Replacement of sulphur with selenium in antimony sulphide thin films

(1)

Replacement of sulphur with selenium in antimony sulphide thin films

ANU KURUVILLA^1,2 , MELDA FRANCIS^1,2, K S SUDHEER²and M LAKSHMI^1,*

1Department of Physics, Mercy College, University of Calicut, Palakkad 678006, India

2Department of Physics, Christ College, University of Calicut, Irinjalakkuda 680125, India

*Author for correspondence (lakshmisethumadhavan@gmail.com) MS received 15 July 2021; accepted 12 December 2021

Abstract. This study aims to determine the extent to which sulphur can be replaced with selenium in the Sb2S3

matrix. The relevance of this work is that this replacement reaction forms the underlying principle for the formation of the ternary compound AgSbSe₂from the binary compound Sb₂S₃. AgSbSe₂is a compound semiconductor belonging to the I-V-VI2group that has applications in photovoltaics. Even though there are numerous reports of heating multilayers of Sb₂S₃/Ag/Se or Sb₂S₃/Ag₂Se/Ag to produce AgSbSe₂, none of them have resulted in a pure ternary phase. This study explores the possibilities and limitations of the replacement of sulphur with selenium in antimony sulphide thin film. In this work, selenium is deposited on Sb2S3 layer and the resulting structure is annealed at 200°C. The replacement reaction was found to be incomplete at this temperature. The temperature of annealing could not be increased any further as the elemental selenium could not withstand higher temperatures. Hence, a protective layer of silver was coated on top of the selenium layer, and the temperature of annealing was increased to higher values. X-ray diffraction, scanning electron microscopy-energy dispersive X-ray and X-ray photoelectron spectroscopy were used to characterize the multilayer film.

Keywords. Antimony selenide; antimony sulphide; AgSbSe2; replacement reaction; XPS; sputtering.

1. Introduction

Metal chalcogenides (sulphides, selenides and tellurides) have important applications in photo-conducting cells, photovoltaic cells and other optoelectronic devices [1–5].

Among these chalcogenides, antimony sulphide (Sb₂S₃) is known for its high refractive index and well-defined quan- tum size effects [6]. This material with a bandgap of 1.78–2.5 eV and an absorption coefficient in the order of 10³cm^–1at a short wavelength serves as promising absorber material in the field of thin-film photovoltaics [7–9]. Of the various methods used for the preparation of antimony sulphide and selenide, chemical vapour deposition has proved to be cost-effective [10–13]. The chemical bath deposition technique is yet another method that can be carried out easily at low temperatures [14,15]. This technique is the least expensive and the most non-pollutant method that can be used for preparing thin films of a large surface area [16].

Chalcopyrite-structured compound semiconductor thin films of class I–III–VI₂(I–Cu, Ag; III–In, Ga, Al; VI–Se, S) are used as p-type absorber materials in high-efficiency solar cells [17–19]. By heating a Sb2S3/Ag stack with the Ag side in contact with a layer of Se thin film, Binduet al [19] reported the formation of AgSbSe₂ thin film.

Another group reported that heating a multilayer of

Sb₂S₃/Ag₂Se/Se/Ag can result in AgSbSe₂ [17]. Here the selenium vaporises during annealing and reacts with the stacked layer. A similar report discusses the annealing of stacked layers of Sb₂S₃/Ag/Se [20]. Though the replacement of sulphur with selenium from the Sb₂S₃ matrix is the underlying premise of all these approaches, none of these processes reports the pure ternary phase of AgSbSe₂. Based on these reports, attempts have been made to understand the possible extent of sulphur replacement with selenium in antimony sulphide thin film. To track the replacement response, the film was analysed structurally, morphologically and chemically.

2. Experimental

The chemical bath deposition method was used to deposit Sb₂S₃and Se thin films. The stacked Sb₂S₃/Se layer was air annealed at 150 and 200°C for about one and a half hours.

The temperature of annealing could not be increased further as selenium cannot withstand higher temperatures [21].

