J Fluoresc (2016) 26:459–469 DOI 10.1007/s10895-015-1732-9

ORIGINAL ARTICLE

Studies on Structural, Morphological and Optical Properties of Chemically Deposited CdS1-xSex Thin Films Soumya R. Deo 1 & Ajaya K. Singh 2 & Lata Deshmukh 1 & Narendra Pratap Singh 3 & Mariya P. Aleksandrova 4

Received: 14 October 2015 / Accepted: 26 November 2015 / Published online: 3 December 2015 # Springer Science+Business Media New York 2015

Abstract The thin films of CdS1-xSex were successfully deposited over glass substrates by chemical bath deposition technique. Cadmium acetate, thiourea and sodium selenosulfate were used as source materials for Cd2+, S2− and Se2− ions, while 2-mercaptoethanol was used as capping agent. The various deposition conditions such as precursor concentration, deposition temperature, pH and deposition time were optimized for the deposition of CdS1-xSex thin films of good quality and the films were annealed at 200° and 300 °C. The structural, morphological, chemical and optical properties were examined by various characterization techniques and discussed in detail. The optical band gap of CdS1-xSex thin film samples were estimated and found in the range from 2.11 to 1.79 eV for as-deposited and annealed thin films. Keywords Cadmium sulfoselenide . 2-ME . XRD . SEM . Annealing . Optical properties

* Ajaya K. Singh [email protected] 1

Dr. Ira Nimdeokar P.G. & Research Centre for Chemistry, Department of Chemistry, Hislop College, Nagpur -440002, India

2

Department of Chemistry, Govt. V. Y. T. P. G. Autonomous College, Durg 491001, India

3

Department of Chemistry, Udai Pratap Autonomous PG College, Varanasi, UP, India

4

Department of Microelectronics, Technical University of Sofia, 8 St.Kliment Ohridski Boulevard, 1756 Sofia, Bulgaria

Introduction Due to the rapid growth in the world economy, energy problems have attracted considerable attention during the past decades [1]. For providing alternative energy sources, the global scientific community has been targeted their researches toward other renewable energy sources such as wind, solar, nuclear, hydraulic and biomass energy [2]. Solar energy conversion into electricity is fast becoming essential source of renewable energy and being an alternative to traditional fossil fuel-based energy sources [3]. To produce chemical energy that can be stored from solar energy is an important aim for the development of clean energy. To develop an efficient solar energy conversion device, the chief requirement is that it should have a band gap whose energy closely corresponds to the maximum light intensity in the visible spectrum to utilize the solar spectrum efficiently. Group II-VI semiconductor materials have received considerable attention because of their wide scientific and technological applications. Ternary semiconductor materials provide a great possibility for tailoring and tuning their structural, morphological and optical properties as per requirements and protrude themselves as prominent semiconductor materials for their applications in the field of device applications [4]. Cadmium sulfoselenide (CdSSe, belongs to II-VI group) is ternary semiconductor material with a tunable band gap from 1.73 to 2.44 eV. It is an important wide band gap semiconductor material due to its potential applications such as solar cells, solar control applications, thin film transistors, photoconductors and other opto-electronic devices [5]. The thin films of CdSSe have been prepared by various techniques such as molecular beam epitaxy [6], laser ablation technique [7], chemical vapor deposition

460 Table 1 Compositional quantities for CdS1-xSex thin films

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Composition ‘x’

Solution of Cd(CH3COO)2

Solution of CS(NH2)2

Solution of Na2SeSO3

0.9 0.5

10 10

12.5 7.5

2.5 7.5

0.1

10

2.5

12.5

[8], successive ionic layer adsorption and reaction (SILAR) [9], electrodeposition [10, 11], chemical bath deposition [12], etc. Among these techniques, chemical bath deposition (CBD) has been attracted much attention because it is a simple and economical technique, which involves low deposition temperature and allows easy deposition on large scale surfaces for industrial applications. In CBD, the deposition of thin film proceeds simultaneously with the controlled precipitation of metal and chalcogenide ions. Thin film deposition is actually a deposition of compound rather than a codeposition of separate elements [13]. In the present investigations, an attempt is made to deposit the thin films of CdSSe by CBD technique over the glass substrates. The as-prepared thin films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infra-red (FTIR) spectroscopy and optical measurement techniques; and their results are thoroughly discussed in this paper.

