Development of a scanning surface probe for nanoscale tip-enhanced desorption/ablation...

We report on the development of a versatile scanning apparatus for nanoscale surface sampling that uses near-field enhancement of laser radiation at a sharp probe tip to effect desorption/ablation on opaque substrates. The process, which currently yields surface craters as small as ~ 50 nm diameter x 5 nm deep, has been demonstrated with both metal-coated and bare silicon tips. Significantly, either a tip field enhancement or a thermal factor results in near-field desorption/ablation at illumination intensities far below the corresponding far-field threshold, suggesting that the latter process should not degrade the spatial resolution attainable for proposed chemical imaging methods based on the scanning surface probe.