# Optimization of Chemical Bath Deposited Mercury Chromium Sulphide Thin Films on Glass Substrate

Authors: H. B. Patil; S. V. Borse
Journal: Indian Journal of Materials Science
 (2013)

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## Abstract

Semiconducting thin films of ternaryHgxCr2-xS4 (x=0.4) have been deposited on glass substrate by the simple and economical chemical bath deposition method. We report the deposition and optimization of the solution growth parameters such as temperature, complexing agent, thiourea, and deposition time that maximizes the thickness of the deposited thin film. The X-ray diffraction deposited HgxCr2-xS4 thin films having cubic structure. The thin films were uniform and adherent to substrate. The composition was found homogeneous and stoichiometric by EDAX analysis.


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## Body

## 1. Introduction

Mercury chromium sulfide (HgCr2S4) is a chalcogenide metal sulfide semiconductor of the II–VI group compound semiconductors. The technological interests in polycrystalline-based devices are mainly caused by their low production cost [1]. The use of HgCr2S4 thin films of semiconductor has attracted much interest because of their role in variety of applications in various magneto-optical and optoelectronics devices [2] as well as magnetocapacitive or magnetoelectric effect devices [3–7]. Many techniques have been reported in the deposition of thin films such as evaporation, sputtering, spray pyrolysis, molecular beam epitaxy, and photochemical deposition. There is a problem in each of these deposition methods [8, 9]. Amongst all, chemical bath deposition (CBD) is simple and of low cost and is suitable for a large area deposition [10]. Thin films of diluted magnetic semiconductors attract many researchers due to their wide range of applications in various fields. The films of HgCr2S4 are usually crystallized in cubic structure with lattice constants 10.2 Ǻ [11].In the present study, the chemical bath process is performed by slow release of S2− ions and controlled free Hg2+ and Cr2+ ions that react to form HgCr2S4 nuclei on glass substrate and in the bath solution in the form of precipitation. The properties of the deposited thin films basically depend on the deposition parameters such as deposition temperature, complexing agent, thiourea, deposition time, pH value, composition of materials, and film thickness. Finally, we report the deposition of HgCr2S4 thin films and the investigation of the different deposition parameters to obtain uniform film having expected thickness.


## 2. Materials and Methods

In the present investigation, thin films ofHgxCr2-xS4(x=0.4) are grown on glass substrate by chemical bath deposition technique. All AR grade chemicals from MERCK are used for growth of HgxCr2-xS4 thin films. For the deposition of HgxCr2-xS4, solutions of HgCl2, CrO3, and NH2-CS-NH2 are prepared separately of concentration 0.1 M using double distilled water as solvent and mixing them in stoichiometric proportion. EDTA is used as complexing agent. pH of the reaction mixture was adjusted by adding ammonia. The deposition was carried out in borosil glass beaker of capacity 100 mL. It is used to put reactant in the form of solution; hence it is served as chemical reaction bath. This chemical reaction bath is put inside the constant temperature oil bath. The chemical reactant in the form of solution is stirred by magnetic stirrer. Well-cleaned glass microslides are dipped vertically in the chemical reaction bath by providing support to glass pot of the reaction bath. The stirring speed of magnetic stirrer is so adjusted that the solution can be stirred slowly during the deposition process. After deposition of HgCr2S4 thin films, the substrates are taken out and washed with double distilled water and dried in air. Finally, they are preserved in an air-tight container. The thickness of deposited thin films is measured by the weight difference technique at room temperature. The structural properties of the films are analyzed by using Bruker AXS D8 Advanced model X-ray diffractometer (CuKα radiation; λ = 0.15405 nm), and the grain size is determined from the Scherrer formula. The grown composition is analyzed by the EDAX technique.


## 3. Results and Discussions

### 3.1. Impact of Preparative Parameters

#### 3.1.1. Impact of Bath Temperature

Figure1 shows the variation of film thickness with deposition temperature, keeping other parameters constant. The temperature of chemical bath was changed from 40°C to 90°C with an interval of 5°C. It can be seen from Figure 1 that the thickness goes on increasing with bath temperature; it reaches maximum thickness at 65°C and further decreases with increase in temperature after 65°C [12–14].Figure 1
Optimization of solution bath temperature forHgxCr2-xS4(x=0.4).


#### 3.1.2. Impact of Complexing Agent

Figure2 shows the variation of film thickness with complexing agent, keeping the other parameters same. The volume of EDTA was changed into a bath solution. The maximum and uniform thin films were obtained with the addition of 4.5 mL EDTA into a chemical bath solution and further decrease with increase in volume of EDTA.Figure 2
Optimization of volume of EDTA forHgxCr2-xS4(x=0.4).