Hence, a layer of silver was deposited on the stacked structure of Sb₂S₃/Se through the sputtering process. This stacked multilayer could then be air annealed up to a https://doi.org/10.1007/s12034-021-02651-8

(2)

temperature of 400°C for 1 h. To track the replacement process of sulphur with selenium during the annealing process, the samples were analysed structurally, morphologically and chemically.

2.1 Antimony sulphide thin film

Antimony chloride and sodium thiosulphate were used as precursors to make antimony sulphide thin films. Solution of antimony chloride (0.5 M) was prepared in 10 ml ace- tone. Under steady stirring, 25 ml of a 1 M sodium thiosulphate solution was added to this solution. The resulting solution was made up to 100 ml by adding 65 ml of distilled water. Precooling the water and thiosulphate solution at 10°C before mixing was done to control the reaction rate [22]. Clean glass slides were placed vertically on the walls of the beaker containing this mixture. A thin film of orange- yellow Sb₂S₃ thin film was formed after 1-h deposition at room temperature. The substrates were taken out of the bath and thoroughly cleaned in distilled water. The films were reflective, smooth, and adhered consistently to the substrate.

2.2 Selenium thin films

By adding dilute acetic acid to a 0.01 M solution of Na₂SeSO₃, the pH of the solution was adjusted to 4.5 [19].

A cryostat was used to keep the temperature of the solution bath at 10°C. The deposition was carried out for 2 h on the appropriate substrate, yielding a homogenous thin selenium coating.

2.3 Silver thin films

A thin layer of silver was deposited using sputtering. Depo- sition parameters such as working pressure, RF sputtering power, time of deposition, and distance between the substrate and the target were optimized to achieve a uniform Ag layer.

Before deposition, a pressure of 10^–6mbar was attained inside the deposition chamber. Under a 20 sccm argon supply, sputtering was carried out for 3 min with a power of 30 W, at a working pressure of 7910^–3mbar. The distance between the target and the substrate was set at 7 cm.

The stacked structure Sb₂S₃/Se was annealed for one and half hour at 150 and 200°C. After coating silver on this stacked layer, further annealing up to 400°C for 1 h was carried out. X-ray diffraction (XRD) was used to characterize the structural properties of the material, while scanning electron microscopy (SEM) was used to examine the morphology. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray (EDAX) studies were used to characterize the chemical composition.

3. Result and discussion 3.1 Structural characterization

XRD patterns were recorded using Cu Kasource of Rigaku D Max X-ray diffractometer. Figure 1a shows the XRD spectrum of pristine Sb₂S₃ thin film. It suggests that the pristine sample is amorphous. Sb₂S₃samples were annealed at 100, 200 and 300°C for 1 h and were checked for crys- tallinity. It was found that the film annealed at 300˚C turned out to be polycrystalline and the XRD pattern is shown in figure 1b. It has an orthorhombic crystal structure with narrow peaks. Thed-values of these peaks obtained were in close agreement with the standard value (JCPDS-06-0474).

Selenium was coated onto this Sb2S3 thin film. Figure 2a depicts the amorphous nature of the selenised Sb₂S₃ film after one and a half hours of annealing at 150°C. Similar behaviour was observed when the sample was annealed at 200°C.

As shown in figure 2b, the Sb₂S₃/Se/Ag sample annealed at 250°C for 1 h revealed mixed phases of orthorhombic Sb₂S₃ (JCPDS-06-0474), orthorhombic Sb₂Se₃ (JCPDS-00-015-0861), monoclinic Se (JCPDS-00- 073-2087) and orthorhombic Ag₂Se (JCPDS-24-1041).

The elemental Se phase that was seen in this sample completely disappeared at 350°C (figure 2c). The peak at 28.79° is found to be a coinciding peak of both Sb₂S₃ and Sb2Se3. Annealing at 350°C has resulted in a new phase of cubic AgSbSe2 (JCPDS-89-3670). A typical peak of silver antimony selenide at 55.5° along with a merged peak at 31° was observed in this sample. A drastic change was observed when the sample was annealed at 400°C (figure 2d). Here the most significant phase was Ag₂O₃ (JCPDS-00-077-1829) and Ag₂O (ICDD-00-041-1104) along with a single peak of Sb₂O₃ (PDF#710365) at 13.26°. A small peak of Ag2Se was found to persist in this sample.

