
tronic properties of the CdS films were analyzed by UV–Vis and Raman spectroscopic methods. Results
revealed that the morphology, size and composition of the films are influenced by the deposition
temperature.
Keywords:
Single source precursors
Cadmium sulfide
AACVD
Thin films
Optical properties
Ó 2015 Elsevier B.V. All rights reserved.
1
. Introduction
[17], sol–gel [18], and metal–organic chemical vapor deposition
(
MOCVD) [19–23], has been used to deposit phase pure films of
CdS.
The MOCVD technique employing precursors is a well estab-
Binary metal chalcogenides as thin films, or particulates in
mono-dispersed form, especially II–VI semiconductors and in par-
ticular cadmium or zinc chalcogenides (CdS, CdSe, CdTe, ZnS, ZnSe)
have attracted considerable attention [1–5]. They have high sym-
metry axis distinguished from all the other axes which serves as
the directional axis for the asymmetric growth for the synthesis
of nanorods [6–8]. Their properties and potential for applications
in photovoltaic technologies which employ the use of cheap and
widely available elements is important [10–12].
Cadmium sulfide is a group II–VI semiconductor with a direct
band gap of 2.42 eV. CdS thin films have been used for a wide vari-
ety of technological applications, including photovoltaic cells, elec-
tro-optic modulators, sensors, electroluminescent and photo
luminescent devices, and antireflection coatings [13–15]. The route
used to prepare or deposit a material can profoundly affect the
phase composition, thermal stability, and morphology, which in
turn can influence the functional behavior of the material. Many
techniques such as spray pyrolysis [16], chemical bath deposition
lished giving high-quality thin films. The use of single-source pre-
cursors (SSPs) can potentially provide several key advantages over
other routes due to the existence of preformed bonds which can
lead to a material with fewer defects and better stoichiometry
[24]. In this work, the aerosol-assisted CVD (AACVD) technique
was used because it could lead to the deposition of nanosized thin
films under soft processing conditions where the volatility of the
precursor is no longer crucial as in the case conventional CVD [25].
The nature, morphology and composition of the final product
can be affected by the single source precursor used to deposit
the materials [26,27]. As initially reported the use of single source
precursor for CdS has also provided an efficient route to high qual-
ity crystalline monodispersed nanoparticles of semiconductors
[28,29]. Various classes of single source precursors have been iden-
tified
and
developed
including
dialkyldithiocarbamates
[21,20,30,31], xanthates [19,32], N-alkyl thioureas [33], and
dithioimidodiphosphinates [34,35], for the preparation of CdS thin
films and nanoparticles.
⇑
Corresponding author. Tel.: +27 35 902 6152; fax: +27 35 902 6568.
http://dx.doi.org/10.1016/j.ica.2015.05.024
020-1693/Ó 2015 Elsevier B.V. All rights reserved.
0

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S. Mlowe et al. / Inorganica Chimica Acta 434 (2015) 181–187
We have recently demonstrated that heterocyclic piperidine
Table 1
Crystal data and structural refinement parameters for complex (1).
and tetrahydroquinoline dithiocarbamato metal complexes can
be used as single source precursors for the preparation of high
quality ZnS, PbS and CdS nanoparticles [8–10,36–38]. The variation
of some reaction parameters such as the temperature, the mono-
mer concentration and the capping molecule showed an effect on
the size and the morphology of the synthesized nanoparticles.
The precursors used for the decomposition were air and moisture
stable at room temperature. The AACVD of CdS thin films
using the pyridine adduct of bis(piperidinedithiocarbamato)
cadmium(II) complex was also reported [39]. In this work, we report
the use of piperidine (1) and tetrahydroquinoline (2)
dithiocarbamato cadmium(II) complexes as single source
precursors for the deposition of CdS thin films at different
temperatures by AACVD. The single crystal X-ray structure of
the bis(piperidinedithiocarbamato)cadmium(II) complex is also
reported.
