QUANTITATIVE NANOMETER-SCALE THERMAL METROLOGY USING SCANNING JOULE EXPANSION MICROSCOPY BY

This thesis presents the development of a quantitative nanometer-scale thermal metrology technique, which is shown to obtain ~10 nm spatial and ~250 mK temperature resolution of the temperature rise of a graphene transistor. This is a large improvement over current state-of-the-art thermal metrology techniques which are on the order of 100 nm spatial and ~200 mK temperature resolution. The atomic force microscope (AFM) based thermal imaging technique is scanning Joule expansion microscopy (SJEM). SJEM operates by supplying a periodic voltage waveform to heat a sample, and the AFM measures the associated thermo-mechanical expansion of the surface. SJEM technique and artifacts are discussed to improve measurement accuracy, and a thermo-mechanical model is developed to correlate surface expansion to sample temperature. To demonstrate the capabilities of SJEM the temperature field of a graphene transistor and its contact to metal electrodes are measured. Thermal images reveal small ~100 nm diameter “hot spots ” which exist on the graphene sheet, which are believed to be due to sample fabrication. Comparison of temperature measurements of graphene-metal contacts with a model of heat dissipation in graphene reveal that Joule heating, current crowding, and thermoelectric effects occur at the graphene contact. The agreement of the measurements with predictions demonstrates the high resolution capabilities of SJEM. The development of a quantitative nanometer-scale thermal measurement technique can have significant impacts on material characterization and the microelectronics industry. II