摘要
The bands of a material may be engineered to achieve desirable properties. In this talk, I will introduce our band structure engineering experiments in trilayer graphene and complex oxide LaTiO3/KTaO3 interfaces. We fabricate dual gated devices on ABC and ABA stacked trilayer graphene. The HfO2 top and bottom gates enable independent tuning of the perpendicular electric field through the trilayer graphene and change its band structure. We observe a resistance change of 6 orders of magnitude in the ABC trilayer, which demonstrates the opening of a band gap. In contrast, the ABA trilayer remains metallic, and the band structure of the ABA trilayer continues to evolve with increasing D. Emergent conducting channels at complex oxide interfaces display a wide range of solid state phenomena, ranging from superconductivity to magnetism. To date, the only transition metal oxide that has been found to host a conducting channel for a 2D electron gas (2DEG) is the perovskite SrTiO3. One serious technological limitation of SrTiO3-based conducting oxide interfaces for electronics applications is the relatively low carrier mobility (0.5 - 10 cm2/Vs) of SrTiO3 at room temperature. We report a new 2DEG system at the interface between LaTiO3 and KTaO3. By using KTaO3, we achieve mobilities in LaTiO3/KTaO3 interfaces as high as 21 cm2/Vs at room temperature, over a factor of 3 higher than observed in doped bulk SrTiO3. Ab initio calculations predict the formation of a 2DEG in the interfacial KTaO3 layers that resides in bands having Ta 5d character. We attribute the higher mobility in the KTaO3 2DEGs, compared to SrTiO3 2DEGs, to the smaller effective mass for electrons in KTaO3 in these bands.
K. Zou et al. Nano Letters, 13, 369-373 (2013).
K. Zou et al. APL Materials, 3 036104 (2015).
报告人简介
B.S. University of Science and Technology of China (2006) Material Physics
Ph. D. The Pennsylvania State University (2012) Physics
Post-doctoral Associate. Yale University (2012-pressent) Applied Physics
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