Fig. 1 XRD patterns for CdS 1-xSe x thin films: a CdS 0.9 Se0.1; b CdS0.5Se0.5; and c CdS0.1Se0.9

pH of reaction bath

Deposition time (h)

11.0

2

Experimental Details Materials Cadmium acetate dihydrate [Cd(CH3COO)2.2H2O], thiourea [CS(NH2) 2], sodium sulfite (Na2SO 3), cadmium chloride (CdCl2), elemental selenium powder (99.9 %), 2-mercaptoethanol (2-ME) and triethanolamine (TEA) were obtained from MERCK (Mumbai, India) and 30 % ammonia solution was purchased from S. D. fine-chem Limited (Mumbai, India). All the reagents used were of AR grade and were used as received without any further purification. All the precursor solutions were prepared with deionized water. Commercially available microscopic glass slides (Blue Star, Polar Industrial Corporation, Mumbai) with the dimensions of 75 mm × 25 mm × 2 mm were used as glass substrates. These substrates were boiled in chromic acid for 2 h, washed with deionized water followed by degreasing with acetone and finally ultrasonicated with deionized water for 15 min, before being used.

Fig. 2 XRD patterns for CdS0.5Se0.5 thin films annealed at a 200° and b 300 °C

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Preparation of CdSSe Thin Films In the deposition of CdSSe thin films over glass substrates, cadmium acetate, thiourea and sodium selenosulfate (which was obtained by heating sodium sulfite and elemental selenium powder at stoichiometric amount with 100 mL of deionized water at 90 °C for 5 h followed by the filtration of excess selenium) were used as Cd2+, S2− and Se2− ion sources, respectively. For the deposition of CdSSe thin films, the reaction mixture was obtained by mixing 10 mL of 1 M cadmium acetate solution with 5 mL of triethanolamine (TEA) in a 100 mL volume beaker with constant stirring by the means of magnetic stirrer for 3–4 min. After stirring the mixture, 15 mL of 30 % ammonia solution was slowly added. When the mixture became clear and transparent equal volume of 1 M thiourea and 1 M sodium selenosulfate were added with vigorous stirring. To obtain CdS1-xSex thin film samples, the volume of metal ion precursor solution was kept fixed (i.e. 10 mL), whereas, the volumes of chalcogenide (thiourea and sodium selenosulfate) precursor solutions were varied. Then, 2 ml of 0.01 M of 2-ME and 2 mL of cadmium chloride were added as capping agent and flux, respectively. The whole reaction mixture was stirred for 6–8 min. The precleaned glass substrates were then immersed vertically in the beaker containing reaction bath and the whole system was kept in a thermostatic water bath at a constant temperature of 343 K (70 °C) for 2 h. The final pH of the reaction bath was 11. Table 2

After the deposition, the thin films of CdS1-xSex were taken out from the beaker and washed with deionized water for several times to remove loosely bounded CdSSe particles to the deposited films and dried in air at room temperature. The thin films of CdSSe (with the composition S:Se::0.5:0.5) were annealed in air at 200 °C and 300 °C for 10 min; and cooled at room temperature and characterized by various techniques. The precursor solutions used for the preparation of CdS1-xSex thin film samples are given in Table 1. Characterization of CdS1-xSex Thin Films The structural, morphological, compositional and optical properties of ternary alloy CdS1-xSex thin films were characterized. X-ray diffraction patterns of the films were recorded by PANalytical X’Pert PRO X-ray diffractometer using CuKα (λ = 1.5406 Å) within the 2θ range from 20° to 80°. The surface morphology and chemical composition analysis were done by JEOL model JSM-6390LV scanning electron microscope and JEOL model JED-2300 energy dispersive spectrometer, respectively. To confirm the presence of 2-ME as capping agent, the FTIR study was performed by Perkin Elmer Spectrum RX-I FTIR spectrophotometer. Optical absorption investigation of these thin films was done by VARIAN Cary 50 Bio UV-Visible spectrophotometer and the spectra were recorded in the wavelength range from 450 to 800 nm at room temperature. The photoluminescence studies were done by

