Evaluation of substrate material and Cu-doping effect on the microstructural and optical behavior of ZnO films

College of Physics and Electronics Engineering, Key Laboratory of Atomic and Molecular Physics & Functional Materials of Gansu Province, Northwest Normal University, Lanzhou, Gansu 730070, P.R. China

^a e-mail: xbsdyfc@163.com

Received: 23 June 2012
Revised: 20 January 2013
Accepted: 22 January 2013
Published online: 28 March 2013

Abstract

In the present work, ZnO and ZnO:Cu thin films with c-axis preferred orientation were prepared on porous silicon, silicon and glass substrates by radio frequency magnetron sputtering technique. X-ray diffraction measurements revealed that the particle size of all samples was in the range of 11.41 ~ 17.67 nm. All the samples exhibited a compressive stress. Fourier transform infrared spectroscopy showed the presence of Si-O-Si stretching appeared at 1067 cm^–1, which was assigned to the transverse optical mode of the asymmetric vibration. The E₂ (high) mode indicated that the residual stress was observed in the Raman spectra. The optical transmission and absorption spectra were studied, indicating that the optical band gap value shifted to a longer wavelength after Cu doping. Effect of substrate material and Cu doping on the photoluminescence properties of ZnO thin films, along with the origin of some emission peaks, was discussed in detail. The experiment results indicate that the ZnO and ZnO:Cu thin films grown directly on the Si substrates have a high quality of crystallization and intense blue luminescent properties.