Shu-Yi Liu

The effect of postannealing on the electrical properties of well-aligned n-ZnO nanorods/p-Si heterojunction

This work investigates the effects of postannealing on the electrical properties of the n-ZnO nanorods/p-Si heterojunction. Well-aligned ZnO nanorods are grown on the p-Si substrate with a ZnO seed layer through a hydrothermal method. The as-grown ZnO nanorods are grown along the preferential [0001] direction with high single crystalline quality. The rectifying characteristics of the heterojunction are effectively improved and the rectification ratio is increased tens of times after annealing in air. The leakage current is decreased by two orders of magnitude and the forward-bias injection efficiency is largely enhanced after annealing. The photoluminescence and x-ray photoelectron spectroscopy results show that annealing in the air ambient can effectively reduce the loosely adsorbed oxygen on the surface of the ZnO nanorods so that the bound free electrons can be released, which can result in larger carrier concentration and improve the injection efficiency of the n-ZnO nanorods/p-Si structure in the for...

The EL properties of well-aligned n-ZnO nanorods / p-GaN structure

Well-aligned ZnO nanorods were grown on the p-GaN substrate by a hydrothermal method and n-ZnO nanorods/p-GaN heterojunction LED structures were formed. The electroluminescence (EL) properties of this structure were studied under both forward and reverse bias. The nanorod LED device only has light output under reverse bias. The I–V characteristic results show that the nanosized junction can increase the carrier injection efficiency of the n-ZnO nanorods/p-GaN LED device.

The effects of high work function electrodes on the electrical properties of solution processed ZnO thin film transistor

In this work, the effects of electrodes on the performance of sol-gel fabricated ZnO thin film transistor were investigated. The metal with high work function such as Pt was employed as the source-drain electrodes. Compared to the device with Al electrodes as reported before, the transistor fabricated with Pt electrode exhibited lower saturation voltage and current, which was due to the Schottky contact between the Pt electrode and the ZnO film. The result has also been proved by the current-voltage (IV) measurement of the Pt-ZnO-Pt structure. For the Schottky contact between the electrodes and the channel layer, the current saturated when the source was depleted. This kind of device reduced the operation voltage and power dissipations effectively.

Highly ordered growth of ZnO nanostructures by combination of nanoimprint lithography and hydrothermal method

By combining nanoimprint lithography and traditional hydrothermal growth method of ZnO nanorods, vertical and well patterned ZnO nanostructures were successfully fabricated. The imprinted SU-8 resist deep trenches above the ZnO seed layer prohibit the lateral growth of ZnO nanorods. Various patterned vertical ZnO nanostructures like nanorods and nanowalls can be obtained. The improvement of photoluminescence property of ZnO nanorods was observed after removing the SU-8 resist from the substrate by O2 reactive ion etching (RIE).

Physical and optical properties of ZnO thin films grown by DC sputtering deposition

The effects of the deposition condition of DC sputtering on the properties of ZnO thin films were systematic investigated. ZnO films have been prepared by DC sputtering on the Si and glass substrates in the Ar and O2/Ar ambient with different substrate temperature ranging from room temperature to 300°C. Optimal results of the ZnO film were obtained with a deposition temperature of 300°C in the O2/Ar ambient. The film has a preferential orientation of (002) and the Zn to O ratio is stoichiometric with a strong band-edge emission in the ultraviolet region. All the films deposited on glass have an optical transmittance over 80 % in the wavelength ranging from 400 nm to 800 nm.

Improvement of the crystallinity and optical properties of sol-gel ZnO thin film by a PVD ZnO buffer layer

The effect of the ZnO homo-buffer layer on the structural, optical and electrical properties of the Sol-gel ZnO films was systematically investigated. The XRD and SEM results show that the homo-buffer layer can improve the degree of the preferential c-axis orientation (the best Lotering orientation factor (F) can reach 0.915), the grain size and the surface morphology of thereon ZnO films. A narrower UV emission at 380 nm was observed with weaker deep-level visible emission for the ZnO films with a homo-buffer layer using room-temperature (RT) photoluminescence (PL) spectra. The electrical results show that the carrier concentration of the films with buffer layer is decreased and the Hall mobility is increased, indicating that a ZnO homo-buffer layer can effectively improve the crystallinity of the films and improve both electrical and optical properties.