Study of electronic and vibrational properties of mercuric cadmium telluride and cadmium telluride.
Item
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Title
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Study of electronic and vibrational properties of mercuric cadmium telluride and cadmium telluride.
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Identifier
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AAI9000708
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identifier
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9000708
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Creator
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Ksendzov, Alexander.
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Contributor
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Adviser: Fred H. Pollak
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Date
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1989
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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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Electronic and vibrational properties of {dollar}\rm Hg\sb{lcub}1-x{rcub}Cd\sb{lcub}x{rcub}Te{dollar} and CdTe have been studied using modulation optical spectroscopy and Raman scattering. Electronic properties of {dollar}\rm Hg\sb{lcub}1-x{rcub}Cd\sb{lcub}x{rcub}Te/SiO\sb2{dollar}- Photox{dollar}\rm \sp{lcub}TM{rcub}{dollar} interface also were investigated using electroreflectance (ER) and capacitance-voltage (C-V) measurements.;We have measured, for the first time, the nonlinear temperature dependence of the E{dollar}\sb1{dollar} transition energy in CdTe using photoreflectance (PR) and in {dollar}\rm Hg\sb{lcub}1-x{rcub}Cd\sb{lcub}x{rcub}Te{dollar} (nominal composition x = 0.3) using ER in a metal-insulator-semiconductor (MIS) configuration. The temperature variation of the broadening parameter was also evaluated.;The temperature dependence of the E{dollar}\sb0{dollar} transition in CdTe has been investigated by PR. Although the sample was not intentionally doped, the optical spectra in the E{dollar}\sb0{dollar} region are dominated by transitions from the valence band to a donor level at temperatures over 200 K.;We have measured the frequency dependence of the PR signal at 77 K for a series of {dollar}\rm Hg\sb{lcub}1-x{rcub}Cd\sb{lcub}x{rcub}Te{dollar} samples (x = 0.14-0.3). This dependence yields the characteristic trap times ({dollar}\tau{dollar}), which fall into 1-4 ms range for our samples.;The vibrational properties of {dollar}\rm Hg\sb{lcub}1-x{rcub}Cd\sb{lcub}x{rcub}Te{dollar} were studied by resonance Raman scattering (RRS). We found that in the forbidden polarization configuration RRS is caused by impurity induced scattering. It has been shown also, that the "LO & TO CdTe-like" peak in {dollar}\rm Hg\sb{lcub}1-x{rcub}Cd\sb{lcub}x{rcub}Te{dollar} belongs to a propagating mode rather than a localized vibration of a Cd atom in HgTe.;Electroreflectance in a MIS configuration was used to study the SiO{dollar}\sb2{dollar} (Photox{dollar}\rm \sp{lcub}TM{rcub}{dollar})/{dollar}\rm Hg\sb{lcub}1-x{rcub}Cd\sb{lcub}x{rcub}Te{dollar} interface. The ER spectra showed that, in addition to the x {dollar}\cong{dollar} 0.3 semiconductor material, islands of the semimetallic (x {dollar}\cong{dollar} 0.1) material are present at the interface. Also, with use of the C-V measurements, the presence of very slow ({dollar}\tau >{dollar} 8 h) trap states at the interface with energy distribution centered approximately 4.5 eV above the valence band of the SiO{dollar}\sb2{dollar} was established.;The influence of the reflection from the back surface of a CdTe sample on its PR and thermoreflectance (TR) spectra in the E{dollar}\sb0{dollar} region was compared. We found that while the TR lineshape was very sensitive to the condition of the back surface of the sample, the changes in the PR lineshape were negligible.
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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.
