4,584 research outputs found
Ge1-ySny (y=0.01-0.10) alloys on Ge-buffered Si: Synthesis, microstructure, and optical properties
No full textabstract: Novel hydride chemistries are employed to deposit light-emitting Ge [subscript 1- y] Sn [subscript y] alloys with y ≤ 0.1 by Ultra-High Vacuum Chemical Vapor Deposition (UHV-CVD) on Ge-buffered Si wafers. The properties of the resultant materials are systematically compared with similar alloys grown directly on Si wafers. The fundamental difference between the two systems is a fivefold (and higher) decrease in lattice mismatch between film and virtual substrate, allowing direct integration of bulk-like crystals with planar surfaces and relatively low dislocation densities. For y ≤ 0.06, the CVD precursors used were digermane Ge [subscript 2]H[subscript 6] and deuterated stannane SnD[subscript 4]. For y ≥ 0.06, the Ge precursor was changed to trigermane Ge [subscript 3]H[subscript 8], whose higher reactivity enabled the fabrication of supersaturated samples with the target film parameters. In all cases, the Ge wafers were produced using tetragermane Ge [subscript 4]H[subscript 10] as the Ge source. The photoluminescence intensity from Ge [subscript 1− y] Sn [subscript y] /Ge films is expected to increase relative to Ge [subscript 1− y] Sn [subscript y] /Si due to the less defected interface with the virtual substrate. However, while Ge [subscript 1− y] Sn [subscript y] /Si films are largely relaxed, a significant amount of compressive strain may be present in the Ge [subscript 1− y] Sn [subscript y] /Ge case. This compressive strain can reduce the emission intensity by increasing the separation between the direct and indirect edges. In this context, it is shown here that the proposed CVD approach to Ge [subscript 1− y] Sn [subscript y] /Ge makes it possible to approach film thicknesses of about 1 μm, for which the strain is mostly relaxed and the photoluminescence intensity increases by one order of magnitude relative to Ge [subscript 1− y] Sn [subscript y] /Si films. The observed strain relaxation is shown to be consistent with predictions from strain-relaxation models first developed for the Si[subscript 1− x] Ge [subscript x] /Si system. The defect structure and atomic distributions in the films are studied in detail using advanced electron-microscopy techniques, including aberration corrected STEM imaging and EELS mapping of the average diamond–cubic lattice.Copyright 2014 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. along with the following message: The following article appeared in 116, 13 (2014) and may be found at http://dx.doi.org/10.1063/1.489678
Atomic layer deposition of crystalline SrHfO3 directly on Ge (001) for high-k dielectric applications
No full textabstract: The current work explores the crystalline perovskite oxide, strontium hafnate, as a potential high-k gate dielectric for Ge-based transistors. SrHfO3 (SHO) is grown directly on Ge by atomic layer deposition and becomes crystalline with epitaxial registry after post-deposition vacuum annealing at ∼700 °C for 5 min. The 2 × 1 reconstructed, clean Ge (001) surface is a necessary template to achieve crystalline films upon annealing. The SHO films exhibit excellent crystallinity, as shown by x-ray diffraction and transmission electron microscopy. The SHO films have favorable electronic properties for consideration as a high-k gate dielectric on Ge, with satisfactory band offsets (>2 eV), low leakage current (<10[superscript −5] A/cm[superscript 2] at an applied field of 1 MV/cm) at an equivalent oxide thickness of 1 nm, and a reasonable dielectric constant (k ∼ 18). The interface trap density (Dit ) is estimated to be as low as ∼2 × 10[superscript 12] cm[superscript −2] eV[superscript −1] under the current growth and anneal conditions. Some interfacial reaction is observed between SHO and Ge at temperatures above ∼650 °C, which may contribute to increased Dit value. This study confirms the potential for crystalline oxides grown directly on Ge by atomic layer deposition for advanced electronic applications.Copyright 2015 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. along with the following message: The following article appeared in JOURNAL OF APPLIED PHYSICS 117, 5 (2015) and may be found at http://dx.doi.org/10.1063/1.490695
OB00040 - Damodarpur Copper Plate 1 (GE 163) of Budhagupta
No full textDamodarpur Copper Plate 1 (GE 163) of Budhagupt
Application of the Monte Carlo method to the analysis of measurement geometries for the calibration of a HP Ge detector in an environmental radioactivity laboratory
No full text[EN] A gamma spectrometer including an HP Ge detector is commonly used for environmental radioactivity measurements. The efficiency of the detector should be calibrated for each geometry considered. Simulation of the calibration procedure with a validated computer
program is an important auxiliary tool for environmental radioactivity laboratories. The MCNP code based on the Monte Carlo method has been applied to simulate the detection process in order to obtain spectrum peaks and determine the efficiency curve for each modelled geometry. The source used for measurements was a calibration mixed radionuclide gamma reference solution, covering a wide energy range (50 2000 keV). Two measurement geometries Marinelli beaker and Petri boxes as well as different materials water, charcoal, sand containing the source have been considered. Results obtained from the Monte Carlo model have been compared with experimental measurements in the laboratory in order to validate the model.Ródenas Diago, J.; Gallardo Bermell, S.; Ballester Pérez, S.; Primault, V.; Ortiz Moragón, J. (2007). Application of the Monte Carlo method to the analysis of measurement geometries for the calibration of a HP Ge detector in an environmental radioactivity laboratory. Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms. 263(1):144-148. doi:10.1016/j.nimb.2007.04.210S144148263
[[alternative]]Raman Study of Folded Acoustic Phonons in Si/Ge Superlattice
No full text[[abstract]]This research presents three Raman Spectrums of Si/Ge superlattices growing on the substrate of Si by MBE. The period of superlattice samples N=5, the growing conditions of superlattice are: the Si-layer is 50nm；the Ge-layers are 2.2nm、3.8nm and 5.4nm. Measuring by TEM of samples firstly, the Si-layers are 50.18nm、48.65 nm and 48.89 nm；the Ge-layers are 2.46 nm、3.78 nm and 4.44 nm。
In the Spectrum, the peak of Si-Si mode is quite obvious；The peak of Ge-Ge mode is comparatively weak. In the room temperature, the peak of Si-Ge mode is quite unobvious due to the fewer periods.
