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使用超快激光光谱探测电子、声子传输
使用超快激光光谱探测电子、声子传输
教师介绍

本讲教师:王亚果
所属学科:工科
人  气:2020

课程介绍
摘要: As fundamental particles, dynamics and transport properties of electrons and phonons determine the performance of modern electronics. For example, in optoelectronics, such as ultrafast photodetectors, relaxation time of excited carriers measures how fast the detector can respond, carrier diffusion length controls how far carriers can travel and hence the efficiency and sensitivity. Phonons are quasiparticles derived from quantized lattice vibrations. Phonons can interact with electrons and phonon transport determines thermal properties of semiconductor devices. Electron/phonon dynamics usually occur in ultrafast time scale, e.g. femtosecond (10-15 s) to picosecond (10-12 s) regime, which could not be captured with traditional steady-state measurements. Pump-probe spectroscopy with femtosecond lasers can provide fs time resolution and has been utilized to detect electron/phonon transport with great details. This talk will demonstrate three examples of electron/phonon transport studied with pump-probe spectroscopies. Firstly, photo-excited carrier relaxation and diffusion process in graphene are probed by incorporating a grating imaging technique into standard femtosecond laser pump-probe spectrometer. The mobility of photo-excited carriers are several orders larger than Hall mobility and Field-Effect mobility measured at room temperature, indicating the remarkably different behavior of photo-excited carriers versus equilibrium carriers, as well as the necessity to use photo-carrier transport properties for optoelecronics. Secondly, phonon transport in thermoelectric materials will be discussed, where strong interface scattering and quantum confinement effect have been observed. Lastly, characterization of both in-plane and cross-plane thermal conductivities in nano metal films with nanosecond laser spectroscopy will be demonstrated. 个人简介(Biography): Yaguo Wang is currently an Assistant Professor of Mechanical Engineering department at University of Texas at Austin. Dr. Wang received her Bachelor's degree in Safety Science and Engineering at the University of Science and Technology of China (USTC) in 2005 and her Ph.D. degree from the Department of Mechanical Engineering, Purdue University, Indiana, in 2011. After one-year's postdoctoral experience at Purdue University, she joined UT Austin in January 2013. Dr. Wang received CAREER award from National Science Foundation in 2014. Dr. Wang's group studies a broad spectrum of topics with laser spectroscopies, including phonon transport in nanostructures, carrier transport in 2D materials, thermoelectrics, thermal transport in extreme environments, etc. She is also interested in atomistic simulations of energy-conversion materials and thermal management in nanoelectronics.

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