Growth optimization and structural characterization of Bi ₂ Se ₃ /CdSe/Bi ₂ Se ₃ multilayer films

Abstract

Abstract The growth conditions for Bi 2 Se 3 /CdSe/Bi 2 Se 3 heterostructures grown by molecular beam epitaxy were investigated. To achieve flat interfaces suitable for topological interface states, the effects of substrate temperature and Se/Bi vapor pressure ratio were systematically examined. The CdSe layers on Bi 2 Se 3 exhibited smooth surfaces with root-mean-square roughness below 1 nm when grown at temperatures ≤275 °C. For the Bi 2 Se 3 layers deposited on CdSe, surface flatness improved significantly under Se/Bi ratios ≥1000. Based on these findings, a seven-period Bi 2 Se 3 (5 nm)/CdSe(15 nm) multilayer film was fabricated at 150 °C and Se/Bi = 1200. X-ray diffraction confirmed c -axis orientation and in-plane alignment, while atomic force microscopy and reflection high-energy electron diffraction measurements revealed smooth morphology and high crystallinity throughout the multilayer structure.