THE STABILITY OF LOW INDEX METAL SURFACES TO TOPOLOGICAL DEFECTS

1991 ◽  
Vol 05 (03) ◽  
pp. 427-459 ◽  
Author(s):  
EDWARD H. CONRAD
Keyword(s):  
Metal Surfaces ◽  
Surface Defects ◽  
Defect Formation ◽  
Fundamental Problem ◽  
Topological Defects ◽  
Surface Roughening ◽  
Thermal Generation ◽  
Diffusion Mechanisms ◽  
The Stability ◽  
And Diffusion

The study of defect formation at metal surfaces is a fundamental problem in surface physics. An understanding of defect formation is pertinent to growth and diffusion mechanisms. In addition, surface roughening, faceting, and surface melting are all defect mediated phase transitions involving the formation of different topological defects. While the importance of defects at surfaces is well recognized, the study of surface defects has been hampered by the lack of sufficiently accurate experimental techniques. In fact, it is only in the past 6 years that experiments on the thermal generation of defects on metal surfaces have been performed. This review attempts to outline both the theoretical and experimental work on surface defect formation on metal systems.

Coverage and Stability of NHx Terminated Cobalt and Ruthenium Surfaces: a First Principles Investigation

2019 ◽  
Author(s):  
Ji Liu ◽  
Michael Nolan
Keyword(s):  
Metal Surfaces ◽  
High Vacuum ◽  
Atomic Layer ◽  
Nitrogen Plasma ◽  
Operating Conditions ◽  
Ultra High Vacuum ◽  
Bridge Site ◽  
Stable Surface ◽  
Saturation Coverage ◽  
The Stability

<div>In the atomic layer deposition (ALD) of Cobalt (Co) and Ruthenium (Ru) metal using nitrogen plasma, the structure and composition of the post N-plasma NHx terminated (x = 1 or 2) metal surfaces are not well known but are important in the subsequent metal containing pulse. In this paper, we use the low-index (001) and (100) surfaces of Co and Ru as models of the metal polycrystalline thin films. The (001) surface with a hexagonal surface structure is the most stable surface and the (100) surface with a zigzag structure is the least stable surface but has high reactivity. We investigate the stability of NH and NH2 terminations on these surfaces to determine the saturation coverage of NHx on Co and Ru. NH is most stable in the hollow hcp site on (001) surface and the bridge site on the (100) surface, while NH2 prefers the bridge site on both (001) and (100) surfaces. The differential energy is calculated to find the saturation coverage of NH and NH2. We also present results on mixed NH/NH2-terminations. The results are analyzed by thermodynamics using Gibbs free energies (ΔG) to reveal temperature effects on the stability of NH and NH2 terminations. Ultra-high vacuum (UHV) and standard ALD</div><div>operating conditions are considered. Under typical ALD operating conditions we find that the most stable NHx terminated metal surfaces are 1 ML NH on Ru (001) surface (350K-550K), 5/9 ML NH on Co (001) surface (400K-650K) and a mixture of NH and NH2 on both Ru (100) and Co (100) surfaces.</div>

scholarly journals (Ti,Al)O2 Whiskers Grown during Glow Discharge Nitriding of Ti-6Al-7Nb Alloy

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2658
Author(s):  
Krzysztof Szymkiewicz ◽  
Jerzy Morgiel ◽  
Łukasz Maj ◽  
Małgorzata Pomorska
Keyword(s):  
Surface Hardening ◽  
Surface Defects ◽  
Plasma Nitriding ◽  
Surface Roughening ◽  
Effective Surface ◽  
Plan View ◽  
Gas Nitriding ◽  
Transmission Electron ◽  
Temperature Window ◽  
20 Nm

Plasma nitriding of titanium alloys is capable of effective surface hardening at temperatures significantly lower than gas nitriding, but at a cost of much stronger surface roughening. Especially interesting are treatments performed at the lower end of the temperature window used in such cases, as they are least damaging to highly polished parts. Therefore identifying the most characteristic defects is of high importance. The present work was aimed at identifying the nature of pin-point bumps formed at the glow discharged plasma nitrided Ti-6Al-7Nb alloy using plan-view scanning and cross-section transmission electron microscopy methods. It helped to establish that these main surface defects developed at the treated surface are (Ti,Al)O2 nano-whiskers of diameter from 20 nm to 40 nm, and length up to several hundreds of nanometers. The performed investigation confirmed that the surface imperfection introduced by plasma nitriding at the specified range should be of minor consequences to the mechanical properties of the treated material.