Formula
2 4 8
C24H40Cd N S
M
r
865.88
Crystal system
Space group
a (Å)
b (Å)
c (Å)
triclinic
P1ꢀ
8.7196(4)
12.5000(9)
15.9023(8)
80.328(5)
89.921(4)
72.778(5)
1629.86(16)
2, 1.764
100(2)
a
(°)
b (°)
(°)
c
3
V (Å )
À3
Z, Dcalc (Mg m
T (K)
)
Refinement method
Reflections collected/unique
full-matrix least-squares on F2
9866/5919, [Rint = 0.0566]
Final R indices [I > 2
R indices (all data)
Largest difference in peak and hole (e Å
Goodness-of-fit (GOF)
r
(I)]
R
R
1
= 0.0613, wR
= 0.0751, wR
2
= 0.1649
= 0.1736
1
2
À3
)
2.189 and À1.473
1.101
2
. Experimental
2.1. Chemicals
2.3. Preparation of the ligands
Cadmium chloride 99%, acetonitrile, 1,2,3,4, tetrahydroquino-
Carbon disulfide (0.1 mol, 6.0 mL) was added in small portions
to an equimolar solution mixture of sodium hydroxide (4.0 g,
0.1 mol) and the corresponding amine (piperidine, tetrahydro-
quinoline, 0.1 mol), cooled in an ice bath at 0 °C. After 15 min, a
precipitate was formed which was then dried in air and re-crystal-
lized in a mixture of acetone/petroleum ether. The final product
was collected, washed with chloroform and suction dried.
line 98% (Aldrich). Piperidine 99% (Sigma–Aldrich). Petroleum
ether, methanol 99.5%, dichloromethane, carbon disulfide 99.5%,
chloroform, sodium hydroxide 98%, and acetone (Merck) were
used as purchased without any further purification.
2
.2. Instrumentation
Na(pip-dtc), Yield: 92.5%. Significant IR bands:
(OÀH)
m :
À1
À1
À1
Microanalysis was performed on a Perkin-Elmer automated
3370 cm
,
m
(C@S): 949 cm
, m(C@N): 1439 cm . Anal. Calc. for
model 2400 series II CHNS/O analyser. Infrared spectra were
recorded on a Bruker FT-IR tensor 27 spectrophotometer directly
C
6
H
10NS
2
NaÁH
6.13; N, 6.98%.
Na(thq-dtc), Yield: 61%. Significant IR bands:
2
O: C, 35.80; H, 6.01; N, 6.96. Found: C, 35.90; H,
–
1
À1
on small samples of the compounds in the range 200–4000 cm
.
m
(OÀH): 3250 cm
(C@N): 1481 cm . Anal. Calc. for C10 10NS
O: C, 44.93; H, 5.28; N, 5.24. Found: C, 45.43; H, 5.09; N, 5.25%.
,
À1
À1
À1
Thermogravimetric analysis was carried out at 20 °C min heating
rate using a Perkin Elmer Pyris 6 TGA up to 600 °C in a closed per-
m(C@S): 968 cm
,
m
H
2
NaÁ
2H
2
2
forated aluminium pan under N gas flow. Optical absorption mea-
surements were carried out using a Varian Cary 50 UV–Vis
spectrophotometer. A Perkin-Elmer LS 55 spectrofluorimeter was
used to measure the photoluminescence of the CdS thin films.
Both measurements were done at room temperature. Raman spec-
tra were recorded using Horiba Jobinyvon Raman spectrometer
using 514.5 nm lasers at room temperature.
Atomic force microscopy (AFM) analysis (Contact mode) of the
CdS thin films was carried by a Bruker Inova instrument using
Nano Drive Software and the images were processed using
Nanoscope analysis. Scanning electron microscopy (SEM) and
EDX measurements were carried out by carbon coating the films
by using Edward’s E306A coating system before carrying out SEM
and EDX analyses. SEM analysis was performed using a Philips
XL 30FEG and EDX was carried out using a DX4 instrument.
Powder X-ray Diffraction (p-XRD were recorded in the high angle
2
.4. Preparation of the cadmium complexes
Cadmium chloride (5.0 mmol) was dissolved in distilled water
(
25.0 mL) and added drop-wise to the corresponding solution of
the dithiocarbamate ligand (10.0 mmol). The reaction mixture
was stirred for 1 h, and the precipitate formed was filtered, washed
with excess distilled water and dried overnight in an oven at 70 °C.
