Hong Minghwei, Cheng Chao-Kai, Lin Yen-Hsun, Young Lawrence Boyu, Cai Ren-Fong, Hsu Chia-Hung, Wu Chien-Ting, Kwo Jueinai
Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan.
Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan.
Nanomaterials (Basel). 2020 Aug 2;10(8):1515. doi: 10.3390/nano10081515.
The role of an atomic-layer thick periodic Y-O array in inducing the epitaxial growth of single-crystal hexagonal YAlO perovskite (H-YAP) films was studied using high-angle annular dark-field and annular bright-field scanning transmission electron microscopy in conjunction with a spherical aberration-corrected probe and in situ reflection high-energy electron diffraction. We observed the Y-O array at the interface of amorphous atomic layer deposition (ALD) sub-nano-laminated (snl) AlO/YO multilayers and GaAs(111)A, with the first film deposition being three cycles of ALD-YO. This thin array was a seed layer for growing the H-YAP from the ALD snl multilayers with 900 °C rapid thermal annealing (RTA). The annealed film only contained H-YAP with an excellent crystallinity and an atomically sharp interface with the substrate. The initial Y-O array became the bottom layer of H-YAP, bonding with Ga, the top layer of GaAs. Using a similar ALD snl multilayer, but with the first film deposition of three ALD-AlO cycles, there was no observation of a periodic atomic array at the interface. RTA of the sample to 900 °C resulted in a non-uniform film, mixing amorphous regions and island-like H-YAP domains. The results indicate that the epitaxial H-YAP was induced from the atomic-layer thick periodic Y-O array, rather than from GaAs(111)A.
利用高角度环形暗场和环形亮场扫描透射电子显微镜，结合球差校正探针和原位反射高能电子衍射，研究了原子层厚的周期性Y-O阵列在诱导单晶六方YAlO钙钛矿（H-YAP）薄膜外延生长中的作用。我们在非晶原子层沉积（ALD）亚纳米层压（snl）AlO/YO多层膜与GaAs(111)A的界面处观察到了Y-O阵列，首次薄膜沉积为三个周期的ALD-YO。这个薄阵列是通过900℃快速热退火（RTA）从ALD snl多层膜中生长H-YAP的籽晶层。退火后的薄膜仅包含结晶性优异且与衬底具有原子级清晰界面的H-YAP。初始的Y-O阵列成为H-YAP的底层，与GaAs的顶层Ga键合。使用类似的ALD snl多层膜，但首次薄膜沉积为三个ALD-AlO周期，在界面处未观察到周期性原子阵列。将样品RTA至900℃会导致薄膜不均匀，混合有无定形区域和岛状H-YAP畴。结果表明，外延H-YAP是由原子层厚的周期性Y-O阵列诱导产生的，而非来自GaAs(111)A。
