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Optical and microstructural properties of ZnO/TiO2 nanolaminates prepared by atomic layer deposition.

Research paper by Yu-Zhu YZ Gu, Hong-Liang HL Lu, Yang Y Geng, Zhi-Yuan ZY Ye, Yuan Y Zhang, Qing-Qing QQ Sun, Shi-Jin SJ Ding, David Wei DW Zhang

Indexed on: 28 Feb '13Published on: 28 Feb '13Published in: Nanoscale Research Letters



Abstract

ZnO/TiO2 nanolaminates were grown on Si (100) and quartz substrates by atomic layer deposition at 200°C using diethylzinc, titanium isopropoxide, and deionized water as precursors. All prepared multilayers are nominally 50 nm thick with a varying number of alternating TiO2 and ZnO layers. Sample thickness and ellipsometric spectra were measured using a spectroscopic ellipsometer, and the parameters determined by computer simulation matched with the experimental results well. The effect of nanolaminate structure on the optical transmittance is investigated using an ultraviolet-visible-near-infrared spectrometer. The data from X-ray diffraction spectra suggest that layer growth appears to be substrate sensitive and film thickness also has an influence on the crystallization of films. High-resolution transmission electron microscopy images show clear lattice spacing of ZnO in nanolaminates, indicating that ZnO layers are polycrystalline with preferred (002) orientation while TiO2 layers are amorphous.