[
Cd(pip-dtc)
2
], (1) (pip = piperidinyl, dtc = dithiocarbamato),
À1
Yield: 86%. IR (cm , ATR): 967,
v
(C@S); 1485,
Cd: C, 33.29; H, 4.66; N, 6.47.
Found: C, 33.47; H, 4.55; N, 6.43%. m.p. 331%.
v(C@N); 388,
20 2 4
v(Cd–S). Anal. Calc. for C12H N S
[
Cd(thq-dtc)
2
], (2) (thq = tetrahydroquinoline, dtc = dithiocar-
À1
bamato), Yield: 69%. IR (cm , ATR): 972,
3
5
v
(C@S); 1492,
Cd: C, 45.40; H, 3.81; N,
.29. Found: C, 44.88; H, 3.61; N, 4.95%. m.p. 320 °C.
v(C@N);
20 2 4
97, v(Cd–S). Anal. Calc. for C20H N S
2
h range of 20–60° using a Bruker AXS D8 Advance X-ray diffrac-
tometer, equipped with nickel filtered Cu radiation
k = 1.5406 Å) at 40 kV, 40 mA and at room temperature.
X-ray crystallographic analysis: Single crystal X-ray diffraction
data for complex (1) were collected using graphite monochro-
mated Cu K radiation (k = 1.54178 Å) on a Bruker APEX diffrac-
K
a
(
2.5. Deposition of films by AACVD
In a typical deposition, 0.2 g (0.4 mmol) of the precursor was
dissolved in 20 ml of acetonitrile in a two-necked 100 ml round-
bottom flask with a gas inlet that allowed the carrier gas (argon)
to pass into the solution to aid the transport of the aerosol. This
flask was connected to the reactor tube by a piece of reinforced
tubing. The argon flow rate was controlled by a Platon flow gauge.
Seven glass substrates (approx. 1 Â 2 cm were placed inside the
reactor tube, which is placed in a Carbolite furnace. The precursor
solution in a round-bottom flask was kept in a water bath above
the piezoelectric modulator of a Pifco ultrasonic humidifier
a
tometer. The structure was solved by direct methods and refined
2
by full-matrix least squares on F . All non-H-atoms were refined
anisotropically. Hydrogen atoms were included in calculated posi-
tions, assigned isotropic thermal parameters and allowed to ride
on their parent carbon atoms. All calculations were carried out
using the SHELXTL package [40]. Crystal data and structural refine-
ment parameters are presented in Table 1. (CCDC reference num-
ber 1008839).

S. Mlowe et al. / Inorganica Chimica Acta 434 (2015) 181–187
183
(
Model No. 1077). The aerosol droplets of the precursor thus gen-
confirmed by elemental analysis, IR, NMR and TGA. The complexes
were obtained in good yield with a simple reaction route. The
piperidine dithiocarbamate and its complex were white while
tetrahydroquinoline dithiocarbamate and its complex were yellow.
The complexes are air and moisture stable at room temperature for
periods of several months.
erated were transferred into the hot wall zone of the reactor by
carrier gas. Both the solvent and the precursor were evaporated
and the precursor vapor reached the heated substrate surface
where thermally induced reactions and film deposition took place.
The reaction temperatures were varied between 350 and 450 °C.
The TGA thermograms show decomposition in single step for
both complexes at 331 and 319.80 °C, displaying a weight loss of
3
. Results and discussion
6
4.9% and 70.9% (calc = 66.6% and 72.7%) for piperidine and
tetrahydroquinoline complexes, respectively (Fig. 1). The final resi-
dues 35.1% and 29.1% were close to 33.4% and 27.3%, higher than
the calculated values for CdS obtained from complexes (1) and
3
.1. Characterization of the ligand and the complexes
The purity of piperidine/tetrahydroquinoline dithiocarbamate
(2) respectively. The final TGA residue were analyzed by EDX and
ligands and the corresponding cadmium complexes were
found to consist of small amount of carbon contamination, which
attributes to the higher experimental values because of bulky alkyl
organic moiety of the ligands.
