Synthesis of Diamond Film as Electromagnetic Window Material by an Ellipsoidal MPCVD Reactor at High Input Microwave Power Levels

Polycrystalline diamond film was grown using H2-CH4 as the source gas in a newly developed ellipsoidal MPCVD reactor at 8 kW microwave power levels.Surface morphology,quality,transmittance,thermal conductivity as well as complex permittivity of the diamond film were examined by scanning electron microscopy,Raman spectroscopy,spectrophotometer,thermal constant tester and cavity resonator method respectively.The result proved that the new ellipsoidal microwave plasma CVD reactor has the ability to deposit high quality diamond films at a high synthesis rate.After polished on both sides,the free-standing diamond film has high transmittance and thermal conductivity.At the same time the film has excellent microwave dielectric properties for complex permittivity less than 1×10-4 in the range of 23-36 GHz,this show the film is one of the perfect electromagnetic window materials.