John A. Carlisle

Preventing Nanoscale Wear of Atomic Force Microscopy Tips Through the Use of Monolithic Ultrananocrystalline Diamond Probes

Nanoscale wear is a key limitation of conventional atomic force microscopy (AFM) probes that results in decreased resolution, accuracy, and reproducibility in probe-based imaging, writing, measurement, and nanomanufacturing applications. Diamond is potentially an ideal probe material due to its unrivaled hardness and stiffness, its low friction and wear, and its chemical inertness. However, the manufacture of monolithic diamond probes with consistently shaped small-radius tips has not been previously achieved. The first wafer-level fabrication of monolithic ultrananocrystalline diamond (UNCD) probes with <5-nm grain sizes and smooth tips with radii of 30-40 nm is reported, which are obtained through a combination of microfabrication and hot-filament chemical vapor deposition. Their nanoscale wear resistance under contact-mode scanning conditions is compared with that of conventional silicon nitride (SiN(x)) probes of similar geometry at two different relative humidity levels (approximately 15 and approximately 70%). While SiN(x) probes exhibit significant wear that further increases with humidity, UNCD probes show little measurable wear. The only significant degradation of the UNCD probes observed in one case is associated with removal of the initial seed layer of the UNCD film. The results show the potential of a new material for AFM probes and demonstrate a systematic approach to studying wear at the nanoscale.

Charging characteristics of ultra-nano-crystalline diamond in RF MEMS capacitive switches

Modifications to a standard capacitive MEMS switch process have been made to allow the incorporation of ultra-nano-crystalline diamond as the switch dielectric. The impact on electromechanical performance is minimal. However, these devices exhibit uniquely different charging characteristics, with charging and discharging time constants 5–6 orders of magnitude quicker than conventional materials. This operation opens the possibility of devices which have no adverse effects of dielectric charging and can be operated near-continuously in the actuated state without significant degradation in reliability.

Heated atomic force microscope cantilevers with wear-resistant ultrananocrystalline diamond tips

We report a wear-resistant ultrananocrystalline diamond (UNCD) tip integrated onto a heated atomic force microscope (AFM) cantilever. The batch-fabricated UNCD tips have tip radii of about 10 nm and heights up to 7 μm. The tips were wear-resistant throughout 1.2 m of scanning over a silicon grating at a force of 200 nN and a speed of 10 μm/s. Under the same conditions, a silicon tip was completely destroyed. When used for thermal imaging, the UNCD tip heated cantilever has a vertical imaging resolution of 1.9 nm. Finally, we demonstrate thermal nanolithography of hundreds of nano structures of polyethylene.