The ORTEP view of the crystal structure of bis(piperidine-
2 4 8
dithiocarbamato)cadmium(II) [C24H40Cd N S ] is shown in Fig. 2
while the crystal data are shown on Table 1 and selected bond
parameters shown on Table 2. The compound is found to crystallise
ꢀ
in the triclinic crystal system, with space group P1 and Z = 2. The
structure shows a dimeric compound with each of the cadmium
center chelated to two dithiocarbamate ligands through their S-
atoms. Two S-atoms from two different dithiocarbamate ligands
form two
3
l -S bridges between the two Cd atoms and a C-atom
of each of the ligands, thus forming a square pyramidal geometry
around each Cd center as shown in Fig. 2. The Cd–S bond lengths
range from 2.513 to 2.971 Å. The short Cd–S bond distances
(
2.513–2.515 Å) lie in the range consistent to Cd–S bond distances
in pentacoordinate complexes (range 2.511–2.518A) [41], shorter
than values reported for four-coordinate complexes (2.5274 Å)
and for six-coordinate complexes (Cd–S range 2.558–2.810Å), thus
supporting the involvement of Cd in electron delocalization
Fig. 1. Thermogravimetric analysis (TGA) plots of complexes (1) and (2) at a heating
rate of 10 °C min under nitrogen atmosphere.
À1
3
[41,42]. The longer Cd–S bond lengths involving the l -S are longer
than those observed for six-coordinate complexes. The
bis(tetrahydroquinolinedithiocarbamato)cadmium(II)complex (2)
did not give the crystals of good enough quality for X-ray single
structure elucidation.
3.2. Optical properties of CdS thin films
The room temperature UV–Vis absorption spectra of the CdS
samples (Fig. 3) in the wavelength range of 320–800 nm, using
glass substrate as a reference, were recorded to calculate the
energy band gap (Eg) from the Tauc plot (Inset Fig. 3). The blue
shift in absorption edge is clearly observed from the UV–Vis
absorption spectra, when CdS thin films were deposited using
complex (1). The UV–Vis absorption results indicate that, with
increasing the annealing temperature from 350 to 450 °C, band
gap changes one insignificant. The band gap energy of the films
was estimated to be 2.38 ± 0.04 eV from the Tauc plot [43]. These
observations are similar to those of CdS thin films deposited when
complex (2) was used as single source precursor, however the
Fig. 2. Single X-ray crystal structure of bis(piperidinedithiocarbamato)cadmium(II)
complex.
Table 2
Selected bond lengths (Å) and angles (°) for complex (1).
Cd(1)–S(2)
Cd(1)–S(3)
Cd(1)–S(1) #1
Cd(1)–S(4)
Cd(1)–S(1)
Cd(2)–S(7)
Cd(2)–S(5)
Cd(2)–S(8) #2
Cd(2)–S(6)
Cd(2)–S(8)
2.513 (2)
2.514 (2)
2.576 (2)
2.640 (2)
2.971 (2)
2.514 (2)
2.515 (2)
2.568 (2)
2.677 (2)
2.917 (2)
S(2)–Cd(1)–S(3)
S(2)–Cd(1)–S(1) #1
S(3)–Cd(1)–S(1) #1
S(2)–Cd(1)–S(4)
S(3)–Cd(1)–S(4)
S(1) #1–Cd(1)–S(4)
S(2)–Cd(1)–S(1)
S(3)–Cd(1)–S(1)
S(1) #1–Cd(1)–S(1)
S(4)–Cd(1)–S(1)
130.86 (9)
104.79 (8)
121.58 (8)
112.54 (8)
70.60 (7)
106.96 (7)
65.70 (7)
97.91 (7)
88.86 (7)
163.67 (7)
S(7)–Cd(2)–S(5)
S(7)–Cd(2)–S(8) #2
S(5)–Cd(2)–S(8) #2
S(7)–Cd(2)–S(6)
S(5)–Cd(2)–S(6)
S(8) #2–Cd(2)–S(6)
S(7)–Cd(2)–S(8)
S(5)–Cd(2)–S(8)
S(8) #2–Cd(2)–S(8)
S(6)–Cd(2)–S(8)
135.70 (9)
102.53 (8)
119.90 (8)
110.91 (8)
70.00 (7)
107.20 (7)
66.31 (7)
97.20 (7)
93.35 (6)
159.19 (7)

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S. Mlowe et al. / Inorganica Chimica Acta 434 (2015) 181–187
Fig. 3. UV–Vis absorption spectra of CdS films deposited on glass substrate using complex (1) at (i) 350 °C, (ii) 400 °C and (iii) 450 °C (Inset: Tauc plot showing the estimated
optical band gap of 2.38 ± 0.04 eV).
