Fabrication Technology Technologies

For creating a single crystal diamond by CVD process, a substrate of single crystal is needed as a seed crystal. It is necessary to slice off in order to take a grown crystal away from the seed because there is no apparent border between them. However, it is not easy to comlete the slicing process especially on large size. Therefore, we employ the Ion-implantation technique, by which carbon cations are injected into surface of a seed before crystal growth and a collapsed crystal layer is created just below the surface. It is possible to grow a single crystal diamond on the seed because the outermost surface maintains crystal stucture of diamond. After the growth, we remove the collapsed layer electrochemically in order to obtain a fabricated single crystal diamond as a plate-shape. A part of the seed is lost during the separation process, however, the thickness of the lost part is just approx. 1µm. We obtain several clone single crystal diamond plates by repetation of the above process on a seed.

Single crystal plates have a limitation of their dimension. In order to create a larger plate, we have developped a complex substrate called "Mosaic crystal" which consists of several single crystals. We can fabricate single crystals with aligned crystal faces by duplication from an idetical seed crystal. Overgrowth on arranged clone crystals results in the fabricatoion of a "mosaic crystal", which is nearly borderless.