Formation of Bi2S3 thin films on Au(111) by electrochemical atomic layer epitaxy:: kinetics of structural changes in the initial monolayers

The kinetics and growth mechanism of the first and second monolayers of Bi2S3 by electrochemical atomic layer epitaxy (ECALE) has been studied using voltammetry and chronoamperometry techniques. Scan rate dependent cyclic voltammetry experiments reveal that the peak current in the stripping of the S layer from a Bi modified Au(111) electrode is a linear function of a 2/3 power of the scan rate, v(2/)3. Similar behavior is observed for the deposition of Bi on to one atomic layer of an S modified Au(111) electrode. The dissolution of the Bi atomic layer from the S modified Au(111) electrode involves an initial Langmuir-type adsorption-desorption accompanied by a nucleation and two-dimensional (2-D) growth process. When Bi atomic layers are used as a first layer, the nucleation and 2-D growth process was observed for both deposition and stripping. Analysis of the reduced variables demonstrates that the stripping of S from Au(111)-Bi and stripping of Bi from Au(111)-S fit the progressive model. Our results suggest that the nucleation and 2-D growth mechanism is the dominant process in the formation of Bi2S3 atomic layers if Bi is used as the first layer in the ECALE method. (C) 2002 Elsevier Science B.V. All rights reserved.