-TEM in situ straining of a Ni-base γ′ single crystal-unlocking of dissociated screw dislocations at low temperature

1989 ◽  
Vol 23 (4) ◽  
pp. 563-568 ◽  
Author(s):  
N. -Clément ◽  
D. Caillard ◽  
P. Lours ◽  
A. Coujou
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
Screw Dislocations

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

Backbone Phosphonamide-Functionalized Imidazol-2-ylidene Complexes

2016 ◽  
Vol 69 (10) ◽  
pp. 1186
Author(s):  
Paresh Kumar Majhi ◽  
Gregor Schnakenburg ◽  
Anthony J. Arduengo ◽  
Rainer Streubel
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
X Ray ◽  
Structure Determinations

The synthesis of M(CO)5 complexes bearing 4-phosphonamide and 4,5-bis(phosphonamide)-imidazol-2-ylidene ligands (NHCP = phosphonamide-based N-heterocyclic carbene) is reported. Deprotonation of respective imidazolium hydrogensulfate salts with potassium tert-butoxide (KOtBu) in the presence of [M(CO)5(CH3CN)] afforded complexes with the formula [M(CO)5(NHCP)]. In a similar fashion, reaction of in situ generated NHCP with [Rh(cod)Cl]2 (cod = 1,5-cyclooctadiene) afforded a complex with the formula [Rh(cod)Cl(NHCP)]. Low-temperature deprotonation of the imidazolium NHCP·H2SO4 with potassium hexamethyldisilazide (KHMDS) in the presence of [AuCl(SMe2)] furnished the corresponding AuI NHC complex. All complexes were characterized by various spectroscopic and spectrometric methods. In addition, further structural confirmation is provided by key single-crystal X-ray structure determinations for three of the new complexes.

scholarly journals Germanium-Silicon Separate Absorption and Multiplication Avalanche Photodetectors Fabricated with Low Temperature High Density Plasma Chemical Vapor Deposited Germanium

2007 ◽  
Vol 989 ◽  
Author(s):  
Malcolm Carroll ◽  
Kent Childs ◽  
Darwin Serkland ◽  
Robert Jarecki ◽  
Todd Bauer ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Low Temperature ◽  
Single Crystal ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Plasma Chemical ◽  
Avalanche Photodetectors ◽  
Geiger Mode ◽  
Density Plasma

AbstractA desire to monolithically integrate near infrared (NIR) detectors with silicon complementary metal oxide semiconductor (CMOS) technology has motivated many investigations of single crystal germanium on silicon (Ge/Si) diodes [1-3]. Reduction of the epitaxy thermal budget below the typical chemical vapor deposition (CVD) in-situ clean temperature (Tin-situ clean > 780°C) is also increasingly desired to reduce integration complexity. Reduced temperature growth approaches have included p+-Ge/n-Si detectors formed with low temperature poly-Ge (e-beam evaporation) or heavily dislocated single crystal germanium (molecular beam epitaxy, T ~ 450°C), which have had dark currents of ~5 mA/cm2 and responsivities of ~15 mA/W at 1310 nm, despite the large number of defects in and at the Ge/Si interface. Responsivities in these materials are however low and believed to be limited by a small diffusion length (i.e., 5-30 nm [2, 4]) due to fast electron recombination in the defect rich germanium. In this paper, we evaluate a commercially available high density plasma chemical vapor deposition (HDP-CVD) process to grow low temperature (i.e., Tin-situ & Tepitaxy < ~450°C) germanium epitaxy for a p+-Ge/p-Si/n+-Si NIR separate absorption and multiplication avalanche photodetectors (SAM-APD). This device structure is of interest both to examine ways to enhance the responsivity with internal gain as well as to examine alternatives to InGaAs-InP structures for NIR Geiger mode (GM) detection. A silicon avalanche region is highly desirable for GM to reduce after-pulsing effects, which are related to defect density that are smaller in Si than in InP [5]. Despite the high defect densities in the Ge and at the interface, the Ge-Si APDs in this work are found to have relatively low dark count rates in Geiger mode.

The low-temperature behaviour of cancrinite:an in situ single-crystal X-ray diffraction study

2012 ◽  
Vol 76 (4) ◽  
pp. 933-948 ◽  
Author(s):  
G. Diego Gatta ◽  
P. Lotti ◽  
V. Kahlenberg ◽  
U. Haefeker
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
Structure Refinement ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Structural Behaviour ◽  
X Ray ◽  
Positional Disorder ◽  
Deformation Processes

AbstractThe low-temperature structural behaviour of natural cancrinite with a formula Na6.59Ca0.93[Si6.12Al5.88O24](CO3)1.04F0.41·2H2O has been investigated by means of in situ single-crystal X-ray diffraction and Raman spectroscopy. High quality structure refinements were obtained at 293, 250, 220, 180, 140, 100 and at 293 K again (at the end of the low-T experiments). The variation in the unit-cell volume as a function of temperature (T) exhibits a continuous trend, without any evident thermoelastic anomaly. The thermal expansion coefficient αV = (1/V)∂V/∂T is 3.8(7) × 10–5 K–1 (between 100 and 293 K). The structure refinement based on intensity data collected at ambient conditions after the low-T experiment confirmed that the low-T induced deformation processes are completely reversible. The extraframework population does not show significant variations down to 100 K. The strong positional disorder of the carbonate groups along the c axis persists within the T range investigated. The structural behaviour of cancrinite at low-T is mainly governed by the continuous framework rearrangement through the ditrigonalization of the six-membered rings which lie in a plane perpendicular to [0001], the contraction of the four-membered ring joint units, the decrease of the ring corrugation in the (0001) plane, and the flattening of the cancrinite cages. A list of the principal Raman active modes in ambient conditions is provided and discussed.

