In Situ TEM Investigations on Thermoelectric Bi2Te3/Sb2Te3 Multilayers

In this work, the impact of heat treatment on the real structure of Bi2Te3/Sb2Te3 multilayers is investigated. The material was heated in situ in the transmission electron microscope (TEM) and ex situ inside a furnace after preparing these layers with the so‐called nanoalloying deposition technique via molecular beam epitaxy (MBE) equipment. The samples were prepared as a lamella for TEM studies using focused ion beam technique. EDX elemental mapping and high angle annular dark field mode‐STEM were performed to monitor changes of the morphology and interdiffusion phenomena after heating up to 250 °C. A grain growth started during heating and the chemical layer structure was smeared out partly but remained in several grains and was found to be adjusted parallel to a major lattice plane in a crystallite. High resolution TEM shows polysynthetic twinning in a number of crystals. The impact of ex situ and in situ (FIB lamella in TEM) heat treatment (250 °C) on the real structure of Bi2Te3/Sb2Te3 multilayers prepared with MBE is investigated. A grain growth started during heating and the chemical layer structure was smeared out partly but remained in several grains and was found to be adjusted parallel to a major lattice plane in a crystallite.