Structural parameters for CdS1-xSex thin films

Material

2θ (deg.) hkl Depo. Temp. (K)

Lattice Spacing Grain Size Disloc. Density Micro Strain Lattice ‘d’ (Å) ‘D’ (nm) δ × 1016 lines/m2 ε × 10−3 Parameter ‘c’

CdS0.9Se0.1

343

CdS0.1Se0.9

CdS0.5Se0.5

CdS0.5Se0.5 (annealed at 200 °C)

CdS0.5Se0.5 (annealed at 300 °C)

26.88 29.97 43.94 52.21 26.10 43.16 5065 26.61 29.46 43.68

002(H) 101(H) 110(H) 103(H) 002(H) 110(H) 112(H) 002(H) 101(H) 110(H)

3.31 2.97 2.05 1.75 3.41 2.09 1.80 3.34 3.03 2.07

51.44 25.07 26.61 43.43 51.44 24.80 26.10 43.16 50.65

201(H) 100(H) 002(H) 110(H) 112(H) 100(H) 002(H) 110(H) 112(H)

1.77 3.55 3.34 2.08 1.77 3.58 3.41 2.09 1.80

15.33

4.25

2.37

6.63

12.38

6.52

2.92

6.82

8.99

12.37

4.02

6.69

9.33

11.48

3.87

6.69

10.39

9.26

3.48

6.82

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Fig. 3 SEM images for CdS1xSex thin films: a CdS0.9Se0.1; b CdS0.5Se0.5; c CdS0.1Se0.9; d CdS0.5Se0.5 annealed at 200 °C; and e CdS0.5Se0.5 annealed at 300 °C

JOBIN YVON Fluorolog-3-11 Spectroflourimeter at room temperature.

Results and Discussions Growth Mechanism The deposition process of CdS1-xSex thin films is based on the slow release of precursor ions i.e. Cd2+, S2− and Se2− ions. In the presence of Cd2+ ions in the chemical bath, CdS12+ 2− xSex will be formed if the ionic product of Cd , S 2− and Se exceeds the solubility product of CdSSe [14]. The release of metal ions in the medium can be controlled by using complexing agents. In the present case, triethanolamine (TEA) was used as complexing agent. The chemical reactions for the deposition of CdS1-xSex proceeds as follow [13]:

The slow release of Cd2+ ions is achieved by the dissociation e quilib riu m of a complex species [Cd(TEA)]2+. ½CdðTEAÞ2þ ⇄Cd2þ þ TEA The sulfide (S2−) and selenide (Se2−) ions are formed due to the hydrolysis of thiourea and sodium selenosulfate, respectively, in alkaline medium according to the following reactions: CSðNH2 Þ2 þ OH → SH þ CH2 N2 þ H2 O SH þ OH → S2 þ H2 O Similarly, Na2 SeSO3 þ OH → Na2 SO4 þ HSe HSe þ OH → Se2 þ H2 O

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Moreover, the hydrolysis of ammonia in water give OH- ions as: NH3 þ H2 O ⇄ NH4 þ þOH When ammonia is added to Cd2+ salt solution, the solubility product of Cd(OH)2 is exceeded and Cd(OH)2 precipitated.

