[001] Surface Structure in SrTiO3 — Atomistic Study

1998 ◽  
Vol 05 (01) ◽  
pp. 341-345 ◽  
Author(s):  
Eugene Heifets ◽  
Simon Dorfman ◽  
David Fuks ◽  
Eugene Kotomin ◽  
Alex Gordon
Keyword(s):  
Dipole Moment ◽  
External Field ◽  
Polarization Effect ◽  
Surface Region ◽  
Superconducting Films ◽  
Surface Layers ◽  
Near Surface ◽  
Atomistic Study ◽  
Model Technique ◽  
Thin Superconducting Films

Thin superconducting films attract great attention as a promising material for plenty of applications. The surface determines most of the physical properties of these films. We studied the polarization effect for the [001] surface of perovskite ABO 3 superconducting crystals on the example of SrTiO 3. Optimization of the ion positions in several surface layers is provided. These ions are placed in the external field of the rest crystal. The interaction between ions is described by means of the shell model technique. We show that Ti +4, Sr 2+ and O -2 ions displace differently from their crystalline sites, which leads to the creation of a dipole moment in the near-surface region.

Atomistic Study of Surface Polarization in Superconducting Perovskites

1996 ◽  
Vol 440 ◽  
Author(s):  
David Fuks ◽  
Simon Dorfman ◽  
Eugene Heifets ◽  
Eugene Kotomin ◽  
Alex Gordon
Keyword(s):  
Dipole Moment ◽  
Ferroelectric Properties ◽  
Surface Relaxation ◽  
Two Dimensional ◽  
Slab Model ◽  
Surface Layers ◽  
Near Surface ◽  
Pair Potentials ◽  
Surface Polarization ◽  
Atomistic Study

AbstractWe simulated the surface relaxation of the cubic perovskite paraelectric SrTiO3 crystal. The atomic positions in ten near-surface layers placed into the electrostatic field of the remainder of the crystal were calculated. Two-dimensional, periodic slab model was combined with the pair potentials treated in terms of the shell-model. Our calculations show that Ti+4, Sr+2 and O−2 ions shift differently from their crystal sites. This leads to a creation of a dipole moment near the surface which might give the paraelectric crystal the ferroelectric properties.

Amortization and Recrystallization of 6H-SiC by ion Beam Irradiation

1994 ◽  
Vol 339 ◽  
Author(s):  
V. Heera ◽  
R. Kögler ◽  
W. Skorupa ◽  
J. Stoemenos
Keyword(s):  
Ion Irradiation ◽  
Ion Beam ◽  
Surface Region ◽  
Ion Beam Irradiation ◽  
Surface Layers ◽  
Near Surface ◽  
Transmission Electron ◽  
Amorphous Surface ◽  
Amorphous Sic

ABSTRACTThe evolution of the damage in the near surface region of single crystalline 6H-SiC generated by 200 keV Ge+ ion implantation at room temperature (RT) was investigated by Rutherford backscattering spectroscopy/chanelling (RBS/C). The threshold dose for amorphization was found to be about 3 · 1014 cm-2, Amorphous surface layers produced with Ge+ ion doses above the threshold were partly annealed by 300 keV Si+ ion beam induced epitaxial crystallization (IBIEC) at a relatively low temperature of 480°C For comparison, temperatures of at least 1450°C are necessary to recrystallize amorphous SiC layers without assisting ion irradiation. The structure and quality of both the amorphous and recrystallized layers were characterized by cross-section transmission electron microscopy (XTEM). Density changes of SiC due to amorphization were measured by step height measurements.

Evaluating Micromechanical Properties at Surfaces Using Nanoindentation With Finite-Element Modeling

2002 ◽  
Author(s):  
J. A. Knapp ◽  
D. M. Follstaedt ◽  
S. M. Myers
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Finite Element Modeling ◽  
Mechanical Damage ◽  
Surface Region ◽  
Small Scale ◽  
Surface Layers ◽  
Near Surface ◽  
Element Modeling ◽  
Surface Modified

Detailed finite-element modeling of nanoindentation data is used to obtain accurate mechanical properties of very thin films or surface-modified layers independently of the properties of the underlying substrates. These procedures accurately deduce the yield strength, elastic modulus, and layer hardness, and greatly increase the usefulness of indentation testing with very thin surface layers. Moreover, extraction of the effective Young’s modulus in the near surface region should enable mechanical damage studies on a small scale. This paper presents a brief overview of the procedures involved and illustrates them with He-implanted Ni.

scholarly journals Structure, physical and chemical properties of near-surface layers of optical materials modified by treatment in hydrogen plasma

2021 ◽  
pp. 12-39
Author(s):  
U. O. Salgaeva ◽  
◽  
A. B. Volyntsev ◽  
S. S. Mushinsky ◽  
◽  
...  
Keyword(s):  
Optical Materials ◽  
Hydrogen Plasma ◽  
Surface Region ◽  
Soda Lime ◽  
Plasma Modification ◽  
Soda Lime Glass ◽  
Structure And Properties ◽  
Surface Layers ◽  
Near Surface ◽  
First Time

