Structure and optical properties of pulsed laser deposited Zr doped-ZnO films

Abstract

The singular combination of optical, electrical and structural properties makes ZnO a promising candidate material in fields as diverse as optoelectronics, optics, ultrasonics or even bactericide applications. In addition, the possibility of doping it with different ions provides ZnO with new or enhanced properties such as ferroelectricity, conductivity, or intense luminescence.[1] In particular doping with Zr is very attractive since it produces minimum lattice distortion, does not leads to intermetallic phases and increases the carrier density, all of which contributes to enhance conductivity and makes Zr-doped ZnO of interest for transparent conducting oxide applications. Most of these applications requires functional thin films or nanostructures. Thus, in this work we study the synthesis of Zr-doped ZnO by pulsed laser deposition (PLD)[2] and compare its structure and optical properties with that of parent sintered ceramics. Doped ZnO thin films have been produced by PLD in an O2 pressure in the 10-2 mTorr range from sintered ZrO2-ZnO ceramic targets. The effect of ZrO2 dopant concentration in the 1-10 weight% range and substrate temperature (RT-500 oC) on the structure and optical properties of the films have been studied by Raman spectroscopy, AFM, Photoluminescence (PL) and UV-Visible optical transmission spectrophotometry. Initial Raman analysis of samples produced at RT shows not well defined Raman bands, which suggests that films are crystalline, but with a very small grain size. AFM analysis confirms the small grain size and shows that film surface is smooth and homogeneous. PL emission is observed in all cases. Emission at the band edge region extends into the blue-green, which suggests a significant contribution of surface states most likely related to the small grain size; while the band related to deep centers is observed in the orange spectral region. Deposited Zr-doped ZnO films exhibit optical properties relevant for optoelectronic applications. References [1] U¿. O¿zgu¿r, Ya. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Dog¿an, V. Avrutin, S.-J. Cho, H. Morkoc¿, ¿A comprehensive review of ZnO materials and devices¿, J. Appl. Phys. 98, 041301 (2005) [2] J. Perrie¿re, E. Millon, V. Craciun >ZnO and ZnO-related compounds¿ in Pulsed Laser deposition of thin films: Applications-led growth of functional materials, ed. by R. Eason (John Wiley & sons Inc., 2007), Ch. 12.