Effect of nitrogen and oxygen addition on morphology and texture of diamond films (from polycrystalline to nanocrystalline)

We investigate the effect of simultaneous nitrogen and oxygen addition into conventional methane–hydrogen plasma on morphology and texture of diamond films produced in a high power high pressure 5 kW microwave plasma chemical vapor deposition (MPCVD) reactor. Diverse diamond films ranging from large-grained polycrystalline to nanocrystalline can be achieved by simply changing the amount of nitrogen and oxygen addition, while keeping other parameters the same. This opens a new operating window for tailoring the growth of diamond for different applications. Our study shows that: (1) a small amount of oxygen addition leads to a {111}facet dominated large-grained polycrystalline diamond film of mixed <211> and <110> texture; (2) a small amount of nitrogen addition favours the formation of a <110> textured nanocrystalline diamond film; whereas (3) the coupled effect of simultaneous nitrogen and oxygen addition is in between them. The versatility of nitrogen and oxygen addition on tailoring diamond growth ranging from polycrystalline to nanocrystalline diamonds with different microstructures, morphologies and textures is clearly demonstrated.