Textured Sb2Te3 films and GeTe/Sb2Te3 superlattices grown on amorphous substrates by molecular beam epitaxy

Abstract

The realization of textured films of 2-dimensionally (2D) bonded materials on amorphous substrates is important for the integration of this material class with silicon based technology. Here, we demonstrate the successful growth by molecular beam epitaxy of textured Sb2Te3 films and GeTe/Sb2Te3 superlattices on two types of amorphous substrates: carbon and SiO2. X-ray diffraction measurements reveal that the out-of-plane alignment of grains in the layers has a mosaic spread with a full width half maximum of 2.8°. We show that a good texture on SiO2 is only obtained for an appropriate surface preparation, which can be performed by ex situ exposure to Ar+ ions or by in situ exposure to an electron beam. X-ray photoelectron spectroscopy reveals that this surface preparation procedure results in reduced oxygen content. Finally, it is observed that film delamination can occur when a capping layer is deposited on top of a superlattice with a good texture. This is attributed to the stress in the capping layer and can be prevented by using optimized deposition conditions of the capping layer. The obtained results are also relevant to the growth of other 2D materials on amorphous substrates.

Impact of Stoichiometry on the Structure of van der Waals Layered GeTe/Sb2Te3 Superlattices Used in Interfacial Phase‐Change Memory (iPCM) Devices

“…Hence, no preferred in‐plane orientation of the crystallites is present. This is a consequence of deposition on an amorphous Si substrate, which does not impose a particular orientation of the crystallites in the Sb 2 Te 3 buffer layer and thus in the SL. The pole figures of the two SLs strongly differ in the ψ range [0°–10°].…”

“…The thickness of one QL (Te–Sb–Te–Sb–Te–vdW gap) is 1.015 nm . VdW epitaxy allows the growth of Sb 2 Te 3 with [001] out‐of‐plane growth axis on various substrates . The thickness of the Sb 2 Te 3 layer in a SL is chosen to contain m QLs with m an integer varying typically between 1 and 8.…”

Phase‐Change Superlattice Materials toward Low Power Consumption and High Density Data Storage: Microscopic Picture, Working Principles, and Optimization

“…The grain size of the GST‐SL by this way can be larger than 200 nm. Recently, Boschker et al have demonstrated that GST‐SL can be also fabricated on amorphous SiO 2 and amorphous carbons by MBE . It is very attractive to prepare GST‐SL or other vdW heterostructures on amorphous substrates because it is favorable to integrate the superlattice with traditional CMOS technology .…”

Growth of crystalline phase change materials by physical deposition methods

“…This layer serves as a template for the subsequent growth of the SL. Experiments have shown that the quality of the texture depends sensitively on the substrate preparation, at least for the growth on oxides [58]. Exposure to Ar + ions or an electron beam prior to the deposition improved the out-of-plane texture significantly [58,59].…”

“…Experiments have shown that the quality of the texture depends sensitively on the substrate preparation, at least for the growth on oxides [58]. Exposure to Ar + ions or an electron beam prior to the deposition improved the out-of-plane texture significantly [58,59]. In Figure 10, the surface morphology and crystal orientation of SL grown on SiO 2 surfaces with different kind of surface preparations are shown.…”