Fig. 6. Raman spectra of CdS thin films deposited by using complexes (2).
Fig. 4. Photoluminescence emission spectra of CdS thin films deposited at (i)
3
50 °C, (ii) 400 °C and (iii) 450 °C (kexc = 380 nm).
Fig. 7. Powder X-ray diffractograms of CdS films deposited on glass substrate using
complex (1) at (a) 350 °C, (b) 400 °C and (c) 450 °C.
Fig. 5. Raman spectra of CdS thin films deposited by using complexes (1).

S. Mlowe et al. / Inorganica Chimica Acta 434 (2015) 181–187
185
À1
and 2LO at 299 and 603 cm respectively. The shift in peak posi-
tion of CdS thin films towards lower wavelength side was noted.
Recently, it has been reported that phonon confinement, strain,
defects and broadening associated with the size distribution were
important factors which affect the Raman spectra [48]. Due to the
phonon confinement and strain effect, we observed the shift in 1LO
and 2LO peak positions of CdS nanoparticles with respect to the
bulk CdS.
3
2
2
1
1
0
0
.0
.5
.0
.5
.0
.5
.0
o
4
50 C
o
3.3. Physical properties of CdS thin films
4
00 C
The powder X-ray diffraction (p-XRD) patterns of the CdS thin
films deposited at the three different temperatures are presented
in Fig. 7 when complex (1) was used as a precursor. The three dom-
inant peaks in diffraction patterns from films grown at 350, 400
and 450 °C can be assigned to the CdS (100), (002), (101) reflec-
tions of pure hexagonal phase and the values are matched to those
in the ICDD values (card # 01–077-2306). The particle size were
calculated using Scherrer equation reported elsewhere [49] and
were found to be 57.37 nm (350 °C), 63.57 nm (400 °C) and
o
3
50 C
2
0
30
40
50
60
2
θ (deg)
Fig. 8. Powder X-ray diffractograms of CdS films deposited using complex (2).
7
2.97 nm (450 °C) from the most prominent peak (101), relatively
closer to the size determined by SEM. A similar diffraction pattern
was observed when complex (2) was used, where the hexagonal
phase of CdS was dominant (Fig. 8). Furthermore, the high inten-
sity of (002) peak in p-XRD pattern of CdS thin films indicated that
the particles were preferably elongated along the c-axis when
complex (2) was used while complex (1) preferred the (101) plane.
Fig. 9 illustrates the scanning electron microscopy (SEM) micro-
graphs of the surfaces of the CdS films deposited using complex (1)
at different substrate temperatures, to achieve better uniformity.
From the images, it can be seen that the coverage area was approx-
imately 100% at the substrate temperature of 450 °C, while at
lower temperature (350 and 400 °C) the coverage of the deposited
films varied from 80–90%. Increasing the deposition temperature
resulted in an increase in nucleation and deposition rates. The sizes
of the thin films were in the ranges of 55–75 nm and 90–110 nm
for CdS deposited at 350 and 450 °C temperatures, respectively.
absorption peaks were not as distinct as those from complex (1)
(
ESI 1). The photoluminescence (PL) properties of the CdS thin
films from complex (1) were also investigated by exciting the films
at 380 nm excitation wavelength. A blue emission peak at 483 nm
with FHWM of 9 nm is observed (Fig. 4). The broad red emission
observed between 520 and 545 nm is due to electron–hole traps
(
surface defect emission from sulfur vacancies) [44]. It could also
be related to microstructure imperfection and lattice defects of
the CdS thin films [45], all leading to the red emission.
