Search results for "Germanium"
showing 10 items of 249 documents
Luminescence of different modifications of crystalline silicon dioxide: Stishovite and coesite
2003
Abstract Luminescence of very small samples of single crystals of coesite and stishovite has been studied. The spectra were detected under ionizing radiation (X-ray and electron beam) and the decay kinetics of cathodoluminescence in the range of time from 10 ns to 3 ms was measured. The coesite luminescence possesses a broad band at 3 eV with exponential decay about 680 μs at 80 K. The nature of this luminescence was explained as a self-trapped exciton creation in tetrahedron framework. The stishovite luminescence possesses two bands—blue (2.8 eV) and UV (4.7 eV). The UV band intensity grows more than 20 times with irradiation dose from initial level. This shows that the corresponding lumin…
EXCITONS, LOCALIZED STATES IN SILICON DIOXIDE AND RELATED CRYSTALS AND GLASSES
2000
The excitons, localized states in crystalline and glassy silicon dioxide, germanium dioxide were studied by photoluminescent and photoelectric experimental methods. Results were compared with analogous investigations of related crystals, such as aluminum and gallium orthophosphates, and of related glasses, such as silica, sodium silicates, germanates, lead and phosphates glasses. Special attention was made to the influence of oxygen deficiency on localized states of glasses, in general, and to the nature of the 7.6 eV band in reduced silica, in particular.
Luminescence of GeO2 glass, rutile-like and α-quartz-like crystals
2006
Abstract The luminescence of GeO 2 rutile-like crystals was studied. Crystals were grown from a melt of germanium dioxide and sodium bicarbonate mixture. Luminescence of the crystal was compared with that of sodium germanate glasses produced in reduced and oxidized conditions. A luminescence band at 2.3 eV was observed under N 2 laser (337 nm). At higher excitation photon energies and X-ray excitation an additional band at 3 eV appears in luminescence. The band at 2.3 eV possesses intra-center decay time constant about 100 μs at 290 K and about 200 μs at low temperature. Analogous luminescence was obtained in reduced sodium germanate glasses. No luminescence was observed in oxidized glasses…
Simulations of Glassforming Network Fluids: Classical Molecular Dynamics versus Car-Parrinello Molecular Dynamics
2010
Abstract Static and dynamic Properties of molten germanium dioxide are studied by two simulation methods, classical Molecular Dynamics (MD) using the Oeffner-Elliott (OE) potential, and “ab initio” Car-Parrinello Molecular Dynamics (CPMD). While CPMD provides a (presumably) more accurate description of the local structure and the forces, it severely suffers from finite size effects when the structure beyond the first neighbor shells is considered. For glassforming fluids, the demanding equilibrium needs are a further reason, why simply MD is still preferable, when a “good” effective potential is available.
Defect Luminescence Study in Tetragonal GeO2 Crystals
2000
The perovskite-or rutile-like GeO2 crystals were grown by the “top-seed” method from a fused germanium dioxide solution with sodium bicarbonate. The luminescence was studied under cathode-, x-ray, and photo-excitation. There are two luminescence bands at 550 nm and 400 nm with slow (100–200 µs) and fast (<20 ns) decay, respectively. The luminescence can be excited either by intra-center and electron-hole recombination processes. An analogous luminescence, however with strong non-exponential decay, is observed in glassy materials obtained from the frozen solution. Sodium-germanate glasses melted under oxygen deficient condition also possess similar luminescence, therefore the luminescence is…
Fabrication of Bismuth Absorber Arrays for NTD-Ge Hard X-ray Microcalorimeters
2020
The high-spectral-resolution detection of hard X-rays (E > 20 keV) is a challenging and nearly unexplored area in space astrophysics. Traditionally hard X-ray detectors present moderate spectral resolutions, although few tens of eV one could open new frontiers in the study of nuclear processes and high-temperature plasma dynamics in energetic processes. This can be achieved by using cryogenic microcalorimeters. Within a research activity aimed at developing arrays of neutron transmutation-doped germanium (NTD-Ge) microcalorimeters for the high-spectral-resolution detection (about 50 eV@60 keV) of hard X-rays (20 keV < E<100 keV), we developed an electroplating process to fabricate …
Study of exotic decay of Cs isotope close to the proton drip line
2020
6 pags., 6 figs. -- 27th International Nuclear Physics Conference (INPC2019) 29 July - 2 August 2019, Glasgow, UK
An AC-assisted single-nanowire electromechanical switch
2013
A unique two-source controlled nanoelectromechanical switch has been assembled from individual, single-clamped Ge nanowires. The switching behaviour was achieved by superimposing the control signals of specific frequencies to the electrostatic potential of the output terminals, eliminating the need for an additional gate electrode. Using an in situ manipulation technique inside a scanning electron microscope, we demonstrate that the pull-out force required to overcome adhesion at the contact can be significantly reduced by exciting mechanical resonant modes within the nanowire.
Über Germanium‐haltige Heterocyclen, II. Molekül‐ und Kristallstruktur von 2,2‐Dichlor‐1,3,6,2‐trithiagermocan
1975
Die Struktur der Titelsubstanz wurde rontgenographisch aus Diffraktometer-Einkristalldaten bestimmt und bis zu einem koventionellen R von 0.052 verfeinert. Der 8-Ring besitzt Wanne-Sessel-Konformation mit transannularer 1,5-GeS-Annaherung. Die Koordination am Ge-Atom ist trigonal-bipyramidal mit aquatorialen Abstanden GeS 2.191(13) und Ge–Cl 2.149(3) A und axialen Abstanden Ge–S 3.005(3) und Ge–Cl 2.208(3) A. Bekannte Ge–S-Abstande werden diskutiert, und Abstandsbereiche fur Ge – S- und Sn – S-Bindungen verschiedenen Typs werden festgelegt. Die Struktur besteht aus 14-fach koordinierten Molekulen. On Heterocyclic containing Germanium, II. Molecular and Crystal Structure of 2,2-Dichloro-1,3,…
Über Germanium‐haltige Heterocyclen, IV. 2,2,4,4,6,6‐Hexaphenyl‐1,3,5‐trioxa‐2,4,6‐trigermacyclohexan, (Ph 2 GeO) 3 , eine monoplanare Zwischenstufe …
1982
Die Titelverbindung 1 wurde durch Hydrolyse von Ph2GeCl2 in acetonischer Losung gewonnen. Die Kristallstruktur wurde bestimmt und bis R = 0.049 verfeinert. Die Konformation des Ge3O3-6-Ringes ist monoplanar und bildet eine mogliche Zwischenstufe einerseits fur die Racemisierung von Twist-Wanne-Enantiomeren und andererseits bei der Sessel-Sessel-Inversion. Ein angeregter Zustand mit umlaufendem Null-Torsionswinkel wird als Alternative zur gangigen Lehrbuchdarstellung dieser Vorgange diskutiert. Die GeOAbstande und GeOGe-Winkel betragen 176–178 pm bzw. 128–130°. Die 1-Molekule sind im Kristall nach Art einer tetragonal-innenzentrierten Kugelpackung mit (10 + 4)-Koordination gepackt. On Hetero…