Optimization of the formation of bismuth telluride thin film by using ECALE

Abstract

The formative optimization of Bi 2Te 3 VA–VIA group compound thin film by using electrochemical atomic layer epitaxy (ECALE) was reported. Cyclic voltammograms were used to analyze electrochemical aspects of tellurium and bismuth. The voltammetric analysis of underpotential shift demonstrates that the first Te UPD on Bi-covered Au and Bi UPD on Te-covered Au fit UPD dynamics mechanism. Using the integrated Faradaic charges of anodic stripping currents, the UPD region of the first Bi UPD on Te-covered Au and Te UPD on Bi-covered Au were determined. An optimized deposition program was developed to form 200 cycles deposits. X-ray diffraction indicated the deposits were Bi 2Te 3 compound. EDX quantitative analysis gave a 2:3 stoichiometric ratio of Bi to Te, which is consistent with the XRD result. The surface morphology was determined by field emission scanning electron microscope (FESEM). It showed that the deposits consist of 30–100 nm crystallites and are conformal with the Au substrate, which suggested an epitaxial growth mechanism for Bi 2Te 3 thin films.