scholarly journals Surface Roughness Changes Induced by Stoichiometric Deviation in Ambient Phase for Two-Component Semiconductor Crystals

Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 151 ◽  
Author(s):  
Noriko Akutsu ◽  
Yoshiki Sugioka ◽  
Naoya Murata
Keyword(s):  
Surface Roughness ◽  
Self Assembly ◽  
Characteristic Length ◽  
Length Scale ◽  
Vicinal Surface ◽  
Semiconductor Crystals ◽  
Maximum Value ◽  
The Monte Carlo Method ◽  
Two Component ◽  
Polar Surfaces

The effects of a deviation in the fraction of the components in the ambient phase of a stoichiometric AB compound, such as GaN or SiC crystals, on the surface roughness and step self-assembly and disassembly on a vicinal surface are studied using the Monte Carlo method based on a staggered restricted solid-on-solid (st-RSOS) model at equilibrium. The (001) and (111) surfaces are typical examples of non-polar and polar surfaces, respectively. Although a stoichiometric deviation of the ambient phase does not affect the surface energy of a non-polar surface, it affects that of polar surfaces such as the ( 111 ) A and ( 111 ) B surfaces. We found that the vicinal surface of an AB compound is atomically smooth and globally rough. Globally, the vicinal surface is not affected by a stoichiometric deviation in the ambient phase. In contrast, in a small area, the structure of the vicinal surface is affected by a stoichiometric deviation in the ambient phase. The vicinal surface consists of local double and quadruple steps. The characteristic length L M F L , which separates the global length scale region and the local length scale region, has a maximum value of 156 a in the present study, where a is the lattice constant. When temperature decreases, L M F L can become large.

Competitive Self-Assembly Manifests Supramolecular Darwinism in Soft-Oxometalates

2015 ◽  
Vol 03 (01n02) ◽  
pp. 1540008 ◽  
Author(s):  
Santu Das ◽  
Saurabh Kumar ◽  
Apabrita Mallick ◽  
Soumyajit Roy
Keyword(s):  
Electron Microscopy ◽  
Self Assembly ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Inorganic Materials ◽  
Time Dependent ◽  
Length Scale ◽  
Topological Transformation ◽  
Two Component ◽  
Scanning Electron

Topological transformation manifested in inorganic materials shows manifold possibilities. In our present work, we show a clear topological transformation in a soft-oxometalate (SOM) system which was formed from its polyoxometalate (POM) precursor [ PMo 12 @Mo 72 Fe 30]. This topological transformation was observed due to time dependent competitive self-assembly of two different length scale soft-oxometalate moieties formed from this two-component host–guest reaction. We characterized different morphologies by scanning electron microscopy, electron dispersive scattering spectroscopy, dynamic light scattering, horizontal attenuated total reflection–infrared spectroscopy and Raman spectroscopy. The predominant structure is selected by its size in a sort of supramolecular Darwinian competition in this process and is described here.

Biomimetic materials: An introduction

1992 ◽  
Vol 50 (2) ◽  
pp. 1020-1021 ◽  
Author(s):  
M. Sarikaya ◽  
J. T. Staley ◽  
I. A. Aksay
Keyword(s):  
Self Assembly ◽  
Structural Control ◽  
Hierarchical Structures ◽  
Ceramic Composites ◽  
Advanced Materials ◽  
Length Scale ◽  
Spider Webs ◽  
Biomimetic Materials ◽  
Synthetic Materials ◽  
All Ceramic

Biomimetics is an area of research in which the analysis of structures and functions of natural materials provide a source of inspiration for design and processing concepts for novel synthetic materials. Through biomimetics, it may be possible to establish structural control on a continuous length scale, resulting in superior structures able to withstand the requirements placed upon advanced materials. It is well recognized that biological systems efficiently produce complex and hierarchical structures on the molecular, micrometer, and macro scales with unique properties, and with greater structural control than is possible with synthetic materials. The dynamism of these systems allows the collection and transport of constituents; the nucleation, configuration, and growth of new structures by self-assembly; and the repair and replacement of old and damaged components. These materials include all-organic components such as spider webs and insect cuticles (Fig. 1); inorganic-organic composites, such as seashells (Fig. 2) and bones; all-ceramic composites, such as sea urchin teeth, spines, and other skeletal units (Fig. 3); and inorganic ultrafine magnetic and semiconducting particles produced by bacteria and algae, respectively (Fig. 4).

