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Electrical and switching property of amorphous defect chalcopyrite ZnGa2Te4 thin films prepared by thermal evaporation technique has been studied. The elemental chemical compositions of the prepared bulk as well as the as-deposited film were determined by means of energy dispersive X-ray spectrometry. X-ray diffraction pattern revealed that the powder compound is polycrystalline and the as-deposited and the annealed films at t ≤ 548 K have the amorphous phase, while that the annealed at t ≥ 573 K are polycrystalline with a single phase of a defect chalcopyrite structure similar to that of the synthesized material. The great advantage of this material is the capability to appear in two different phases, the amorphous and the crystalline phases, with rather different electrical properties. Both dynamic and static I-V characteristics and the switching phenomenon at 601 nm are investigated. The threshold switching mechanism was explained by a thermal model of switching, i.e., joule heating with an electrically conducting channel. ZnGa2Te4 is good candidate in phase change memory device. [ABSTRACT FROM AUTHOR]

GeSbTe (GST) is a technologically important phase-change material for data storage, where the fast reversible phase transition between crystalline and amorphous states is used for recording information. The encoding is achieved by the large contrast in physical properties between the two states. Ge vacancies (V) and Sb antisite atoms (Sb) are primary point defects in crystalline GST. The effect of V and Sb on the atomic arrangements in amorphous GST is unknown, which, however, has significant effects on the performance of GST. In this work, by means of ab initio molecular dynamics calculations, the atomic arrangements in amorphous ideal and defective GST have been investigated. The results show that the amorphous structure of GST with Sb ( St-GST) or with V ( V-GST) has the same cubic framework and close chemical ordering to ideal GST, and hence similar fast reversible phase transition behavior is expected in the defective phases. Furthermore, the presence of Sb or V in the crystalline phase will result in much more Ge atoms in a tetrahedral geometry as well as in a fourfold octahedral environment in the amorphous state. Especially in V-GST, around 36 % Ge atoms occupy a fourfold octahedral geometry. As fourfold octahedral Ge atoms can enhance the large contrast in physical properties between the crystalline and amorphous phases, introducing Ge vacancies would be an efficient way to improve the performance of GST phase-change materials. [ABSTRACT FROM AUTHOR]