The present paper aims to investigate the structure and properties of the near-surface layers of optical materials modified by treatment in hydrogen plasma (H-plasma). For this the quartz and soda-lime glasses, lithium niobate (LN) as delivered and LN after proton exchange were used. The structure and properties of the near-surface layers of optical materials were investigated by IR spectroscopy, Raman spectroscopy, X-ray diffraction analysis, atomic force microscopy, mode spectroscopy, scanning electron microscopy, and wet chemical etching. During the treatment in H-plasma the hydrogen penetrated into the near-surface layers and caused increasing the number of defects in the structure of materials. Changes of the shape and intensity of the absorption peaks of OH–-groups and the θ/2θ- curves recorded from the LN samples processed in H-plasma were inconsequent, probably due to the thin modified layer. For the first time, a huge volume “swelling” (above 10 %) of the near-surface layers of LN and soda-lime glass after the processing in H-plasma was revealed. Also for the first time, the formation of thin strained layers on the surface of the LN after treatment in H-plasma was shown; the density reduction of the near-surface layers of the LN modified in H-plasma was described; the features of blistering and flaking were found on the surface of LN and soda-lime glass after their treatment for a long time (120–150 min). For the first time, the multilayer structure of the near-surface region of the LN was detected after treatment in H-plasma. In this paper we proposed the model of changes the structure and properties of LN after the treatment in H-plasma. The model explains the experimental results obtained in this study and previously published studies of other research groups. Due to the high concentration in the near-surface layers of optical materials after the H-plasma treatment, hydrogen predominantly forms pores and bubbles. Presumably the compounds of the Li2O–Nb2O5 system with a low Li content formed in the near-surface region of LN after the treatment in H-plasma. Modification of near-surface layers of optical materials in hydrogen plasma could be used to form elements of integrated-optical circuits, particularly the diffraction gratings.

Microstructure and Composition of Surface Layers Formed by Ion Implantation of Nitrogen in High-Purity Aluminum

1988 ◽  
Vol 100 ◽  
Author(s):  
Robert C. Mccune ◽  
W. T. Donlon ◽  
H. K. Plummer ◽  
L. Toth ◽  
F. W. Kunz
Keyword(s):  
Ion Implantation ◽  
Ion Beam ◽  
Pure Aluminum ◽  
Surface Region ◽  
Nuclear Reaction Analysis ◽  
Surface Layers ◽  
Near Surface ◽  
Transmission Electron ◽  
High Purity Aluminum ◽  
Nitrogen Contents

ABSTRACTSurface layers with overall thickness <∼300 nm were produced by ion implantation of N+ or N2+ at energies of 50 or 100 keV in 99.99% pure aluminum. These surfaces were characterized by scanning and transmission electron microscopy, Auger electron spectroscopy, Rutherford backscattering, nuclear reaction analysis and particle-induced X-ray analysis. At doses above 2×1017 N2/cm2 , blistering of the surfaces was observed along with a reduction in the extent of the coulometric dose retained by the material. Oxygen is believed to be introduced into the near-surface region by a process of reaction and ion-beam mixing, as well as possible CO contamination of the beam. A phase, isostructural with AlN, forms semi-coherently with parent aluminum grains, however, some fraction of the metallic aluminum phase remains in the reaction layer, even at overall nitrogen contents which exceed the stoichiometry of AlN.

Residual stresses in rolling contact

1969 ◽  
Vol 4 (3) ◽  
pp. 208-218 ◽  
Author(s):  
R J Pomeroy ◽  
K L Johnson
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Surface Region ◽  
Rolling Contact ◽  
Surface Layers ◽  
Friction Forces ◽  
Near Surface ◽  
Contact Loads ◽  
Pure Rolling ◽  
Theoretical Predictions

The paper reports an experimental investigation into the residual strsses induced into cylndrical discs by the action of rolling-contact loads sufficiently high to cause some plastic deformation in the near-surface layers. A general method is first described for finding both circumferential and axial components of residual stress in cylindrical bodies in circumstances where the stresses vary with the radial co-ordinate only. This method is believed to be an improvement on previous methods for separating the two components of residual stress, particularly where only specimens of restricted length are available. For example, the method could be applied to thick-walled tubes. Measurements have been made of the residual stresses due to rolling contact, in pure rolling and in combined rolling and sliding. In all cases both components of residual stress were compressive and reached a maximum value below the surface at about the depth of the maximum Hertz shear stress. The measured residual stresses in the sub-surface region were roughly in agreement with the theoretical predictions of Merwin, Johnson, and Jefferis. A subsidiary peak of compressive stress was found at the surface itself. Neither the surface nor the subsurface stresses were found to be greatly influenced by the presence of friction forces when sliding accompanied rolling.

