应力对蓝宝石衬底上生长二氧化钒薄膜结构和光电性能的调控

利用脉冲激光沉积技术在蓝宝石衬底上生长不同厚度的VO₂薄膜, 对薄膜的结构、表面形貌和光电性能进行研究。结果表明: 所沉积的VO₂薄膜为具有单晶性能、表面平整的单斜晶相的VO₂薄膜, 相变前后, 方块电阻的变化可达到3~4个数量级, 在波长为2500 nm的透过率变化最高可达56%, 优化的可视透过率(T_lum)和太阳能调节率( ?T_sol )为43.2%和8.7%。薄膜受到的应力对VO₂薄膜有重要影响, 可以通过调节薄膜的厚度对VO₂薄膜光电性能实现调控。当VO₂薄膜厚度较小时, 薄膜受到拉应力, 拉应力能使相变温度显著降低, 金属-绝缘体转变性能(MIT)不但与载流子浓度的变化相关, 而且还受载流子迁移率变化的影响;当VO₂薄膜厚度较大时, 薄膜受到压应力, VO₂薄膜的相变温度接近块体VO₂的相变温度, MIT转变主要来自于载流子浓度在相变前后的变化, 其载流子迁移率几乎不变。

Stress Induced Modulation of the Structure and Photoelectric Property of Vanadium Oxide Films on Sapphire Substrate

VO₂ thin films with different thicknesses were deposited on sapphire substrates by pulsed laser deposition. Structure, surface morphologies and photoelectric properties of the films were characterized. The results indicated that the Monoclinic-VO₂ thin films deposited on the sapphire substrates were high quality poly-crystalline stoichiometric with no detectable impurities, and the sheet resistance changed up to 3-4 orders of magnitude and the transmittance at 2500 nm up to 56% across metal-insulator transition (MIT). The optimized integral luminous transmittance (T_lum) and solar regulation rate (?T_sol) were 43.2% and 8.7%, respectively. The stress on the interface had important influence on the VO₂ thin film, and the photoelectric properties of VO₂ thin films could be regulated by adjusting the film thickness. When the VO₂ film was thinner, the film was subjected to tensile stress, which could significantly reduce the phase-change temperature, and the increase of the carrier concentration as well as carrier mobility accounted for the decrease of electrical resistance across the MIT. While the VO₂ film was thicker, the film was subjected to compressive stress and the phase transition temperature of VO₂ film was close to that of body VO₂. The increase of the carrier concentration accounted almost entirely for the decrease of electrical resistance and the change in mobility had little contribution to the MIT.