氧分压对磁控溅射VO_2薄膜相变性能的影响

Influence of oxygen partial pressure on phase transition characteristics of VO_2 thin films prepared by magnetron sputtering

采用直流反应磁控溅射工艺在不同氧分压下制备VO2相变薄膜.分别用X射线衍射仪、扫描电子显微镜、四探针方阻测量系统和分光光度计对薄膜微结构、表面形貌、电学及光学特性进行表征.测量结果表明,薄膜样品是由包含VO2相在内的多相复杂体系构成的,随着氧分压的增加,薄膜中高价态相的钒氧化物增多.所有薄膜均呈现出压应力,压应力大小随着氧分压的升高而逐渐减小.方块电阻温变结果表明,薄膜具有明显半导体-金属相变特性,相变性能随着氧分压的升高呈先增后减特征.高低温透射谱表明,薄膜具有良好红外开关特性.氧分压改变导致膜中氧空位缺陷密度和微结构变化是VO2薄膜半导体-金属相变性能改变的主因.本实验条件下,具有良好热致相变性能的VO2薄膜的最佳生长氧分压是0.04 Pa.

Vanadium dioxide （VO2） thin films were prepared by reactive magnetron sputtering under different oxygen partial pressures. Microstructure, surface morphology, electrical and optical properties of the samples were characterized by X-ray diffraction instrument, four-point probe system, speetrophotometer, and scanning electron microscopy, respectively. Experimental results indicate that the samples are composed of different complex vanadium oxide phases. With an increase of oxygen partial pressure, the films become higher-valence vanadium oxides. All the samples exhibit compressive intrinsic stresses, and the stress value decreases with the increase of the oxygen partial pressure. The relationship between sheet resistance and temperature reveals remarkable semiconductor-metal transition （SMT） characteristics, and the SMT performance exhibits an initial higher degree and then gets weakened. The transmittance spectra under high and low temperatures reveal that films have a high performance of optical switching in IR range. Variations in oxygen vacancy defect density and microstructure with oxygen partial pressure are the main reasons for SMT variation. In our study, the optimal oxygen partial pressure is 0. 04 Pa for high SMT performance VO2 films deoosition.