Atomically transparent vertically aligned ZnO-based van der Waals material have been developed by surface passivation and encapsulation with atomic layers of MgO using materials by design; the physical properties investigated. The passivation and encapsulation led to a remarkable improvement in optical and electronic properties. The valence-band offset ΔEv between MgO and ZnO, ZnO and MgO/ZnO, and ZnO and MgO/ZnO/MgO heterointerfaces are determined to be 0.37 ±0.02, -0.05±0.02, and -0.11±0.02 eV, respectively; the conduction-band offset ΔEc is deduced to be 0.97±0.02, 0.46±0.02, and 0.59±0.02 eV 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.
@article{arxiv.1906.08352,
title = {Surface passivated and encapsulated ZnO atomic layer by high-$\kappa$ ultrathin MgO layer},
author = {C. E. Ekuma and S. Najmaei and M. Dubey},
journal= {arXiv preprint arXiv:1906.08352},
year = {2019}
}