Characterizing the local oxidation nanolithography on highly oriented pyrolytic graphite

Here, we characterize the patterns obtained through local oxidation nanolithography (LON) on highly oriented pyrolytic graphite as the write bias, speed, and force were varied. Different types of patterns-bumps, cracked bumps, and trenches-were obtained and characterized using four shape descriptors-pattern width, pattern height, cut width and cut depth. With an increase in write bias the obtained pattern type varied from bumps to cracked bumps to trenches. The use of a bias above 7.25 V resulted in trenches with increased variability in shape descriptor values. Similarly, an increase in write speed demonstrated a transition from trenches to cracked bumps to bumps. An increase in write force from 75 to 150 nN showed a shift in the threshold voltage from 4.25 V to just under 3.75 V and formed cracked bumps instead of bumps. These findings help solve the mystery of why bumps were not reported at threshold voltages before 2008. We believe these findings will be enable uniform reproduction and report of LON pattern.