CdSe Thin Film Preparation by Unipolar Current Pulse Electrodeposition Technique
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CdSe Thin Film Preparation by Unipolar Current Pulse Electrodeposition Technique Kiran Jain1, N.Karar and H.Chandra Electronic Materials Division, National Physical Laboratory Dr. K.S.Krishnan Marg, New Delhi, India-110012 ABSTRACT CdSe thin films were prepared using unipolar current pulse electrodeposition technique on fluorine doped SnO2 coated glass plates. The electrodeposition bath consisted of aqueous solution including CdSO4, SeO2 and pH was adjusted using H2SO4. Growth of CdSe was accomplished under wide range of variables like current density, pulse on and off time in order to elucidate the effect on crystalline structure, grain size and optical properties. A low current density and increased off time favored grain orientation and crystallinity. Increased current density and on time favored grain size reduction. INTRODUCTION CdSe is one of the widely studied II-VI semiconductor materials because of its promising applications as photoanode in photoelectrochemical cell [1]. The conversion of solar light to electrical energy efficiency of 16.7 % has already been realized. More recently nano crystalline semiconductor have attracted extensive interest due to their significant potential applications in various areas since the wavelength of the emitted light may be changed merely by changing the nanocrystallite size. A large variety of methods are employed for synthesizing nanocrystalline powders and thin films. Compared to other processing routes the electrochemical deposition has the advantages in terms of simplicity, relative cost, purity and large-scale production capability. In electrodeposition, in contrast to chemical routes, one can easily control the reaction rate of the system by working at a given current density or easily select the magnitude of the driving force for the reaction by the adjustment of electrode potential. Recently pulse electrodeposition process has emerged as one of efficient processing techniques for the deposition of nanocrystalline materials [2,3]. Pulse electrodeposition is one of the novel processing technique utilizing the advantages of high current density. A high cathodic overpotential usually caused by high current density, speeds up the nucleation process and results in fine grained deposit. Even though pulse electrodeposition technique have been utilized to prepare nanocrystalline metallic films, but the use of this technique for the fabrication of semiconductor deposition is still scarce. Recently, our group have used rectangular current pulse to grow CdTe and observed that stoichiometric CdTe thin films can be prepared under optimum conditions. [4,5]. In an earlier investrigation Murali et al. [6] have prepared CdSe film by pulse electrodeposition, in which on time was 1 sec and off time was varied from 1 to 15 sec, a reduction in grain size was reported on decrease in duty cycle. In the present work, we report the electrodeposition of CdSe thin films using unipolar current pulse electrodeposition technique having shorter pulse periods. CdSe films were grown unde
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