Phase Stability and Anisotropic Sublimation of Cubic Ge–Sb–Te Alloy Observed by In Situ Transmission Electron Microscopy

Abstract

Phase stability and anisotropic sublimation dynamics of the cubic Ge−Sb−Te alloy have been investigated by in situ transmission electron microscopy (TEM). The starting point of the phase-transition study is an epitaxially aligned Ge 1 Sb 2 Te 4 grain on a Si(111) substrate. Upon in situ heating, the cubic phase remains stable up to the sublimation point without a transition to the thermodynamically stable trigonal crystal structure which is attributed to Si diffusion into the Ge 1 Sb 2 Te 4 grain. The sublimation process is made visible with atomic resolution. The anisotropic process leads to the formation of stable {111} facets via kink nucleation on stable steps and subsequent sublimation from those kink sites as predicated by the terracestep-kink model. Kink nucleation sites are identified and are in accordance with the broken-bond model approach.

Atomic-Scale Observation of Carbon Distribution in High-Performance Carbon-Doped Ge2Sb2Te5 and Its Influence on Crystallization Behavior

“…At the beginning, three carbon atoms and one single C atom are put in both sides of the amorphous region to represent different carbon existing species in CGST. Interestingly, as shown in Figure a, the final structure of pure GST at 90 ps has a rock-salt phase with randomly distributed vacancies, agreeing well with the crystalline phase observed in experimental studies. , As shown in Figure b, at the first 30 ps, the right plane (Figure b at 30 ps) of CGST has the similar growth velocity as the pure GST until it encounters the single carbon atom. 90 ps is required to achieve the growth of four layers of CGST (Figure b at 90 ps), whereas 60 ps is needed for GST (Figure a at 60 ps).…”

Lattice Thermal Conductivity of mGeTe•nSb2Te3 Phase-Change Materials: A First-Principles Study

“…Besides the stable hexagonal structure, GST phases also have a meta-stable rock-salt phase, and these stoichiometric compounds inevitably contain vacancies. Both theoretical and experimental studies indicate that vacancies prefer ordering on the (111) plane [31][32][33][34]. In order to study the effect of vacancy on thermal conductivity, we rebuilt the rock-salt structure in terms of hexagonal stacking based on the (111) planes along the [111] direction.…”

Selective Vertical and Horizontal Growth of 2D WS2 Revealed by In Situ Thermolysis using Transmission Electron Microscopy

“…[14] In another approach, metal substrates or inert or insulating substrates were used instead, with the advantage of metal that it can catalytically promote the reaction from the precursor. [31,32] High spatial and temporal resolution by in situ transmission electron microscopy (TEM) provides real-time monitoring of various physical and chemical processes including, growth, [33][34][35][36] phase transformations, [37][38][39][40] sublimation, [41][42][43][44][45][46][47] and electron beam induced modifications. [48][49][50] The in situ TEM technique is extensively used to capture dynamics of processes in TMDs as well.…”