Laser heating induced phase changes of VO2 crystals in air monitored by Raman spectroscopy
Laser heating induced phase changes of VO2 crystals in air monitored by Raman spectroscopy
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DOI：
10.1016/j.jallcom.2015.11.174
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发表时间：
2016-03
影响因子：
6.2
通讯作者：
P. Vilanova-Martínez;J. Hernández-Velasco;Á. Landa-Cánovas;Fernando Agulló-Rueda
中科院分区：
文献类型：
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作者：
P. Vilanova-Martínez;J. Hernández-Velasco;Á. Landa-Cánovas;Fernando Agulló-Rueda
本文通过提高激光功率，测量显微拉曼光谱，研究了强可见光对空气中二氧化钒晶体的影响。使用632.8nm的激光波长。对于高于500 MW/m2的功率密度，激光加热触发相变，已知相变发生在68° C左右，从室温绝缘VO 2（M）单斜相到高温半导体VO 2（R）四斜金红石相。这种变化是完全可逆的，当激光功率降低到初始值时，晶体会回到单斜相。这种转变也在真空下的电子衍射实验中观察到，在这种情况下，加热由电子束产生。对于高于1300 MW/m2的激光功率密度，变化是不可逆的，激光加热引起与空气中的氧气反应并氧化成V2 O 5。为了比较，我们还进行了20° C至600° C的热重和差示扫描量热实验。
We have studied the effect of intense visible light on vanadium dioxide crystals in air by measuring micro-Raman spectra for increasing laser powers. A laser wavelength of 632.8 nm was used. For power densities above 500 MW/m2laser heating triggers the phase transition, which is known to occur at around 68° C, from the room temperature insulating VO2(M) monoclinic phase to the high temperature semiconductor VO2(R) tetragonal rutile phase. The changes are fully reversible and the crystal goes back to the monoclinic phase when the laser power is lowered to the initial value. This transition is also observed in electron diffraction experiments under vacuum, heating in this case produced by the electron beam. For laser power densities above 1300 MW/m2the change is irreversible and laser heating provokes a reaction with the oxygen in air and an oxidation into V2O5. For comparison we have also done thermogravimetric and differential scanning calorimetry experiments from 20° C to 600° C.