X-ray absorption fine-structure and optical studies of AlZnO nano-thin films grown on sapphire by pulsed laser deposition

Al-doped ZnO can replace tin-doped indium oxide (ITO) as a good transparent conductive oxide (TCO) in LEDs and optoelectronic applications. We investigate on nanometer scale AlZnO thin film materials epitaxied on sapphire substrates in 350-650°C from pulsed laser deposition (PLD). Synchrotron radiation X-ray absorption fine-structure spectroscopy on O K-edge indicates that Al-doped ZnO can not form alloy at growth temperature 350°C without Al-O bonding feature. The Al-O transition of AZO550 is stronger than AZO650. These are correlated to Raman scattering measurements and analyses. Al-doped ZnO grown at 350°C possesses weak/broad Raman signals indicating a poor crystalline film. The E2 (high) mode is strong and narrow in AZO550. All these experimental results indicate that PLD grown AlZnO film on sapphire could get a better crystalline quality at 550°C than 350°C and 650°C.