Current Search: Liu, Da Wei (x)
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- Title
- Photoluminescence characterization of aluminum gallium arsenide/gallium arsenide quantum well interfacial quality.
- Creator
- Wan, Zhong, Florida Atlantic University, Liu, Da Wei
- Abstract/Description
-
A photoluminescence (PL) study of Al(x)Ga(1-x)As/GaAs quantum wells (QWs) was undertaken at low temperature by using the HeNe laser. The temperature dependence of heavy hole exciton peak energies indicated that the PL signals are contributed by the recombination of excitons bound to interface defects at low temperature and the recombination of free excitons at high temperature. The temperature dependence of the PL profile of a single QW sample with growth interruption at the interfaces was...
Show moreA photoluminescence (PL) study of Al(x)Ga(1-x)As/GaAs quantum wells (QWs) was undertaken at low temperature by using the HeNe laser. The temperature dependence of heavy hole exciton peak energies indicated that the PL signals are contributed by the recombination of excitons bound to interface defects at low temperature and the recombination of free excitons at high temperature. The temperature dependence of the PL profile of a single QW sample with growth interruption at the interfaces was successfully interpreted by the enlarged monolayer fluctuation. The linewidth of low temperature PL peaks was used to characterize the interfacial quality of QWs. The quality improvement of single QWs by tilting (001) substrate 4 degrees toward (111) Ga direction was observed.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/14835
- Subject Headings
- Quantum wells, Photoluminescence
- Format
- Document (PDF)
- Title
- Picosecond spectroscopic study of modulation doped gallium arsenide-aluminum gallium arsenide quantum wells.
- Creator
- Xu, Xumou, Florida Atlantic University, Liu, Da Wei
- Abstract/Description
-
CW photoluminescence and picosecond excitation correlation spectroscopy techniques were utilized to characterize two dimensional carriers modulation doped in GaAs-Al0.3Ga0.7As multiple quantum wells. Three characteristic transitions have been confirmed. Temperature variation measurements showed a strong carrier-phonon coupling in the samples, which is the main mechanism responsible for the fast carrier relaxation observed. In the time resolved experiments, it was found that the carrier...
Show moreCW photoluminescence and picosecond excitation correlation spectroscopy techniques were utilized to characterize two dimensional carriers modulation doped in GaAs-Al0.3Ga0.7As multiple quantum wells. Three characteristic transitions have been confirmed. Temperature variation measurements showed a strong carrier-phonon coupling in the samples, which is the main mechanism responsible for the fast carrier relaxation observed. In the time resolved experiments, it was found that the carrier relaxation slowed down as the excitation intensity increased, which we attribute to the buildup of non-equilibrium phonons rather than the dynamic screening effect. A theoretical calculation based upon hot phonon effect is presented.
Show less - Date Issued
- 1991
- PURL
- http://purl.flvc.org/fcla/dt/14754
- Subject Headings
- Modulation spectroscopy
- Format
- Document (PDF)
- Title
- Raman spectroscopic study of yttrium barium(2)(copper(1-x)iron(x))oxygen(7+delta).
- Creator
- Tanabe, Makoto., Florida Atlantic University, Liu, Da Wei
- Abstract/Description
-
Polycrystalline bulk samples with the chemical formula YBa2(Cu1-xFex)3O7+delta were fabricated by the standard solid-state reaction method, and studied through magnetic susceptibility and Raman scattering experiments. In the Raman experiments, the Cu(1)-O(1) c-axial Ag stretching mode at ~502cm^-1 was investigated extensively at temperatures ranging from 23K to 773K. The room-temperature Raman spectra indicated a trend for saturation in frequency shift (as a function of iron concentration)....
Show morePolycrystalline bulk samples with the chemical formula YBa2(Cu1-xFex)3O7+delta were fabricated by the standard solid-state reaction method, and studied through magnetic susceptibility and Raman scattering experiments. In the Raman experiments, the Cu(1)-O(1) c-axial Ag stretching mode at ~502cm^-1 was investigated extensively at temperatures ranging from 23K to 773K. The room-temperature Raman spectra indicated a trend for saturation in frequency shift (as a function of iron concentration). This was interpreted as evidence supporting the occurrence of a type of iron clustering in the (001) basal plane. Effects of such a cluster formation upon the mechanism of superconductivity were considered. The low temperature Raman spectra show that the 502cm^-1 mode frequency increased slightly with decreasing temperature for all of the studied values of iron concentration without exhibiting any anomalous behavior. In the high temperature Raman spectra, a significant softening of the 502cm^-1 mode, indicative of a phase transition onset, was observed.
Show less - Date Issued
- 1990
- PURL
- http://purl.flvc.org/fcla/dt/14597
- Subject Headings
- Raman spectroscopy, Copper oxide superconductors
- Format
- Document (PDF)