原子层沉积制备VO_2薄膜及特性研究

Growth of VO_2 Films by Atomic Layer Deposition and its Properties

原子层沉积（ALD）技术在制备薄膜时因具有厚度精确可控、三维均匀性好以及可以实现大面积成膜和低的成膜温度等优点而使其在各个领域受到广泛关注。本文采用ALD技术,以VO（acac）2和O2分别为钒源和氧源,使用不同的沉积温度（420-480℃）和退火条件（自然冷却、4和8h程序降温）在玻璃基底表面制备VO2薄膜。通过X-射线光电子能谱、X-射线衍射以及扫描电镜对薄膜的价态、结晶状况及表面微观形貌进行表征;通过四探针测试仪对所制备薄膜的半导体-金属相变特性进行了研究。实验结果表明：VO2薄膜相变特性与其微观结构和晶体取向有着直接关系。选择ALD脉冲时序为[10s-20s-20s-20s],循环周期数为300,在450℃沉积且采取自然冷却所制备的VO2薄膜结晶状态良好,相变前后薄膜方块电阻突变量大,具有良好的热致相变特性。因此,该ALD技术可以制备相变特性较好的VO2薄膜。

The VO2 thin films,with precisely-controlled thickness,3-D uniformity and large area,were synthesized by atomic layer deposition（ALD）at a low temperature on glass substrate.The impact of the growth conditions,including but not limited to the V/O sources,substrate temperature,cooling rate and ALD cycles,on the microstructures and semiconductor-metal（S-M）phase transition of VO2 films was investigated with X-ray diffraction,X-ray photo-electron spectroscopy,scanning electron microscopy.The preliminary results show that high quality VO2 films,highly-uniform and well-controlled at atomic scale,can be synthesized under the optimized conditions.Grown with VO（acac）2and O2 as V/O sources,at a substrate temperature of 450℃,for 300 ALD cycles and by spontaneous cooling,the highly-crystallized,011 preferentially oriented VO2-phase dominated.We found that the S-M phase transition results in a large change of sheet resistance,indicating good thermally-induced phase-transition characteristics.