Correlation between growth mechanism of macrocrystalline diamond-ultrananocrystalline diamond composite and mechanical properties of its thin THz TWT windows

Through engineering a multilayered structure of microcrystalhne diamond (MCD) and ultrananocrystalline diamond (UNCD), we have recently fabricated a 60 μm thick composite diamond film for THz TWT windows. Tests showed that such a composite diamond film possessed sufficient mechanical strength and air-tightness. The surface roughness of the composite was managed via structural design that the lapping and polishing process could be avoided. Correlation between Growth mechanism of MCD-UNCD composite and mechanical properties of its thin THz TWT windows is given and discussed.