Large diamond crystal substrates and methods for producing the same

A method for producing a single-crystal diamond substrate having a large area, comprising the steps of:

• (1) implanting ions into a parent substrate of single-crystal diamond to form a graphitized, non-diamond layer near a surface of the parent substrate, and subsequently etching the non-diamond layer to separate therefrom a single-crystal diamond layer above the non-diamond layer;
• (2) repeatedly subjecting the parent substrate used in Step (1) to the operation of Step (1), to further separate from the parent substrate one or more single-crystal diamond layers;
• (3) placing the plurality of single-crystal diamond layers separated in Steps (1) and (2) on a flat support such that side faces of adjacent diamond layers are in contact with each other, and faces of the diamond layers where the diamond layers have been separated from the parent substrate are in contact with a surface of the support;
• (4) growing a single-crystal diamond by a vapor-phase synthesis method on the plurality of single-crystal diamond layers placed on the support in Step (3), thereby bonding the plurality of single-crystal diamond layers;
• and
• (5) inverting the single-crystal diamond layers bonded in Step (4) on the support, and subsequently growing a single-crystal diamond on the diamond layers by a vapor-phase synthesis method, thereby growing a single-crystal diamond on faces of the diamond layers where the diamond layers have been separated from the parent substrate.