Ekuma C E, Najmaei S, Dubey M
Department of Physics, Lehigh University, Bethlehem, PA 18015, USA.
Sensors and Electron Devices Directorate, United States Army Research Laboratory, Adelphi, MD 20783, USA.
Nanoscale. 2019 Jul 14;11(26):12502-12506. doi: 10.1039/c9nr03288f. Epub 2019 Jun 26.
Atomically transparent vertically aligned ZnO-based van der Waals materials have been developed by surface passivation and encapsulation with atomic layers of MgO using materials by design, and their physical properties have been investigated. The passivation and encapsulation led to a remarkable improvement in the optical and electronic properties. The valence-band offset ΔE between MgO and ZnO, ZnO and MgO/ZnO, and ZnO and MgO/ZnO/MgO heterointerfaces is determined to be 0.37 ± 0.02, -0.05 ± 0.02, and -0.11 ± 0.02 eV, respectively, and the conduction-band offset ΔE is deduced to be 0.97 ± 0.02, 0.46 ± 0.02, and 0.59 ± 0.02 eV, respectively, indicating straddling type-I in MgO and ZnO, and staggering type-II heterojunction band alignment in ZnO and the various heterostructures. The band-offsets and interfacial charge transfer are used to explain the origin of n-type conductivity in the superlattices. Enhanced optical absorption due to carrier confinement in the layers demonstrates that MgO is an excellent high-κ dielectric gate oxide for encapsulating ZnO-based optoelectronic devices.
通过材料设计，利用氧化镁原子层进行表面钝化和封装，开发出了原子级透明的垂直排列氧化锌基范德华材料，并对其物理性质进行了研究。钝化和封装显著改善了光学和电子性质。氧化镁与氧化锌、氧化锌与氧化镁/氧化锌以及氧化锌与氧化镁/氧化锌/氧化镁异质界面的价带偏移量ΔE分别确定为0.37±0.02、-0.05±0.02和-0.11±0.02电子伏特，导带偏移量ΔE分别推导为0.97±0.02、0.46±0.02和0.59±0.02电子伏特，表明氧化镁和氧化锌中为跨越型I，氧化锌及各种异质结构中为交错型II异质结能带排列。利用能带偏移和界面电荷转移来解释超晶格中n型导电性的起源。由于层中载流子限制导致的光吸收增强表明，氧化镁是用于封装氧化锌基光电器件的优良高κ介电栅氧化物。
