Structural investigation of GeSb₆Te₁₀ and GeBi₆Te₁₀ intermetallic compounds in the chalcogenide homologous series

Abstract

The crystal structures of GeSb(6)Te(10) and GeBi(6)Te(10) were scrutinized using an X-ray powder diffraction method, which revealed that these compounds crystallize in trigonally distorted cubic close-packed structures with a 51-layer period (R3m). Each layer consists of a triangular atomic net; Te atoms occupy their own specific layers, whereas Ge, Sb and Bi atoms are located in the other layers. In these pseudobinary compounds, random atomic occupations of Ge and Sb/Bi are observed and the layers form two kinds of elemental structural blocks by their successive stacking along the c axis. These compounds can be presumed to be isostructural. It is known that the chemical formula of the chalcogenide compounds with the homologous structures found in these pseudobinary systems can be written as (GeTe)(n)(Sb(2)Te(3))(m) or (GeTe)(n)(Bi(2)Te(3))(m) (n, m: integer); the GeSb(6)Te(10) and GeBi(6)Te(10) investigated in this study, which correspond to the case in which n = 1 and m = 3, naturally have 3 x l = 51-layer structures according to a formation rule l = 2n + 5m commonly found in the compounds of these chalcogenide systems (l represents the number of layers in the basic structural unit). Calculations based on the density functional theory revealed that these materials are compound semiconductors with very narrow band gaps.

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

“…In fact, as early as 1998, Karpinsky et al and Shelimova et al have proposed that the stable (GeTe) n –(Sb 2 Te 3 ) m compounds exhibit Ge/Sb intermixing in cation planes. Also, several articles confirmed such model of Ge/Sb intermixing in the GST blocks . As mentioned above, recent experiments demonstrated again that the intermixing is a general phenomenon in GST‐SLs fabricated by MBE, PLD, and sputtering.…”

Observation of a highly spin-polarized topological surface state in GeBi2Te4

“…12 A homologous series of pseudobinary compounds, nGeTemBi 2 Te 3 , was intensively studied in terms of its thermoelectric, galvanomagnetic, and thermomagnetic properties. [27][28][29][30] Among them, GeBi 2 Te 4 was theoretically proposed as a member of the 3D TIs. [31][32][33] It was experimentally verified to be a 3D TI possessing a single TSS by an angleresolved photoemission spectroscopy (ARPES) experiment.…”

Effects of stoichiometry on the transport properties of crystalline phase-change materials

“…6), it becomes increasingly difficult to obtain a cubic phase experimentally. It has been found that Sb 2 Te 3 -rich compounds exhibit stable hexagonal structures with very elongated primitive cells: for instance, GeSb 6 Te 10 displays a 51-layer periodicity along the c direction4041. No rocksalt-like structure has been reported in these experimental works.…”