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.

In Situ Etching Rate Measurement of Si with XeF2

1986 ◽  
Vol 68 ◽  
Author(s):  
K. R. Padmanabhan ◽  
S. Bhowmick ◽  
R. Shaver ◽  
Zhang Zu Hua ◽  
J. C. Buchholz
Keyword(s):  
Single Crystal ◽  
Etching Rate ◽  
Experimental Results ◽  
Rate Measurement ◽  
Random Orientation ◽  
Appreciable Difference ◽  
Induced Decomposition ◽  
Ion Backscattering

AbstractIon backscattering and channeling techniques have been employed to measure the etching rate of amorphous and single crystal Si by XeF2 under similar conditions.Both (100) Si on sapphire and (111) Si on spinel showed higher etching rates compared to amorphous Si.However, measurements of the etching rate using a Si cell aligned to the axis and along the planes under similar conditions did not show appreciable difference in the etching rate compared to the etching rate with random orientation of the cell.Presence of the analyzing 4He+ beam during etching enhances the etching rate to twice the value when compared to post etching analysis with the same beam.The enhancement of the etching rate due to ion induced decomposition of XeF2 have been considered in the explanation of the experimental results.

In situ high-pressure single-crystal X-ray study of aegirine, NaFe3+Si2O6, and the role of M1 size in clinopyroxene compressibility

2008 ◽  
Vol 93 (11-12) ◽  
pp. 1829-1837 ◽  
Author(s):  
A. C. McCarthy ◽  
R. T. Downs ◽  
R. M. Thompson ◽  
G. J. Redhammer
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
X Ray

The Role of Low-Dimensional Systems in Electrochemical Phase Formation and Dissolution Processes

2002 ◽  
Vol 149 (12) ◽  
pp. K47 ◽  
Author(s):  
W. J. Lorenz ◽  
G. Staikov ◽  
W. Schindler ◽  
W. Wiesbeck
Keyword(s):  
Phase Formation ◽  
Low Dimensional

PORTEVIN–LE CHÂTELIER INSTABILITY IN L10-TiAl SINGLE CRYSTAL

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4189-4194 ◽  
Author(s):  
Y. L. CHIU ◽  
P. PENHOUD ◽  
P. VEYSSIÈRE
Keyword(s):  
Stress Relaxation ◽  
Slip System ◽  
Single Crystal ◽  
Plastic Flow ◽  
Temperature Regime ◽  
Deformation Behaviour ◽  
Experimental Results ◽  
Screw Dislocations ◽  
Strain Ageing ◽  
First Time

We studied the deformation behaviour of γ Ti -54.5% Al single crystal at temperatures ranging from 200°C to 700°C along [153] orientation, where the major operative slip system is [Formula: see text]. During this temperature regime, deformation microstructure consists of long heavily pinned screw dislocations. Serrated plastic flow has been observed at 500°C, the serration amplitude decreases with strain. The combination of the strain ageing and stress relaxation experimental results demonstrate for the first time the Portevin–Le Châtelier type instability in TiAl single crystal.

Determination of the relevant magnetic interactions in low-dimensional molecular materials: the fundamental role of single crystal high frequency EPR

2011 ◽  
Vol 40 (41) ◽  
pp. 10843 ◽  
Author(s):  
R. A. Allão ◽  
A. K. Jordão ◽  
J. A. L. C. Resende ◽  
A. C. Cunha ◽  
V. F. Ferreira ◽  
...  
Keyword(s):  
Single Crystal ◽  
High Frequency ◽  
Magnetic Interactions ◽  
Molecular Materials ◽  
Low Dimensional

Activation energy for Pt2Si and PtSi formation measured over a wide range of ramp rates

1995 ◽  
Vol 10 (8) ◽  
pp. 1953-1957 ◽  
Author(s):  
E.G. Colgan
Keyword(s):  
Activation Energy ◽  
Single Crystal ◽  
Phase Formation ◽  
Heating Rates ◽  
Sapphire Substrates ◽  
Conventional Furnace ◽  
Wide Range ◽  
High Heating ◽  
Pt Films

The activation energies, Ea's, for Pt2Si and PtSi formation were determined using in situ resistance measurements with ramp rates ranging from 0.4 °C/m to 100 °C/s. Measurements were performed using both conventional furnace and rapid thermal annealing (RTA). Pt films were evaporated on undoped polycrystalline Si and single-crystal Si on sapphire substrates. The Ea's determined from Kissinger plots were 1.63 ± 0.05 and 1.61 ± 0.06 eV for Pt2Si formation and 1.83 ± 0.06 and 1.83 ± 0.07 eV for PtSi formation with polycrystalline Si and silicon on sapphire substrates, respectively. These are the first reported measurements of Ea's for Pt2Si and PtSi formation over such a wide range of heating rates (greater than four orders of magnitude) and at such high heating rates. The phase formation sequence remained the same for the range of heating rates examined.

Stumbling on Extrinsic Effects in Super-hard Nanobuttons

2009 ◽  
Vol 1224 ◽  
Author(s):  
Antonio Rinaldi ◽  
Pedro Peralta ◽  
Cody Friesen ◽  
Dhiraj Nahar ◽  
Silvia Licoccia ◽  
...  
Keyword(s):  
Single Crystal ◽  
Test Data ◽  
Crystal Plasticity ◽  
A Priori ◽  
Critical Value ◽  
Compression Tests ◽  
Plastic Strength ◽  
Extrinsic Effects

AbstractThe compressive plastic strength of nanosized single crystal metallic pillars is known to depend on the diameter D, but little attention has been given to the pillar height h. The important role of h is analyzed here, observing the suppression of generalized crystal plasticity below a critical value hCR that can be estimated a priori. Novel in-situ compression tests on regular pillars (D = 300-900 nm) as well as nanobuttons (i.e. very short pillars with h less than hCR, such as D = 200 nm and h < 120 nm in this case) show that the latter ones are exceedingly harder than ordinary Ni pillars, withstanding stresses greater than 2 GPa. This h-controlled transition in the plastic behaviour is accompanied by extrinsic plastic effects in the harder nanobuttons. Such effects normally arise as Saint-Venant’s assumption ceases to be accurate. Some bias related to those effects is identified and removed from test data. Our results underline that nanoscale testing is challenging when current methodology and technology are pushed to the limit.

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