Pulsed laser deposition of highly oriented Sb2Te3 and GeTe-Sb2Te3 thin films on amorphous SiOx layers at low temperatures

Abstract

Sb₂Te₃ is researched as phase change alloy, topological insulator as well as thermoelectric material. The layered structure of the material leads to orientation dependent properties of Sb₂Te₃ thin films. For the deposition of thin films with the desired microstructure precise control of the growth parameters is crucial. In this work, 30 nm Sb₂Te₃ thin films were grown onto native SiO_x/Si substrates by pulsed laser deposition at low temperatures. To determine the best conditions for fast deposition of highly c-axis oriented Sb₂Te₃ layers a systematic parameter study was conducted. For this purpose, the microstructure of the grown thin films was thoroughly investigated by sereval X-ray diffraction methods and transmission electron microscopy. The deposition of strongly {00l} fiber textured Sb₂Te₃ layers with a high crystal quality was achieved by application of thin Sb₂Te₃ seed layer deposition combined with thin film growth at low temperatures without annealing. Evidence is found that thin film growth occurs in absence of a passivation layer at the substrate-layer interface. In contrast, ex situ heated Sb₂Te₃ layer exhibits a more misoriented and defective microstructure. Lastly, the optimized parameters were used to successfully grow superlattice thin films which consist of alternating c-axis oriented Sb₂Te₃ and Ge-Sb-Te layers. Overall, the results of this study pave the way for the growth of highly oriented Sb₂Te₃ as well as Sb₂Te₃-based multilayered thin films on amorphous surfaces as needed for thermally unstable substrates used in flexible electronics.