2002 Fiscal Year Final Research Report Summary
Coordination Environment in n-type Conductive Amorphous (GeSe3.5)100-xBix System
| Project/Area Number |
13650731
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | Yamagata University |
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Principal Investigator |
USUKI Takeshi Yamagata Univ., Dep. Mat. Bio. Chem., Associate Prof., 理学部, 助教授 (70250909)
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| Project Period (FY) |
2001 – 2002
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| Keywords | amorphous semiconductor / n-type conductor / local atomic structure / mechanical alloying / EXAFS / X-ray diffraction |
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| Research Abstract |
Amorphous (GeSe3.5)100-xBix systems have been prepared by mechanical milling method, and their structural changes have been investigated using X-ray diffraction and EXAFS measurements.
Sharp diffraction patterns of crystalline Bi and Se were easily replaced by halo patterns during milling. On the other hand, the disappearance of the Bragg lines of crystalline Ge occurs very slowly. It is of interest that new Bragg lines assigned to an intermediate compound Bi2Se3 were observed at the early stage of the milling, although the amorphous halo patterns can be obtained finally.
Least-squares fitting analysis for the experimental X-ray and EXAFS structure functions have been carried out under the assumption that first coordination shell is composed of Ge-Se, Se-Se and Bi-Se correlations. Short-range order of GeSe4/2 tetrahedral units remains almost unchanged. The bond-length and coordination number of the Bi-Se bond are determined to be 0.276 nm and 3.0, respectively, implying that the BiSe3/2 pyramidal units are formed in the present amorphous alloys, which is strongly related to the n-type electronic conduction.
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