The Raman spectra of CdS thin films with 514.5 nm excitation
wavelengths are shown in Figs. 5 and 6. The typical peaks of the
longitudinal optical (LO) modes of CdS are evident from the
Raman spectra. The fundamental frequencies at 297.5 and
À1
5
99 cm correspond to the 1LO and 2LO of the bulk hexagonal
CdS system [46,47], while the deposited CdS thin films have 1LO
Fig. 9. SEM images of CdS films deposited on glass substrate using complex (1) at deposition temperatures (a) 350 °C, (b) 400 °C and (c) 450 °C and (d) cross section
thickness) of the CdS films obtained at 450 °C.
(

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S. Mlowe et al. / Inorganica Chimica Acta 434 (2015) 181–187
Fig. 10. SEM images of CdS films deposited on glass substrate by AACVD using complex (2) at deposition temperatures (a) 350 °C, (b) 400 °C and (c) 450 °C and (d) EDX.
Fig. 11. 3D AFM height profiles of CdS thin films at (a) 350 °C and (b) 450 °C using complex (1) single source precursor.
The thickness of the sample obtained at 450 °C was estimated and
found to be ca. 615 nm (Fig. 9d).
associated with an increase in grain size. Similarly well defined
and densely packed isolated nanocrystallites were observed from
films deposited at 350 °C when complex (2) was used (ESI 3.),
while larger relatively non uniform crystalline grains were
obtained at 450 °C with root-mean-square roughness (Rq) of
29.86 nm and 38.70 nm at deposition temperature 300 °C and
450 °C, respectively.
The SEM images of the cadmium sulfide (CdS) thin films depos-
ited using complex (2) are showed in Fig. 10. There was a remark-
able difference in grain sizes and their uniformity as the
temperature was varied from 350 to 450 °C. The films deposited
at 450 °C show smaller spherical particle aggregates (ca. 100 nm),
while at 350 and 400 °C roughly cubic to spherical particles with
uniform and regular patterns were observed. The particle sizes
were larger in the 160–220 nm range. The EDX measurements
4
. Conclusion
(
Fig. 10d) showed that the average percentage ratio of Cd:S is 1
Piperidine and tetrahydroquinoline cadmium dithiocarbamato
for both cases.
complexes have been synthesized and the single crystal X-ray
structure of [Cd(pip-dtc) ] elucidated. Deposition of thin films by
AFM analysis from the films deposited using precursor (1) at
different temperatures is shown in Fig. 11 and ESI 2. The film
deposited at 350 °C consists of continuous film, composed of
columnar and uniform nanosized grains, while the films deposited
at 450 °C are slightly uniform, spherical crystallites with the typi-
cal root-mean-square roughness (Rq) of 17.65 and 23.36 nm at
deposition temperatures 300 and 450 °C, respectively. The increase
in surface roughness with increasing deposition temperature is
2
AACVD at various temperatures showed that the growth of CdS
was influenced by deposition temperature. The morphologies of
CdS films obtained showed that the thin films become increasingly
dense with increase in temperature. The UV–Vis spectra of the
films showed blue shift in absorption edge compared to bulk
CdS. The fundamental frequency for CdS particles at 297.5 (1LO)
À1
and the first overtone at 599 cm (2LO) are observed from the

S. Mlowe et al. / Inorganica Chimica Acta 434 (2015) 181–187
187
Raman spectrum. The XRD, SEM/EDX and AFM analyses confirm
the formation of hexagonal CdS thin films, with well-defined mor-
phologies and precise elemental ratios. We plan to extend the use
of these precursors for the deposition of others metal sulfides such
as PbS. The synthetic parameters would also be varied in order to
optimize the optical properties while controlling modifications of
the crystal structure and morphology for potential applications.
