| 研究実績の概要 |
In the past fiscal year studies of chalcogenide van der Waals (vdW) superlattices were continued. The main results are as follows.
-For vdW interfacial phase-change memory we demonstrated that (1) the Kooi-like structure is obtained not as a result of Ge in-diffusion (as previously believed) but due to atomic plane reversal in the first SbTe bilayer. (2) reconfiguration of vdW gaps in GeTe-Sb2Te3 superlattices that involves Sb atoms leads to a semiconductor-metal transition that can be responsible for the experimentally observed switching. (3) Reconfiguration of vdW gaps was confirmed experimentally using e-beam exposure as acting stimulus.
-The bulk band structures of a variety of artificially constructed vdW chalcogenide heterostructures IVTe/ V2VI3 (IV: C, Si, Ge, Sn, Pb; V: As, Sb, Bi; VI: S, Se, Te) were examined and it was found that a Dirac cone is formed when tensile stress is applied to a GeTe/Sb2Te3 heterostructure, and the band gap can be controlled by tuning the stress.
-Sb2Te3/MoTe2 heterostructures/superlattices were studied and stress was shown to result in the overall metallic structure.
-Sb2Te3 slabs cut along different crystal orientations were studied and it was shown that while the slab obtained at vdW gaps did possess Dirac cones (as expected), slabs obtained by cutting the structure along generic directions underwent surface reconstruction resulting in the loss of Dirac cones.
-Strain was demonstrated to be an efficient tool to tune electronic structure of few-monolayer GaN, both free-standing and interacting with MoS2 through vdW forces.
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