Mass Flow and Stability of Nanoscale Features on AU(111)

1992 ◽  
Vol 280 ◽  
Author(s):  
B. H. Cooper ◽  
D. R. Peale ◽  
J. G. Mclean ◽  
R. Phillips ◽  
E. Chason
Keyword(s):  
Mass Flow ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Time Dependent ◽  
Two Dimensional ◽  
Island Size ◽  
Dependent Mass ◽  
Nanoscale Features ◽  
Linear Decay

ABSTRACTWe present the use of an STM to make quantitative observations of time-dependent mass flow associated with the decay of two-dimensional clusters on the Au(111) surface. When formed and observed in air, layered islands with well-defined edges located on larger terraces are generally found to decay in such a way that their areas decrease linearly in time over periods ranging from minutes to several hours depending on the island size. This is in contrast to the behavior of similar features formed and observed under ultra high vacuum conditions, which do not appear to decay over experimental periods of several days. The linear decay is consistent with models that have been used previously to describe growth of 2-dimensional clusters on surfaces. We discuss possible decay mechanisms, and the role that adsorbates may play in influencing the decay.

scholarly journals Time Dependent Indentation Testing At Non-Ambient Temperatures Utilizing the High Temperature Mechanical Properties Microprobe

1994 ◽  
Vol 356 ◽  
Author(s):  
B. N. Lucas ◽  
W. C. Oliver
Keyword(s):  
High Vacuum ◽  
Ultra High Vacuum ◽  
Time Dependent ◽  
Depth Sensing ◽  
Ambient Temperatures ◽  
High Temperature Mechanical Properties ◽  
Wide Range ◽  
Stress Changes ◽  
Laser Interferometric ◽  
Initial Results

AbstractTime dependent indentation data for pure indium from -100 °C to 75 °C is presented. The properties reported include hardness, indentation strain rate, stress exponent and apparent activation energy for creep. These properties were measured using a depth-sensing indentation system capable of performing experiments between -100 °C and 300 °C in ultra-high vacuum. In addition, by employing laser interferometric techniques, this system can obtain displacement data with time constants as low as 50 ns. This allows the investigation of the material response to very fast stress changes over an extremely wide range of strain rates. The adverse and beneficial dynamic effects of step-loading the indenter into the surface of the material will be discussed. Initial results obtained from this type of experiment show that it is possible to obtain energy dissipation or damping information from the material being studied.

High Mobility Two-Dimensional Electron Gas in Modulation-Doped Si/SiGe Heterostructures

1991 ◽  
Vol 220 ◽  
Author(s):  
P. J. Wang ◽  
B. S. Meyerson ◽  
K. Ismail ◽  
F. F. Fang ◽  
J. Nocera
Keyword(s):  
High Vacuum ◽  
Electron Gas ◽  
Ultra High Vacuum ◽  
Threading Dislocation ◽  
High Electron ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Vapor Deposition Technique ◽  
Dimensional Electron Gas

ABSTRACTWe report record-high electron mobilities obtained in the Si/SiGe alloy system via single-junction n-type modulation-doped Si/Si0.7Ge0.9 heterostructurcs grown by the ultra-high vacuum chemical vapor deposition technique. Peak electron mobilities as high as 1,800 cm2/Vs, 9,000 cm2/Vs and 19,000 cm2/Vs were measured at room temperature, 77K and 1.4K, respectively. These high mobilities resulted from excellent Si/SiGe interfacial properties by employing a compositional graded Si/SiGe superlattice prior to the growth of a thick S0.7Ge0.3 buffer, which brought about a dramatic reduction of the threading dislocation density in the active Si channel. Two thin phosphorous-doped layers were incorporated in the SiGe barrier and at its surface to supply electrons to the Si channel and to suppress the surface depletion, respectively. The transport properties of these heterostructurcs were determined to be those of a two dimensional electron gas at Si/SiGe heterointerfaces at low temperatures.

