关于举办徐勇博士学术报告会的通知

题目：Work function tuning at hybrid inorganic/organic interfaces
报告人：Yong Xu（Fritz Haber Institute, Berlin, Germany）
时间：2012年9月24日（星期一）上午10：30
地点：18号楼二楼213室物理系报告厅

报告摘要：A key task for optimizing optoelectronic devices comprising hybrid inorganic/organic systems is to control the energy level alignment at interfaces. The use of thin interlayers that introduce interface dipoles provides a pathway to solve this challenge. This concept has been well demonstrated for metal/organic systems. However, whether similar concept works for semiconductor/organic systems remains an open question. In this work, we investigated the polar surfaces of ZnO, modified by the prototypical organic electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). We show that the work function (f) of ZnO surfaces can be increased from below 4.5 eV up to 6.5 eV by depositing F4TCNQ. Photoemission experiments and hybrid density functional theory calculations reveal that the f increase is due to partial occupation and pinning of the lowest unoccupied molecular orbital (LUMO) of F4TCNQ at the Fermi-level of the n-doped ZnO substrate. However, compared to metal/F4TCNQ interfaces, the f increase here is accompanied by much less charge transfer into the F4TCNQ LUMO, which is explained by the distinctly different orbital hybridization and adsorption geometry. We identify the doping level of the inorganic semiconductor substrate and the associated band banding at the surface as key parameters for understanding and controlling the level alignment.

个人简历：

Family Name / First Name:  Xu / Yong
Institute:   Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
Email:     yongxu@fhi-berlin.mpg.de

Research Interests ： 
Understand and predict novel materials properties by first-principles approaches
Develop methods for mesoscopic electronic and thermal transport

Experience ：                                            
Postdoctoral Fellow (Alexander von Humboldt Fellowship):  06/2011 – present
Postdoctoral Fellow (Max-Planck-Gesellschaft Fellowship):  09/2010 – 05/2011
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
Advisor: Prof. Matthias Scheffler

Education ：                                                       
Ph.D. in Condensed Matter Physics:                     09/2005 – 07/2010
Institute for Advanced Study, Tsinghua University, Beijing, China
Advisor: Prof. Bing-Lin Gu and Prof. Wenhui Duan
B.S. in Physics:                                     09/2001 – 07/2005
Department of Physics, Tsinghua University, Beijing, China