Cu 2 S thin films were produced by simple chemical bath deposition technique at various bath temperatures ranging from 55 °C to 75 °C. For chemical bath deposited thin films, copper sulphate solution was employed as Cu 2+ source while thiourea solution provided the S 2-ions. The morphological, compositional and optical properties were investigated using scanning electron microscopy, energy dispersive analysis of X-ray and UV-Visible spectrophotometer, respectively. The grain size and average atomic ratio of Cu/S increased when the bath temperature was increased from 55 °C to 75 °C. The films deposited at 75 °C indicated high absorbance as compared with other bath temperatures

Anuar Kassim

HO SOON MIN a , LIM Kian Siang

Saravanan Nagalingam

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Chalcogenide Letters      Vol. 8, No. 7, July 2011, p. 405 – 410 
 
 
 
 
SEM, EDAX AND UV-VISIBLE STUDIES ON THE PROPERTIES OF  
Cu2S THIN FILMS 
 
 
ANUAR KASSIMa*
 
, HO SOON MINa, LIM KIAN SIANGa, SARAVANAN 
NAGALINGAMb 
aDepartment of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 
Serdang,Selangor, Malaysia. 
bFaculty of Science, Universiti Tunku Abdul Rahman, 31900 Kampar, Perak, 
Malaysia 
 
Cu2S thin films were produced by simple chemical bath deposition technique at various 
bath temperatures ranging from 55 °C to 75 °C. For chemical bath deposited thin films, 
copper sulphate solution was employed as Cu2+ source while thiourea solution provided 
the S2- ions. The morphological, compositional and optical properties were investigated 
using scanning electron microscopy, energy dispersive analysis of X-ray and UV-Visible 
spectrophotometer, respectively. The grain size and average atomic ratio of Cu/S increased 
when the bath temperature was increased from 55 °C to 75 °C. The films deposited at                
75 °C indicated high absorbance as compared with other bath temperatures. 
 
(Received May 23, 2011; Accepted July 1, 2011) 
 
Keywords: copper sulfide, chemical bath deposition, thin films, bath temperature 
 
 
1. Introduction  
 
Copper sulfide thin films receiving ever-increasing attention due to its wide variety of 
applications such as solar cells, optoelectronic device and tubular solar collectors. Several 
techniques have been used to produce copper sulfide thin films such as spray pyrolysis [1], 
successive ionic layer adsorption and reaction technique [2], photochemical deposition [3], 
electrodeposition [4] and chemical bath deposition [5]. Among them, the chemical bath deposition 
method is hugely attractive since the technique possesses a number of advantages over 
conventional thin films deposition methods. The main advantages of this method are low cost, low 
deposition temperature and easy coating of large surfaces. The chemical bath deposition method 
has been actively investigated by other researchers for the growth of binary compound (CdS [6], 
In2S3 [7], CdSe [8], SnS [9], BaSe [10], SnSe [11], FeS [12] and NiSe [13]) and ternary thin films 
(Cd0.5Zn0.5Se [14], CuBiS2 [15] and CdZns [16]).   
In this paper, we present for the first time the effects towards the chemical bath deposited 
Cu2S thin films properties by varying the bath temperatures in the presence of tartaric acid as 
complexing agent. The morphological, compositional and optical properties of thin films were 
investigated using scanning electron microscopy, energy dispersive analysis of X-ray and UV-
Visible spectrophotometer. 
 
2. Experimental  
 
2.1 Preparation of thin flms 
 
Microscope glass slides were used as the substrate during the deposition process. The 
substrates were first cleaned in ethanol solution, subsequently ultrasonically washed with distilled 
                                                          
*Corresponding author: anuar@science.upm.edu.my  
406 
water. Substrates were then dried in an oven at 90 °C. Copper sulfate, thiourea, tartaric acid and 
hydrochloric acid of analytical reagent grade were used as received. Deionized water (Alpha-Q 
Millipore) with a resistivity of 18.4 MΩcm was used as solvent. Aqueous solutions of copper 
sulfate, thiourea and tartaric acid were separately prepared before experiment. 25 mL of copper 
sulfate (0.15 M) and 25 mL of tartaric acid (0.15 M) were mixed in a beaker. The tartaric acid was 
served as complexing agent to chelate with Cu2+ to obtain complex solution. Then, 25 mL of 
thiourea (0.15 M) was added and the pH of the solution was adjusted to 2.5 by addition of 
hydrochloric acid. Substrates were immersed vertically in the beaker. The beaker was not stirred 
during the thin films deposition. In order to determine the best conditions for the deposition 
process, the films were deposited at different bath temperatures (55, 65 and 75 °C). After 
completion of films deposition (120 min), the deposited films were then washed with distilled 
water and dried in air at room temperature for further characterization. 
 
