Analysis of carrier parameters and bandgap of electroplated Bi₂Te₃ films by infrared spectroscopic ellipsometry

Abstract

Polycrystalline thin films have been grown on gold substrates by electrodeposition, leading to different film compositions. In particular, our conditions allow growing smooth and shiny surface films in a thickness range of nanometers to micrometers. In this article, electroplated layers were analysed by InfraRed Spectroscopic ellipsometry. The dielectric functions have been obtained from ellipsometry analyses using the Drude and Tauc‐Lorentz models. We attributed the scattering distribution of the mobility with the carrier concentration to the presence of grain boundaries in the films. The energy bandgap appears to be constant whatever the carrier concentration. This result can be interpreted by bandgap shrinkage that occurs simultaneously with bandgap widening. These results were supported by additional Hall Effect Measurements. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth Mechanism during the Early Stages of electrodeposition of Bismuth telluride films

“…Infrared ex situ analyses allow accessing to electronic properties e.g. highlight of band gap balance between shrinkage and broadening effects of this narrow bandgap semiconductor [37,38]. Due to the absorption peak energy located at near infrared, the visible dielectric functions show a monotonous trend in both n(l) and k(l) spectra with no strong dependence on stoichiometry [18].…”

Electrodeposition of Bi2Te3 films and micro‐pillar arrays on p‐Si(100) wafers

“…In recent years, electrodeposition of functional materials on silicon wafers has been studied by several groups 9–11, because electrochemical process is cost‐efficient and easy to operate. Some studies show that Bi 2 Te 3 films or nanowires can be electrodeposited on metal substrates from Bi 3+ and HTeO acidic solution 12–21, which provides an effective method to fabricate on‐chip thermoelectric devices 20. The electrodeposition reaction of Bi 2 Te 3 can be expressed in Eq.…”