1996 Fiscal Year Final Research Report Summary
Examination of dimensionality for Low Dimensional Conductors Using High Pressure Transport Measurement
| Project/Area Number |
07640439
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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 |
固体物性Ⅰ(光物性・半導体・誘電体)
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| Research Institution | Japan Advanced Institute of Science and Technology |
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Principal Investigator |
KOYANO Mikio JAIST,School of Materials Science, Associate Professor, 材料科学研究科, 助教授 (60195873)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Dimensionality of transport / Low Dimensional Conductor / Transport Properties / TiS_3 / Carrier Scattering / eta-Mo_4O_<11> / Charge Density Wave / Sliding Motion |
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| Research Abstract |
I have found the following results for one dimensional semiconductor TiS_3 and Quasi two dimensional conductor eta-Mo_4O_<11>.
*One dimensional semiconductor TiS_3
1.I have established the most optimum condition for crystal growth of TiS_3 using a chemical vapor transport technique ; A sealed quartz tube kept at high temperature end is 520ﾟC and low temperature one is 480ﾟC,the ratio of starting materials Ti : S is 1 : 4.
2.The TiS_3 is an n-type impurity semiconductor. It has the 10^<17>cm^<-3> intrinsic carriers in a conduction band pinned by some impurity levels. The 10^<18>cm^<-3> donors which make a level at below 24 meV from conduction band minima donate carriers above 100K.
3.Below 100 K,the impurity scattering is dominant ; while above 100 K some scattering mechanisms have occurred in addition to a conventional LA phonon scattering. The origin of the scattering are anomalous carrier scattering reflects the low dimensional band structure and (or) polar optical phonon scattering known to the case of the non-inversion semiconductors such as GaAs.
4.Raman bands are observed at 295,365,553cm^<-1> due to optical-active phonons at room temperature.
*Quasi two dimensional conductor eta-Mo_4O_<11>
1.When the electric field beyond a threshold field is applied along the b-axis of the eta-Mo_4O_<11>, the Charge Density Wave (CDW) is depinned and contributes to the electrical conduction.
2.In the bc-plane (2-dimensional conduction plane), the CDW slides along the b-axis only. It means that the sliding motion of CDW in these Quasi two dimensional conductor is one-dimensional rather than two-dimensional.
3.These results suggest that the dimensionality of CDW sliding is influenced by the symmetry of nesting vector rather than the crystal structure.
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