3.2 Surface morphology

The morphology of the samples was studied using JEOL Model JSM-6390LV Scanning Electron Microscope (SEM).

Figure 3a and b shows micrographs of pristine Sb₂S₃ and annealed samples at 300°C. The grains in both samples are homogeneous and uniform in appearance. Figure3c shows an SEM image of selenised Sb₂S₃annealed at 150°C. The spherical grains are evenly dispersed across the surface of the selenised film. The SEM image of Sb₂S₃/Se/Ag annealed at 350°C is also included in figure 3d. The film shows spherical grains distributed over the surface. Here particles are more densely packed and are evenly dispersed across the surface.

(3)

3.3 Chemical characterization

Elemental characterization of Sb₂S₃ thin film by EDAX analysis is illustrated in figure 4. The result shows the presence of Sb and S in the sample. The stoichiometry of the prepared sample is found to be around 2:3, as obtained from the data of atomic percentage. This result is as expected for Sb₂S₃ composition.

In the case of the selenised sample, the presence of Se was observed along with Sb and S. Due to the bilayer structure, EDAX analysis could not be used to determine the exact stoichiometry of the resulting compound and hence the spectrum is not included here. EDAX analysis of a series of samples annealed at various temperatures showed that the amount of Se decreased with annealing temperature. This justifies the fact that Se cannot withstand Figure 1. XRD patterns of Sb2S3thin film: (a) pristine and (b) annealed at 300°C.

Figure 2. XRD pattern of (a) selenised Sb₂S₃films annealed at 150°C for one and a half hours. Sb₂S₃/Se/Ag sample annealed at (b) 250°C, (c) 350°C and (d) 400°C for 1 h.

(4)

high temperatures. Hence, a protective layer of silver was given to this Sb₂S₃/Se stacked bilayer to minimize the evaporation of selenium and also to give provision for higher annealing temperatures for the completion of replacement of sulphur with selenium.

Table 1shows the elemental composition of the stacked sample Sb₂S₃/Se/Ag annealed at 250°C. Due to the

multilayer configuration, despite the detection of the presence of Sb, Se, S, and Ag in this annealed Sb₂S₃/Se/Ag structure, the EDAX data could not be used to determine the precise stoichiometry of the compound. Another useful information from the EDAX investigation is that complete replacement of sulphur with selenium is not possible from the sample matrix on annealing at 350°C. Se/S ratio in the sample annealed at 250°C was found to be around 17.2%

and it could only be increased to 37.48% on annealing at Figure 3. SEM image of (a) pristine Sb₂S₃film, (b) Sb₂S₃film annealed at 300°C, (c) selenised Sb₂S₃annealed at

150°C and (d) Sb2S3/Se/Ag annealed at 350°C.

Figure 4. EDAX analysis of Sb₂S₃thin film.

Table 1. Elemental composition of stacked Sb₂S₃/Se/Ag annealed at 250°C.

Element Line type Wt% Atomic %

Se L series 8.40 8.04

Ag L series 8.80 6.18

Sb L series 63.00 39.09

S K series 19.80 46.69

Total 100 100

(5)

350°C (table2). This indicates the removal of sulphur from the sample matrix following the replacement of sulphur with selenium. At an annealing temperature of 400°C, Se content also decreased to trace levels. These results were further verified using XPS analysis.

3.4 XPS analysis

XPS depth profiling was used to investigate the replacement reaction in detail. After consecutive etching of the thin film surface by argon sputtering, deeper layers of the sample were investigated using the depth-profiling mode. During each etching cycle, the sample was etched for a time interval of 40 s. The compound formation was studied using the binding energy spectrum obtained after two etch cycles of the sample surface.

The depth profiles of Sb and S in pristine Sb₂S₃thin film is shown in the inset of figure5a and b. The distribution of the elements was found to be uniform throughout the sample. Figure5a illustrates the presence of 3d_5/2and 3d_3/2 peaks after the two etch cycles of antimony sulphide thin film.

The sulphur binding energies of S 2p_3/2 and S 2p_1/2 of pristine samples were assigned to Sb₂S₃phase as in table3 (figure 5b). Thus, the XPS analysis of the pristine sample

revealed the formation of antimony trisulphide (table 3).

