Temperature Measurement by Using Metal Thin Film Thermocouples

Abstract

We fabricate metal thin film thermocouples (TFTCs). Au-Pt, Cu-Ni, and W-Ni are deposited on a glass plate using standard thin film processes. The dimension of thermocouple junction is 300μm × 300μm. The thermoelectric powers of TFTCs are different from those of bulk because diffusion of electrons is restricted by the very thin film. The film thickness of TFTCs is of the same order as the mean free path of electrons. However TFTCs are still useful for temperature measurements because the thermoelectric voltage is proportional to measured temperature at thermocouple junction. The response time of Au-Pt TFTCs is about 30ns when the surface of the glass is heated by a YAG pulsed laser. The result compares favorably with measurements by a thermoreflectance method. We also describe W-Ni nano-TFTCs fabricated by Focused Ion Beam for the measurement of temperature distribution in a sub-micron area. In order to reduce the size of the TFTCs we employ a 3-dimensional structure.