463

of the medium. In the present case, the above mentioned preparative conditions, i.e. concentration of precursors [Cd2+ ], [S 2− ] and [Se 2− ] = 1 M; deposition temperature = 343 K (70 °C); deposition time = 2 h; and pH = 11, were optimized. XRD Studies

Cd2þ þ 2OH → CdðOHÞ2 While, excess of ammonia dissolves the Cd(OH)2 precipitate and form the complex cadmium tetramine ions, [Cd(NH3)4]2+.  2þ Cd2þ þ 4NH3 ⇄ CdðNH3 Þ4 And finally, the deposition of CdS1-xSex thin film takes place according to the following chemical reaction: Cd2þ þ ð1  xÞS2 þ xSe2 → CdS1x Sex þ waste product The availability of the nucleation centre over the substrate is essential requirement for the deposition of film. Generally, these centres are formed due to the adsorption of metalhydroxo species over the substrate surface. An initial layer of metal chalcogenide film is formed, when this hydroxo group would be substituted by the sulfide and selenide ions. The surface, on which the deposition of thin film undergoes via the condensation of the metal sulfide and selenide ions, acts as a catalytic surface [15]. Further, the rate of deposition of thin film is also affected by the concentration of precursor solutions, deposition temperature, deposition time, and the pH Fig. 4 EDS pattern for CdS0.5Se0.5 thin film

The x-ray diffraction patterns for CdS1-xSex thin films are given in Fig. 1(a)-(c). XRD patterns revealed that the deposited thin films have stable hexagonal structure. Several reflections of hexagonal phase are indexed and the following reflections have been identified: [002, 101, 110, 103, 201, 112]. All of these orientations can be regarded to the hexagonal phase of CdS1-xSex alloy thin films. The intensity of [002] peak was found dominant in all the patterns. A slight shift in the peak position with an increment in the composition ‘x’ explains the formation of CdS1-xSex ternary alloy system of II-VI group. In the present case, the deposition of CdS1-xSex thin film was proceeds by ion-by-ion process, which causes the formation of hexagonal phase. The patterns exhibit that the CdS1-xSex thin films possessed the mixed crystallites of CdS and CdSe, i.e. these thin films are the mixture of hexagonal CdS and CdSe crystallites. Fig. 2(a) and (b) displays the XRD patterns for CdS0.5Se0.5 thin films deposited at 70 °C and annealed at 200° and 300 °C. Both of the patterns also suggests the hexagonal phase for these annealed samples. After annealing at 200° and 300 °C, both XRD patterns had shown more intense and sharper peaks due to the better crystallinity.

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Fig. 5 FTIR spectrum for 2-mercaptoethanol capped CdS0.5Se0.5 thin film

The average particle size has been calculated by DebyeScherrer’s relation:

SEM and EDS Studies

D ¼ Kλ=βcosθ

SEM micrographs of CdS1-xSex thin films deposited over glass substrates via chemical bath deposition (CBD) technique are shown in Fig. 3(a)-(c). The samples had a homogeneous and smooth background without any cracks or pinholes and well covered to the surface of glass substrate and the large particles were grown over them with spherical shape and embedded on the surface. It can be expected that these particles were formed in the solution and adsorbed on the surface during the growth of the films. Figure 3(d) and (e) display the SEM images of CdS0.5Se0.5 thin films annealed at 200 °C and

where, D is the average particle size, β is full width at half maximum (FWHM), θ is the diffraction angle, K is a constant [commonly known as shape factor = 0.94 (for spherical shaped grains)] and λ is the wavelength of the x-ray radiation. The calculated average particle size for all CdS1-xSex thin film samples are given in Table 2. The dislocation density ‘δ’ was evaluated from Williamson and Smallman’s formula: δ ¼ 1=D2 lines=m2 The micro strain ‘ε’ for each sample was obtained by using the relation:

Table 3 FTIR band positions of 2-ME capped CdS0.5Se0.5 thin films with their assignments Assignments

