Focused-Ion-Beam Induced Nano Feature Self-Assembly on Glassy Carbon

Glassy carbon is an advanced non-graphitizing carbon material with many unique properties. This work explores the surface modification and machining characteristics of glassy carbon when subject to a Focused Ion Beam (FIB) over a range of incident angles. A FIB system delivering a 30 keV Ga+ ion beam was used to irradiate the surface of polished glassy carbon substrates. On irradiation at incident angles less 40 degrees, the surface is smooth and uniform. Nano particle deposits were observed on the irradiated floor and sidewalls after prolonged irradiation. With incident angles over 40, the irradiated area exhibits nano-scale patterns in the form of ripples, steps and columnar features. The evolution of these structures increases with the incident angle. The orientation of the nano features changes from parallel to perpendicular with respect to the direction of propagation of the ion beam. Although the simultaneous formation of nano features could be problematic for applications such as ion milling or polishing, they offer an effective means of developing nano-scale surface modification at the point of irradiation. Possible applications are discussed.