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arXiv 1004.0040cond-mat.mtrl-sci
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脉冲Laser分步流动沉积SrTiO3(001)薄膜的原子分辨表面结构

Atomically Resolved Surface Structure of SrTiO3(001) Thin Films Grown in Step-Flow Mode by Pulsed Laser Deposition

Katsuya Iwaya, Takeo Ohsawa, Ryota Shimizu, Tomihiro Hashizume, Taro Hitosugi

摘要:

利用低温扫描隧道显微镜(STM)研究了脉冲激光(PLD)分步流动外延生长SrTiO 3(001)薄膜的表面结构。结果表明,在薄膜表面形成了一维TiO_x纳米结构,其密度随薄膜厚度的增加而增加。大多数的一维纳米结构消失后,沉积后退火,表明这种结构是亚稳态的,由于非平衡生长模式。退火后得到的表面表现出与较薄的膜相似的特征,具有(2x1)和(1x2)重构的畴结构,但具有较少的氧空位型缺陷。这些结果意味着,阶梯流生长是可能产生富TiO x的表面和Ti的薄膜中的缺陷。通过沉积后退火,富TiOx将从表面扩散到膜中,以补偿与Ti空位和氧空位相关的缺陷,导致具有较少氧空位的稳定表面结构。因此,STM测量可以为我们提供一个微观图片的表面化学计量的薄膜起源于生长过程的动力学,并可以提出一种新的方法来设计功能氧化物薄膜。

英文摘要:

The surface structure of SrTiO3(001) thin films homoepitaxially grown by PLD in step-flow mode was characterized using low temperature STM. It was found that one-dimensional (1D) TiOx-based nanostructures were formed on the thin film surface and their density increased with increasing thin film thickness. Most of the 1D nanostructures disappeared after a post-deposition annealing, indicating that this structure is metastable due to the nonequilibrium growth mode. The resulting surface after annealing exhibited similar features to that of a thinner film, having a domain structure with (2x1) and (1x2) reconstructions, but with fewer oxygen-vacancy-type defects. These results imply that the step-flow growth is likely to produce TiOx-rich surface and Ti deficiencies in the film. By the post-deposition annealing, the rich TiOx would diffuse from the surface into the film to compensate defects associated with Ti vacancies and oxygen vacancies, resulting in the stable surface structure with fewer oxygen vacancies. Thus, STM measurements can provide us with a microscopic picture of surface stoichiometry of thin films originating in the dynamics of the growth process, and can present a new approach for designing functional oxide films.

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