科学研究

材料学院学术报告五:Anomalous signchange in the Seebeck Coefficient of few layer MoS2

发表于: 2017-03-31 19:02 点击:

报告人/报告内容简介:

Biography:

Dr. Wu Jing obtained his Bachelor’s degree (Hons) in Physics form Zhejiang University (China), in 2010. He then received his Ph.D. in physics in 2015 from National University of Singapore under the supervision of Prof. Barbaros Özyilmaz. Dr. Wu joined the Centre of advanced 2D materials as a research Assistant in 2014. Later he joined the Department of electrical and computing engineering at the National University of Singapore in 2015 as a Research Fellow. In 2016, he joined Institute of Materials Research and Engineering(IMRE) under A*STAR, where he is presently a Research Scientist.

Dr. Wu’s fields of interest are in experimental studies of thermo/opto-electronics transport through 2D systems and work on the nano-scale device physics. His experimental skills of expertise are nano-device fabrication and low-temperature measurements. His current research works focus on thermoelectric transport of thin film MoS2and Black Phosphorous.

Abstract:

Thermoelectrics provides a means to harvest energy sustainably from the environment and also plays an important role in materials science. Such environmentally friendly energy conversion sources are considered to be promising for supplementing future global energy demands. In recent years, low dimensionality (one-dimensional and two-dimensional) has openedup new routes to achieve high efficiency thermoelectric devices. High mobility two-dimensional (2D) transition metal dichalcogenides semiconductors represent a new class of thermoelectric materials due to theirenhanced density of states of confined carriers, as well as their large effective masses and valley degeneracies.

In most cases, the Seebeckcoefficient is determined by a normal energy-dependent electronic density of statesnear the Fermi level and the charge carrier type (electrons or holes). Thusin previous studies, only a negative Seebeckcoefficientdue to conduction electrons was observed in MoS2based devices.In this study, we observe for the first time, a positive Seebeck coefficient in n-doped six-layer MoS2at temperatures below ~70K, which indicatesthat theSeebeck effect originates from the change in energy dependence of the charge-carrier relaxation times. The measured mobility undergoes a concomitant change in the slope at the same temperature, which corroborates a change in the relaxation time as a function of temperature and resultsin a sizable positive addition to the Seebeck coefficient. At low temperatures, we observe a large positive Seebeck(~ 1.5 mV/K at 50K). This new finding advances the study of thermoelectric physics in 2D materials and demonstrates a new avenue for superior thermoelectric performance by tuning the energy-dependent relaxation time.

报告时间:2017年4月1日 下午2:00

报告地点:F220

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深圳大学材料学院

2017年3月31日

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