Cvd Diamond Film Adhesion Properties And Applications

Adhesion is a basic factor for the application of CVD diamond film. In the present work, some general factors affecting CVD diamond film structures were studied, such as growth mechanism, existing form of sp2 bonding carbon atoms, and essence of textured growth. The effect of the films' structure feature on adhesion was also discussed. Some major factors affecting adhesion property were analyzed in several applied examples, and the parameters satisfying these apply to some extent were given.[1] The evaluation of the major factors affecting adhesion: the essence of the mechanical locked role is the elastic interaction between grains of the films and the polycrystalline substrates when a tangential force exerts the films. Compared to the chemical combining power and residual stress, the mechanical locked role also has the same impact on the adhesion.[2] The theory of the dynamics and thermodynamics on the growth process of the diamond film: It includes the rational elements in the models of dynamics control, surface reaction and the hydrogen atoms etching. Considering the template dynamics control factors' role of the surface, descriptions of growth mechanism of CVD diamond film such as thermodynamics factors, dynamics control, and surface reaction could be integrated into a unitary theory:a. The chemistry potential of carbon atoms is higher in the state of hydrocarbon gases than in solid state. The carbon atoms in hydrocarbon gases may probably drop to graphite or diamond phase that have a lower chemistry potential.b. The gas-state carbon atoms change into the solid-state through surface reaction.c. The effect of surface template is a major factor for controlling the way of conversion of the gas-state carbon atoms. The different surfaces (surfaces with different orientation of graphite and diamond) can choose the structure and energy state of the carbon atoms dropped onto them.d. Therefore, several kinds of different and independent surface reaction processes can occur at different sites of the substrate. These reactions are corresponding to growth on different surfaces.e. The orientation and velocity of these surface reactions are affected by thermodynamics factor of surface neighborhood. The reacting direction determines whether growth or etching occur for certain crystal surface. Growth of diamond and etching of graphite may be realized in a special range of temperature, of pressure, of flow ratio of different gases.f. The critical condition of nucleation was determined by the thermodynamics conditions such as local crystal lattice structure of the substrate, bonding structure, the gas temperature on the substrate surface, pressure, the fractional pressure of every kind of gas, and so on.g. The plasma system, having the energy change with the surroundings, and series of chemistry reactions occurred in gas phase, and only provide the required non-equilibrium thermodynamics condition and chemistry condition maintaining the growth of certain solid phase surface.[3] The detailed explanation to the concept and effect of the template included in the theory of the dynamics and thermodynamics: The template concept is an abstraction to the features of the surface structure, such as the atoms species, geometrical symmetry, electronic symmetry, bonds structure and surface periodicity. The dynamics control effect can be depicted as follows:a. The template effect of the surface of diamond or graphite can maintain the added carbon layers the same structure as the template structure. The diamond template has the tendency to maintain the added carbon atoms as sp3 hybridization under the condition of hydrogen-passivity on the surface. Meanwhile the graphite template could induce the carbon atoms degenerating from sp3 to sp2 state.b. Although the higher energy of the sp3 state compared to sp2, only having sp3 state of the added carbon atoms integrated into diamond surface could have lower energy to maintain stability, while sp2 could induce the higher syste...