Molecular beam epitaxial growth of EuTe/SnTe strained superlattices

In this work, we report on the growth of EuTe/SnTe superlattices (SLs) on BaF2(111) substrates by molecular beam epitaxy. Reflection high energy electron diffraction allowed to find the growth modes at each growth stage, while high resolution X-ray diffraction (HRXRD) was employed to evaluate the heterostructure crystalline quality. In four subsequent stages, we studied the growth of SnTe buffer layers, the growth of EuTe on SnTe, the growth of SnTe on EuTe, and finally undertook the SLs growth. EuTe grows in the Stranski–Krastanov mode on SnTe, with a critical thickness for island formation that increases for lower temperatures and higher Te/Eu flux ratios. On the other hand, SnTe starts growing in the Volmer–Weber mode on EuTe, with evolution to layer-by-layer growth after the SnTe islands merge, which occurs faster for higher temperatures. As confirmed by HRXRD ω/2θω/2θ scans measured along the (2 2 2) SL Bragg peak, high structural quality EuTe/SnTe SLs were grown with EuTe layers below the critical thickness for island formation and SnTe layers thick enough for layer-by-layer growth to be restored. The X-ray spectra were fitted with those calculated using dynamical diffraction theory in order to find accurately the individual layer thicknesses and strain status.