Ultrathin VO₂ films with insulator-metal transition (IMT) were successfully fabricated on sapphire (001) substrates by utilizing radio frequency-biased reactive sputtering. We realized a 6 nm-thick VO₂ film that shows resistance change over 2 orders of magnitude. Microscopic observations combined with energy dispersive x-ray analyses revealed characteristic networking morphology in VO₂ films with thickness up to around 10 nm. It was found through micro-Raman analyses that a 30 nm-thick film possessed flat surface and ordered lattice with strong in-plane tensile stress. We evaluated the thickness dependence of optical switching performance for infrared-light. The results suggest that the thickness of the VO₂ films should be carefully selected for realizing required performances of optical switching, which depends on not only IMT but also characteristic morphological aspects.

中文翻译：

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通过偏置反应溅射在蓝宝石 (001) 衬底上接近超薄 VO2 薄膜：特征形态及其对红外光开关的影响

通过利用射频偏置反应溅射在蓝宝石 (001) 衬底上成功制造了具有绝缘体-金属转变 (IMT) 的超薄 VO ₂薄膜。我们实现了 6 nm 厚的 VO ₂薄膜，其电阻变化超过 2 个数量级。显微镜观察结合能量色散 X 射线分析揭示了厚度高达 10 nm 左右的VO ₂薄膜的特征网络形态。通过显微拉曼分析发现，30 nm 厚的薄膜具有平坦的表面和有序的晶格，具有很强的面内拉伸应力。我们评估了红外光光学开关性能的厚度依赖性。结果表明 VO ₂的厚度 应仔细选择薄膜以实现所需的光开关性能，这不仅取决于 IMT，还取决于特征形态方面。