Band position of 2-ME capped Cd0.5Zn0.5Se thin films (in cm−1)

OH- group Symmetric and asymmetric stretching in CH2 vibrations of alkyl chain -CH2 bending -CH2 wagging -CH2 rocking C-O stretching C-S stretching

3304 2875, 2919

ε ¼ βcosθ=4 The lattice spacing ‘d’ was calculated by the Bragg’s formula for all the CdS1-xSex thin film samples by, d ¼ λ=2sinθ Since, all the samples of CdS1-xSex thin films possessed hexagonal phase, the lattice parameter ‘c’ for all the samples were evaluated by using the following relations [16]: c ¼ ðλ=2sinθÞ l

1429 1384 1155 1003 630

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Fig. 6 (a) UV-Visible absorption spectra for CdS1-xSex thin films: a CdS0.9Se0.1; b CdS0.5Se0.5; and c CdS0.1Se0.9 (b) UV-Visible absorption spectra for CdS0.Se0.5 thin films: a CdS0.5Se0.5 annealed at 200 °C; and b CdS0.5Se0.5 annealed at 300 °C

300 °C. Both of the samples exhibit the effect of annealing on their surface morphology. It was observed that the texture of both of the samples became densified and the nanoparticles convert into bigger clusters due to agglomeration or fusion of large number of nanoparticles. The distribution of particles became more ordered and vacant spaces became lesser than before. On annealing, the recrystallization process densified the film and the particles transformed into

the nest like structures which can be clearly seen in the images. Figure 4 shows a representative EDS pattern for CdS0.5Se0.5 thin film sample prepared by CBD technique at 70 °C. The pattern confirms the presence of cadmium, sulfur and selenium as constituting elements in the sample. In CdS 0.5Se0.5 thin film, the average atomic percentage of Cd:S:Se was 48.87:26.46:24.67.

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Fig. 7 Plot of (αhν)2 v/s hν of CdS1-xSex thin films: a CdS0.9Se0.1; b CdS0.5Se0.5; c CdS0.1Se0.9; d CdS0.5Se0.5 annealed at 200 °C; and e CdS0.5Se0.5 annealed at 300 °C

FTIR Studies In order to study the adsorption of 2-mercaptoethanol as capping agent, on the surface of as-deposited CdS0.5Se0.5 thin film sample, Fourier transform infrared (FTIR) spectroscopy was

performed. Fig 5 displays the FTIR spectrum for 2-ME capped CdS0.5Se0.5 thin film and the representative spectrum were recorded on the dried powder of CdS0.5Se0.5 thin film in the KBr pellet. All the data regarding to the spectrum is summarized in the Table 3. From Fig. 5, it can be seen that the –CH2 symmetric

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Table 4 Estimated band gap values for CdS1-xSex (as-deposited and annealed at 200° and 300 °C) thin film samples Material

Band Gap (eV)

CdS0.9Se0.1 CdS0.1Se0.9 CdS0.5Se0.5 CdS0.5Se0.5 (annealed at 200 °C)

2.11 1.79 2.01 1.95

CdS0.5Se0.5 (annealed at 300 °C)

1.88

and asymmetric vibrations of 2-ME bound CdS0.5Se0.5 nanoparticles appeared at 2875 and 2919 cm−1, respectively. A distinct peak at 2555 cm−1 was found disappeared in the spectrum, which can be attributed to the cleavage of S-H bond and the formation of a new S-CdS0.5Se0.5 bond. This phenomenon gives the strong evidence to the fact that 2-ME has been assembled on the CdS0.5Se0.5 nanoparticle surface. The singlets at 1429, 1384 and 1155 cm−1 can be explained as –CH2 scissoring, −CH2 wagging and –CH2 twisting vibrations, whereas the singlets at 1003 and 630 cm−1 belongs to C-O and C-S stretching, respectively. A broad band around 3304 cm−1 can be assigned to the O-H stretching vibration. These observations conclude that the capping of CdS0.5Se0.5 nanoparticle surface by 2-ME is caused by the contribution of the deprotonated mercapto groups to the particle surfaces [17].

