本期学术论坛由Universityof California, Berkeley的Dr.Liang Guo主讲
题目：Study of Nanoscale Heat Transfer Based on Ultrafast Spectroscopy
报告人：Dr.Liang Guo
时间：12月9日下午3:30
地点：机械楼南高厅
报告摘要:
Nanoscale heat transfer focuses ontransport properties of energy carriers within nanoscale dimensions and innon-equilibrium state and utilization or modification of these properties forapplication. Such study provides direction for design of nanoscale electronicsand development of new materials with energy application such asthermoelectrics and solar cell. Ultrafast spectroscopy is powerful in trackingtransient (femtosecond to picosecond) dynamics of energy carriers withfemtosecond time resolution, which unravels excitation, relaxation andinteraction of energy carriers including electrons, holes, phonons, photons andexcitons. This non-contact optical technique can easily work with control oftemperature, pressure and voltage, facilitating exploration of the environmenteffect on energy carrier transportation. In addition, ultrafast spectroscopy couldprovide theoretical guide for precision processing with consideration of thegrowing application of ultrafast laser for cutting, welding and 3D printing.
Thispresentation will introduce the physics of ultrafast spectroscopy and analysisof the signals and show the application for studying energy transportation innovel materials. Presented works include: selection of probe wavelength intime-domain thermoreflectance (TDTR) for particular temperature transducer toimprove matching with simulation and signal-to-noise ratio; Generation ofcoherent phonons by impulsive stimulated Raman scattering and mode-wisedetection according to selection rules of Raman scattering for phonon dynamics;two-dimensional electronic spectroscopy (2DES) with high resolution in bothtime and frequency domains for exciton dynamics in low-dimensional materials.
Dr.LiangGuo received Bachelor degree in Mechanical Engineering, Tsinghua University in2009. He conducted graduate research on nanoscale heat transfer in Prof. XianfanXu’s group in Mechanical Engineering, Purdue University. His projects includeheat transfer across metal-dielectric interfaces, wavelength tuning effect inTDTR, and phonon dynamics in thermoelectrics based on Bi2Te3and skutterudites. He obtained PhD degree in 2014, after which he utilizedfemtosecond four-wave mixing (FWM including two-pulse photo echo, three-pulsephoto echo and 2DES) to study energy transfer in novel semiconductors in Prof.Graham Fleming’s group in Chemistry, University of California, Berkeley. Hiscurrent project is exciton dynamics in monolayer transition metal dichalcogenides(TMDCs).
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