Glancing-angle ion-assisted deposition of ZnO thin films

Undoped ZnO thin films were deposited on unheated sapphire and glass substrates under concurrent glancing-angle Ar+ ion bombardment. Surface roughness decreased from 18 to 3.5 nm in films grown on glass, and from 11 to 0.5 nm on sapphire, as the ion-to-neutral atom ratio increased from 0 to 0.25. Film microstructure observations by cross-sectional electron microscopy indicated increased film density when glancing-angle ions were used. The glancing-angle ions had little effect on film residual stress; this is in contrast to normal-incidence ion bombardment that typically increases compressive stresses. (C) 2003 Elsevier Science B.V. All rights reserved.