钽掺杂对二氧化钒多晶薄膜相变特性的影响

将Ta_2O_5与V_2O_5均匀混合,压制成溅射靶,用离子束增强沉积方法在二氧化硅衬底上沉积掺Ta氧化钒薄膜.在氮气中适当退火,形成掺杂二氧化钒多晶薄膜.X射线衍射结果显示,薄膜具有单一的(002)取向.XPS测试表明,膜中V为+4价,Ta以替位方式存在.温度-电阻率测试表明,薄膜具有明显的相变行为,原子比为3%的Ta掺杂后,二氧化钒多晶薄膜相变温度降低到约48℃.Ta原子的半径大于V原子的半径,Ta的掺入在薄膜中引入了张应力;5价Ta 替代4价V,在d轨道中引入多余电子,产生施主能级,这些是掺钽二氧化钒多晶薄膜相变温度降低的原因.

The Influence of Tantalum Doping on the Phase Transition of IBED VO_2 Polycrystalline Film

The vanadium oxide film was deposited on the SiO_2 substrate by modified Ion Beam Enhanced Deposition (IBED) method. The V2_O_5 and Ta_2O_5 mixing powders were pressed as the sputtering target. After annealing in N_2 the polycrystalline IBED VO_2 film doped with tantalum was obtained. The Ta doped film was orientated only to (002) of VO_2 structure measured by X-ray Diffraction (XRD). The valence of vanadium and doped Ta in the film was +4 confirmed by X Ray Photoelectron Spectroscopy(XPS), it means that the doped Ta was substitution atom. The results of resistance-temperature testing showed that the phase transition temperature was decreased from 68℃ to 48℃. The reasons would be as following: With the atomic size of Ta was larger than the size of vanadium atom Ta doping would induce a tension stress into the film; When Ta~(5+) replaced V~(4+) it introduced excrescent electrons in the d valence shell, then make the gap of d energy band to decreasing.