Probing Nanoscale Heat and Force Interactions Using Atomic Force Microscopes (afm)

Many devices and instruments such as magnetic hard disk drives and atomic force microscopes (AFM) rely on the stable operation of their small probing heads at nanoscale gaps. Due to the small scale of the probing heads, the force interactions (Casimir force and electrostatic force) between the small probes and the surrounding become more significant. The local heating caused by read/write electric currents in hard disk drives or probing laser beams in AFM on the probes inevitably leads to the heat transfer between them and the surrounding. The nanoscale heat and force interactions play a critical role in the performances of those instruments. In this paper, we use a bimaterial AFM cantilever to measure the nanoscale air heat conduction, radiation and force between a microsphere and a substrate. The resulting “heat transfer-distance” and “force-distance” curves clearly show the strong dependence of nanoscale interactions with gap distances. Recently, there have been general interests in measuring force [1-3] and heat transfer [4-6] interactions between bodies at nanoscale gaps. When two objects are very close to each other, the so-called Casimir force effects occur because of the fluctuation of the zeropoint energy of the electromagnetic field [1]. Casimir force can be attractive and repulsive depending on the way that materials interact with light [3]. In the nanoscale, thermal radiation can be significantly enhanced beyond the Planck’s blackbody radiation limit due to the photon tunneling [4, 7]. Many devices such as hard disk drives and atomic force microscopes (AFM) rely on the stable operation of their small probing heads at nanoscale gaps [8], thus the force and heat transfer effects between the probe and the substrate (or the sample) can become significant and influence the performance of the devices under certain circumstances. FIG. 1 Schematic diagram of experimental setup.