Thermal Stability of Si/Si0.85Ge0.15/Si Modulation Doped Double Heterostructures

1989 ◽  
Vol 160 ◽  
Author(s):  
P.J. Wang ◽  
B.S. Meyerson ◽  
P.M. Fahey ◽  
F. LeGoues ◽  
G.J. Scilla ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Vacuum ◽  
Chemical Vapor ◽  
Ultra High Vacuum ◽  
Misfit Dislocations ◽  
Two Dimensional ◽  
Double Heterostructures ◽  
Vapor Deposition Technique ◽  
P Type ◽  
Thermal Stability Of

AbstractThe thermal stability of Si/Si0.85Ge0.15/Si p-type modulation doped double heterostructures grown by the Ultra High Vacuum/ Chemical Vapor Deposition technique has been examined by Hall measurement, transmission electron microscopy, secondary ion mass spectroscopy, and Raman spectroscopy. As deposited heterostructures showed two-dimensional hole gas formation at the abrupt Si/SiGe and SiGe/Si interfaces. Annealing at 800 °C. for 1 hr. caused the diffusion of boron acceptors to the heterointerfaces, degrading the hole mobilities observed in the two dimensional hole gas. Rapid redistribution of boron, causing a loss of the 2 dimensional carrier behavior, was observed after a 900 °C, 0.5 hr. anneal. Neither Ge interdiffusion nor the generation of misfit dislocations were observed in the annealed heterostructures, evincing the defect-free crystal quality of these as-grown strained heteroepitaxial layers. The superior stability of these heterostructures have strong positive implications for Si:Ge heterojunction devices.

scholarly journals Principles of molecular assemblies leading to molecular nanostructures

2013 ◽  
Vol 371 (2000) ◽  
pp. 20120304 ◽  
Author(s):  
Kunal S. Mali ◽  
Steven De Feyter
Keyword(s):  
Self Assembly ◽  
Contemporary Literature ◽  
High Vacuum ◽  
Building Blocks ◽  
Ultra High Vacuum ◽  
Two Dimensional ◽  
Ambient Conditions ◽  
Solid Interface ◽  
Metal Organic ◽  
Molecular Nanostructures

Self-assembled physisorbed monolayers consist of regular two-dimensional arrays of molecules. Two-dimensional self-assembly of organic and metal–organic building blocks is a widely used strategy for nanoscale functionalization of surfaces. These supramolecular nanostructures are typically sustained by weak non-covalent forces such as van der Waals, electrostatic, metal–ligand, dipole–dipole and hydrogen bonding interactions. A wide variety of structurally very diverse monolayers have been fabricated under ambient conditions at the liquid–solid and air–solid interface or under ultra-high-vacuum (UHV) conditions at the UHV–solid interface. The outcome of the molecular self-assembly process depends on a variety of factors such as the nature of functional groups present on assembling molecules, the type of solvent, the temperature at which the molecules assemble and the concentration of the building blocks. The objective of this review is to provide a brief account of the progress in understanding various parameters affecting two-dimensional molecular self-assembly through illustration of some key examples from contemporary literature.

Interfacial Dislocations in (111) Ag-Cu Bilayers

1973 ◽  
Vol 31 ◽  
pp. 112-113
Author(s):  
C. T. Homg ◽  
R. W. Vook
Keyword(s):  
High Vacuum ◽  
Ultra High Vacuum ◽  
Two Dimensional ◽  
Double Diffraction ◽  
Cu Films ◽  
Interfacial Dislocations ◽  
Residual Gas ◽  
Diffraction Effects ◽  
Work Up

Smooth (111) single crystal Cu films (1200Å) were evaporated on NaCl/mica in an ultra-high vacuum RHEED systemI (base pressure ≤1×10−9 torr) The total residual gas pressure during Cu evaporation was less than 1×10−8 torr. These Cu films served as substrates for thin epitaxial monolayer Ag growth ranging in thickness from 1Å to 20Å, as measured by a quartz thickness monitor. These Ag-Cu bilayers were formed and examined in-situ in the RHEED system.The unusual RHEED patterns first re orted by Gradmann and Krause were observed in the present work up to l0Å of Ag. Beyond 10Å, only Ag and Cu lines plus double diffraction effects were detected. A typical example of the former is given in Fig. 1. The pattern was previously interpreted as due to a two dimensional grid of interfacial dislocations.