Low-temperature and high-pressure polymorphs of isopropyl alcohol

CrystEngComm ◽  
2014 ◽  
Vol 16 (32) ◽  
pp. 7397-7400 ◽  
Author(s):  
Joe Ridout ◽  
Michael R. Probert
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Single Crystal ◽  
Isopropyl Alcohol ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray

Single-crystal X-ray diffraction has been used to elucidate the structure of two polymorphs of isopropyl alcohol, one grown through in situ cryo-crystallisation, the other through high-pressure crystallisation.

The structure of chloromethyl thiocyanate, CH2ClSCN, in gas and crystalline phases

2015 ◽  
Vol 17 (24) ◽  
pp. 15805-15812 ◽  
Author(s):  
Y. Berrueta Martínez ◽  
L. S. Rodríguez Pirani ◽  
M. F. Erben ◽  
C. G. Reuter ◽  
Y. V. Vishnevskiy ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Low Temperature ◽  
Single Crystal ◽  
Gas Phase ◽  
Solid Phase ◽  
Gas Electron Diffraction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Conformational Properties

The structural and conformational properties of chloromethyl thiocyanate, CH2ClSCN, were studied in the solid phase and in the gas phase usingin situlow-temperature single-crystal X-ray diffraction experiments (XRD) and gas electron diffraction (GED), respectively.

scholarly journals Low-Temperature Crystal Chemistry of Hingganite-(Y), from the Wanni Glacier, Switzerland

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 322 ◽  
Author(s):  
Liudmila Gorelova ◽  
Oleg Vereshchagin ◽  
Stéphane Cuchet ◽  
Vladimir Shilovskikh ◽  
Dmitrii Pankin
Keyword(s):  
Thermal Expansion ◽  
Low Temperature ◽  
Single Crystal ◽  
Layer Plane ◽  
X Ray Diffraction ◽  
Wavelength Dispersive Spectroscopy ◽  
X Ray ◽  
Thermal Expansion Anisotropy ◽  
High Thermal Expansion

Hingganite from the Wanni glacier (Switzerland) was studied by means of energy dispersive and wavelength-dispersive spectroscopy, Raman spectroscopy, and low-temperature single-crystal X-ray diffraction. According to its chemical composition, the investigated mineral should be considered as hingganite-(Y). It showed a relatively high content of Gd, Dy, and Er and had limited content of lighter rare-earth element (REE), which is typical for Alpine gadolinite group minerals. The most intense Raman bands were 116, 186, 268, 328, 423, 541, 584, 725, 923, 983, 3383, and 3541 cm−1. Based on data of low-temperature [(−173)–(+7) °C] in situ single-crystal X-ray diffraction, it was shown that the hingganite-(Y) crystal structure was stable in the studied temperature range and no phase transitions occurred. Hingganite-(Y) demonstrated low volumetric thermal expansion (αV = 9(2) × 10−6 °C−1) and had a high thermal expansion anisotropy up to compression along one of the directions in the layer plane. Such behavior is caused by the shear deformations of its monoclinic unit cell.

scholarly journals The role of crystal imperfections in electrochemical phase formation and growth

1997 ◽  
Vol 75 (11) ◽  
pp. 1624-1634 ◽  
Author(s):  
G. Staikov ◽  
W.J. Lorenz
Keyword(s):  
Single Crystal ◽  
Phase Formation ◽  
Experimental Results ◽  
Spiral Growth ◽  
Screw Dislocations ◽  
Crystal Imperfections ◽  
Low Dimensional ◽  
Stepwise Formation

The role of different crystal imperfections and surface inhomogeneities in the processes of electrochemical phase formation and crystal growth is discussed on the basis of experimental results obtained by electrodeposition of metals on native and foreign single crystal substrates in selected model systems. The major role of screw dislocations in the electrochemical growth of real crystals is demonstrated in the case of silver electrodeposition on silver single crystal faces prepared by the so-called capillary technique. Experimental results show that the electrochemical spiral growth of silver crystal faces with low dislocation density can be used for a preparation of surfaces with a defined and uniform density of monatomic steps. Combined electrochemical and in situ scanning probe microscopy (SPM) studies of underpotential deposition (UPD) of metals on foreign single crystal substrates show that surface inhomogeneities induce a stepwise formation of different low-dimensional (0D, 1D, and 2D) metal phases. The thermodynamic, kinetic, and structural aspects of the stepwise formation of Me phases of different dimensionality in the UPD range are discussed on an atomic level using results of electrochemical and in situ SPM measurements in various systems. Keywords: electrocrystallization, screw dislocations, spiral growth, surface inhomogeneities, underpotential deposition, low-dimensional phases, scanning tunneling microscopy.

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