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.

The Use of Leed for the Characterization of Surface Damage from Pulsed Laser Irradiation

1985 ◽  
Vol 48 ◽  
Author(s):  
Aubrey L. Helms ◽  
Chin-Chen Cho ◽  
Steven L. Bernasek ◽  
Clifton W. Draper
Keyword(s):  
Thermal Stresses ◽  
Profile Analysis ◽  
High Vacuum ◽  
Surface Damage ◽  
Laser Pulses ◽  
Ultra High Vacuum ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Laser Fluences ◽  
Dislocation Sources

ABSTRACTLow Energy Electron Diffraction (LEED)-Spot Profile Analysis and Auger Electron Spectroscopy (AES) have been used to study the response of Mo(100) single crystal surfaces to Q-switched, frequency doubled Nd:YAG laser pulses. The experiments were conducted in a special ultra-high vacuum (UHV) system which allowed the surfaces to be irradiated under controlled conditions. Laser fluences both above and below the melt threshold were employed. For the melted surfaces, good epitaxial regrowth was observed. The spot profile analysis indicates the formation of random islands on the surfaces. Surfaces which had been previously disordered by 3 KeV Ar+ implantation were laser surface melted and observed to regrow epitaxially as has been observed in the case of ion implanted silicon. The formation of the islands and stepped structures is explained by considering the activation of dislocation sources by the induced thermal stresses resulting in slip.

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.

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 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.

Magnetic Anisotropy of Co Films Annealed by Laser Pulses

2008 ◽  
Vol 140 ◽  
pp. 69-74 ◽  
Author(s):  
J. Kisielewski ◽  
Kamil Postava ◽  
I. Sveklo ◽  
A. Nedzved ◽  
P. Trzciński ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Perpendicular Magnetic Anisotropy ◽  
Laser Pulses ◽  
Ultra High Vacuum ◽  
Mica Substrate ◽  
Induced Magnetic Anisotropy ◽  
Coercivity Field ◽  
Pulsed Laser Beam

The magnetic properties of an ultrathin cobalt film were modified by a focused femtosecond pulsed laser beam. The Co wedge, with a thickness ranging from 0 to 2 nm, sandwiched by Au films was prepared using ultra-high vacuum magnetron sputtering on a mica substrate. The modifications of the laser induced magnetic anisotropy were investigated using magneto-optic Kerr microscopy and MFM/AFM techniques. The laser induces: (i) local reorientation of magnetization from an in-plane to a perpendicular state and (ii) an increase of the coercivity field. A corresponding increase of the perpendicular magnetic anisotropy is discussed considering an improvement of the Co/Au interfaces.

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.

STM Study of Self-assembly of Quantum Dot Formed by Selective Laser Heating

2013 ◽  
Vol 1527 ◽  
Author(s):  
Haeyeon Yang ◽  
Casey M. Clegg
Keyword(s):  
Self Assembly ◽  
High Vacuum ◽  
Laser Pulses ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Mbe Growth ◽  
Optical Wavelength ◽  
Growth Method ◽  
Dot Density ◽  
Average Size

ABSTRACTScanning Tunneling Microscope (STM) was used to examine the morphologies of selfassembled InGaAs quantum dots (QDs). In order to induce the self-assembly, unlike the conventional Stranski-Krastanov (S-K) growth method, spatial thermal modulations in nanoscale were created in-situ on strained-but-flat InGaAs surfaces in a Molecular Beam Epitaxy (MBE) growth reactor by applying interferential irradiations of laser pulses (IILP). As-irradiated surfaces were examined using an attached ultra-high vacuum (UHV) STM. STM images indicate that the irradiation of 7 nano second laser pulse induces self-assembly of QDs. The average size of laser-induced QDs is smaller while their density is larger than that of QDs formed by annealing strained but flat epilayers conventionally. Furthermore, the dot density is modulated sinusoidally with a periodicity commensurate with that of the interference, which suggests that the placement of QDs can be controlled on the scale of the optical wavelength used. QD volume analysis suggests that dots grow faster laterally than vertically so that dots become flattened as they get larger.

scholarly journals Femtosecond-Laser Nanostructuring of Black Diamond Films under Different Gas Environments

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5761
Author(s):  
Marco Girolami ◽  
Alessandro Bellucci ◽  
Matteo Mastellone ◽  
Stefano Orlando ◽  
Valerio Serpente ◽  
...  
Keyword(s):  
Optical Properties ◽  
High Vacuum ◽  
Diamond Films ◽  
Cost Effective ◽  
Laser Pulses ◽  
Ultra High Vacuum ◽  
Infrared Light ◽  
Ambient Conditions ◽  
Combined Use ◽  
Fs Laser

Irradiation of diamond with femtosecond (fs) laser pulses in ultra-high vacuum (UHV) conditions results in the formation of surface periodic nanostructures able to strongly interact with visible and infrared light. As a result, native transparent diamond turns into a completely different material, namely “black” diamond, with outstanding absorptance properties in the solar radiation wavelength range, which can be efficiently exploited in innovative solar energy converters. Of course, even if extremely effective, the use of UHV strongly complicates the fabrication process. In this work, in order to pave the way to an easier and more cost-effective manufacturing workflow of black diamond, we demonstrate that it is possible to ensure the same optical properties as those of UHV-fabricated films by performing an fs-laser nanostructuring at ambient conditions (i.e., room temperature and atmospheric pressure) under a constant He flow, as inferred from the combined use of scanning electron microscopy, Raman spectroscopy, and spectrophotometry analysis. Conversely, if the laser treatment is performed under a compressed air flow, or a N2 flow, the optical properties of black diamond films are not comparable to those of their UHV-fabricated counterparts.

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.

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