Study of the Temperature Dependence of E2 and A1(LO) Modes in ZnO

2006 ◽  
Vol 957 ◽  
Author(s):  
Esther Alarcon-Llado ◽  
Ramon Cusco ◽  
Jordi Ibanez ◽  
Luis Artus ◽  
Juan Jimenez ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Fermi Resonance ◽  
Bulk Single Crystal ◽  
Temperature Dependent ◽  
Resonance Model ◽  
Carrier Relaxation ◽  
Relevant Role ◽  
Order Of Magnitude ◽  
Anharmonic Decay ◽  
The Continuum

ABSTRACTRaman scattering measurements were carried out on a bulk, single crystal of wurtzite ZnO over a temperature range from 80 to 760 K and the temperature-dependent shift and broadening of the E2high and A1(LO) modes was analyzed. The E2high mode exhibits a visibly asymmetric line shape that can be related to the interaction with the continuum of acoustic two-phonon density of states. A Fermi resonance model was used to describe the E2high temperature dependence. On the other hand, the anharmonic shift and broadening of the A1(LO) mode are adequately accounted for by a decay model with a dominating Ridley channel involving TO and LA modes. Phonon lifetimes of ∼0.9 and 0.5 ps are found for the E2high and A1(LO) modes, respectively, which corroborates that anharmonic decay involves in both cases a three-phonon process. The A1(LO)lifetime is one order of magnitude lower than that of GaN, which suggests that hot phonon effects should be expected to play a less relevant role in carrier relaxation in ZnO as compared with GaN.

scholarly journals PRODUCTION OF THERMAL PHOTONS IN VISCOUS FLUID DYNAMICS WITH TEMPERATURE-DEPENDENT SHEAR VISCOSITY

2012 ◽  
Vol 27 (09) ◽  
pp. 1250050 ◽  
Author(s):  
J. PERALTA-RAMOS ◽  
M. S. NAKWACKI
Keyword(s):  
Viscous Fluid ◽  
Temperature Dependence ◽  
Quark Gluon Plasma ◽  
Equations Of State ◽  
Fluid Dynamic ◽  
Gluon Plasma ◽  
Temperature Dependent ◽  
Dynamic Simulations ◽  
Production Processes ◽  
Order Of Magnitude

We compute the spectrum of thermal photons created in Au+Au collisions at [Formula: see text], taking into account dissipative corrections in production processes corresponding to the quark–gluon plasma and hadronic phases. To describe the evolution of the fireball, we use a viscous fluid dynamic model with different parametrizations for the temperature-dependence of η/s. We find that the spectrum significantly depends on the values of η/s in the QGP phase, and is almost insensitive to the values in the hadronic phase. We also compare the influence of the temperature-dependence of η/s on the spectrum of thermal photons to that of using different equations of state in the fluid dynamic simulations, finding that both effects are of the same order of magnitude.

19F Nuclear Quadrupole Coupling in some Halomethanes

1986 ◽  
Vol 41 (1-2) ◽  
pp. 171-174 ◽  
Author(s):  
M. Frank ◽  
F. Gubitz ◽  
W. Ittner ◽  
W. Kreische ◽  
A. Labahn ◽  
...  
Keyword(s):  
Angular Distribution ◽  
Simple Model ◽  
Temperature Dependence ◽  
Coupling Constants ◽  
Temperature Dependent ◽  
Distribution Method ◽  
Quadrupole Coupling ◽  
Time Differential ◽  
Nuclear Quadrupole

The 19F quadrupole coupling constants in CF4, CHF3, CClF3 and CHClF2 are reported. The measurements were carried out temperature dependent using the time differential perturbed angular distribution method (TDPAD). The temperature dependence can be satisfactorily described in the framework of the Bayer-Kushida theory. A simple model is used to explain the appearance of H-F and Cl-F coupling constants in CHF3/CHClF2 and CClF3, respectively.

Electronic Properties of Bismuth Nanowires

2001 ◽  
Vol 679 ◽  
Author(s):  
Stephen B. Cronin ◽  
Yu-Ming Lin ◽  
Oded Rabin ◽  
Marcie R. Black ◽  
Gene Dresselhaus ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Band Structure ◽  
Temperature Dependence ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Temperature Dependent ◽  
Si Substrates ◽  
Bismuth Nanowires ◽  
Bi Nanowire ◽  
Anodic Alumina Templates

ABSTRACTThe pressure filling of anodic alumina templates with molten bismuth has been used to synthesize single crystalline bismuth nanowires with diameters ranging from 7 to 200nm and lengths of 50μm. The nanowires are separated by dissolving the template, and electrodes are affixed to single Bi nanowires on Si substrates. A focused ion beam (FIB) technique is used first to sputter off the oxide from the nanowires with a Ga ion beam and then to deposit Pt without breaking vacuum. The resistivity of a 200nm diameter Bi nanowire is found to be only slightly greater than the bulk value, while preliminary measurements indicate that the resistivity of a 100nm diameter nanowire is significantly larger than bulk. The temperature dependence of the resistivity of a 100nm nanowire is modeled by considering the temperature dependent band parameters and the quantized band structure of the nanowires. This theoretical model is consistent with the experimental results.

