Growth Kinetics of Bi-In-Se ternary alloys monitored in-situ via Spectroscopic Ellipsometry

By coupling in-situ spectroscopic ellipsometry (SE) into a molecular-beam epitaxy growth chamber, growth parameters of ternary compounds can be immediately measured during the entire growth cycle of a sample. Several heterostructures of (BixIn1-x)2Se3, with Bi compositions ranging from 0% to 100% were grown and characterized by X-ray reflectivity, X-ray photoemission spectroscopy and Rutherford backscattering. SE spectra were fitted to these heterostructures by representing the dielectric functions with Kramers-Kronig-consistent oscillators. As a result, composition-dependent dielectric functions of (BixIn1-x)2Se3 were parameterized that enabled the creation of a material file that determines the composition of an unknown (BixIn1-x)2Se3 film. Both, the composition and thickness of a (BixIn1-x)2Se3 film can be obtained immediately at any stage of the growth cycle by using this method. Further investigations tested the model for universality among MBE growth systems, which found that the model was transferable between systems. Most importantly, the generalized model allows to monitor sticking and desorption coefficients as well as temperature-dependent composition changes in the (BixIn1-x)2Se3 thin films and heterostructures in-operando.