Scaling approach toward nano electro-discharge machining: Nanoscale patterning of carbon nanotube forests

Micro-electro-discharge machining (mu EDM) is a versatile technique for micromachining of electrically conductive materials with resolutions limited within the micrometer scale. This paper reports an approach to pushing the resolution limit of mu EDM down to the nanometer scale. EDM with different electrode tip sizes is performed on carbon nanotube forests and the results reveal a favorable scaling effect of the tip size on the working voltage required for the breakdown of the dielectric between the electrode and workpiece, suggesting that downsizing of the electrode tip assists in the reduction of the discharge pulse energy. Based on this finding, controlled patterning of grating-like structures with similar to 200 nm height is demonstrated on carbon nanotube forests with an estimated pulse energy of 1 nJ, achieved using a tungsten electrode with a tip radius of 3 mu m. Theoretical analysis of this process setting shows a close match with the experimental results, further supporting the scaling effect. These results suggest the feasibility of the approach toward nano-EDM for an extensive range of potential applications in micro/nanodevice and nanotechnology areas. (C) 2015 Elsevier B.V. All rights reserved.