scholarly journals SYNTHESIS AND ELECTRICAL CONDUCTIVITY OF SOLID SOLUTIONS OF THE SYSTEM RbF-PbF2-SnF2

2019 ◽  
Vol 85 (5) ◽  
pp. 60-68
Author(s):  
Yuliay Pogorenko ◽  
Anatoliy Omel’chuk ◽  
Roman Pshenichny ◽  
Anton Nagornyi
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Temperature Dependence ◽  
Solid Solutions ◽  
Basic Structure ◽  
Elementary Cell ◽  
Initial Structure ◽  
Fluoride Ions ◽  
Temperature Range ◽  
Order Of Magnitude

In the system RbF–PbF2–SnF2 are formed solid solutions of the heterovalent substitution RbxPb0,86‑xSn1,14F4-x (0 < x ≤ 0,2) with structure of β–PbSnF4. At x > 0,2 on the X-ray diffractograms, in addition to the basic structure, additional peaks are recorded that do not correspond to the reflexes of the individual fluorides and can indicate the formation of a mixture of solid solutions of different composition. For single-phase solid solutions, the calculated parameters of the crystal lattice are satisfactorily described by the Vegard rule. The introduction of ions of Rb+ into the initial structure leads to an increase in the parameter a of the elementary cell from 5.967 for x = 0 to 5.970 for x = 0.20. The replacement of a part of leads ions to rubium ions an increase in electrical conductivity compared with β–PbSnF4 and Pb0.86Sn1.14F4. Insignificant substitution (up to 3.0 mol%) of ions Pb2+ at Rb+ at T<500 K per order of magnitude reduces the conductivity of the samples obtained, while the nature of its temperature dependence is similar to the temperature dependence of the conductivity of the sample β-PbSnF4. By replacing 5 mol. % of ions with Pb2+ on Rb+, the fluoride ion conductivity at T> 450 K is higher than the conductivity of the initial sample Pb0,86Sn1,14F4 and at temperatures below 450 K by an order of magnitude smaller. With further increase in the content of RbF the electrical conductivity of the samples increases throughout the temperature range, reaching the maximum values at x≥0.15 (σ573 = 0.34–0.41 S/cm, Ea = 0.16 eV and σ373 = (5.34–8.16)•10-2 S/cm, Ea = 0.48–0.51 eV, respectively). In the general case, the replacement of a part of the ions of Pb2+ with Rb+ to an increase in the electrical conductivity of the samples throughout the temperature range. The activation energy of conductivity with an increase in the content of RbF in the low-temperature region in the general case increases, and at temperatures above 400 K is inversely proportional decreasing. The nature of the dependence of the activation energy on the concentration of the heterovalent substituent and its value indicate that the conductivity of the samples obtained increases with an increase in the vacancies of fluoride ions in the structure of the solid solutions.

On Free Vibrations at Temperature-Dependent Material Properties and Transient Temperature Fields

1972 ◽  
Vol 39 (3) ◽  
pp. 723-726 ◽  
Author(s):  
U. Olsson
Keyword(s):  
Temperature Dependence ◽  
Analytical Solutions ◽  
Material Properties ◽  
Free Vibrations ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Material Damping ◽  
Temperature Dependent ◽  
Temperature Variations ◽  
Damping Parameter

The influence of the temperature-dependence of the material properties on the free vibrations of transiently heated structures is investigated. Analytical solutions are given for linear, exponential, and harmonic temperature variations when the material damping parameter, Poisson’s ratio, and Young’s modulus depend on the temperature.

Temperature dependent electronic band structure of wurtzite GaAs nanowires

Nanoscale ◽  
2018 ◽  
Vol 10 (3) ◽  
pp. 1481-1486 ◽  
Author(s):  
Neimantas Vainorius ◽  
Simon Kubitza ◽  
Sebastian Lehmann ◽  
Lars Samuelson ◽  
Kimberly A. Dick ◽  
...  
Keyword(s):  
Band Structure ◽  
Temperature Dependence ◽  
Electronic Band Structure ◽  
Temperature Dependent ◽  
Electronic Band ◽  
Gaas Nanowires

Temperature dependence of the indicated transitions in wurtzite GaAs.

On the time delay of the photoplastic effect

1986 ◽  
Vol 1 (1) ◽  
pp. 3-6 ◽  
Author(s):  
Joseph Pellegrino ◽  
J. M. Galligan
Keyword(s):  
Time Delay ◽  
Temperature Dependence ◽  
Cadmium Telluride ◽  
Deformation Temperature ◽  
Mercury Cadmium Telluride ◽  
Charge Carriers ◽  
Temperature Dependent ◽  
Simple Analysis ◽  
Photoplastic Effect

Photoplasticity in mercury cadmium telluride, Hg1-x Cdx Te with x = 0.3, has been studied as a function of light frequency and deformation temperature. We show that there is an easily measurable time delay accompanying irradiation of the crystal and the change in stress. This time delay is temperature dependent, suggesting a diffusion of charge carriers, introduced by the light, to the interior of the crystal. A simple analysis is given of the observed temperature dependence that is consistent with the experiments.