Raman Spectrum of three superlattices shows many and obvious folded phonon signals in the low frequency (0 ~100 cm-1) area , so does the doublets of phonon are quite obvious. Fittting the frequency of folded phonons by Rytov’s theory finds that the Si-layers are 49.65nm、45.98 nm and 45.95 nm, the Ge-layers are 2.12 nm、3.78 nm and 5.01 nm. All the errors are within 6%, so Rytov’s theory is a good foundation to study Raman Spectrum of superlattice.
Fitting the intensity of folded spectrum of phonon with photoelastic mode , in the wavelength far away the energy of resonance ( As 476 nm) can get good result. Also getting the ratio of Si-layer thickness and the period of superlattice are 0.96（632 nm）、0.93（476 nm）and 0.93（476 nm）, compared with the result of fitting frequency of folded phonon by Rytov’s theory：0.96、0.92及0.90, matchs very well, except the 3% difference of sample-N107.
Besides, examining Ge-Ge mode in the spectrum with LCM, the roughness of Ge-layer can be examed, and the calculating layers are 2.22nm、3.83 nm and 5.37 nm, the difference is within 7% comparing with the result of fitting phonons.
In the various temperature (10 K~300 K) Raman Sprctrum, there are signals of continuous scattering of phonons around 200 cm-1 , and the lower the temperature, or the thinner the Ge-layer, the more obvious the continuous scattering of phonon is. We can find the phenomenon that E1 energy of Ge-layer is in the vicinity of 2.3 eV and distributed widely ,when we observe the folded phonon in low frequency, the resonance of Ge-Ge Mode, and the fluorescence in high frequency.
The English Translation of the Epitaph of the Wu Kingdom Transcendent Duke Ge of the Left Palace of the Grand Bourne by Tao Hongjing
No full textabstract: This thesis is a translation and analysis of the “Epitaph of the Wu Kingdom
Transcendent Duke Ge of the Left Palace of the Grand Bourne” (Epitaph below). The author was Tao Hongjing (456 CE-536 CE). The subject of this Epitaph inscribed on a stele was Ge Xuan (trad. 164 CE-244 CE). Ge Xuan had two titles attributed to him by later Daoists. According to the Lingbao scriptures, Ge was appointed by the Perfected of Grand Bourne, a heavenly title. Later, in the Shangqing scriptures, Ge Xuan was said to be an earthly transcendent without any heavenly appointment. This debate occurred before Tao Hongjing began to write. This stele epitaph is essential, as it records sayings from both Lingbao and Shangqing scriptures. By reading this translated epitaph, scholars can know more about different versions of Ge Xuan's legend, as well as how Ge Xuan's legend was constantly rewritten by later Daoists.Dissertation/ThesisMasters Thesis Religious Studies 202
Large-area selective CVD epitaxial growth of Ge on Si substrates
No full textSelective epitaxial growth of crystalline Ge on Si in a standard ASM Epsilon 2000 CVD reactor is investigated for the fabrication of Ge p+n diodes. At the deposition temperature of 700?C, most of the lattice mismatch-defects are trapped within first 300nm of Ge growth and good quality single crystal Ge is achieved within a layer thickness of approximately 1 ?m on window sizes up to hundreds of ?m2. For p+n junction fabrication, a sequence of pure-Ga and then pure-B depositions are utilized for the ultrashallow p-doping of As-doped Ge-islands. The I-V characterization of the diodes confirms the good quality of the Ge and ideality factors of ~ 1.1 with low saturation currents are reliably achievedDIMESElectrical Engineering, Mathematics and Computer Scienc
Large scale circulation in turbulent Rayleigh-Bénard convection
No full textStatistical properties of turbulent Rayleigh-Bénard convection (RBC) are investigated experimentally in a cylindrical cell of aspect ratio one. We specifically analyze the large scale circulation of RBC based on measurements of temperature fluctuations by small Ge sensors placed inside the cell. The resulting dependencies of Reynolds numbers on Rayleigh number up to 2x10^13 are compared to available theoretical and experimental results for similar geometries
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