利用噪声谱表征二氧化钒薄膜的光学相变特性

Optical phase transition properties of vanadium dioxide thin film characterized by noise spectra

利用自主搭建的实验系统,同步实时地测量了热致相变材料二氧化钒(VO2)薄膜在相变过程中的反射率及其涨落(噪声谱).实时傅里叶变换采集卡测得的噪声谱不仅可以像反射率测量一样给出样品的相变温度(55℃),还在样品的高温区金属相里发现了一个明显的噪声峰(位于15~20 MHz),而低温区半导体相的噪声谱几乎是平坦的.这种噪声峰也反映了薄膜样品中低温半导体相和高温金属相的晶体结构差异.噪声谱测量可以广泛地应用于相变材料的研究.

The reflectance of thermochromatic material vanadium dioxide(VO 2)and its fluctuation(noise spectrum)were measured simultaneously during the semiconductor-metal phase transition via self-built experimental system.The noise spectra were measured by a Data-Acquisition Card with real time fast Fourier transforms(FFTs-DAC),showing the same phase-transition temperature(55℃)of the sample as that measured via reflectance measurement.A significant noise peak(around 15~20 MHz)was found in high temperature regime(the metal phase),while being almost flat in low temperature regime(the semiconductor phase).Such a noise peak also reflects that the low-temperature semiconductor phase and the high-temperature metallic phase have different crystal structures.Noise spectroscopy may be widely used to study phase-transtion materials.