Island growth kinetics during vapor deposition of Cu onto the Zn-terminated ZnO(0001) surface

During the vapor deposition of Cu onto the Zn-terminated ZnO(0001) surface, it has previously been observed that at room temperature and below, the Cu grows first as two-dimensional islands up to a certain critical coverage ( theta(1,cr)) near 0.3 monolayers. As the Cu coverage increases above theta( 1,cr), these islands thicken into three-dimensional particles but the clean ZnO spaces between the Cu particles fill only very slowly. This occurs due to a kinetic limitation, since the islands thermodynamically prefer to be thicker and larger. Here, the dependencies of the critical coverage upon th e substrate temperature and Cu vapor flux are measured. No significant chan ge in critical coverage is seen when the flux is varied by similar to 30-fo ld, but it decreases weakly with temperature. These trends are discussed wi thin a kinetic model which incorporates the various Cu adatom migration and island nucleation steps. (C) 1999 Elsevier Science B.V. All rights reserve d.