#### 3.1.3. Impact of Thiourea Concentration

Figure3 shows the variation of film thickness with volume of thiourea, keeping other parameters the same. The volume of thiourea was changed into a bath solution. The maximum and well-uniformed thin films were obtained with the addition of 10 mL thiourea into a chemical bath solution. pH of the chemical bath solution was 10 at room temperature. Figure 3 indicates that the thickness went on increasing with volume of thiourea reaching to maximum (10 mL) and then decreases with further increase in volume of thiourea.Figure 3
Optimization of volume of thiourea forHgxCr2-xS4(x=0.4).


#### 3.1.4. Impact of Deposition Time

The impact of deposition time on thickness was studied in Figure4, keeping the other parameters the same. The thickness of thin film went on increasing with time of deposition, reaching to maximum at 120 minute.Figure 4
Optimization of deposition time forHgxCr2-xS4(x=0.4).


### 3.2. Structural Analysis

#### 3.2.1. X-Ray Diffractograph

XRD of the as grown films with optimum growth parameters was carried out. It is shown in Figure5. The observed XRD pattern shows cubic crystal structure with noticeable growth along the (220) plane [15], in addition to the other small peaks, namely, (311), (331), and (422). Table 1 shows the observed and standard XRD data. This confirmed the formation of HgxCr2-xS4(x=0.4) [16].Table 1
Experimental and standard “2θ” and “d” spacing.
Planes (hkl)
2 Theta (degree)
d-spacing values  d (Å)
JCPDS data card
Experiment
JCPDS
Experiment
2 2 0
24.572
24.580
3.62000
3.61967
3 1 1
28.899
28.900
3.08700
3.08687
3 3 1
38.269
38.260
2.35000
2.34875
4 2 2
43.254
43.260
2.09000
2.08982Figure 5
XRD pattern ofHgxCr2-xS4(x=0.4) thin film.


#### 3.2.2. EDAX Analysis

Table2 shows the composition  of element in  HgxCr2-xS4 thin films measured by EDAX analysis. The composition was found to be homogeneous and stoichiometric. Figure 6 shows EDAX spectrum of HgxCr2-xS4 compound. The composition of element in thin films and in initial reactant in chemical bath is similar.Table 2
Elemental composition ofHgxCr2-xS4 (x=0.4) thin film deposited by chemical bath method.
Element
Weight%
Atomic%
Hg
77.69
19.35
Cr
3.28
30.31
S
19.03
50.34Figure 6
EDAX spectrum of aHgxCr2-xS4(x=0.4) compound.


## 3.1. Impact of Preparative Parameters

### 3.1.1. Impact of Bath Temperature

Figure1 shows the variation of film thickness with deposition temperature, keeping other parameters constant. The temperature of chemical bath was changed from 40°C to 90°C with an interval of 5°C. It can be seen from Figure 1 that the thickness goes on increasing with bath temperature; it reaches maximum thickness at 65°C and further decreases with increase in temperature after 65°C [12–14].Figure 1
Optimization of solution bath temperature forHgxCr2-xS4(x=0.4).


### 3.1.2. Impact of Complexing Agent

Figure2 shows the variation of film thickness with complexing agent, keeping the other parameters same. The volume of EDTA was changed into a bath solution. The maximum and uniform thin films were obtained with the addition of 4.5 mL EDTA into a chemical bath solution and further decrease with increase in volume of EDTA.Figure 2
Optimization of volume of EDTA forHgxCr2-xS4(x=0.4).


### 3.1.3. Impact of Thiourea Concentration

Figure3 shows the variation of film thickness with volume of thiourea, keeping other parameters the same. The volume of thiourea was changed into a bath solution. The maximum and well-uniformed thin films were obtained with the addition of 10 mL thiourea into a chemical bath solution. pH of the chemical bath solution was 10 at room temperature. Figure 3 indicates that the thickness went on increasing with volume of thiourea reaching to maximum (10 mL) and then decreases with further increase in volume of thiourea.Figure 3
Optimization of volume of thiourea forHgxCr2-xS4(x=0.4).


### 3.1.4. Impact of Deposition Time

The impact of deposition time on thickness was studied in Figure4, keeping the other parameters the same. The thickness of thin film went on increasing with time of deposition, reaching to maximum at 120 minute.Figure 4
Optimization of deposition time forHgxCr2-xS4(x=0.4).


## 3.1.1. Impact of Bath Temperature

Figure1 shows the variation of film thickness with deposition temperature, keeping other parameters constant. The temperature of chemical bath was changed from 40°C to 90°C with an interval of 5°C. It can be seen from Figure 1 that the thickness goes on increasing with bath temperature; it reaches maximum thickness at 65°C and further decreases with increase in temperature after 65°C [12–14].Figure 1
Optimization of solution bath temperature forHgxCr2-xS4(x=0.4).