This result could not be confirmed through XRD as the pristine sample is amorphous.

The depth profile of antimony and sulphur in a selenised antimony sulphide thin film annealed at 150°C for one and a half hours is shown as the inset of figure 6a and b. This profile reveals a uniform distribution of antimony and sulphur. Figure6a shows two main binding energy peaks that correspond to 3d_5/2and 3d_3/2orbitals of Sb. Deconvolution of the first peak yields binding energy values of 528.22 and 529.65 eV, which match the standard value of 3d_5/2orbitals of Sb in Sb₂Se₃ and Sb₂S₃ (table 4). Similarly, deconvolution of the second peak yields 537.52 and 538.92 eV, which correspond to 3d_3/2 orbitals of Sb in Sb₂Se₃ and Sb₂S₃, respectively (table 4). Figure 6b depicts the deconvoluted sulphur binding energy peaks at 161.48 and 162.72 eV. This matches with the reported binding energy of the 2p_3/2and 2p_1/2sulphur orbitals in Sb₂S₃. The depth profile of Se in the inset of figure6c shows that selenium is present only up to two or three layers on the surface.

The deconvoluted surface signal shows binding energy values (figure 6c) corresponding to 3d5/2and 3d3/2doublet of elemental Se (54.96 and 55.80 eV) and 3d5/2orbitals of Sb₂Se₃(54.11 eV) [25,26]. Thus, XPS spectra of selenised Sb₂S₃ film reveal that Sb₂Se₃ formation is restricted to a few surface layers of the sample. The result suggests that sulphur replacement by selenium may be possible only at an annealing temperature greater than 150°C.

As selenium thin film could not withstand high temperatures [21], high-temperature annealing was carried out after coating a protective layer of silver over the Se layer.

The depth profile of Sb in the Sb₂S₃/Se/Ag stack annealed at 250°C (figure 7a) shows that the distribution of Sb is uniform throughout the film. Deconvolution of the two Sb peaks presents after two etch cycles of the sample resulted in two doublet peaks. The low intensity peaks at 528.34 and 537.66 eV are assigned to Sb2Se3[24]. The other two peaks Table 2. Elemental composition of stacked Sb2S3/Se/Ag

annealed at 350°C.

Element Line type Wt% Atomic %

Se L series 16.42 15.74

Ag L series 16.85 11.82

Sb L series 48.94 30.42

S K series 17.8 42.02

Total 100 100

Figure 5. XPS spectrum of (a) antimony and (b) sulphur in pristine Sb2S3film.

(6)

are assigned to Sb₂S₃. This result shows that only partial replacement of sulphur with Se is occurring at this annealing temperature.

Though the depth profile showed uniform distribution of silver in the sample (figure 7b), the formation of AgSbSe2

was not detected at this temperature and this might be because a temperature of 250°C is not adequate for the formation of this ternary compound. Though the binding energy values of Ag 3d_5/2 and Ag 3d_3/2 are in close agreement with that of elemental Ag, it was assigned to Ag₂Se. This is because the peaks corresponding to

elemental Ag was not present in the XRD spectrum of this sample. The binding energy values from XPS analysis are tabulated in table5. Depth profile in the inset of figure7c shows that sulphur is present throughout the sample annealed at 250°C. Deconvolution of this binding energy graph leads to two peaks corresponding to sulphur binding energies of 2p_3/2and 2p_1/2orbitals of Sb₂S₃, at 161.69 and 162.85 eV (table5). The above sulphur 2p overlap with Se 3p peaks (at 160.57 and 166.12 eV; (figure7c) [20]. Apart from this, the characteristic 3d orbital binding energy of Se can be easily interpreted (figure7d). The deconvolution of Table 3. Binding energy values of pristine Sb2S3.

Element Binding energy values (eV) Standard value (eV) Peak identified

Sb First peak 529.88 529.7 [23] 3d5/2of Sb2S3

Second peak 539.28 539.1 [23] 3d3/2of Sb2S3

S First peak 161.43 161.2 [23] 2P3/2of Sb2S3

Second peak 162.60 162.3 [23] 2P1/2of Sb2S3

Figure 6. XPS spectrum of (a) antimony, (b) sulphur and (c) selenium in selenised Sb2S3film annealed at 150°C.

