Interface modifications to influence the adhesion of chemical vapor deposited diamond thin films

Diamond has many useful properties, however the largest potential applications of chemical vapor deposited (CVD) diamond thin films depend on adhesion to the substrate. Large strides have been achieved in understanding nucleation and growth of CVD diamond, but adhesion of CVD diamond to substrates is poor and there is little understanding of the factors that influence adhesion.;The focus of this study is to measure this interface strength and learn the factors that modify it. The interface bond is also important for other applications of CVD diamond including heat sinks and electrical contacts.;The principles of measuring adhesion borrow much from fracture mechanics. This is applied to adapt the blister test to overcome difficulties unique to CVD diamond. In this test a pressure difference is applied across a thin film and the pressure when the film separates from the substrate is measured.;Silicon is chosen as a substrate because diamond on silicon is a brittle substrate and film combination and thus the influence of plasticity is eliminated, diamond deposits easily on silicon, it is easy to implement methods to chemically etch silicon and mask silicon from etching, and since silicon forms a carbide the results obtained should apply to most other substrate materials.;The blister test experimental apparatus to measure critical pressure and volume was constructed and applied to measure several films. The substrate surfaces are modified before deposition to influence bonding of the diamond. Diamond films are grown on an optimally mechanically roughened and seeded substrate, using direct current (DC) plasma on a smooth substrate and biased enhanced nucleation (BEN) diamond on a smooth substrate. Two main factors, carbon in-diffusion and incomplete coverage of the seeds on the substrate, that increase the bonding for the roughened and seeded sample are emulated without mechanical damage using predeposition diffusion and abbreviated BEN. An experimental matrix tests these treatments and shows that these treatments increase adhesion. Possible reasons these factors increase adhesion are that in-diffusion might assist with chemical bonding of surface carbon atoms to the substrate and incomplete seeding contributes to in-diffusion in normal diamond growth ambients.