Focused ion beam milling of diamond: Effects of H2O on yield, surface morphology and microstructure

The effects of H2O vapor introduced during focused ion beam ~FIB! milling of diamond~100! are examined. In particular, we determine the yield, surface morphology, and microstructural damage that results from FIB sputtering and H2O-assisted FIB milling processes. Experiments involving 20 keV Ga bombardment to doses ;10 ions/cm are conducted at a number of fixed ion incidence angles, u. For each u selected, H2O-assisted ion milling shows an increased material removal rate compared with FIB sputtering ~no gas assist!. The amount by which the yield is enhanced depends on the angle of incidence with the largest difference occurring at u575°. Experiments that vary pixel dwell time from 3 ms to 20 ms while maintaining a fixed H2O gas pressure demonstrate the additional effect of beam scan rate on yield for gas-assisted processes. Different surface morphologies develop during ion bombardment depending on the angle of ion incidence and the presence/absence of H2O. In general, a single mode of ripples having a wave vector aligned with the projection of the ion beam vector forms for u as high as 70°. H2O affects this morphology by lowering the ripple onset angle and decreasing the ripple wavelength. At high angles of incidence (u.70°) a step/terrace morphology is observed. H2O-assisted milling at u.70° results in a smoother stepped surface compared with FIB sputtering. Transmission electron microscopy shows that the amorphized thickness is reduced by 20% when using H2O-assisted FIB milling. © 2003 American Vacuum Society. @DOI: 10.1116/1.1619421#