A novel method for making high aspect ratio solid diamond tips

A novel method for making high aspect ratio solid diamond tips is presented. The new method is based on focused ion beam (FIB) milling of high aspect ratio inverted conical-shape holes in silicon, then the holes are filled with diamond by hot-filament chemical vapor deposition (HFCVD) method, the solid diamond tips are formed after removal of silicon by wet chemical etching. Inverted conical shape holes of high aspect ratio with controllable depth and curvature has been achieved by optimising the beam current, the diameter of the milled holes, the milling time and the scan scheme. SEM inspection has revealed that the diamond tip has up to 7.5:1 aspect ratio, and tip apex radius can be as small as sub-50 nm. The micro-Raman (mRm) spectrum from a diamond tip shows dominant diamond line at 1332 cm−1 and a slight peak at 1500 cm−1 from the sp2 bonded carbon. The high aspect ratio solid diamond tips have potential applications in indenters and electron emitters due to the excellent mechanical and negative electron affinity (NEA) properties of diamond.