PLD growth of CuAlO2

Abstract

Copper aluminium oxide, CuAlO2 ("CAO") films were deposited by pulsed laser deposition ("PLD") on a variety of substrates. As-deposited films were X-ray amorphous. Films formed at 200 degrees C were insulating, whereas films formed on sapphire at 720 degrees C were conducting. Specific conductivity and light transmittance were optimized for CAO/sapphire. Best values for the conductivity of around 0.3 S/cm for 280 nm thick films on sapphire were obtained for 3.5 J/cm(2)/pulse, substrate to target distance 6.5 cm, 400 mTorr oxygen and 720 degrees C, deposition time 90 min at 10 Hz. Films obtained under these conditions were specular and had a refractive index around 2.1 as derived from reflectivity measurements. Transmission spectra showed an onset around 400 nm and a non-negligible unspecific absorption above. Annealing of as-deposited, X-ray amorphous films on sapphire at 1050 degrees C in air for 5 min led to crystallization in combination with disruption of film continuity (and therefore loss of conductivity) as seen by optical microscopy, where hexagonal platelets could be clearly distinguished. X-ray analysis showed highly preferential orientation (< 003 >, < 006 >, < 009 >, < 0012 >). Post-annealing in situ (15 min-8 h) at 720 degrees C had no effect on film properties. (c) 2007 Elsevier B.V. All rights reserved.