Characterization of Y-Ba-Cu-O films grown on silicon substrates by sequential evaporation

1988 ◽  
Vol 46 ◽  
pp. 866-867
Author(s):  
E. L. Hall ◽  
A. Mogro-Campero ◽  
L. G. Turner ◽  
N. Lewis
Keyword(s):  
Thin Film ◽  
Thin Film Deposition ◽  
Superconducting Films ◽  
Electron Beam Evaporation ◽  
Film Deposition ◽  
Silicon Substrates ◽  
Superconducting Properties ◽  
Sequential Electron ◽  
Thin Superconducting Films

There is great interest in the growth of thin superconducting films of YBa2Cu3Ox on silicon, since this is a necessary first step in the use of this superconductor in a variety of possible electronic applications including interconnects and hybrid semiconductor/superconductor devices. However, initial experiments in this area showed that drastic interdiffusion of Si into the superconductor occurred during annealing if the Y-Ba-Cu-O was deposited direcdy on Si or SiO2, and this interdiffusion destroyed the superconducting properties. This paper describes the results of the use of a zirconia buffer layer as a diffusion barrier in the growth of thin YBa2Cu3Ox films on Si. A more complete description of the growth and characterization of these films will be published elsewhere.Thin film deposition was carried out by sequential electron beam evaporation in vacuum onto clean or oxidized single crystal Si wafers. The first layer evaporated was 0.4 μm of zirconia.

Preparation of cross-sectional samples for near-surface TEM studies

1987 ◽  
Vol 45 ◽  
pp. 380-381
Author(s):  
R.C. Dickenson ◽  
K.R. Lawless
Keyword(s):  
Standard Sample ◽  
Surface Region ◽  
Specimen Preparation ◽  
Thick Sheet ◽  
Drill Bit ◽  
Sample Holder ◽  
Metal Interface ◽  
Cross Sectional ◽  
Near Surface ◽  
Cold Worked

In thermal oxidation studies, the structure of the oxide-metal interface and the near-surface region is of great importance. A technique has been developed for constructing cross-sectional samples of oxidized aluminum alloys, which reveal these regions. The specimen preparation procedure is as follows: An ultra-sonic drill is used to cut a 3mm diameter disc from a 1.0mm thick sheet of the material. The disc is mounted on a brass block with low-melting wax, and a 1.0mm hole is drilled in the disc using a #60 drill bit. The drill is positioned so that the edge of the hole is tangent to the center of the disc (Fig. 1) . The disc is removed from the mount and cleaned with acetone to remove any traces of wax. To remove the cold-worked layer from the surface of the hole, the disc is placed in a standard sample holder for a Tenupol electropolisher so that the hole is in the center of the area to be polished.

The Effects of Ion Implantation on the Surface Features of Inconel 600

1985 ◽  
Vol 43 ◽  
pp. 288-289
Author(s):  
John D. Rubio
Keyword(s):  
Grain Boundary ◽  
Ion Implantation ◽  
Nuclear Power ◽  
Power Plants ◽  
Surface Region ◽  
Selective Dissolution ◽  
Boundary Region ◽  
Near Surface ◽  
Inconel 600 ◽  
Steam Generator Tubing

The degradation of steam generator tubing at nuclear power plants has become an important problem for the electric utilities generating nuclear power. The material used for the tubing, Inconel 600, has been found to be succeptible to intergranular attack (IGA). IGA is the selective dissolution of material along its grain boundaries. The author believes that the sensitivity of Inconel 600 to IGA can be minimized by homogenizing the near-surface region using ion implantation. The collisions between the implanted ions and the atoms in the grain boundary region would displace the atoms and thus effectively smear the grain boundary.To determine the validity of this hypothesis, an Inconel 600 sample was implanted with 100kV N2+ ions to a dose of 1x1016 ions/cm2 and electrolytically etched in a 5% Nital solution at 5V for 20 seconds. The etched sample was then examined using a JEOL JSM25S scanning electron microscope.

Microstructural changes of Aluminum Nitride after laser irradiation and electroless copper deposition

1994 ◽  
Vol 52 ◽  
pp. 636-637
Author(s):  
S. Cao ◽  
A. J. Pedraza ◽  
L. F. Allard
Keyword(s):  
Aluminum Nitride ◽  
Laser Irradiation ◽  
Electroless Deposition ◽  
Thermal Evaporation ◽  
Surface Region ◽  
Near Surface ◽  
Laser Patterning ◽  
Electroless Copper ◽  
Excimer Laser Irradiation ◽  
Laser Effect

Excimer-laser irradiation strongly modifies the near-surface region of aluminum nitride (AIN) substrates. The surface acquires a distinctive metallic appearance and the electrical resistivity of the near-surface region drastically decreases after laser irradiation. These results indicate that Al forms at the surface as a result of the decomposition of the Al (which has been confirmed by XPS). A computer model that incorporates two opposing phenomena, decomposition of the AIN that leaves a metallic Al film on the surface, and thermal evaporation of the Al, demonstrated that saturation of film thickness and, hence, of electrical resistance is reached when the rate of Al evaporation equals the rate of AIN decomposition. In an electroless copper bath, Cu is only deposited in laser-irradiated areas. This laser effect has been designated laser activation for electroless deposition. Laser activation eliminates the need of seeding for nucleating the initial layer of electroless Cu. Thus, AIN metallization can be achieved by laser patterning followed by electroless deposition.

Sign in / Sign up

Export Citation Format

Share Document