| 日時: |
2007-11-12 16:00 - |
| 場所: |
4号館2階輪講室1 |
| 会議名: |
NSRL XAFS station and its applications to the studies of dilute magnetic semiconductors and quantum dots |
| 連絡先: |
野村昌治 |
| 講演者: |
Dr. Zhiyun Pan (National Synchrotron Radiation Laboratory, ) |
| 講演言語: |
英語 |
| アブストラクト: |
X-ray absorption fine structure (XAFS) is used to probe local structures of
condensed matters, and provides the quantitative local structural information around
an element species in a complex material. The general performance of U7C-XAFS station
of National Synchrotron Radiation Laboratory (NSRL) will be introduced in detail.
The XAFS studies on GaN- and ZnO-based dilute magnetic semiconductors show the
occupation sites of Mn and Co atoms in a variety of GaN- and ZnO-based DMS materials
prepared by different methods such as MBE, CVD, PLD and sol-gel method. It indicates
that at low doping concentrations, the dopants Mn and Co are substitutionally incorporated
into the host lattice; at higher Mn and Co doping concentrations, the metal clusters
and secondary phases are formed. The structural results are well correlated with the
observed magnetic properties and are helpful for understanding the complicated nature of
the magnetic interactions in DMSs. The studies on the self-assembled GeSi quantum
dots (QDs) grown on Si(001) substrate by multiple-scattering (MS) EXAFS reveal that
the degree of Ge-Si intermixing for Ge-Si QDs strongly depends on the temperature.
The compressively strained nature of the QDs is discussed in detail, demonstrating
that the MS-EXAFS provides detailed information on the QDs strain and
the Ge-Si mixing beyond the nearest neighbors.
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