Effect of annealing on structural, optical and electrical properties of CdS thin films grown by ILGAR

Abstract

CdS thin films were deposited by ILGAR(ion lay gas reaction) method. The effect of annealing temperature under N₂ atmosphere on the structural, chemical, topographical development and optical and electrical properties of CdS thin films was investigated by XRD, SEM, XPS, UV-VIS and two-probe technique. It is found that the cubicphase of as-deposited CdS film transforms to hexagonal phase with a perfected orientation along (002) plane at 300 °C. The band gap decreases with increasing annealing temperature until 300 °C, which is consistent with the grain growth. The fall of dark and light resistivitiy is obvious with increasing annealing temperature, corresponding to the continuous grain growth and deviation of stoichiometry at higher temperature. The smooth and uniform surface of as-deposited films becomes rougher through thermal treatment, which is related to grain growth and sublimation of CdS at a higher annealing temperature.

Keywords

CdS thin films / ILGAR / annealing

References

[1] Salata 0 V, Dobsib P J, Hull P J. Preparation of Nanoparticulate CdS Films Suitable for Opto-Electronic Device Applications. Thin Solid Films, 1996, 288: 235-238.

[2] Guillen C, Martinez M A, Hereero J. CuInSe₂ Thin Films Obtained by a Novel Electrodeposition and Sputtering Combined Method. Vacuum, 2000, 58: 594-601.

[3] Toyama T. Interfacial Mixed-Crystal Layer in CdS/CdTe Heterostructure Elucidated by Electroreflectance Spectroscopy. Solar Energy Materials and Solar Cell, 1997, 49: 213-218.

[4] Kumar Anil, Jai Arvind Kumar. Photophysics and Photochemistry of Colloidal CdS-TiO₂ Coupled Semiconductors-Phtocatalytic Oxidation of Indole. Journal of Molecular Catalysis, 2001, 165: 265-273.

[5] Oliva A I. Quintana. Comparison of Properties of CdS Thin Films Grown by Two Techniques. Applied Surface Science, 2003, 205: 56-64.

[6] Belbruno. Mechanistic Details for Dimethylcadmium Decomposition and CdS Production by MOCVD. Journal of Crystal Growth, 1997, 182: 321-328.

[7] Enriquez Pantoja Joel, Mathew. Influence of the Thickness on Structural, Optical and Electrical Properties of Chemical Bath Deposited CdS Thin Films. Solar Energy Materials and Solar Cell, 2003, 76: 313-322.

[8] Pence S, Bates C W, Varner L. Morphological Features in Films of CdS Prepared by Chemical Spray Pyrolysis. Materials Letters, 1995, 23: 195-201.

[9] Sankapal B R, Mane R S, Lokhande C D. Deposition of CdS Thin Films by the Successive Ionic Layer Adsorption and Reaction (SIIAR) Method. Materials Research Bulletin, 2000, 35: 177-184.

[10] Cordoncillo E, Escribano P, Monros G. The Preparation of CdS Particles in Silica Glasses by a Sol-Gel Method. Journal of Solid State Chemistry, 1995, 118: 1-5.

[11] Nel J M, Gaigher H L, Auret F D. Microstructures of Electrodeposited CdS layers. Thin Solid Films, 2003, 436: 186-195.

[12] Bar M, Fischer Ch-H, Lux-Steiner M C. ILGAR-Technology: ILGAR Thin Film Technology Extended to Metal Oxides. Solar Energy Materials & Solar Cells, 2001, 67: 121-127.

[13] MoEller J, Fischer Ch-H, Muffer H J, KoEnenkamp R. IL-GAR-A Novel Thin-Film Technology for Sulfides. Thin Solid Films, 2000, 361: 113-117.

[14] Metin H, Esen R. Annealing Studies on CBD Grown CdS Thin Films. J. Crystal Growth, 2003, 258: 141-148.

[15] Bon R Ramirez. Band-gap Shift in CdS: Phase Transition From Cubic to Hexagonal on Thermal Annealing. Vacuum, 1995, 46: 1083-1085.

[16] Narayanan K L, Vijayakumar K P, Nair K G M, Thampi N S. Structural and Optical Properties of CdS Thin Films. J. Mater. & i., 1997, 32: 4837-4841.

[17] Zinoviev K V, Zelaya-Angel 0. Influence of Low Temperature Thermal Annealing on the Darkresistivity of Chemical Bath Deposited CdS Films. Materials Chemistry and Physics, 2001, 70: 100-102.