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强磁场科学论坛邀请了台湾成功大学黄荣俊教授访问中心并作学术报告，欢迎大家参加，请感兴趣的老师同学相互转告！
时间：
地点：磁体装备大厅203会议室
报告题目：Large ON/OFF ratio of ultrathin (Bi1-xSbx)2Se3 field effect transistor and magnetic proximity effect in (Bi1-xSbx)2Se3/CoFe2O4
报告摘要：
Ultrathin films of topological insulator (TI) are well known the promising candidates for the large ON/OFF ratio field effect transistor (FET). Owing to their unique chemical potential-dependent spin polarization, spin-current transistors are expected to be realized and become one of the major research goal towards nanoscaled spintronic device applications. To date, most of the studies mainly focused on the prototype TI, namely the Bi2Te3, Bi2Se3, Sb2Te3 and ternary (Bi1-xSbx)2Te3. However, tunable TI systems with topological phase transition such as antimony-doped Bi2Se3 are rarely explored in this ultrathin regime. We have demonstrated the strong and robust topological surface states (TSS) in this (Bi1-xSbx)2Se3 ternary compound as revealed by ARPES and transport measurement. In this work, we further studied the field-effect properties of ultrathin (Bi1-xSbx)2Se3 that grown on SrTiO3 (111) by MBE. By increasing the Sb doping level and reducing the film thickness down to ~5 nm, there is a crossover of transport phenomena from quantum diffusive to intermediate insulating regime (kFl~1) or strong disorder regime (kFl<<1). Large ON/OFF ratio was obtained in 5-nm FET in which the resistance has increased by almost two order of magnitude (~14000%) when Fermi level (EF) is shifted downward by applying negative back gate voltage, Vg. The presence of ambipolar-like behavior and very large Rxx, max with kFl<<1 suggest that the EF is tuned inside the surface gap that opened due to the hybridization of the top and bottom surface states. In comparison to other system with similar thickness, the obtained ON/OFF ratio in our finding is among the largest. The reduction of the sheet carrier concentration due to the Sb doping and the ultrathin thickness should be the main ingredient for such a high ON/OFF. The magnetic proximity effect in (Bi1-xSbx)2Se3/CoFe2O4 and other key progress of 3D TIs and 2D TIs recently developed in our research group will also be presented in this talk.
报告人简介：
黄荣俊教授1985年于台湾大学物理系获学士学位；1992年于美国伊利诺伊大学厄本纳-香槟分校（UIUC）物理系获博士学位。1992年10月至今先后任台湾成功大学物理系副教授、教授、特聘教授以及成功大学理学院光电科学与工程研究所与工学院奈米科技暨系统工程研究所合聘教授。期间，先后兼任高雄大学应用物理系主任与理学院院长、成功大学研究发展处副研发长、台湾欧盟计划南部办公室主任、台湾物理学会理事长、台湾磁性技术协会副理事长、台湾同步辐射中心监事、台湾工业技术研究院审查委员、台湾国科会自然处审议委员、台湾南部科学工业园区咨询委员会委员、合肥工业大学客座教授。黄教授从事自旋电子学薄膜与纳米结构材料以及相关磁性与光电器件的研究工作超过20年，研究涉及磁性金属、稀磁半导体、自旋零禁带半导体、拓扑绝缘体、多铁性材料、有机光电材料与器件、磁性隧道结、自旋发光二极管、磁性随机存储器、磁性发光二极管等领域。近20年来承担台湾国科会各类研究项目近40项（其中包括3项台湾奈米国家型计划，类似于973计划），研究经费超过1亿元新台币，已发表学术论文180余篇，合著（译）专著3本。
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