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Issue 26, 2019
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Surface passivated and encapsulated ZnO atomic layers by high-κ ultrathin MgO layers

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Abstract

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 ΔEv 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 ΔEc 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.

Graphical abstract: Surface passivated and encapsulated ZnO atomic layers by high-κ ultrathin MgO layers

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Supplementary files

Article information


Submitted
17 Apr 2019
Accepted
15 Jun 2019
First published
18 Jun 2019

Nanoscale, 2019,11, 12502-12506
Article type
Communication
Author version available

Surface passivated and encapsulated ZnO atomic layers by high-κ ultrathin MgO layers

C. E. Ekuma, S. Najmaei and M. Dubey, Nanoscale, 2019, 11, 12502
DOI: 10.1039/C9NR03288F

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