[14] M. Nyman, K. Jenkins, M.J. Hampden-smith, T.T. Kodas, E.N. Duesler, Chem.
Mater. 10 (1998) 914.
[
[
15] M. Wei, K.L. Choy, Chem. Vap. Deposition 8 (2002) 15.
16] H.H. Afifi, S.A. Mahmoud, A. Ashour, Thin Solid Films 263 (1995) 248.
[17] P. Nèmec, I. Nèmec, Y. Nahalkova, F. Trojaner, P. Maly, Thin Solid Films 403–
04 (2002) 9.
4
[
[
18] W. Tang, D.C. Cameron, Thin Solid Films 280 (1996) 221.
19] D. Barreca, A. Gasparotto, C. Maragno, E. Tondello, C. Sada, Chem. Vap.
Deposition 10 (2004) 229.
[
20] M.B. Hursthouse, M.A. Malik, M. Motevalli, P. O’Brien, Organometallics 10
(
1991) 730.
Acknowledgements
[
[
21] D.M. Frigo, O.F.Z. Khan, P. O’Brien, J. Cryst. Growth. 96 (1989) 989.
22] C. Byrom, M.A. Malik, P. O’Brien, A.J.P. White, D.J. Williams, Polyhedron 19
(
2000) 211.
The authors thank the National Research Foundation (NRF),
South Africa through the South African Research Chair Initiative
[
[
23] K. Ramasamy, M.A. Malik, P. O’Brien, J. Raftery, Dalton Trans. 39 (2010) 1460.
24] D. Barreca, A. Gasparotto, C. Maragno, R. Seraglia, E. Tondello, A. Venzo, V.
Krishnan, H. Bertagnolli, Appl. Organometal. Chem. 19 (2005) 129.
25] M.A. Malik, M. Afzaal, P. O’Brien, Chem. Rev. 110 (2010) 4417.
26] F. Maury, Chem. Vap. Deposition 2 (1996) 113.
27] A.N. Gleizes, Chem. Vap. Deposition 6 (2000) 115.
[28] T. Trindade, P. O’Brien, Adv. Mater. 8 (1996) 161.
29] T. Trindade, P. O’Brien, X. Zhang, Chem. Mater. 9 (1997) 523.
30] C. Byrom, M.A. Malik, P. O’Brien, A.J.P. White, D.J. Williams, Polyhedron 19
(
SARChI) and Royal Society-DFID program for financial support.
[
[
[
Dr. LD Nyamen also acknowledges the Organization for Women
Scientists for the Developing World (OWSDW) formerly TWOWS
for a Sandwich Postgraduate Fellowship.
[
[
Appendix A. Supplementary material
(
2000) 211.
[
[
31] M.A. Malik, M. Motevalli, T. Saeed, P. O’Brien, Adv. Mater. 5 (1993) 653.
32] D. Barreca, A. Gasparotto, C. Maragno, E. Tondello, J. Electrochem. Soc. 151
CCDC 1008839 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.
uk/data_request/cif. Supplementary data associated with this arti-
cle can be found, in the online version, at http://dx.doi.org/10.
(
2004) G428.
[
[
[
[
[
[
[
33] M.J. Moloto, P. O’Brien, M.A. Malik, N. Revaprasadu, J. Mater. Sci. Mater.
Electron. 15 (2004) 13.
34] D. Fan, M. Afzaal, M.A. Mallik, C.Q. Nguyen, P. O’Brien, P.J. Thomas, Coord.
Chem. Rev. 251 (2007) 1878.
35] C.Q. Nguyen, A. Adeogun, M. Afzaal, M.A. Malik, P. O’Brien, Chem. Commun.
(2006) 2182.
36] L.D. Nyamen, A.A. Nejo, V.S.R. Pullabhotla, P.T. Ndifon, M.A. Malik, J. Akhtar, P.
O’Brien, N. Revaprasadu, Polyhedron 67 (2014) 129.
37] L.D. Nyamen, V.S.R. Pullabhotla, A.A. Nejo, P.T. Ndifon, J.H. Warner, N.
