| The thermal conductivity of substrates applied in electronic industry become interested by researchers because the devices become smaller,faster and higher power. Beryllia (BeO) ceramics are optimum materials for applications on electronic device because of high thermal conductivity (TC) at room temperature and low dielectric constant. However, the TC of BeO is still a limit for electronic device developing to minitype and high-density. In the present work, diamond films were deposited on beryllia substrates by Hot Filament Chemical Vapor Deposition (HFCVD) to improve the thermal behavior of BeO. The surface morphologies of diamond films were characterized by metallographic microscopes scanning electron microscope (SEM) and atom force microscope(AFM), and the components and textures were analyzed by X-ray diffractometer(XRD), while the thermal conductivity were calculated according to the thermal diffusivity measured by laser-diathermometer. Influences of depositional conditions on the quality of diamond films and the properties of composites were analyzed according to the experiments.The following conclusions can be drawn from this work:1,The cohesion of films and substrates can be improved by scratching BeO with waterproof abrasive paper, and HF pre-treatment can be effective to prevent the films scaling off from BeO, thus uniform diamond films can be obtained.2,The grain size and the crystallinity of diamond reduced with the increasing of the concentration of CH4, or the total flow rate of CH4 and H2. Uniform and lower roughness films can be obtained when ratio of CH4 and H2 was 48.5 sccm to 1.5 sccm.3,Diamond grown on frontal surface and side face of BeO can enhance the thermal conductivity of diamond/BeO composites by 15% and 11% respectively, while the contribution of diamond on back surface is not so remarkable. Besides, textured diamond with larger grain size can enhance the thermal conductivity of the composite by 35% compared with original BeO. |
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