Growth of Group IV-IV Heterostructures: Initial Stages of Interface Formation

1986 ◽  
Vol 67 ◽  
Author(s):  
H.-J. Gossmann ◽  
L. C. Feldman
Keyword(s):  
Surface Segregation ◽  
Substrate Surface ◽  
Group Iv ◽  
Necessary Condition ◽  
Ion Scattering ◽  
Interface Formation ◽  
General Role ◽  
Low Energy Electron ◽  
Critical Coverage

ABSTRACTThe two major issues in the growth of a heterostructure are (1) the degree of perfection of the overlayer and (2) the sharpness of the interface. The initial stages of interface formation play a crucial role in this respect. Relevant questions are addressed under atomically clean conditions in the Si/Ge Si/Si and Ge/Sn systems, using ion scattering surface analysis, low energy electron diffraction and Auger electron spectroscopy. Of particular interest with respect to (1) is the general role of reconstruction in epitaxial growth: A necessary condition for perfect growth is the reordering of the substrate surface reconstruction. We show that the deposition temperature necessary to achieve this reordering depends strongly on the topography of the substrate reconstruction. For example, Ge deposition at room-temperature reorders the Si(100)2×1 reconstruction but not the Si(111)7×7, implying different epitaxial temperatures for these two substrates. To illustrate (2) we discuss the complex growth and anomalous diffusion found in the Ge/Sn system. Below a certain critical coverage Θc (1.15·1015 cm−2) no indiffusion of the Sn overlayer takes place, even at 700 K, although above Θc severe indiffusion does occur at this temperature. This result is discussed in terms of theories of surface segregation.

Initial Stages of Interface Formation in the Si/Sn System

1986 ◽  
Vol 77 ◽  
Author(s):  
M. Zinke-Allmang ◽  
H.-J. Gossmann ◽  
L. C. Feldman ◽  
G. J. Fisanick
Keyword(s):  
Room Temperature ◽  
Group Iv ◽  
Necessary Condition ◽  
Interface Formation ◽  
Island Formation ◽  
Simple Growth ◽  
Critical Coverage

ABSTRACTGroup IV-IV heterostructures with Sn as one constituent have potentially important applications. We report on an investigation of the initial stages of interface formation for deposition of Sn on Si(100)2×1 and Si(111)7×7. We find that simple growth occurs up to a critical coverage θc. (α1.25×1015 cm-2), independent of temperature. Beyond θc. growth continues to be laminar for deposition at 150 K only, while island formation is observed at temperatures at and above room temperature. The Si(111)7×7 reconstruction seems unperturbed by Sn deposition at room temperature while the Si(100)2×1 begins to order. However, the reordering, a necessary condition for perfect growth, is incomplete.

THE INFLUENCE OF RECONSTRUCTION ON THE INITIAL STAGES OF SILICON MOLECULAR BEAM EPITAXY

1985 ◽  
Vol 56 ◽  
Author(s):  
H.-J. Gossmann ◽  
L.C. Feldman
Keyword(s):  
Substrate Surface ◽  
Strong Dependence ◽  
Direct Consequence ◽  
High Energy ◽  
Necessary Condition ◽  
Layer By Layer ◽  
Ion Scattering ◽  
Surface Deposition ◽  
Low Energy Electron ◽  
Pseudomorphic Growth

AbstractHigh energy ion scattering/channeling and low energy electron diffraction are usedfor an investigation of the initial stages of interface formation during Si homoepitaxy. We find a strong dependence of the atomic. reordering – a necessary condition for pseudomorphic growth – on substrate surface, deposition temperature and Si coverage: (1) Si deposition at 300 K reorders the Si(100) substrate reconstruction in a layer by layer manner. In contrast Si( 111) is unaffected by Si deposition at that temperature. This difference between Si(100) and Si( 111) can be understood in terms of different structural models. (2) On both surfaces deposition at 300 K results in a disordered overlayer. (3) As a direct consequence of the dependence of the reordering on reconstruction we find a lower epitaxial temperature (≈570 K) for Si(100) than for Si(l 11) (≈790 K).

