Thermal Stress Effect on the Structure and Properties of Single and Double Stacked Films of GeTe and SnSe

Abstract

The thermal stress effect on the structure of phase change memory materials, namely single films and double stacked films of GeTe and SnSe, is evaluated. The crystallization temperatures of GeTe and SnSe single films are 138 °C and 292 °C, respectively. The films are amorphous before annealing and crystallize in rhombohedral and orthorhombic structures afterwards. Ge is tetrahedrally bonded and Se is bivalent after deposition. Both Ge and Se have an octahedral configuration after annealing. The double stacked structure is studied in the as‐deposited state and after annealing at temperatures of 100, 210, and 350 °C. Pulsed laser deposition produces the crystallization of both as‐deposited layers when stacked, mostly of SnSe, but also some crystalline GeTe is present. GeTe fully crystallizes after annealing at 210 °C, in the face‐centred cubic structure. Annealing at 350 °C leads to the evaporation of a significant quantity of Se and to the formation of a cubic Ge0.75Sn0.25Te solid solution. Ge has an octahedral coordination, while Se is tetrahedrally bonded as a result of a combination of bivalent amorphous Se and octahedral Se from crystalline SnSe. The study shows that diffusion between layers at high annealing temperatures might suppress the memory property and determines the formation of irreversible solid solutions.

Excellent thermal stability and thermoelectric properties of Pnma -phase SnSe in middle temperature aerobic environment

“…Besides, the thermoelectric properties of SnSe at moderate and low temperature scales need to be further improved. [33] Many studies have been devoted to improving the thermoelectric properties of SnSe at moderate and low temperatures. [34][35][36][37][38][39][40] For example, the ZT value of Na-doped SnSe can be as high as 2.0 and Bi-doped SnSe reached 2.2.…”

Influence of Deposition Method on the Structural and Optical Properties of Ge2Sb2Te5

“…The MS sample is not completely crystalline: it has 18% amorphous phase left. It was shown that the films obtained by magnetron sputtering crystallize at a higher temperature than in the case of PLD [10,30]. On the other hand, in the other two samples (PLD and MSPLD), a minor hexagonal GeSb 4 Te 4 is obtained, which can be regarded as a seed for the hcp-GST-225 formation at a higher annealing temperature [3].…”

Multilevel Memristive GeTe Devices

“…[12] Another proposed approach is to stack different films of memory materials. [13][14][15] However, these approaches are either complex from a fabrication point of view or difficult to control to achieve multiple resistive states.…”