Graphene-coated atomic force microscope tips for reliable nanoscale electrical characterization.

Graphene single-layer films are grown by chemical vapor deposition and transferred onto commercially available conductive tips for atomic force microscopy. Graphene-coated tips are much more resistant to both high currents and frictions than commercially available, metal-varnished, conductive atomic force microscopy tips, leading to much larger lifetimes and more reliable imaging due to a lower tip-sample interaction.

Calibration of the spring constant of AFM cantilever.

Several methods have been developed in recent years to calibrate the spring constant of atomic force microscopy (AFM) cantilever. In the present work, an effective and practical improvement is made on these methods to provide a more convenient calibration method. Simplifying the originally tedious procedures by just examining the cantilever's dimensions in scanning electron microscopy (SEM) and the resonance frequency of the cantilever from Q curves in AFM system, the spring constants of different cantilevers are calculated by the methods of Cleveland and Sader. The results are close to the nominal values provided by the manufacturers, which indicates that simplifying the procedures is valid and reliable. Moreover, it shows that spring constants acquiring by Cleveland method is more close to their nominal values than Sader's method does.