Role of Ge surface segregation in Si/Ge interfacial ordering: Interface formation on a monohydride surface

1995 ◽  
Vol 51 (20) ◽  
pp. 14786-14789 ◽  
Author(s):  
Nobuyuki Ikarashi ◽  
Atsushi Oshiyama ◽  
Akira Sakai ◽  
Toru Tatsumi
Keyword(s):  
Surface Segregation ◽  
Interface Formation

scholarly journals Patterning Luminescent Nanocrystalline  : Eu and  : Tb Particles Embedded in Hybrid Organosilica with Soft-Lithographic Techniques

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Sajid U. Khan ◽  
Johan E. ten Elshof
Keyword(s):  
Photoelectron Spectroscopy ◽  
Substrate Surface ◽  
Solution Chemistry ◽  
Ion Scattering ◽  
X Ray Diffraction ◽  
X Ray ◽  
Low Energy Ion Scattering ◽  
Pattern Shape ◽  
Secondary Ion

Eu3+-doped LaPO4and Tb3+-doped CePO4luminescent nanoparticles embedded in hybrid organosilica were patterned by two soft lithographic techniques. The role of various parameters such as solution chemistry, thermal protocols, and modification of the mold-substrate surface energies related to pattern shape formation and adhesion to the substrates have been studied. The shrinkage of the oxide patterns and shape evolution during the process was also examined. The patterns were characterized with optical and photoluminescence (PL) microscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Compositional analyses were carried out with X-ray photoelectron spectroscopy (XPS), low-energy ion scattering (LEIS), and secondary ion mass spectroscopy (SIMS). The results indicated that the final patterns obtained with these two techniques for the same material have different shapes and adherence to the substrates.

Surface segregation of gold for Au/Pd(111) alloys measured by low-energy electron diffraction and low-energy ion scattering

2008 ◽  
Vol 602 (5) ◽  
pp. 1084-1091 ◽  
Author(s):  
Zhenjun Li ◽  
Octavio Furlong ◽  
Florencia Calaza ◽  
Luke Burkholder ◽  
Hin Cheuk Poon ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Surface Segregation ◽  
Low Energy ◽  
Energy Electron ◽  
Ion Scattering ◽  
Low Energy Electron Diffraction ◽  
Low Energy Ion Scattering ◽  
Low Energy Electron

THE STUDY OF SURFACE SEGREGATION, STRUCTURE, AND VALENCE BAND DENSITY OF STATES OF Pt3Ni(100), (110), AND (111) CRYSTALS

2006 ◽  
Vol 13 (05) ◽  
pp. 697-702 ◽  
Author(s):  
B. S. MUN ◽  
M. WATANABE ◽  
M. ROSSI ◽  
V. STAMENKOVIC ◽  
N. M. MARKOVIC ◽  
...  
Keyword(s):  
Single Crystals ◽  
Valence Band ◽  
Density Of States ◽  
Surface Segregation ◽  
Low Energy ◽  
Ion Scattering ◽  
Low Energy Ion Scattering ◽  
Low Energy Electron ◽  
Valence Bands ◽  
Segregation Structure

The surface segregation, structure, and valence band density of states of Pt 3 Ni (100), (110), and (111) single crystals are characterized with low energy ion scattering (LEIS), low energy electron diffraction (LEED), and ultraviolet photoemission spectroscopy (UPS). The results of LEIS clearly reveal the complete surface segregation of Pt to the top layer on all crystal alloys. LEED indicates the (5 × 1) surface reconstruction on the Pt 3 Ni (100), while (110) and (111) surfaces show (2 × 1) and (1 × 1) patterns, respectively, identical to Pt single crystals. The valence bands density of states on Pt 3 Ni alloys are compared to those of Pt single crystals via UPS measurements.

Initial Stages of Interface Formation: The Influence of Surface Reconstruction

1987 ◽  
Vol 94 ◽  
Author(s):  
H.-J. Gossmann
Keyword(s):  
Surface Reconstruction ◽  
Growth Parameters ◽  
Substrate Surface ◽  
Necessary Condition ◽  
Molecular Beam Epitaxy Growth ◽  
Interface Formation ◽  
Lattice Match ◽  
The Difference ◽  
Reconstructed Surface ◽  
Substrate Temperatures

ABSTRACTThe initial stages of interface formation are crucial for the growth of an overlayer, particularly for ultra-thin films. While growth rate, growth temperature and lattice match are important parameters in molecular beam epitaxy, growth of semiconductor heterostructures always begins on a reconstructed surface. The effect of this reconstruction has to be known before a complete understanding of the growth process is possible. Two examples will be discussed: (1) A necessary condition for perfect growth is the reordering of the substrate surface, i.e. those atoms at the interface which are originally displaced due to the reconstruction have to be brought back to bulk positions. Si(111)7×7 and Si(100)2×1 surfaces behave differently in this respect. The 2×1 orders upon deposition of Si, Ge or Sn at room-temperature whereas the 7×7 does not. This result will be correlated with the different classes of reconstruction to which these surfaces belong. The possible rela-tionship with the difference in substrate temperatures required to achieve homo-epitaxial growth on Si(100) and Si(111) surfaces will be discussed. (2) Perfect growth also relies on proper control of the growth-mode. As an example, the island-ing behavior found for deposition of Sn on Si will be discussed. While surface diffusion over macroscopic distances is observed, dramatic changes in the affinity for clustering occur depending on surface reconstruction and preparation, suggesting that clustering in this system may be controlled by appropriate choices of growth parameters.

