Thermal conductivity measurement and microscopy of thin film structures

This work discusses two techniques for thermophysical property characterization: scanning laser thermoelectric microscope (SLTM) and scanning thermal microscope (SThM). The SLTM can be used to measure thermal diffusivity of thin films as well as bulk materials. In SLTM, a modulated laser beam is focused through a transparent substrate onto the film-substrate interface. The generated thermal wave is detected using a fast responding thermocouple formed between the sample surface and the tip of a sharp probe. By scanning the laser beam around the thermocouple, the amplitude and phase distributions of the thermal wave are obtained with micrometer resolution. Thermal diffusivity of the film is determined by fitting the obtained phase signal with a three dimensional heat conduction model. The SThM technique is based on measuring the temperature variations of a laser heated nanoscale temperature sensor when the sensor is scanned over the sample surface. The temperature sensor is a thermistor film deposited onto the tip of an atomic force microscope cantilever. Although the SThM shows a high spatial resolution, the thermal image is strongly coupled to topographical variations.