2.2. Characterization of thin films 
 
The surface morphology was observed by a scanning electron microscopy (JEOL, JSM-
6400). All the samples taken at 20 kV with a 500 X magnification. The elemental composition of 
the films was studied by scanning electron microscope attached with energy dispersive analysis of 
X-ray (EDAX) analyzer. Optical absorption study was carried out using the Perkin Elmer UV/Vis 
Lambda 20 Spectrophotometer. The film-coated microscope glass slide was placed across the 
sample radiation pathway while the uncoated microscope glass slide was put across the reference 
path. 
 
3. Results and discussion 
 
Fig. 1 shows the scanning electron microscopy (SEM) micrographs for the films deposited 
at various bath temperatures from 55 °C to 75 °C. The morphologies are very different in these 
thin films as shown in Figure 1. Considering first the films deposited at lower bath temperature (55 
°C), the films obtained present less compact morphology due to less materials deposited on the 
surface of the substrate. Ii is also observed that fine grains (2-3 μm) are distributed randomly 
throughout the substrate. In contrast, the grain sizes are found to increase with bath temperature 
and found to be 8-10 μm for films deposited at 65 °C. Based on the SEM micrographs, it is clearly 
observed that the grains of sample deposited at the highest bath temperature (75 °C) is relatively 
larger in size than that of the films prepared at lower bath temperature (55 °C and 65 °C). The 
grain size ranges from 25 μm to 30 μm and they are agglomerated in some places. These grains are 
distributed to cover the surface of the substrate completely. It was evident that with the increase in 
bath temperature, the grains become larger in diameter.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
407 
 
 
a 
 
 
 
b 
 
 
 
c 
 
Fig. 1. Scanning electron microscopy (SEM) micrographs of Cu2S thin films deposited at 
different bath temperatures (a) 55 °C (b) 65 °C (c) 75 °C 
 
 
408 
 The optical properties of the chemical bath deposited Cu2S thin films were investigated 
from the absorption measurement in the range of 350-800 nm as shown in Figure 2. All the films 
show the same patterns with higher absorption on the shorter wavelength side.  The films 
deposited at 75 °C have high absorbance as compared with other bath temperatures, indicating 
more surface area could be observed for these thin films.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 2. Optical absorbance versus wavelength of Cu2S thin films deposited at different 
bath temperatures (a) 55 °C (b) 65 °C (c) 75 °C 
 
 The compositional analysis of the thin films was investigated by energy dispersive 
analysis of X-ray (EDAX) method (Figure 3). Table 1 lists the atomic ratio of the copper sulfide 
thin films prepared at various bath temperatures. EDAX analysis indicates the presence of copper 
and sulphur for all the deposited films. The average atomic ratio of Cu/S calculated from the 
quantification of the peaks, gives the value of 1.89, 1.95 and 2.25 for different bath temperatures 
of 55 °C, 65 °C and 75 °C, respectively. These results indicate that the average atomic ratio of 
Cu/S increases with increasing bath temperature.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
409 
 
 
 
 
 
 
Fig. 3. Energy dispersive analysis of X-ray (EDAX) spectra of Cu2S thin films deposited at different bath 
temperatures (a) 55 °C (b) 65 °C (c) 75 °C. 
(b) 
(a) 
(c) 
410 
Table 1: Atomic percentage composition of Cu2S thin films deposited at different bath temperatures 
 
Bath temperature (°C) Atomic percentage of 
copper (%) 
Atomic percentage of 
sulphur (%) 
Cu:S 
55 65.44 34.56 1.89 
65 66.05 33.95 1.95 
75 69.20 30.80 2.25 
 
 
4. Conclusion 
 
Synthesis of Cu2S thin films was carried out by chemical bath depsoition method using 
copper sulfate, thiourea and tartaric acid. Based on the SEM analsyis, the grain size decreased as 
the thin films prepared at lower bath temperature. The average atomic ratio of Cu/S increased to 
2:1 as the bath temperature was increased from 50 °C to 70 °C.  The films deposited at 70 °C have 
high absorbance as compared with other bath temperatures. 
 
 
Acknowledgements 
 
The authors would like to thank the Department of Chemistry, Universiti Putra Malaysia 
for the provision of laboratory facilities and MOSTI for the National Science Fellowship.  
 
 
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SEM, EDAX AND UV-VISIBLE STUDIES ON THE PROPERTIES OF Cu 2 S THIN FILMS

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SEM, EDAX AND UV-VISIBLE STUDIES ON THE PROPERTIES OF Cu 2 S THIN FILMS

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