National Synchrotron Radiation Laboratory , University of Science and Technology of China , Hefei , Anhui 230026 , China.
ACS Appl Mater Interfaces. 2018 Dec 19;10(50):43802-43808. doi: 10.1021/acsami.8b16592. Epub 2018 Dec 4.
High-speed electronics require epitaxial films with exceptionally high carrier mobility at room temperature (RT). Alkaline-earth stannates with high RT mobility show outstanding prospects for oxide electronics operating at ambient temperatures. However, despite significant progress over the last few years, mobility in stannate films has been limited by dislocations because of the inability to grow fully coherent films. Here, we demonstrate the growth of coherent, strain-engineered phases of epitaxial SrSnO (SSO) films using a radical-based molecular beam epitaxy approach. Compressive strain stabilized the high-symmetry tetragonal phase of SSO at RT, which, in bulk, exists only at temperatures between 1062 and 1295 K. We achieved a mobility enhancement of over 300% in doped films compared with the low-temperature orthorhombic polymorph. Using comprehensive temperature-dependent synchrotron-based X-ray measurements, electronic transport, and first principles calculations, crystal and electronic structures of SSO films were investigated as a function of strain. We argue that strain-engineered films of stannate will enable high mobility oxide electronics operating at RT with the added advantage of being optically transparent.
高速电子学需要在室温下具有极高载流子迁移率的外延薄膜。室温下迁移率高的碱土锡酸盐在环境温度下运行的氧化物电子学方面显示出了极好的前景。然而，尽管在过去几年中取得了重大进展，但由于无法生长完全相干的薄膜，锡酸盐薄膜中的迁移率一直受到位错的限制。在这里，我们展示了使用基于自由基的分子束外延方法生长外延 SrSnO（SSO）薄膜的相干、应变工程相。压缩应变在室温下稳定了 SSO 的高对称性四方相，而在块状材料中，四方相仅存在于 1062 至 1295 K 之间的温度范围内。与低温正交多晶型相比，掺杂薄膜的迁移率提高了 300%以上。使用综合的基于同步加速器的温度相关 X 射线测量、电子输运和第一性原理计算，研究了 SSO 薄膜的晶体和电子结构随应变的变化。我们认为，应变工程化的锡酸盐薄膜将能够实现室温下具有高迁移率的氧化物电子学，并且具有光学透明的额外优势。
