Quantum resonance of nanometre-scale metal-ZnO-metal structure and its application in sensors

Lijie Li,Paul Rees

doi:10.1063/1.4939815

Abstract

Analysis of the thickness dependence of the potential profile of the metal-ZnO-metal (MZM) structure has been conducted based on Poisson’s equation and Schottky theory. Quantum scattering theory is then used to calculate the transmission probability of an electron passing through the MZM structure. Results show that the quantum resonance (QR) effect becomes pronounced when the thickness of the ZnO film reaches to around 6 nm. Strain induced piezopotentials are considered as biases to the MZM, which significantly changes the QR according to the analysis. This effect can be potentially employed as nanoscale strain sensors.

Highlights

Nanometer-scale structures thin films and nanowires exhibit different current-voltage characteristics to bulk, especially when the dimensions are comparable to the depletion thickness of the junction and the quantum length, i.e. de Broglie wavelength of an electron
The photocatalytic performance could be significantly improved using graphene/Zinc oxide (ZnO) nanocomposites.[6]
In this work it is assumed that the metal is contacting with a n-type ZnO film forming a MZ junction, in which electrons are induced on the metal-ZnO interface leaving holes in the depleted region of the ZnO body, which pulls down the conduction band to match the Fermi aEmail: L.Li@swansea.ac.uk 2158-3226/2016/6(1)/015003/8

Summary

INTRODUCTION

FIG. 1. schematic hypothesis of the size dependence effect of the metal-ZnO-metal structure. (a), Thickness of the ZnO film is much larger than the thickness of the depletion layer. (b), ZnO thickness is close to the depletion layer thickness. (c), Thickness of the film is much thinner than the depletion layer, causing the quantum confinement effect to appear. (c), Thickness of the film is much thinner than the depletion layer, causing the quantum confinement effect to appear. Further reducing the thickness, merged depletion layers lifts up the conduction band, eventually forming a quantum well. Quantum scattering theory is used to validate the energy quantization effect for the MZM structure with ultra thin ZnO film. As the dimension of the device reduces to sufficiently small, the electrons treated as travelling waves can have the probability to tunnel through the barrier for those electrons with the energy corresponding approximately to the virtual resonant frequency level of the quantum well, in which case the transmission coefficient is close to unity. To calculate the transmission probability Tp for the thinned ZnO film, a well established method for electrons passing through arbitrary potential.

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Findings

CONCLUSION