Surface investigations by scanning thermal microscopy

Abstract

A scanning thermal microscope has been developed which is capable of imaging thermal properties of materials with high spatial resolution. First results indicate a lateral resolution less than 200 nm. The microscope employs a miniaturized thermal probe whose tip is formed as a thermocouple. The probe is laser heated to generate a thermovoltage. A sample approaching the heated tip leads to a heat flow from the tip to the cooler sample surface and thus to a decrease of the measured voltage. In the initial experiments we scanned the tip above the sample surface with open feedback loop and mapped the thermovoltage at each location of the scan range. Furthermore, we closed the feedback loop keeping the thermovoltage constant and measured the z displacement of the piezoelectric tube carrying the probe. All these measurements yield topographical as well as thermal information of the sample surface.