Showing papers by "Kandasamy Prabakar published in 2005"

UV, violet and blue‐green luminescence from RF sputter deposited ZnO:Al thin films

Abstract: The mechanism of ultraviolet (UV), violet and blue green emission from ZnO:Al (AZO) thin films deposited at different radio frequency (r.f.) powers on glass substrates was investigated. The structure and surface morphology of AZO films have also been observed. The optical transmittance spectra shows more than 80% transmittance in the visible region and the band gap is found to be directly allowed. From the photoluminescence measurement, intense UV and blue green luminescence is obtained for the samples deposited at higher sputtering powers. The mechanism of luminescence suggests that UV luminescence of AZO thin film is related to the transition from near band edge to the valence band and the concentration of antisite oxide (Ozn) increases with increase in r.f. power which in turn increases the intensity of green band emission while the violet PL is due to the defect level transition in the grain boundaries of AZO films. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Structure and Photoluminescence Properties of ZnO:Al/Porous Silicon Thin Films

Abstract: Al doped ZnO (AZO) films were deposited on porous silicon (PS) substrates by a reactive rf-cosputtering process from two targets of ZnO and Al. The effect of ZnO target rf-sputtering power on the structural and photoluminescence (PL) properties of AZO/PS heterojunctions were studied. Strong monochromatic blue emission located at 2.78 eV was observed for the AZO films deposited at 150 W. Freshly prepared PS showed an emission band in the green spectral region. We show that deposition of AZO on PS does not degrade the skeleton of the PS and enhance the PL intensity. The PL band shifted to the high energy for AZO films deposited on PS and the intensity became stable.