Nanofabrication with carbon nano-cone as indenter tips

The indention behavior of both solid (sp³) and hollow (sp²) nano-cones on a thin cooper film is investigated by using the molecular dynamics (MD) simulation method. The hollow carbon nanocone is of graphitic nature and the solid one has the diamond-like structure. For the MD simulation, we adopt the Tersoff-Brenner potential for the carbon-carbon interaction, many-body tight-binding, second-moment-approximation (SMA) potential for copper-copper interaction, and a Morse-type pair potential for carbon-copper interactions. In addition, the Nose-Hoover method is utilized for maintaining temperature during the indentation. It can be envisaged that the graphitic cone tip is structurally weaker than diamond-like cone. However, our simulation results show that using this weaker tip can produce large aspect-ratio indents than a solid nano-cone. The rationale is that the hollow cone is sharpened during the indentation process due to shell buckling. The hollow cone remains its structural integrity after being pulled out from the substrate, indicating the elastic behavior of the shell buckling. Furthermore, hollow nano-cones require less force to reach a desired indentation depth due to this buckling-induced shape change providing easier pathway for penetration. The findings here may provide an alternative method for high aspect-ratio nanofabrication that is required by certain industrial applications.