(7)

Se 3d peak gives binding energy values of 53.99 and 54.86 eV (table 5). This corresponds to 3d_5/2 and 3d_3/2of Ag₂Se.

These binding energy values also have correspondence with the binding energy values of elemental Se.

The depth profile of Sb₂S₃/Se/Ag thin film annealed at 350°C showed a uniform presence of antimony, silver and selenium throughout the sample (figure 8a, b and d).

Spectra of binding energy in the range of 525–545 eV showed two prominent peaks of Sb_5/2and Sb_3/2(figure8a).

Deconvolution of these peaks suggests the existence of Sb2S3phase along with a new binding energy doublet peak at 530.31 and 539.68 eV (table 6). This suggests the formation of a ternary compound of silver antimony selenide at 350°C. In the case of silver, the two binding energy peaks of Ag 3d_5/2and Ag 3d_3/2 were deconvoluted into two sets of Table 4. Binding energy values of selenised Sb2S3.

Element Binding energy values (eV) Standard value (eV) Peak identified

Sb First peak 528.22 528.47 [24] 3d5/2of Sb2Se3

529.65 529.7 [23] 3d5/2of Sb2S3

Second peak 537.52 537.87 [24] 3d3/2of Sb2Se3

538.92 539.1 [23] 3d3/2of Sb2S3

S First peak 161.48 161.2 [23] 2P3/2of Sb2S3

Second peak 162.72 162.3 [23] 2P1/2of Sb2S3

Se First line 54.11 54.22 [25] 3d_5/2of Sb₂Se₃

54.96 54.90 [26] 3d5/2of Se

55.80 55.7 [26] 3d_3/2of Se

Figure 7. XPS spectrum of (a) antimony, (b) silver, (c) sulphur and (d) selenium in the multilayer of Sb₂S₃/Se/Ag annealed at 250°C.

(8)

doublets peaks (figure 8b). One doublet is referred to Ag₂Se, while the other doublet is assigned to the ternary phase of AgSbSe₂ (table 6). The solid-state reaction of sequentially deposited Se and Ag is well established [27].

In the small binding energy window of 52–56 eV of selenium, deconvolution was not possible due to the possibility of the existence of 3 different doublets corresponding to Ag₂Se, Sb₂Se₃and AgSbSe₂, as suggested by

the XRD spectrum in figure 2c. A better extent of replacement of sulphur with selenium is found to take place at this annealing temperature and it is evident from the decrease in signal strength in the binding energy range of sulphur, while signal strength in the binding energy range of selenium is maintained (figure8c and d). The depth profile of multilayer of Sb2S3/Se/Ag annealed at 400°C further shows that antimony is still uniformly present throughout Table 5. Binding energy values of Sb, Ag and Se in Sb2S3/Se/Ag annealed at 250°C.

Element Binding energy (eV) Standard value (eV) Peak identified

Sb 528.34 528.47 [24] 3d5/2of Sb2Se3

529.91 529.7 [23] 3d5/2of Sb2S3

537.66 537.87 [24] 3d3/2of Sb2Se3

539.17 539.1 [23] 3d3/2of Sb2S3

Ag 368.28 367.8 [27] 3d5/2of Ag2Se

374.28 373.8 [27] 3d3/2of Ag2Se

S 161.69 161.2 [24] 2p_3/2of Sb₂S₃

162.85 162.3 [24] 2p1/2of Sb2S3

Se 53.99 53.30 [27] 3d_5/2of Ag₂Se

54.86 54.2 [27] 3d3/2of Ag2Se

Figure 8. XPS spectrum of (a) antimony, (b) silver, (c) sulphur and (d) selenium in Sb2S3/Se/Ag annealed at 350°C.

