In-situ monitoring of the growth of Bi2 Te2 and Sb2 Te3 films and Bi2 Te3-Sb2 Te3 superlattice using spectroscopic ellipsometry

Abstract

In this work, we present in-situ monitoring of the growth of bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thin films as well as Bi2 Te3-Sb2Te3 superlattice using a spectroscopic ellipsometer (SE). Bi2Te3 and Sb2 Te3 films were grown by metalorganic chemical vapor deposition (MOCVD) at 350 C. A44-wavelength ellipsometer with spectral range from 404 nm to 740 nm was used in this work. The optical constants of Bi2 Te3 and Sb2Te3 at growth temperature were determined by fitting a model to the extracted in-situ SE data of optically thick Bi2 Te3 and Sb2 Te3 films. Compared to the optical constants of Bi2 Te3 and Sb2 Te3 at room temperature, significant temperature dependence was observed. Using their optical constants at growth temperature, the in-situ growth of Bi2 Te3 and Sb2 Te3 thin films were modeled and excellent fit between the experimental data and data generated from the best-fit model was obtained. In-situ growth of different Bi2 Te3-Sb2 Te3 superlattices was also monitored and modeled. The growth of Bi2 Te3 and Sb2 Te3 layers can be seen clearly in in-situ SE data. Modeling of in-situ superlattice growth shows perfect superlattice growth with an abrupt interface between the two constituent films.