MOSAIC DIAMOND SUBSTRATES APPROACHING SINGLE-CRYSTAL QUALITY USING CUBE-SHAPED DIAMOND SEEDS

Large-area (approximately 1 cm(2)) mosaic diamond substrates were obtained by orienting smaller (250 mu m on a side) diamond cubes and fusing them homoepitaxially. The orientation starts by distributing a single layer of several hundred cubes on a smooth substrate. The cubes are then wetted with a mixture of isopropyl alcohol and glycerin, whose surface tension causes the cubes to coalesce into domains consisting of 20-30 cubes. The cubes in each domain have the same crystallographic orientation, but the domains are randomly oriented to each other. Two techniques were found to produce consistent orientation of the domains. One technique is to orient the domains physically against to 1 mm high, vertical, square walls on the substrate. The other technique is to push physically on the layer of cubes, which deforms the domains causing them to rotate and form a layer with consistent orientation. After the layer of cubes is oriented, homoepitaxial diamond is grown on it to obtain a continuous mosaic substrate. Depending on the techniques used, orientation with a standard deviation from 1 degrees to 5 degrees can be achieved.