High pressure high temperature (HPHT) method for the production of single crystal diamonds

A method for synthesizing single crystal diamond comprising:

• (a) selecting a single crystal diamond seed having a growth surface with two orthogonal dimensions a* and b*, where a* is the longest dimension of the growth surface substantially aligned along a <100> or <110> direction in the plane of the growth surface, and b* is the longest dimension of the growth surface in a direction orthogonal to a* lying in the plane of the growth surface, where the aspect ratio of the growth surface which is defined as a*/b* is at least 1 and the growth surface is substantially parallel to a {110} crystallographic plane;
• (b) mounting the seed on or into a surface of a substrate such that the growth surface of the seed is exposed and the growth surface of the seed is substantially parallel to the surface of the substrate;
• and
• (c) effecting crystal growth in a high pressure high temperature environment at a temperature greater than 1280° C. under conditions such that a single crystal diamond is produced on at least the growth surface of the seed;
• wherein the synthesized single crystal diamond has a longest dimension a# aligned along a <100> or <110> direction, which exceeds at least 2 mm.