Spectroscopy of Semiconductor Nano-Crystals at High Pressure

1992 ◽  
Vol 272 ◽  
Author(s):  
John Schroeder ◽  
Markus R. Silvestri ◽  
Xue-Shu Zhao ◽  
Peter D. Persans ◽  
Lih-Wen Hwang
Keyword(s):  
High Pressure ◽  
Raman Scattering ◽  
Bulk Material ◽  
Semiconductor Nanocrystals ◽  
Electronic States ◽  
Wurtzite Phase ◽  
Glass Composites ◽  
Rocksalt Phase ◽  
Electron Phonon Coupling ◽  
Pressure Stability

ABSTRACTThe optical and vibrational properties of small CdSe and CdS particles embedded in a glass matrix and as a colloid have been studied as a function of pressure up to 90 kbar using Raman scattering and photoluminescence techniques. We will discuss the use of high pressure optical spectroscopy techniques, where the sample is contained in a diamond anvil.cell with optical access, to study the nature of the electronic states in semiconductor nanocrystals. Raman scattering is employed to establish the enhanced pressure stability of the wurtzite phase in the II-VI nanocrystalline composites. Photolurninescence is used to study the energies of electronic states. The wurtzite to rocksalt phase transition behavior in the nanocrystallite systems is quite different from that in the bulk material. This different behavior is attributed to a large number of defects (vacancies) in the nanocrystallite system. This work demonstrates that the main defects in the CdS glass composites are cadmium vacancies; while in CdSe Selenium vacancies exist in the conduction band. The pressure dependence of the Huang-Rhys parameter, characteristic for the strength of the electron-phonon coupling, will also be discussed for the nanocrystalline samples versus the bulk material.

In situ Raman scattering studies of high-pressure stability and transformations in the matrix of a nanostructured glass-ceramic composite

2005 ◽  
Vol 36 (10) ◽  
pp. 938-945 ◽  
Author(s):  
Kristina E. Lipinska-Kalita ◽  
Stephen A. Gramsch ◽  
Patricia E. Kalita ◽  
Russell J. Hemley
Keyword(s):  
High Pressure ◽  
Raman Scattering ◽  
Glass Ceramic ◽  
Ceramic Composite ◽  
In Situ Raman ◽  
The Matrix ◽  
Pressure Stability ◽  
Glass Ceramic Composite

Raman Scattering Studies of the High-Pressure Stability of Pentaerythritol Tetranitrate, C(CH2ONO2)4

2005 ◽  
Vol 109 (41) ◽  
pp. 19223-19227 ◽  
Author(s):  
Kristina E. Lipinska-Kalita ◽  
Michael G. Pravica ◽  
Malcolm Nicol
Keyword(s):  
High Pressure ◽  
Raman Scattering ◽  
Pentaerythritol Tetranitrate ◽  
Pressure Stability

NEW CRYSTAL STRUCTURE OF INDIUM NITRIDE: A PRESSURE-INDUCED ROCKSALT PHASE

1994 ◽  
Vol 08 (05) ◽  
pp. 345-350 ◽  
Author(s):  
QING XIA ◽  
HUI XIA ◽  
ARTHUR L. RUOFF
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Diamond Anvil Cell ◽  
Indium Nitride ◽  
Wurtzite Phase ◽  
Rocksalt Structure ◽  
Rocksalt Phase ◽  
Volume Collapse ◽  
Diamond Anvil ◽  
First Order Phase

Crystal structures of the III–V compound InN were studied under high pressure in a diamond anvil cell to 35 GPa by energy-dispersive X-ray diffraction. A pressure-induced phase transformation from a wurtzite structure to a rocksalt structure was observed in polycrystalline InN during compression. This is a first-order phase transformation with a volume collapse of 20%. The high pressure rocksalt phase started to appear at 10 GPa and the transformation was completed at 14 GPa. The rocksalt phase remained stable to at least 35 GPa, the upper pressure limit of this experiment. During unloading of the diamond anvil cell, InN started to transform back to the wurtzite phase at a pressure of 5 GPa and a small amount of high pressure rocksalt phase persisted after completely releasing the pressure cell. The equilibrium transformation pressure lies on the interval of 5 to 10 GPa.

Thermal and high-pressure stability of purified polygalacturonase and pectinmethylesterase from four different tomato processing varieties

2006 ◽  
Vol 39 (4) ◽  
pp. 440-448 ◽  
Author(s):  
Dolores Rodrigo ◽  
Clara Cortés ◽  
Elke Clynen ◽  
Liliane Schoofs ◽  
Ann Van Loey ◽  
...  
Keyword(s):  
High Pressure ◽  
Tomato Processing ◽  
Pressure Stability

scholarly journals High Pressure X-ray Diffraction as a Tool for Designing Doped Ceria Thin Films Electrolytes

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 724
Author(s):  
Sara Massardo ◽  
Alessandro Cingolani ◽  
Cristina Artini
Keyword(s):  
Thin Films ◽  
High Pressure ◽  
Rare Earth ◽  
Ionic Conductivity ◽  
Bulk Material ◽  
Threshold Temperature ◽  
Doped Ceria ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rare Earth Doped

Rare earth-doped ceria thin films are currently thoroughly studied to be used in miniaturized solid oxide cells, memristive devices and gas sensors. The employment in such different application fields derives from the most remarkable property of this material, namely ionic conductivity, occurring through the mobility of oxygen ions above a certain threshold temperature. This feature is in turn limited by the association of defects, which hinders the movement of ions through the lattice. In addition to these issues, ionic conductivity in thin films is dominated by the presence of the film/substrate interface, where a strain can arise as a consequence of lattice mismatch. A tensile strain, in particular, when not released through the occurrence of dislocations, enhances ionic conduction through the reduction of activation energy. Within this complex framework, high pressure X-ray diffraction investigations performed on the bulk material are of great help in estimating the bulk modulus of the material, and hence its compressibility, namely its tolerance toward the application of a compressive/tensile stress. In this review, an overview is given about the correlation between structure and transport properties in rare earth-doped ceria films, and the role of high pressure X-ray diffraction studies in the selection of the most proper compositions for the design of thin films.

scholarly journals Resonance and antiresonance in Raman scattering in GaSe and InSe crystals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. Osiekowicz ◽  
D. Staszczuk ◽  
K. Olkowska-Pucko ◽  
Ł. Kipczak ◽  
M. Grzeszczyk ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Temperature Effect ◽  
Band Gap ◽  
Raman Spectra ◽  
Quantum Interference ◽  
Optical Band Gap ◽  
Phonon Coupling ◽  
Phonon Modes ◽  
Electron Phonon Coupling ◽  
Resonant Raman

AbstractThe temperature effect on the Raman scattering efficiency is investigated in $$\varepsilon$$ ε -GaSe and $$\gamma$$ γ -InSe crystals. We found that varying the temperature over a broad range from 5 to 350 K permits to achieve both the resonant conditions and the antiresonance behaviour in Raman scattering of the studied materials. The resonant conditions of Raman scattering are observed at about 270 K under the 1.96 eV excitation for GaSe due to the energy proximity of the optical band gap. In the case of InSe, the resonant Raman spectra are apparent at about 50 and 270 K under correspondingly the 2.41 eV and 2.54 eV excitations as a result of the energy proximity of the so-called B transition. Interestingly, the observed resonances for both materials are followed by an antiresonance behaviour noticeable at higher temperatures than the detected resonances. The significant variations of phonon-modes intensities can be explained in terms of electron-phonon coupling and quantum interference of contributions from different points of the Brillouin zone.

Sign in / Sign up

Export Citation Format

Share Document