Probing deep interaction potentials with white-noise-driven atomic force microscope cantilevers

Perturbations to the thermally driven motion of an atomic force microscope (AFM) cantilever can be used to probe tip-sample interactions. One limitati on of such thermal-noise-based measurements is that they fail for large att ractive interactions with force gradients that exceed the stiffness of the cantilever. In such cases, the AFM tip jumps to the surface and is trapped there for long periods of time. Here, we describe an approach to overcome t his limitation by driving the AFM cantilever with white noise, essentially simulating high temperatures. Effective temperatures of several thousand Ke lvin are easily obtained. We show that this approach allows the AFM tip to "thermally" sample interactions that would otherwise capture the tip. (C) 2 000 American Institute of Physics. [S0003-6951(00)03520-8].