Structural, optical and electrical properties of ZnO films grown by pulsed laser deposition (PLD)

Abstract

ZnO thin films were grown on single-crystal Si(1 0 0) and quartz glass substrates by pulsed laser deposition (PLD) technique using a KrF excimer laser with wavelength of 248 nm. The structural, optical and electrical properties of the as-grown films were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electronic microscopy (FE-SEM), transmittance spectrometry, and Hall-effect measurement. The films show c-axis oriented hexagonal wurtize crystal structure even at low substrate temperature of 200 °C. With the increase of substrate temperature and oxygen pressure, the crystallinity is enhanced and the film presents smooth, dense and uniformed microstructure, and strong interface bonding with substrate. The films grown at higher substrate temperature and oxygen pressure exhibit high average transmittance about 90% in the visible region and very sharp absorption edge at 378 nm. The energy band gap calculated from the transmittance spectra is about 3.25∼3.27 eV. Hall measurement indicates that the resistivity of films increases with substrate temperature and oxygen pressure.