Evaluating the temperature dependence of bedrock hillslope erosion in the Mont Blanc massif using in situ cosmogenic 3He-10Be-14C

2021 ◽  
Author(s):  
Donovan P. Dennis ◽  
Dirk Scherler ◽  
Samuel Niedermann ◽  
Kristina Hippe ◽  
Hella Wittmann ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Erosion Rates ◽  
Close Proximity ◽  
Order Of Magnitude ◽  
Stochastic Events ◽  
Exposure Ages ◽  
Alpine Environments ◽  
Magnitude Difference ◽  
Mont Blanc Massif

&lt;p&gt;The erosion of cold bedrock hillslopes in alpine environments depends not only on rates of frost weathering and accumulated rock damage, but additionally on the removal of the weathered material from the bedrock surface. In the Mont Blanc massif, steep bedrock faces with exposure ages sometimes much older than 50,000 years sit in close proximity to actively-eroding rockwalls, suggesting a more complex relationship between temperature and erosion rates than encompassed by the proposed &amp;#8220;frost-cracking window.&amp;#8221; Stochastic events like rockfalls and rock avalanches, despite their rarity, contribute a non-trivial proportion of the total sediment budget in alpine permafrost regions, adding to the contribution from background &amp;#8220;steady-state&amp;#8221; erosion. Employing a methodology based on the combination of in-situ cosmogenic nuclides &lt;sup&gt;3&lt;/sup&gt;He -&lt;sup&gt;10&lt;/sup&gt;Be-&lt;sup&gt;14&lt;/sup&gt;C, we test the temperature-dependence of high-alpine erosion while taking into account erosional stochasticity.&lt;/p&gt;&lt;p&gt;From cosmogenic &lt;sup&gt;10&lt;/sup&gt;Be concentrations of amalgamated samples collected on the Aiguille du Midi (3842 m a.s.l.) in the Mont Blanc massif, we find an order of magnitude difference in erosion rate across the peak&amp;#8217;s surface. Our preliminary measured erosion rates, ranging between appx. 0.03 mm yr&lt;sup&gt;-1&lt;/sup&gt; and 1.0 mm yr&lt;sup&gt;-1&lt;/sup&gt;, correlate neither with modern temperature measurements from borehole thermistors, nor with our current estimates of bedrock cosmogenic &lt;sup&gt;3&lt;/sup&gt;He-derived paleotemperatures. The corresponding cosmogenic &lt;sup&gt;14&lt;/sup&gt;C/&lt;sup&gt;10&lt;/sup&gt;Be ratios (between 1.70 and 4.0) for these erosion rates indicate that our measurements are not biased by recent stochastic rockfall events. Our current results therefore suggest that on geomorphic timescales, bedrock hillslope erosion rates are not set solely by rates of frost-cracking, but rather by the combined effects of frost-cracking and permafrost thaw-induced rockfalls. These insights are relevant both for short-term monitoring of alpine permafrost and associated geohazards under a warming climate, as well as studies of proposed &amp;#8220;buzzsaws&amp;#8221; operating on glacial-interglacial timescales.&lt;/p&gt;

scholarly journals Topological susceptibility with a single light quark flavour

2018 ◽  
Vol 175 ◽  
pp. 14017 ◽  
Author(s):  
Julien Frison ◽  
Ryuichiro Kitano ◽  
Norikazu Yamada
Keyword(s):  
Quark Mass ◽  
Continuum Limit ◽  
Light Quark ◽  
The Other ◽  
Theoretical Argument ◽  
Up Quark ◽  
Order Of Magnitude ◽  
Quark Flavour ◽  
Definition Of ◽  
The Continuum

One of the historical suggestions to tackle the strong CP problem is to take the up quark mass to zero while keeping md finite. The θ angle is then supposed to become irrelevant, i.e. the topological susceptibility vanishes. However, the definition of the quark mass is scheme-dependent and identifying the mu = 0 point is not trivial, in particular with Wilson-like fermions. More specifically, up to our knowledge there is no theoretical argument guaranteeing that the topological susceptibility exactly vanishes when the PCAC mass does. We will present our recent progresses on the empirical check of this property using Nf = 1 + 2 flavours of clover fermions, where the lightest fermion is tuned very close to [see formula in PDF] and the mass of the other two is kept of the order of magnitude of the physical ms. This choice is indeed expected to amplify any unknown non-perturbative effect caused by mu ≠ md. The simulation is repeated for several βs and those results, although preliminary, give a hint about what happens in the continuum limit.

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