Study of A Nanocrystalline Diamond for Composite Diamond Windows in THz TWTs

摘要

Previously we have developed an extremely thin composite diamond film for THz TWT windows by incorporating ultrananocrystalline diamonds (UNCDs) into microcrystalline diamonds (MCDs). Given that the processing conditions for UNCD differ from those of MCD, we investigated a process of nanocrystalline diamond (NCD) as an alternative to UNCD. This type of NCD is grown at relatively high substrate temperature (~8700C) under the same gas mixture (CH4/H2) as MCD that the fabrication processing can be facilitated. Testing results show that the fabricated NCD films have an average mechanical strength of $1565pm 88$ MPa, no less than UNCD.