450–800 nm at room temperature. Figure 6 shows the absorption spectra for all the CdS1-xSex thin film samples. From the spectra, red shift was observed in the absorption edge with increase in Se content in CdS0.5Se0.5 thin films. The two thin film samples of CdS0.5Se0.5, which were annealed at 200° and 300 °C, also showed red shift in comparison with unannealed CdS0.5Se0.5 thin film sample. It can be explained as due to annealing, an increased interatomic spacing decreases the potential seen by the electrons in the material, results in reduction of the band gap energy [18]. The optical band gap energy for all as-deposited and annealed CdS1-xSex thin films were determined according to the Tauc’s equation as given below [19–21]: αhν ¼ A hν  Eg


1=2

where, A is a constant, α is the absorption coefficient, hν is the photon energy and Eg is band gap energy. Figure 7 shows the plots of (αhν) 2 versus hν for the as-deposited and annealed samples of CdS1-xSex thin films. The extrapolation of the straight line in the graph to (αhν)2 = 0 gives the value of the band gap energy for different CdS1-xSex samples. The band gap energies for CdS1-xSex thin films were calculated and found to be in the range from 2.11 to 1.79 eV as given in Table 4. Photoluminescence Studies

Optical Studies UV-Visible Absorption Studies The optical absorbance of CdS1-xSex thin films was measured on UV-Visible spectrophotometer in the wavelength range of Fig. 8 Photoluminescence spectra for CdS1-xSex thin films: a CdS0.5Se0.5 annealed at 300 °C; b CdS0.5Se0.5 annealed at 200 °C; and e as-deposited CdS0.5Se0.5 thin film

Photoluminescence is a nondestructive and contactless method of investigating the optical properties of material. Basically, it is a charge transfer process associated with the combination of electron from conduction band and the holes of valence bands [18, 22]. Figure 8 shows

Cd(SSe):CdCl2, Sm CdS1-xSex

(b)

(c)

CdS1-xSex

(a)

Chemical Bath Deposition

Si-CdSSe

(b)

6

CdS1-xSex

Thermal evaporation

5

(a)

Screen printing followed CdS0.5Se0.5 by sintering

CdSxSe1-x

4

3 400 °C

Thin films, grown on glass substrates

Thin films, grown on Si (111) substrate

Hexagonal phase with (002) direction, an enhancement in PL spectrum was observed due to compositional disorder. polycrystalline nature with wurtzite structure; high absorption coefficient; activation energy comes out about 0.13 eV.

Crystalline wurtzite nanocrystals with [0001] direction; exhibited red shiftwith increase of shell thickness; PL emission decresed with increasing shell thickness. Pure wurtzite structure with [010] direction; uniform and smooth surface; thickness of 30 nm, narrow near band edge emission peak at 580 nm. Cubic structure; nature of fluorescence quenching dependent on the surface functional groups.

Remarks

60 °C

Cd(CH3COO)2, CS(NH2)2, Na2SeSO3, Sm(NO3)3 Cd(CH3COO)2, CS(NH2)2, Na2SeSO3

70 °C

80 ± 5 °C

[27]

[26]

[4]

[25]

[24]

[23]

[9]

Ref.

[28] Thin films, grown over polycrystalline nature with [100] orientation; glass substrates surface morphology and grain size changed with increasing Se concentration; band gap varied from 2.5 to 1.7 eV. [29] Thin films, grown over ball type structures; have both cubic and hexagonal glass substrates. phases; increase in CdSe concentration decreases the bandgap. Thin films, grown over hexagonal structure with [002] plane; highly absorptive Present work glass substrates and have direct bandtransition; spherical shaped nanoparticles converted to bigger cluster with nest like structures during annealing; band gap varied from 2.11 to 1.79 eV.

polycrystalline nature; hexagonal structure 700°, 750° Nanoribbons, grown with (0001) direction; sharp band gap and 800 °C over Si substrates emission shifts from coated with 30 nm 542 to 668 nm. Au film 1080 °C Core/shell nanowires, Core was cubic crystalline Si with [111] and shell grown over Si wafers was hexagonal CdSSe with [0002] direction; have strong light emission in the visible range; have uniform radial size with diameter of 50 nm.

