Thermal Expansion and Temperature Measurement in a Microscopic Scale by Using the Atomic Force Microscope

An experimental study on microscopic scale measurements of thermal expansion and temperature by using the Scanning Joule Expansion Microscope (SJEM) based on the Atomic Force Microscope (AFM) was conducted. While the AFM is scanning on the sample heated by AC current, topographical and thermal expansion images are measured simultaneously by detecting DC and AC motions of the cantilever. In order to apply this technique to the temperature measurement in microscopic scale, the sample was covered with a thin film of polymer (PMMA) which has a high thermal expansion coefficient compared with metals and dielectric materials. Merits of this technique are (1) quite simplicity of measurement because of using the commercial cantilever instead of complicated thermal cantilever for the typical Scanning Thermal Microscopy (SThM) and (2) a higher spatial resolution of 20 nm which is restricted by the point contact scale between the cantilever and the sample.