Dissent in the Atlantic World, 1787–1830

2018 ◽  
Author(s):  
Katherine Carté Engel
Keyword(s):  
United States ◽  
African Americans ◽  
First Amendment ◽  
Church And State ◽  
State Level ◽  
The United States ◽  
American Population ◽  
Simple Fact ◽  
General Role

The very term ‘Dissenter’ became problematic in the United States, following the passing of the First Amendment. The formal separation of Church and state embodied in the First Amendment was followed by the ending of state-level tax support for churches. None of the states established after 1792 had formal religious establishments. Baptists, Congregationalists, Presbyterians, and Methodists accounted for the majority of the American population both at the beginning and end of this period, but this simple fact masks an important compositional shift. While the denominations of Old Dissent declined relatively, Methodism grew quickly, representing a third of the population by 1850. Dissenters thus faced several different challenges. Primary among these were how to understand the idea of ‘denomination’ and also the more general role of institutional religion in a post-establishment society. Concerns about missions, and the positions of women and African Americans are best understood within this context.

The Temptations of Christ and Other Stories

2018 ◽  
Author(s):  
Eleonore Stump
Keyword(s):  
Human Person ◽  
Necessary Condition ◽  
Biblical Narratives ◽  
God's Love ◽  
The Way

This chapter examines biblical narratives to illuminate the role of Christ’s passion and death in bringing a person to a life in grace. Reflection on the narratives shows that Christ’s passion and death are a most promising way for God to help a human person to the surrender which is the necessary condition for spiritual and moral regeneration. The stories of the temptations of Christ show the way in which Christ’s suffering and death are connected to justification and sanctification. A person’s ceasing to resist the grace of God and surrendering to God’s love is the pinnacle on which her salvation has to stand. If we focus on this necessary condition for salvation, we can see the reason for Christ’s suffering. What can be gained by weakness that could not be gotten through power is the melting of a heart accustomed to willed loneliness and hardened against joy.

scholarly journals Tethering-induced destabilization and ATP-binding for tandem RRM domains of ALS-causing TDP-43 and hnRNPA1

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mei Dang ◽  
Yifan Li ◽  
Jianxing Song
Keyword(s):  
Conformational Dynamics ◽  
Md Simulations ◽  
Atp Binding ◽  
Rna Recognition Motif ◽  
Rna Recognition ◽  
Nucleic Acid Binding ◽  
General Role ◽  
Nmr Characterization ◽  
Lateral Sclerosis

AbstractTDP-43 and hnRNPA1 contain tandemly-tethered RNA-recognition-motif (RRM) domains, which not only functionally bind an array of nucleic acids, but also participate in aggregation/fibrillation, a pathological hallmark of various human diseases including amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), alzheimer's disease (AD) and Multisystem proteinopathy (MSP). Here, by DSF, NMR and MD simulations we systematically characterized stability, ATP-binding and conformational dynamics of TDP-43 and hnRNPA1 RRM domains in both tethered and isolated forms. The results reveal three key findings: (1) upon tethering TDP-43 RRM domains become dramatically coupled and destabilized with Tm reduced to only 49 °C. (2) ATP specifically binds TDP-43 and hnRNPA1 RRM domains, in which ATP occupies the similar pockets within the conserved nucleic-acid-binding surfaces, with the affinity slightly higher to the tethered than isolated forms. (3) MD simulations indicate that the tethered RRM domains of TDP-43 and hnRNPA1 have higher conformational dynamics than the isolated forms. Two RRM domains become coupled as shown by NMR characterization and analysis of inter-domain correlation motions. The study explains the long-standing puzzle that the tethered TDP-43 RRM1–RRM2 is particularly prone to aggregation/fibrillation, and underscores the general role of ATP in inhibiting aggregation/fibrillation of RRM-containing proteins. The results also rationalize the observation that the risk of aggregation-causing diseases increases with aging.

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