A two-dimensional crystal formed by pentamers on Au(111)

2019 ◽  
Vol 55 (38) ◽  
pp. 5427-5430 ◽  
Author(s):  
Chenyang Yuan ◽  
Na Xue ◽  
Xue Zhang ◽  
Yajie Zhang ◽  
Na Li ◽  
...  
Keyword(s):  
Low Temperature ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Two Dimensional ◽  
Scanning Tunnelling Microscope ◽  
Scanning Tunnelling ◽  
New Type ◽  
Temperature Scanning ◽  
Dimensional Crystal

A new type of two-dimensional crystal comprising supramolecular pentamers on Au(111) is studied using an ultra-high vacuum low-temperature scanning tunnelling microscope.

scholarly journals Research progress of monolayer two-dimensional atomic crystal materials grown by molecular beam epitaxy in ultra-high vacuum conditions

2020 ◽  
Vol 69 (11) ◽  
pp. 118101
Author(s):  
Xing-Yue Wang ◽  
Hui Zhang ◽  
Zi-Lin Ruan ◽  
Zhen-Liang Hao ◽  
Xiao-Tian Yang ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Research Progress ◽  
Two Dimensional ◽  
Atomic Crystal

Construction of carbon-based two-dimensional crystalline nanostructure by chemical vapor deposition of benzene on Cu(111)

Nanoscale ◽  
2014 ◽  
Vol 6 (14) ◽  
pp. 7934-7939 ◽  
Author(s):  
Qinghua Han ◽  
Huan Shan ◽  
Jialiang Deng ◽  
Aidi Zhao ◽  
Bing Wang ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
High Vacuum ◽  
Chemical Vapor ◽  
Ultra High Vacuum ◽  
Two Dimensional ◽  
Carbon Based

A new carbon-based two-dimensional crystalline nanostructure was constructed by chemical vapor deposition of benzene on Cu(111) in ultra-high vacuum.

Laser-Induced Desorption of in and Ga from Si(100) and Adsorbate Enhanced Surface Damage

1991 ◽  
Vol 236 ◽  
Author(s):  
Paul G. Strupp ◽  
April L. Alstrin ◽  
Brenda J. Korte ◽  
Stephen R. Leone
Keyword(s):  
High Vacuum ◽  
Surface Damage ◽  
Laser Pulses ◽  
Laser Induced Fluorescence ◽  
Ultra High Vacuum ◽  
Two Dimensional ◽  
Adsorbate Layer ◽  
Exponential Factors ◽  
Enhanced Surface ◽  
532 Nm

AbstractLaser-induced desorption (LID) of In and Ga from Si(100) under ultra-high vacuum conditions is investigated. The frequency doubled 532 nm, 2-6 ns output of a Nd:YAG laser is focussed to 0. 14±0.03 J/cm2 on the Si surface to induce desorption. Desorbed In or Ga atoms are detected by laser-induced fluorescence initiated by a pulsed dye laser propagating in front of the surface. LID occurs by thermal desorption with approximate desorption energies and pre-exponential factors in agreement with literature values from previous isothermal desorption measurements. Experiments at higher coverages suggest that desorption occurs predominantly from the two-dimensional (2D) adsorbate layer with little desorption occurring directly from adsorbate islands. The 2D layer is resupplied by either diffusion out of adsorbate islands or by diffusion of incorporated adsorbate out of the bulk. Adsorbate-enhanced laser-induced surface damage is also observed; only 0.2 monolayer of In reduces the number of laser pulses required to observe damage by greater than a factor of 30.

Morphological Evolution During Ge/Si(100) Heteroepitaxy

1995 ◽  
Vol 399 ◽  
Author(s):  
Loren I. Espada ◽  
Sergio Chaparro ◽  
Jose Aguilar ◽  
Melissa Dorrance ◽  
Michael McKay ◽  
...  
Keyword(s):  
Driving Forces ◽  
Morphological Evolution ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Native Oxide ◽  
Vacuum System ◽  
Specimen Preparation ◽  
Size Distributions ◽  
Island Size ◽  
Plan View

ABSTRACTWe have investigated the morphological evolution of islanded Ge/Si(100) samples formed by > 3 monolayer (ML) Ge deposition. Ge was deposited onto Si(100) surfaces cleaned by flash desorption of the native oxide at rates near 1/2 ML per minute. Growths were performed in an ultra-high vacuum system with a base pressure of < 10−9 Torr. Substrate temperature during growth was 500 °C. Post-deposition processing ranged from no additional treatment to 1 hour at 560 °C anneals. Samples removed from the growth chamber were processed using standard transmission electron microscopy (TEM) specimen preparation techniques and characterized using plan-view TEM. Micrographs were computer analyzed to generate island size distributions (histograms of island size). These size distributions fall into general classes. First, samples with only coherent Ge islands exhibit relatively narrow size distributions. Secondly samples with both coherent and incoherent islands presented bi-modal size distributions with coherent islands populating the smaller radii. These results will be discussed in the context of a model which includes elastic as well as surface and interface energies as driving forces for ripening.

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