CdCl2, CS(NH2)2, Na2SeSO3

CdS and CdSe powders (99.995 %)

CdSe powder (99.99 %), annealed in 10 % H2S and 90 % Ar atmosphere

Core-shell nanowires

Form

Not mentioned nanobelts grown over sapphire substrates 130 °C Quantum dots

500–800 °C

Depo. Temp.

High purity CdS, CdSe, 120 °C anhy. CdCl2, ethylene glycol

Se powder (99.8 %), Na2SO3 (97 %), CdCl2 (99 %) High purity (99.999 %) CdS and CdSe powder

CdSeS alloy

2

Microwave irradiated aqueous phase method Laser ablation

CdSSe nanobelts Evaporated elemental sources of Cd, S and Se

(b)

Zn powder (99.99 %), CdS powder (99.995 %) and CdSSe (99.99 %)

ZnO-CdSSe core-shell nanowires

Chemical Vapor Deposition

Precursors

(a)

1

Material

A comparative study on previously reported methods/techniques and present work

S. No. Method/Technique

Table 5

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the photoluminescence spectra for CdS0.5Se0.5 as-deposited and annealed (at 200 ° and 300 °C) thin films at room temperature with an excitation wavelength of 325 nm. From Fig. 8, the enhanced photoluminescence intensity was observed for the film annealed at 300 °C. It can be attributed as the reduction in the defect density due to better crystallinity during annealing [23]. Such type of enhancement in the emission intensity is due to increase in betterment of crystallinity and change in the band gap with respect to annealing temperature. These as-deposited and annealed thin films represent themselves as a highly efficient and continuously tunable by merely varying the size of nanocrystallites.

Significance of the Work Ternary II-IV-VI semiconducting materials are found to have band gaps in the range of interest for solar energy conversion, photoconduction and photoelectrochemical devices. Various workers have been reported the preparation of CdS1-xSex nanoparticles in various forms by using different preparation techniques which are summarized in the Table 5. The present work seeks to determine the factors affecting the structural, morphological and optical properties in a positive way that have an impact on the use of these materials in various scientific and technological applications.

469 Acknowledgments The authors gratefully acknowledge SAIF, Panjab University, Chandigarh, for XRD and FTIR analysis, SAIF-STIC, Kochi, Kerala, for SEM and EDS measurements, Department of Chemistry, Govt. V.Y.T.P.G. Autonomous College, Durg, C.G., for UV-Visible optical absorption studies and SAIF, Indian Institute of Technology, Chennai, for PL studies.

References: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

Conclusion In the present work, the significance of chemical bath deposition technique and the structural, morphological and optical properties of CdS1-xSex thin films are discussed. All the samples of CdS1-xSex thin films (as-deposited and annealed) showed hexagonal structure. Annealing of thin film samples increased the particle size and decreased the dislocation density. The optical studies revealed that the films are highly absorptive and have direct band transition. SEM studies exhibited the surface morphology for all the CdS1-xSex thin film samples, which were found more ordered and densified due to recrystallization during annealing and nest like structures of particles were also observed. EDS pattern confirmed the presence of cadmium, sulfur and selenium as constituting elements of the material deposited. FTIR spectrum displayed the presence of 2-mercaptoethanol as capping agent and revealed that it is a good capping agent. Hence, it can be concluded that chemical bath deposition is a suitable and convenient technique for the deposition of variety of metal chalcogenide and alloy thin films.

16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.

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