学术报告：Is There High Temperature Ferromagnetism in Wide Band Gap Oxides?

发布者：系统管理员发布时间：2011-03-14浏览次数：14

报告人：Prof Tom Wu （吴韬）, Nanyang Technological University

邀请人：王金兰
时间：3月18号（周五）下午15:00pm
地点：田家炳南楼203

 

Abstract: The prospect of incorporating magnetic properties into semiconductor devices has provoked intensive research in developing diluted magnetic semiconductors. Recently, many works have been conducted on wide band gap oxides, aiming to achieve ferromagnetism at room temperature. But the major obstacle is: the magnetism is often so weak that it is often buried in extrinsic artifacts originating from metal clustering or contamination. Here I will discuss some of our recent efforts on this topic, including Cu-doped ZnO nanowires, Cr-doped In2O3 nanomaterials, and band-engineered Zn1-xMgxO films. I will argue that a comparative methodology should be considered as a critical component in experimental approaches. Furthermore, defects can be and must be controlled in order to achieve reproducible results, which often links with the formation of bound magnetic polarons. Finally, doping rare earth ions appears to be an effective route towards robust ferromagnetism with giant magnetic moments and anisotropy.

 

Relevant references:

1.       G. Z. Xing, D. D. Wang, J. B. Yi, L. L. Yang, M. Gao, M. He, J. H. Yang, Q. X. Zhao, J. Ding, T. C. Sum, and T. Wu*,  "Correlated d0 magnetism and photoluminescence in undoped ZnO nanowires" Appl. Phys. Lett. 96, 112511 (2010).

  1. Y. F. Li, R. Deng, G. Z. Xing, B. Yao and T. Wu*, "Tuning ferromagnetism in MgZnO thin films by band gap and defect engineering" Appl. Phys. Lett. 97, 102506(2010).
  2. G. Z. Xing, J. B. Yi, D. D. Wang, L. Liao, T. Yu, Z. X. Shen, C. H. A. Huan, T. C. Sum, J. Ding, and T. Wu*, "Strong correlation between ferromagnetism and oxygen deficiency in Cr-doped In2O3 nanostructures" Phys. Rev. B 79, 174406 (2009).
  3. G. Z. Xing, J. B. Yi, J. G. Tao, T. Liu, L. M. Wong, Z. Zhang, G. P. Li, S. J. Wang, J. Ding, T.. C. Sum, C. H. A. Huan, and T. Wu*, " Comparative study of structural inhomogeneity enhanced room-temperature ferromagnetism in Cu-doped ZnO nanowires" Adv. Mater. 20, 3521(2008).

Biography:

Dr. Tom Wu (吴韬) attended Zhejiang University and received his B. S. in physics in 1995. From 1996 to 2002, he studied in the Centre for Superconductivity Research in the University of Maryland, College Park, and received Ph. D. in electrical engineering. Then he joined Argonne National Laboratory, both in the Materials Science Division and the Centre for Nanoscale Materials as a postdoctorial researcher. Since July, 2006, he has been an assistant professor in the Division of Physics and Applied Physics, Nanyang Technological University (NTU). Dr. Wu’s major research interests are complex oxide thin films, nanowires, spintronics, and multiferroics. He has published more than 80 papers in peer reviewed journals, and was invited to give talks in many conferences like the American Physical Society March Meeting, the International Materials Research Congress, the International Union Materials Research Society, the ICAM Workshop, the APCTP workshop Villa Conference EMRS, and others. He is also the Co-PI of two ten-million SGD Competitive Research Programs supported by the Singapore National Research Foundation.

More information can be found at http://www1.spms.ntu.edu.sg/~tomwu/index.htm.