Methods of fabricating synthetic diamond materials using microwave plasma activated chemical vapour deposition techniques and products obtained using said methods
A method of fabricating synthetic diamond material using a microwave plasma activated chemical vapour deposition technique is provided which utilizes high and uniform microwave power densities applied over large areas and for extended periods of time. Products fabricated using such a synthesis technique are described including a single crystal CVD diamond layer which has a large area and a low nitrogen concentration, and a high purity, fast growth rate single crystal CVD diamond material.
1 . A method of fabricating a single crystal CVD diamond layer using a microwave plasma activated chemical vapour deposition technique, the single crystal CVD diamond layer having a total nitrogen concentration as measured by secondary ion mass spectrometry of no more than 2 ppm and an area of at least 324 mm 2 , the method comprising:
introducing a substrate into a plasma chamber;
introducing process gases into the plasma chamber, the process gases including hydrogen gas and a carbon source gas; and
introducing microwaves into the plasma chamber to activate the process gases and form a plasma proximate to a growth surface of the substrate wherein synthetic diamond material is grown over the growth surface of the substrate,
wherein during growth of the synthetic diamond material a microwave power density is maintained at a power density of at least 3 W/mm 2 over a growth surface area of at least 2500 mm 2 for a time period of at least 24 hours said microwave power density being calculated by dividing input microwave power by substrate growth surface area; and
the single crystal CVD diamond layer exhibits substantially no fluorescence from dislocation defects in addition to substantially no fluorescence from nitrogen-vacancy defects.
2 . A method according to claim 1 , wherein the microwave power density is at least 3.2 W/mm 2 , 3.4 W/mm 2 , or 3.6 W/mm 2 .
3 . A method according to claim 1 , wherein the microwave power density is no more than 10 W/mm 2 , 8 W/mm 2 , 6 W/mm 2 , 5 W/mm 2 , or 4 W/mm 2 .
4 . A method according to claim 1 , wherein the microwave power density is maintained at a target value with a variation over time of no more than ±5%, ±3%, ±2%, or ±1% as measured by fluctuations in total power input to the plasma chamber averaged over 5 second measurement periods for a time period forming at least 30%, 50%, 70%, 90%, or 95% of a total growth time period.
5 . A method according to claim 1 , wherein the growth surface area is at least 2827 mm 2 , 3848 mm 2 , 5027 mm 2 , 6362 mm 2 , or 7054 mm 2 .
6 . A method according to claim 1 , wherein the growth surface area is no more than 15394 mm 2 , 13273 mm 2 , 11310 mm 2 , or 9503 mm 2 .
7 . A method according to claim 1 , wherein the time period is at least 48 hours, 72 hours, 96 hours, 120 hours, 168 hours, 216 hours, 288 hours, 360 hours, 432 hours, or 504 hours.