Identification of the characteristic length scale for fatigue cracking in fretting contacts

1998 ◽  
Vol 08 (PR8) ◽  
pp. Pr8-159-Pr8-166 ◽  
Author(s):  
S. Fouvry ◽  
Ph. Kapsa ◽  
F. Sidoroff ◽  
L. Vincent
Keyword(s):  
Characteristic Length ◽  
Fatigue Cracking ◽  
Length Scale ◽  
Characteristic Length Scale

scholarly journals Lettau’s Contribution to the Obukhov Length Scale: A Scientific Historical Study

2021 ◽  
Author(s):  
Thomas Foken ◽  
Michael Börngen
Keyword(s):  
Characteristic Length ◽  
Stability Parameter ◽  
Historical Study ◽  
Length Scale ◽  
Characteristic Length Scale ◽  
Obukhov Length ◽  
The Future

AbstractIt has been repeatedly assumed that Heinz Lettau found the Obukhov length in 1949 independently of Obukhov in 1946. However, it was not the characteristic length scale, the Obukhov length L, but the ratio of height and the Obukhov length (z/L), the Obukhov stability parameter, that he analyzed. Whether Lettau described the parameter z/L independently of Obukhov is investigated herein. Regardless of speculation about this, the significant contributions made by Lettau in the application of z/L merit this term being called the Obukhov–Lettau stability parameter in the future.

Reactive Ion Etching Induced Surface Damage of Silicon Carbide

2005 ◽  
Vol 483-485 ◽  
pp. 765-768 ◽  
Author(s):  
Jun Hai Xia ◽  
E. Rusli ◽  
R. Gopalakrishnan ◽  
S.F. Choy ◽  
Chin Che Tin ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Reactive Ion Etching ◽  
Surface Damage ◽  
Textured Surface ◽  
Rf Power ◽  
Power Devices ◽  
Ion Etching ◽  
Maximum Value ◽  
Wide Range ◽  
Coarse Surface

Reactive ion etching of SiC induced surface damage, e.g., micromasking effect induced coarse and textured surface, is one of the main concerns in the fabrication of SiC based power devices [1]. Based on CHF3 + O2 plasma, 4H-SiC was etched under a wide range of RF power. Extreme coarse and textured etched surfaces were observed under certain etching conditions. A super-linear relationship was found between the surface roughness and RF power when the latter was varied from 40 to 160 W. A further increase in the RF power to 200 W caused the surface roughness to drop abruptly from its maximum value of 182.4 nm to its minimum value of 1.3 nm. Auger electron spectroscopy (AES) results revealed that besides the Al micromasking effect, the carbon residue that formed a carbon-rich layer, could also play a significant role in affecting the surface roughness. Based on the AES results, an alternative explanation on the origin of the coarse surface is proposed.

Gold Nanoparticle Self-Assembly in Two-Component Lipid Langmuir Monolayers†

Langmuir ◽  
2011 ◽  
Vol 27 (4) ◽  
pp. 1260-1268 ◽  
Author(s):  
Alina Mogilevsky ◽  
Raz Jelinek
Keyword(s):  
Gold Nanoparticle ◽  
Self Assembly ◽  
Langmuir Monolayers ◽  
Two Component

Hard Materials with Tunable Porosity

MRS Bulletin ◽  
2009 ◽  
Vol 34 (8) ◽  
pp. 561-568 ◽  
Author(s):  
Jonah Erlebacher ◽  
Ram Seshadri
Keyword(s):  
Porous Materials ◽  
Self Assembly ◽  
Porous Metal ◽  
Ceramic Materials ◽  
Equilibrium Temperature ◽  
Length Scale ◽  
Porous Metals ◽  
Hard Materials ◽  
Mesoporous Zeolites ◽  
Pattern Forming

AbstractPorous metals and ceramic materials are of critical importance in catalysis, sensing, and adsorption technologies and exhibit unusual mechanical, magnetic, electrical, and optical properties compared to nonporous bulk materials. Materials with nanoscale porosity often are formed through molecular self-assembly processes that lock in a particular length scale; consider, for instance, the assembly of crystalline mesoporous zeolites with a pore size of 2–50 nm or the evolution of structural domains in block copolymers. Of recent interest has been the identification of general kinetic pattern-forming principles that underlie the formation of mesoporous materials without a locked- in length scale. When materials are kinetically locked out of thermodynamic equilibrium, temperature or chemistry can be used as a “knob” to tune their microstructure and properties. In this issue of the MRS Bulletin, we explore new porous metal and ceramic materials, which we collectively refer to as “hard” materials, formed by pattern-forming instabilities, either in the bulk or at interfaces, and discuss how such nonequilibrium processing can be used to tune porosity and properties. The focus on hard materials here involves thermal, chemical, and electrochemical processing usually not compatible with soft (for example, polymeric) porous materials and generally adds to the rich variety of routes to fabricate porous materials.

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