The metal-insulator transition in boron-doped silicon: Transport properties.
Item
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Title
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The metal-insulator transition in boron-doped silicon: Transport properties.
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Identifier
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AAI9207063
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identifier
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9207063
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Creator
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Dai, Peihua.
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Contributor
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Adviser: Myriam P. Sarachik
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Date
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1991
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Condensed Matter
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Abstract
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The conductivity has been studied for a series of uncompensated p-type boron-doped silicon samples with dopant concentrations near the metal-insulator transition. For ten metallic samples, data were taken at temperatures down to 55 mK, and in magnetic fields up to 9 Tesla in a dilution refrigerator. Some data were also taken at dilution refrigerator temperatures, for barely insulating samples.;Our study in zero magnetic field shows the interesting result that the critical conductivity exponent for Si:B is 0.65{dollar}\sbsp{lcub}-0.14{rcub}{lcub}+0.05{rcub}{dollar}, which is close to the anomalous value of 1/2 found for other n-type uncompensated silicon systems, and different from the value near 1 found in most other materials. This indicates that spin-orbit scattering, which is important in Si:B, does not determine the critical exponent as the theory predicts. Our results also indicate that the critical exponent is shifted to a value near 1 by the application of a strong magnetic field. This is consistent with the prediction of the theory and is the first observation of such a clear shift.;Our study also shows that the correction to the zero-temperature conductivity arising from electron-electron interactions is comparable in size for n- and p-type silicons. Further, the temperature dependence of the conductivity in various fixed magnetic fields is similar for Si:P and Si:B. This is surprising, given the differences between the conduction and valence bands of silicon, such as anisotropy and the nature of the scattering.;The single important difference between n- and p-type silicons is the sign and size of the magnetoresistance. Our systematic study of the Si:B samples shows that the magnetoresistance of Si:B is always positive, unlike Si:P which has both positive and negative components. We attribute this to the strong spin-orbit scattering in p-type silicon associated with the degenerate valence bands.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
