Methods of fabricating synthetic diamond materials using microwave plasma activated chemical vapour deposition techniques and products obtained using said methods

Abstract

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 single crystal CVD diamond layer comprising:
 a total nitrogen concentration as measures by secondary ion mass spectrometry of no more than 2 ppm; and   an area of at least 324 mm 2 .   
     
     
         2 . A single crystal CVD diamond layer according to  claim 1 , wherein the total nitrogen concentration is no more than 1.5 ppm, 1.0 ppm, 0.8 ppm, 0.5 ppm 0.1 ppm, 0.05 ppm, or 0.01 ppm. 
     
     
         3 . A single crystal CVD diamond layer according to  claim 1 , wherein the area of the single crystal CVD diamond layer is at least 361 mm 2 , 400 mm 2 , 484 mm 2 , 625 mm 2 , 900 mm 2 , 1600 mm 2 , or 2500 mm 2 . 
     
     
         4 . A single crystal CVD diamond layer according to  claim 1 , wherein the single crystal CVD diamond layer has a thickness of at least 30 micrometers, 60 micrometers, 100 micrometers, 150 micrometers, 200 micrometers, 250 micrometers, 300 micrometers, or 500 micrometers. 
     
     
         5 . A single crystal CVD diamond layer according to  claim 1 , wherein the single crystal CVD diamond layer is comprises a plurality of inter-crossing dislocation lines. 
     
     
         6 . A single crystal CVD diamond layer according to  claim 1 , wherein the single crystal CVD diamond layer exhibit one or both of the following characteristics:
 (i) an optical absorption coefficient at a wavelength of 1.064 μm of less than 0.09 cm −1 , 0.05 cm −1 , 0.02 cm −1 , or 0.01 cm −1 .   (ii) an optical absorption coefficient at a wavelength of 10.6 μm of less than 0.04 cm −1 , 0.03 cm −1 , 0.02 cm −1 , or 0.01 cm −1 .   
     
     
         7 . A single crystal CVD diamond layer according to  claim 1 , wherein the single crystal CVD diamond layer is in the form of a free-standing single crystal CVD diamond wafer. 
     
     
         8 . A single crystal CVD synthetic diamond material according to  claim 1  comprising:
 substantially no orange luminescence from nitrogen-vacancy defects as viewed under photoluminescent conditions; and 
 substantially no blue luminescence from dislocation defects as viewed under photoluminescent conditions. 
 
     
     
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         16 . A method of fabricating a single crystal CVD diamond layer according to  claim 1  using a microwave plasma activated chemical vapour deposition technique, 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 1963 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. 
 
     
     
         17 . A method according to  claim 16 , wherein the microwave power density is at least 3.2 W/mm 2 , 3.4 W/mm 2 , or 3.6 W/mm 2 . 
     
     
         18 . A method according to  claim 16 , 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 . 
     
     
         19 . A method according to  claim 16 , 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. 
     
     
         20 . A method according to  claim 16 , wherein the growth surface area is at least 2827 mm 2 , 3848 mm 2 , 5027 mm 2 , 6362 mm 2 , or 7054 mm 2 . 
     
     
         21 . A method according to  claim 16 , wherein the growth surface area is no more than 15394 mm 2 , 13273 mm 2 , 11310 mm 2 , or 9503 mm 2 . 
     
     
         22 . A method according to  claim 16 , 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.