Effect of kinks and concerted diffusion mechanisms on mass transport and growth on stepped metal surfaces

1997 ◽  
Vol 387 (1-3) ◽  
pp. 167-182 ◽  
Author(s):  
J. Merikoski ◽  
I. Vattulainen ◽  
J. Heinonen ◽  
T. Ala-Nissila
Keyword(s):  
Mass Transport ◽  
Metal Surfaces ◽  
Diffusion Mechanisms

DIFFUSION MECHANISMS AT fcc METAL SURFACES — EMBEDDED ATOM METHOD CALCULATIONS

1995 ◽  
Vol 09 (01) ◽  
pp. 1-44 ◽  
Author(s):  
CHUN-LI LIU
Keyword(s):  
Metal Surfaces ◽  
Diffusion Processes ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Simulation Techniques ◽  
Theoretical Investigations ◽  
Diffusion Mechanisms ◽  
Fcc Metal ◽  
Dynamic Diffusion ◽  
Computer Simulation Techniques

Recent development in theoretical investigations using computer simulation techniques and the embedded atom method (EAM) on diffusion processes critical to nucleation and growth of thin films at fcc metal surfaces is reviewed. Through these investigations, interactions between adatoms and substrate, adatoms and steps, and clusters and substrate and the effect of these interactions on dynamic diffusion processes are further understood. The results from these theoretical investigations are generally consistent with available experimental data and have provided explanations for some experimental observations. Some predictions made a few years ago from these studies have been confirmed by the latest experiments.

Li+ionic conductivities and diffusion mechanisms in Li-based imides and lithium amide

2012 ◽  
Vol 14 (5) ◽  
pp. 1596-1606 ◽  
Author(s):  
Wen Li ◽  
Guotao Wu ◽  
Zhitao Xiong ◽  
Yuan Ping Feng ◽  
Ping Chen
Keyword(s):  
Ionic Conductivities ◽  
Lithium Amide ◽  
Diffusion Mechanisms ◽  
And Diffusion

Energetics of Adsorbed Dimers VIA Self-Consistent Scattering Theory

1987 ◽  
Vol 111 ◽  
Author(s):  
Peter J. Feibelman
Keyword(s):  
Scattering Theory ◽  
Surface Defects ◽  
Numerical Application ◽  
Surface Electronic Structure ◽  
Impurity Species ◽  
Substrate Atom ◽  
Self Consistent ◽  
Structure Problem ◽  
And Diffusion ◽  
Field Ion Microscope

AbstractA new approach to the surface electronic structure problem, based on a self-consistent scattering theory of point defects, permits 1st-principles calculations for an isolated cluster of adatoms and defects on an otherwise perfect infinite crystalline surface. A first numerical application of the method explains important observations concerning the interaction and diffusion of adatom dimers on Field Ion Microscope tips. Further studies will shed light on questions such as: What impurity species migrate to what kind of surface defects? What is the contribution of substrate atom positional relaxation to adsorption and diffusion barrier energies?

Global Hopf Bifurcation in a Phytoplankton–Zooplankton System with Delay and Diffusion

2021 ◽  
Vol 31 (08) ◽  
pp. 2150114
Author(s):  
Ming Liu ◽  
Jun Cao ◽  
Xiaofeng Xu
Keyword(s):  
Hopf Bifurcation ◽  
Global Existence ◽  
Upper And Lower Solutions ◽  
Positive Periodic Solutions ◽  
Global Hopf Bifurcation ◽  
System With Delay ◽  
Local Hopf Bifurcation ◽  
Distribution Of Eigenvalues ◽  
The Stability ◽  
And Diffusion

In this paper, the dynamics of a phytoplankton–zooplankton system with delay and diffusion are investigated. The positivity and persistence are studied by using the comparison theorem and upper and lower solutions method. The stability of steady states and the existence of local Hopf bifurcation are obtained by analyzing the distribution of eigenvalues. And the global existence of positive periodic solutions is established by using the global Hopf bifurcation result given by Wu [1996]. Finally, some numerical simulations are carried out to illustrate the analytical results.

Facet-dependent evolution of surface defects in anatase TiO2 by thermal treatment: implications for environmental applications of photocatalysis

2019 ◽  
Vol 6 (6) ◽  
pp. 1740-1753 ◽  
Author(s):  
Tong Li ◽  
Zelin Shen ◽  
Yiling Shu ◽  
Xuguang Li ◽  
Chuanjia Jiang ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
Surface Defect ◽  
Surface Defects ◽  
Defect Formation ◽  
Anatase Tio2 ◽  
Environmental Applications

Exposed crystal facets of TiO2 nanomaterials significantly affect the surface defect formation of the materials during thermal treatment.

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