ISSN Online: 2377-424X
International Heat Transfer Conference 12
Development of Scanning Thermal Microscopy for Nano-scale Real Temperature Measurement
Resumo
Scanning Thermal Microscopy (SThM) takes a thermal image by scanning a cantilever probe with a tiny
thermal sensor over sample surface. Spatial resolution of thermal measurement has been improved by reducing
sensor size, and reached to less than 30nm. However, an important issue remains: quantitative temperature
measurement. It is difficult to convert measured values to temperature or properties because conventional SThM
essentially measures not temperature, but heat flow rate between the sample and the cantilever; this depends on
both temperature and a contact thermal conductance influenced by such factors as thermal properties, sample
surface shape, adsorption layer, contact force, and so on. Therefore, we propose an active temperature
measurement method using a thermal feedback system. In the active method, feedback control maintains
equality of the cantilever temperature and the sample by detecting heat flow along the cantilever and feeding
power proportional to it to the cantilever; then, cantilever temperature is measured by another sensor. This active
method can measure real temperature in principle as long as conductance has finite value, no matter how it
changes. We have experimentally examined the active method by producing and modifying multi-function
cantilevers with a micro-fabrication technique. The first micro-fabricated cantilever with a differential
thermocouple as a heat flow sensor had insufficient sensitivity for measuring real temperature under low contact
conductance conditions. In contrast, a modified cantilever with a thermopile demonstrated good performance in
real temperature measurement regardless of difference in sample thermal conductivity. Furthermore, imaging
tests demonstrated that the active method can take a temperature image by compensating the influence of change
in the contact condition based on sample properties and shape.