Effect of ECR etching conditions of (100)Ib diamond substrates on homoepitaxial low boron doped diamond layer quality

The effect of oxygen electron cyclotron resonance (ECR) microwave plasma etching on the crystallinity of low boron doped thin diamond films grown on Ib (100)-oriented diamond substrates by MPCVD has been investigated with respect to the main experimental conditions: microwave power and O-2 pressure at a constant DC bias. The substrates were exposed to ECR oxygen plasma to remove from 0.8 mu m to 3.5 mu m(depending on the value of the microwave power). The optimization of these two parameters has been performed in order to get the lowest surfaces roughness. This study aims also at demonstrating that oxygen ECR plasma etching is a powerful tool to remove surface and subsurface defects of diamond substrates as polishing grooves, subsurface damaged zone (polishing process induced defects) and various substrate roughness according to the observed growth sector. Low boron doped layers ([acceptors] = 4 x 10(16) atoms/cm(3)) were grown by MPCVD on either O-2 ECR plasma etched or merely chemically prepared (100) Ib diamond substrates. Cathodoluminescence analysis showed, for specific substrate etching conditions, a decrease of the band A emission (2.8 eV) in a low boron doped layer deposited on an etched substrate compared to a layer grown on a chemically prepared one. The FWHM of the FETO excitonic line of all theses layers is comprised between 16 meV and 13 meV for the best ones at 5 K. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.