Revaprasadu, Dalton Trans. 41 (2012) 8297.
38] T. Mthethwa, V.S.R. Pullabhotla, P.S. Mdluli, J. Wesley-Smith, N. Revaprasadu,
Polyhedron 28 (2009) 2977.
39] S. Mlowe, D. Lewis, A.M. Malik, J. Raftery, E.B. Mubofu, P. O’Brien, N.
Revaprasadu, New J. Chem. 38 (2014) 6073.
40] SHELXTL, version 6.12, Bruker AXS Inc, Madison, WI, 2001.
41] T. Mandal, V. Stavila, I. Rusakova, S. Gosh, K.H. Whitmire, Chem. Mater. 21
1
016/j.ica.2015.05.024.
References
[
[
1] N. Revaprasadu, M.A. Malik, P. O’Brien, J. Mater. Res. 14 (1999) 3237.
2] M.A. Malik, M. Motevalli, P. O’Brien, J.R. Walsh, Organometallics 11 (1992)
3
136.
3] D.J. Binks, S.P. Bants, D.P. West, M.A. Malik, P. O’Brien, J. Mod. Optic. 50 (2003)
99.
[
2
[
[
[
[
4] M.A. Malik, M. Motevalli, P. O’Brien, Inorg. Chem. 34 (1995) 6223.
5] C.Q. Nguyen, M.A. Malik, M. Motevalli, T. Saeed, P. O’Brien, Adv. Mater. 5 (1993)
(
2009) 5617.
42] K. Ramasamy, M.A. Malik, M. Hilliwell, J. Raftery, P. O’Brien, Chem. Mater. 23
2011) 1471.
6
53.
[
[
[
[
[
6] A. Panneerselvam, C.Q. Nguyen, M.A. Malik, P. O’Brien, J. Raftery, J. Mater.
Chem. 19 (2009) 419.
7] A.A. Memon, M. Afzaal, M.A. Malik, C. Nguyen, P. O’Brien, J. Raftery, Dalton
Trans. (2006) 4499.
8] L.D. Nyamen, V.S.R. Pullabhotla, A.A. Nejo, P.T. Ndifon, N. Revaprasadu, New J.
Chem. 35 (2011) 1133.
9] L.D. Nyamen, N. Revaprasadu, A.A. Nejo, V.S.R. Pullabhotla, P.T. Ndifon, M.A.
Malik, P. O’Brien, Polyhedron 56 (2013) 62.
(
[
[
[
43] A. Rakhshani, J. Phys. Condens. Matter. 12 (2000) 4391.
44] J. Dilag, H. Kobus, A.V. Ellis, Forensic Sci. Int. 187 (2009) 97.
45] X. Yang, Z.G. Jin, Y. Chai, H. Du, T. Liu, T. Wang, Thin Solid Films 517 (2009)
6617.
[
[
46] V. Singh, P.K. Sharma, P. Chauhan, Mater. Chem. Phys. 121 (2010) 202.
47] A. Pan, R. Liu, Q. Yang, Y. Zhu, G. Yang, B. Zou, J. Phys. Chem. B. 109 (2005)
2
4268.
48] J.E. Spanier, R.D. Robinson, F. Zhang, S.W. Chan, I.P. Heraman, Phys. Rev. B. 64
2001) 245407.
[
10] L.D. Nyamen, N. Revaprasadu, P.T. Ndifon, Mater. Sci. Semicond. Process. 27
2014) 191.
[
[
(
(
[
[
[
11] D. Qi, M. Fischbein, M. Drndic, S. Selmic, Appl. Phys. Lett. 86 (2005) 093103.
12] T.K. Chaudhuri, S. Chatteries, Proc. Int. Conf. Thermoelectrics 11 (1992) 40.
13] Y.F. Nicolau, M. Dupuy, M. Brunel, J. Electrochem. Soc. 137 (1990) 2915.
49] R.J. Bandaranayake, G.W. Wen, J.Y. Lin, H.X. Jiang, C.M. Sorensen, Appl. Phys.
Lett. 67 (6) (1995) 831.