(9)

the sample, but the binding energy has slightly shifted to a single value of 529.60 and 538.95 eV, which is characteristic of oxide formation (figure9a). A similar result was also suggested in the XRD analysis of this sample. Thus, both the analysis confirms the formation of Sb₂O₃ and the dis- appearance of Sb₂S₃at 400°C. With this in the background, the binding energy values obtained for Sb can be assigned to Sb2O3(table7). It is interesting to note that the silver in the samples annealed at 400°C shows the presence of Ag binding energy corresponding to silver oxide (figure 9b).

Moreover, the depth profile of sulphur and selenium from figure9c and d reveals that these elements were almost lost from the sample matrix at 400°C. The slight presence of selenium signal may justify the presence of a minute quantity of silver selenide as observed in XRD spectrum (figure2d).

From this detailed XPS study, it can be concluded that an annealing temperature of 350°C is optimum for the replacement reaction resulting in the formation of a ternary compound of AgSbSe₂, but the presence of binary phases Table 6. Binding energy values of Sb and Ag in Sb2S3/Se/Ag annealed at 350°C.

Elements Binding energy (eV) Standard value (eV) Peak identified

Sb 529.92 529.7 [23] 3d5/2of Sb2S3

530.31 Not available 3d5/2of AgSbSe2

539.24 539.1 [23] 3d3/2of Sb2S3

539.68 Not available 3d3/2of AgSbSe2

Ag 367.55 Not available 3d5/2of AgSbSe2

368.08 367.8 [27] 3d5/2of Ag2Se

373.55 Not available 3d_3/2of AgSbSe₂

374.082 373.8 [27] 3d3/2of Ag2Se

Figure 9. XPS spectrum of (a) antimony, (b) silver, (c) sulphur and (d) selenium in Sb2S3/Se/Ag annealed at 400°C.

(10)

cannot be avoided at this temperature. On increasing the annealing temperature to 400°C, it is found that binary impurity phases of metal oxides are the major products.

4. Conclusion

Pristine Sb2S3thin film prepared by chemical method turns crystalline when annealed at 300°C. Incorporation of selenium on to Sb₂S₃thin film through the process of bilayer annealing was found to be unsuccessful. In this attempt to selenise Sb₂S₃film, it was found that at 150°C, selenium does not diffuse into the Sb₂S₃matrix to effectively replace sulphur. The Sb₂S₃/Se/Ag stack annealed at 350°C resulted in the formation of the ternary phase of AgSbSe₂. At this annealing temperature, though there is a significant replacement of sulphur with selenium it does not result in the pure phase of AgSbSe₂. Further increase in annealing temperature above 350°C is not recommended, as it increases the risk of oxidation of antimony and silver. This study has investigated the extent of the possibility of replacing sulphur with selenium in the Sb₂S₃matrix by the process of multilayer annealing. In this study, the various stages involved in the formation of the AgSbSe2film was successfully traced. The solid-state replacement reaction of sulphur with selenium is found to be incapable of producing a pure ternary phase of AgSbSe₂. Hence, an alternate method of heating the stacked layers of Sb₂Se₃and Ag is suggested for the ternary compound formation.

Acknowledgements

We acknowledge the financial support provided by UGC through the minor project 1600-MRP/14-15/KLCA021/

UGC-SWRO to carry out this study. We also acknowledge DST-FIST (grant number SR/FST/College-237/2014(C)) for providing financial support for developing the laboratory facilities for carrying out the research. We express sincere gratitude to Dr Sadasivan Shaji and Dr Bindu K, Facultad de Ingenierıá Mecańica y Elećtrica, Universidad Autońoma de Nuevo Leoń, Mexico, for helping with X-ray photoelectron spectroscopy analysis. Acknowledgement is also extended to STIC, CUSAT, Cochin, for the analytical facilities SEM, EDS and XRD.

