A method is disclosed for producing large single crystals. In one embodiment, a single crystal of electronic grade diamond is produced having a thickness of approximately 100-1000 microns and an area of substantially greater than 1 cm..sup.2. and having a high crystalline perfection which can be used in electronic, optical, mechanical and other applications. A single crystalline diamond layer is first deposited onto a master seed crystal and the resulting diamond layers can be separated from the seed crystal by physical, mechanical and chemical means. The original master seed can be restored by epitaxial growth for repetitive use as seed crystal in subsequent operations. Large master single crystal diamond seed can be generated by a combination of oriented smaller seed crystals by lateral epitaxial fusion. Since there is no limit to how many times seed combination step can be repeated, large diamond freestanding wafers comparable in size to silicon wafers can be manufactured.