ElectroDeposicion De In

Electrodeposition of indium onto Mo/Cu for the deposition of Cu(In,Ga)Se2 thin films
R.C. Valderramaa, M. Miranda-Hernándeza, 1, P.J. Sebastiana, , , A.L. Ocampob
a | Centro de Investigación en Energía, Universidad Nacional Autómona de México, Temixco 62580, Morelos, Mexico |
b | Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria 04510, Mexico, D.F., Mexico |Received 30 July 2007; revised 17 November 2007; Accepted 19 November 2007. Available online 4 December 2007.
Abstract
A study of the electrodeposition and the oxidation process of indium on Mo/Cu substrates from a bath containing 0.008 M InCl3, 0.7 M LiCl at pH 3 is described in this work. The voltamperometric study showed a reduction process which corresponds to the conversion of In3+ to In0and an oxidation process which takes place in different steps. Utilizing the chronoamperometric technique the total efficiency of process, the number of monolayers, the film thickness and the diffusion coefficient were evaluated. The analysis of current transients, using theoretical growth model, showed that the electrodeposition of indium adjusts to a three-dimensional growth under instantaneousnucleation limited by diffusion. The kinetic growth parameters were evaluated through a non-linear fit. The films were characterized by X-ray diffraction and scanning electron microscopy techniques. These studies showed that the films were of crystalline in nature with compact and uniform surface, even for the film with a deposition time of 1 min.
Keywords: Indium; Electrodeposition; Nucleationand growth; CuIn alloy; Cu(In,Ga)Se2

Article Outline
1. Introduction
2. Experimental details
3. Results and discussion
3.1. Voltamperometric study
3.2. Chronoamperometric study
3.3. Physical characterization

4. Conclusions
Acknowledgements
References

1. Introduction

Despite a number of publications that refer to the electrodeposition (ED) of CuInSe2 (CIS) thin films, only a fewreports have been published on a systematic study of the growth and incorporation of the elements during the ED of the films. Mishra and Rajeshwar [1] were the first to publish the CIS film formation mechanism, concluding that CIS films grow on an initial deposit of Cu2−xSe. Another important contribution was made by Thouin et al. [2] and [3], who suggested that the stoichiometry of the CIS filmis controlled by the ratio between selenium and copper fluxes ([Se4+]/[Cu2+]) on the electrode which in turn controls the insertion of In by the Kroger's mechanism between excess Se in the copper selenide (CuxSey) film and In ions. The CIS film is precursor to the quaternary phase Cu(In,Ga)Se2 (CIGS) and for a long time the formation of CIGS by ED in one step was not well understood, as it was verydifficult to incorporate the Ga into the standard range of potential in which the CIS electrodeposition was commonly carried out. Bhattacharya et al. [4] were the first to demonstrate the Ga incorporation by ED, but at very low levels. To get the device quality films it was necessary to supplement the films by physical vapor deposition of Cu, In, and Ga up to 50% of the total film thickness.Calixto et al. [5] reported that bath concentration affects the composition of electrodeposited CIGS films. A bath ratio of [Se4+]/[Cu2+] equals to 1.75 was required for maintaining the suitable deposit levels of Se and Cu, while [In3+] could be adjusted to control the deposits of In and Ga.

With the purpose of knowing more about the film formation mechanism of Cu(In,Ga)Se2 obtained through the EDtechnique, a systematic study on the growth and incorporation of the elements using the electrocrystallization theories reported in the literature [6], [7], [8], [9] and [10] is suggested. It is proposed to study the nucleation and growth process of: In, Ga, Cu–Se, In–Ga–Se and Cu–In–Ga–Se. In this paper, the electrodeposition of In is presented. The study was carried out not only because of our...