References

[1] Petkov K, Todorov R, Kozhuharova D, Tichy L, Cernoskova E and Ewen P J S 2004J. Mater. Sci.39961

[2] Versavel M Y and Haber J A 2007Thin Solid Films515 7171

[3] Rajpure K Y and Bhosale C H 2000J. Phys. Chem. Solids61 561

[4] Aousgi F and Kanzari M 2011Energy Procedia10313 [5] Maghraoui-Meherzi H, Ben Nasr T, Kamoun N and

Dachraoui M 2011C. R. Chimie14471

[6] Salem A M and Selim M S 2001J. Phys. D: Appl. Phys.34 12

[7] Messina S, Nair M T S and Nair P K 2007Thin Solid Films 5155777

[8] Ben Nasr T, Maghraoui-Meherzi H, Ben Abdallah H and Bennaceur R 2011Phys. B: Condens. Matter406287 [9] Zhou Y, Leng M, Xia Z, Zhong J, Song H, Liu Xet al2014

Adv. Energy Mater.41301846

[10] Escorcia-Garcı´a J, Becerra D, Nair M T S and Nair P K 2014 Thin Solid Films56928

[11] Mane R S, Sankapal B R and Lokhande C D 1999Thin Solid Films35329

[12] Rajpure K Y and Bhosale C H 2002Mater. Chem. Phys.736 [13] Lokhande C D, Sankapal B R, Mane R S, Pathan H M,

Muller M, Giersig Met al2002Appl. Surf. Sci.1931 [14] Ezema F I, Ekwealor A B C, Asogwa P U, Ugwuoke P E,

Chigbo C and Osuji R U 2007Turk. J. Phys.31205 [15] Krishnan B, Arato A, Cardenas E, Das Roy T K and Castillo

G A 2008Appl. Surf. Sci.2543200

[16] Hamam M, EL-Gendy Y A, Selim M S, Teleb N H and Salem A M 2009Chalcogenide Lett.6359

[17] Garza J G, Shaji S, Rodriguez A C, Das Roy T K and Krishnan B 2011Appl. Surf. Sci.25710834

[18] Madelung O 1992 Semiconductors other than group IV elements and III–V compounds(Data in Science and Tech- nology), 1st edn. (Berlin: Springer)

[19] Bindu K, Campos J, Nair M T S, Sanchez A and Nair P K 2005Semicond. Sci. Technol.20496

[20] Gonza´lez J O, Shaji S, Avellaneda D, Castillo A G, DasRoy T K and Krishnan B 2013Mater. Res. Bull.481939 [21] Bindu K, Lakshmi M, Bini S, Sudha Kartha C,

Vijayakumar K P, Abe T et al 2002 Semicond. Sci.

Technol. 17 270

[22] Garza J G, Shaji S, Arato A M, Perez-Tijerina E, Rodriguez A C, Das Roy T Ket al2009Mater. Res. Soc. Symp. Proc.

1165M08-25

[23] Xiao K, Xu Q-Z, Ye K-H, Liu Z-Q, Fu L-M, Li N, Chen Y-B et al2013ECS Solid State Lett.2P51

Table 7. Binding energy values of Sb in Sb2S3/Se/Ag annealed at 400°C.

Element Binding energy (eV) Standard value (eV) Peak identified

Sb 529.60 529.90 [28] 3d5/2of Sb2O3

538.95 539.50 [29] 3d3/2of Sb2O3

Ag 367.49 367.7 [30] 3d5/2of Ag2O

373.48 373.9 [31] 3d3/2of Ag2O

(11)

[24] Tian Y, Sun Z, Zhao Y, Tan T, Liu H and Chen Z 2018 J. Nanomater. Article ID 4273945 https://doi.org/10.1155/

2018/4273945

[25] Kamruzzaman M, Liu C, Farid Ul Islam A K M and Zapien J A 2017Semiconductors511615

[26] Zhang J-Y, Lv L, Tian Y, Li Z, Ao X, Lan Yet al2017ACS Appl. Mater. Interfaces933833

[27] Mohanty B C, Malar P, Osipowicz T, Murty B S, Varma S and Kasiviswanathan S 2009Surf. Interface Anal.41170

[28] Morgan W E, Stec W J and Van Wazer J R 1973 Inorg.

Chem.12953

[29] Izquierdo R, Sacher E and Yelon A 1989Appl. Surf. Sci.40 175

[30] Kaushik V K 1991J. Electron Spectrosc. Relat. Phenom.56 273

[31] Tjeng L H, Meinders M B J, Van Elp J, Ghijsen J, Sawatzky G A and Johns R L 1990 Phys. Rev. B 41 3190