## 3.1.2. Impact of Complexing Agent

Figure2 shows the variation of film thickness with complexing agent, keeping the other parameters same. The volume of EDTA was changed into a bath solution. The maximum and uniform thin films were obtained with the addition of 4.5 mL EDTA into a chemical bath solution and further decrease with increase in volume of EDTA.Figure 2
Optimization of volume of EDTA forHgxCr2-xS4(x=0.4).


## 3.1.3. Impact of Thiourea Concentration

Figure3 shows the variation of film thickness with volume of thiourea, keeping other parameters the same. The volume of thiourea was changed into a bath solution. The maximum and well-uniformed thin films were obtained with the addition of 10 mL thiourea into a chemical bath solution. pH of the chemical bath solution was 10 at room temperature. Figure 3 indicates that the thickness went on increasing with volume of thiourea reaching to maximum (10 mL) and then decreases with further increase in volume of thiourea.Figure 3
Optimization of volume of thiourea forHgxCr2-xS4(x=0.4).


## 3.1.4. Impact of Deposition Time

The impact of deposition time on thickness was studied in Figure4, keeping the other parameters the same. The thickness of thin film went on increasing with time of deposition, reaching to maximum at 120 minute.Figure 4
Optimization of deposition time forHgxCr2-xS4(x=0.4).


## 3.2. Structural Analysis

### 3.2.1. X-Ray Diffractograph

XRD of the as grown films with optimum growth parameters was carried out. It is shown in Figure5. The observed XRD pattern shows cubic crystal structure with noticeable growth along the (220) plane [15], in addition to the other small peaks, namely, (311), (331), and (422). Table 1 shows the observed and standard XRD data. This confirmed the formation of HgxCr2-xS4(x=0.4) [16].Table 1
Experimental and standard “2θ” and “d” spacing.
Planes (hkl)
2 Theta (degree)
d-spacing values  d (Å)
JCPDS data card
Experiment
JCPDS
Experiment
2 2 0
24.572
24.580
3.62000
3.61967
3 1 1
28.899
28.900
3.08700
3.08687
3 3 1
38.269
38.260
2.35000
2.34875
4 2 2
43.254
43.260
2.09000
2.08982Figure 5
XRD pattern ofHgxCr2-xS4(x=0.4) thin film.


### 3.2.2. EDAX Analysis

Table2 shows the composition  of element in  HgxCr2-xS4 thin films measured by EDAX analysis. The composition was found to be homogeneous and stoichiometric. Figure 6 shows EDAX spectrum of HgxCr2-xS4 compound. The composition of element in thin films and in initial reactant in chemical bath is similar.Table 2
Elemental composition ofHgxCr2-xS4 (x=0.4) thin film deposited by chemical bath method.
Element
Weight%
Atomic%
Hg
77.69
19.35
Cr
3.28
30.31
S
19.03
50.34Figure 6
EDAX spectrum of aHgxCr2-xS4(x=0.4) compound.


## 3.2.1. X-Ray Diffractograph

XRD of the as grown films with optimum growth parameters was carried out. It is shown in Figure5. The observed XRD pattern shows cubic crystal structure with noticeable growth along the (220) plane [15], in addition to the other small peaks, namely, (311), (331), and (422). Table 1 shows the observed and standard XRD data. This confirmed the formation of HgxCr2-xS4(x=0.4) [16].Table 1
Experimental and standard “2θ” and “d” spacing.
Planes (hkl)
2 Theta (degree)
d-spacing values  d (Å)
JCPDS data card
Experiment
JCPDS
Experiment
2 2 0
24.572
24.580
3.62000
3.61967
3 1 1
28.899
28.900
3.08700
3.08687
3 3 1
38.269
38.260
2.35000
2.34875
4 2 2
43.254
43.260
2.09000
2.08982Figure 5
XRD pattern ofHgxCr2-xS4(x=0.4) thin film.


## 3.2.2. EDAX Analysis

Table2 shows the composition  of element in  HgxCr2-xS4 thin films measured by EDAX analysis. The composition was found to be homogeneous and stoichiometric. Figure 6 shows EDAX spectrum of HgxCr2-xS4 compound. The composition of element in thin films and in initial reactant in chemical bath is similar.Table 2
Elemental composition ofHgxCr2-xS4 (x=0.4) thin film deposited by chemical bath method.
Element
Weight%
Atomic%
Hg
77.69
19.35
Cr
3.28
30.31
S
19.03
50.34Figure 6
EDAX spectrum of aHgxCr2-xS4(x=0.4) compound.


## 4. Conclusion

In conclusion,HgxCr2-xS4(x=0.4) thin films can be deposited by simple chemical bath deposition technique. The films are sensitive to different growth parameters. The grown material is cubic crystal structure. The composition was found homogenous and stoichiometric. The optimum conditions are found to obtain HgxCr2-xS4 films with maximum thickness.



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