Crystallization characteristics and local grain abnormal growth of amorphous Ge2Sb2Te5 films induced by a Gaussian picosecond laser
| Autor: | Zhang Yongzhi, F.R. Liu, W.Q. Li, Y H Wang, W. Xiao, Fencheng Liu, Nian X. Sun, J.C. Guo |
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| Rok vydání: | 2019 |
| Předmět: |
010302 applied physics
Materials science Nucleation Physics::Optics 02 engineering and technology 021001 nanoscience & nanotechnology Laser Microstructure 01 natural sciences Fluence Molecular physics Atomic and Molecular Physics and Optics Nanocrystalline material Electronic Optical and Magnetic Materials law.invention Amorphous solid Condensed Matter::Materials Science symbols.namesake law 0103 physical sciences symbols Electrical and Electronic Engineering Crystallization 0210 nano-technology Raman spectroscopy |
| Zdroj: | Optics & Laser Technology. 111:585-591 |
| ISSN: | 0030-3992 |
| Popis: | In this paper, crystallization characteristics of amorphous Ge2Sb2Te5 (a-GST) films induced by a Gaussian picosecond laser with different laser fluence were carried out using transmission electron microscopy (TEM), Raman spectra and ab initio molecular dynamics (AIMD) simulations. TEM observations presented a solid-state phase transition with nanocrystalline microstructure at lower fluence, while a liquid-solid phase transition accompanied by an ingot-like crystalline microstructure was found at higher fluence, including a central coarse and an outer fine equiaxed regions as well as a columnar crystal region between them. In spite of the remarkable difference in microstructure, the composition of different regions kept constant from the Energy Dispersive Spectrometer (EDS) measurements. Different phase change behavior and laser fluence affected the shift of Raman peaks due to the phase change stress and thermal stress. A laser irradiation coupled AIMD simulation was then developed to study the preferential nucleation possibility. AIMD simulation results indicated that a thermal process in the central coarse equiaxed regions, with a higher cooling rate (10 k/ps) generated by the Gaussian picosecond laser irradiation, reduced the nucleation rate remarkably, causing crystal nucleus have enough space to grow up even to the micrometer scale. This is different from the morphology induced by nano- or femtosecond pulsed laser. |
| Databáze: | OpenAIRE |
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