Transmission electron microscopy study of the very early stages of diamond growth on iridium

The diamond nuclei generated during bias enhanced nucleation (BEN) on iridium were not detected so far by high resolution transmission electron microscopy (HRTEM). The aim of the present work was to investigate their earliest appearance after BEN by applying very short growth steps, ranging from 5 s to 1 min. On all the samples with growth step crystalline diamond could be identified unequivocally by HRTEM and reflection high energy electron diffraction (RHEED). After 5 s the former nuclei have evolved into crystallites of 2 nm thickness and about 10 nm width. At that time the carbon precursor phase which appears amorphous in HRTEM and which was formed by the ion bombardment has largely disappeared. After 10 s no residues are left, which proves that the 1-2 nm-thick amorphous carbon layer is only stable under biasing conditions. The rapid etching of the precursor phase and the simultaneous slow increase in volume of the tiny diamond crystals results in a minimum in carbon coverage several seconds after termination of the BEN process. (C) 2008 Elsevier B.V. All rights reserved.