Sina passed his doctoral dissertation defense titled: “Sub-Continuum Thermal Transport in Tip-Based Thermal Engineering”
For the past two decades, tip-based thermal engineering has made remarkable advances to realize unprecedented nanoscale thermal applications, such as thermomechanical data storage, thermophysical/chemical property characterization of materials in nanometer scale, and scanning thermal imaging and analysis. All these applications involve localized heating with elevated temperature, generally in the order of mean free paths of heat carriers, thus necessitates fundamental understanding of sub-continuum thermal transport across point constrictions and within thin films. This dissertation presents, for the first time, numerical modeling of transient ballistic-diffusive heat transfer, by solving Boltzmann transport equation for phonons, combining finite element analysis (FEA) with discrete ordinate method (DOM) in two-dimension using a commercial package, easily accessible to public, seeking to provide insight on sub-continuum thermal transport. In addition, for the first time, a three-dimensional FEA simulation is provided to predict full-spectrum behavior of a thermal cantilever, the main tool in tip-based thermal engineering, showing good agreement with measurements applying with 3w characterization technique. Finally, a home-built, smallest ever fabricated four-probe resistive nanothermometer/heater is used to quantitatively measure tip-substrate thermal transport. The Pt-Au nanothermometer/heater on Si-SiNx substrate is fabricated using combination of electron-beam lithography and photolithography. An atomic force microscope (AFM) cantilever at room temperature is used to scan over the 250nm x 350nm sensing area at an elevated temperature causing local cooling, used to measure tip-substrate thermal interactions. The outcomes of these studies provide a strong platform to fundamentally understand thermal transport in micro/nanometer scale.Congratulations Dr. Hamian!!!
