scholarly journals Second-Order Nonlinear Optical Microscopy of a H–Si(111)1 × 1 Surface in Ultra-High Vacuum Conditions

2012 ◽  
Vol 2012 ◽  
pp. 1-14
Author(s):  
Yoshihiro Miyauchi
Keyword(s):  
Delay Time ◽  
Second Harmonic ◽  
High Vacuum ◽  
Life Time ◽  
Hydrogen Desorption ◽  
Ultra High Vacuum ◽  
Pump Light ◽  
Time Resolved ◽  
Sum Frequency ◽  
Intensity Images

This paper reviews the use of optical sum frequency generation (SFG) and second harmonic generation (SHG) microscopy under ultra-high vacuum (UHV) conditions to observe the dynamics of a hydrogen terminated Si(111)1 × 1 surface. First, we took SFG and SHG microscopic images of the surface after IR light pulse irradiation and found that the SHG and nonresonant SFG signals were enhanced, probably due to the formation of dangling bonds after hydrogen desorption. Second, we observed time-resolved SFG intensity images of a H–Si(111)1 × 1 surface. After visible pump light irradiation, the nonresonant SFG signal increased at probe delay time 0 ps and then decreased over a life time of 565 ps. The resonant SFG signal reduced dramatically at 0 ps and then recovered with an anisotropic line shape over a life time of 305 ps. The areas of modulated SFG signals at delay time 277 ps were expanded with an anisotropic aspect. Finally, we observed SFG intensity images of hydrogen deficiency on a Si(111)1 × 1 surface as a function of temperature. These images of the H–Si(111) surface, taken with a spatial resolution of 5 μm at several temperatures from 572 to 744 K, showed that the hydrogen desorbs homogeneously.

Picosecond Optical Second Harmonic Studies of Adsorbate Reduction Kinetics on Cadmium Sulfide

1993 ◽  
Vol 334 ◽  
Author(s):  
T. W. Scott ◽  
J. Martorell ◽  
Y. J. Chang
Keyword(s):  
Cadmium Sulfide ◽  
Near Infrared ◽  
Transient Absorption ◽  
Second Harmonic ◽  
Harmonic Signal ◽  
Recombination Luminescence ◽  
Kinetic Measurements ◽  
Time Resolved ◽  
Sum Frequency ◽  
Kinetics Of

AbstractTime resolved surface second harmonic generation has been used to probe the photoreduction kinetics of malachite green adsorbed onto single crystal cadmium sulfide. A detailed analysis is presented of how the adsorbates and the noncentrosymmetric substrate contribute separately to the total second harmonic signal. Conditions under which the adsorbates can be cleanly detected are described. To complement kinetic measurements of adsorbate reduction, the time evolution of conduction band carriers was determined using sum frequency up conversion of the recombination luminescence. In addition, the formation and decay of surface trapped carriers was monitored using near infrared transient absorption. Comparing the time scale for photoreduction with the relaxation kinetics of mobile and trapped charge carriers indicates that short lived mobile carriers rather than longer lived surface trapped carriers dominate interfacial charge transfer in this system.

Ultra-High Vacuum Optical Second Harmonic Microscope

2000 ◽  
Vol 39 (Part 2, No. 3A/B) ◽  
pp. L253-L255 ◽  
Author(s):  
Yasuyuki Sonoda ◽  
Goro Mizutani ◽  
Haruyuki Sano ◽  
Sukekatsu Ushioda ◽  
Takao Sekiya ◽  
...  
Keyword(s):  
Second Harmonic ◽  
High Vacuum ◽  
Ultra High Vacuum

scholarly journals Development of optical choppers for time-resolved measurements at soft X-ray synchrotron radiation beamlines

2017 ◽  
Vol 24 (3) ◽  
pp. 560-565 ◽  
Author(s):  
Hitoshi Osawa ◽  
Takuo Ohkochi ◽  
Masami Fujisawa ◽  
Shigeru Kimura ◽  
Toyohiko Kinoshita
Keyword(s):  
Synchrotron Radiation ◽  
Signal To Noise Ratio ◽  
High Vacuum ◽  
Magnetic Bearing ◽  
Ultra High Vacuum ◽  
Time Resolved ◽  
X Ray ◽  
Pump And Probe ◽  
Air Spindle ◽  
Time Resolved Measurements

Two types of optical choppers for time-resolved measurements at synchrotron radiation soft X-ray beamlines have been developed. One type uses an air-spindle-type rotation mechanism with a two-stage differential pumping system to maintain the ultra-high vacuum of the X-ray beamline, and the other uses a magnetic bearing. Both can be installed at the soft X-ray beamlines at SPring-8, greatly improving the accessibility of pump-and-probe spectroscopy. The combination of X-ray chopper and pump-and-probe photoemission electron microscope at SPring-8 provides drastic improvements in signal-to-noise ratio and resolution compared with techniques using high-voltage gating of channel plate detectors. The choppers have the capability to be used not only at synchrotron radiation facilities but also at other types of soft X-ray and VUV beamlines.

Correlation Between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts

2012 ◽  
Vol 1429 ◽  
Author(s):  
Pedro A. Autreto ◽  
Maureen J. Lagos ◽  
Daniel Ugarte ◽  
Douglas S. Galvao
Keyword(s):  
Electron Microscopy ◽  
Structural Properties ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Quantum Conductance ◽  
Microscopy Imaging ◽  
Atomic Size ◽  
Time Resolved ◽  
Transmission Electron ◽  
Different Temperatures

ABSTRACTIn this work we have studied the importance of thermal effects on the structural and transport properties of Ag atomic-size nanowires (NWs) generated by mechanical stretching. Our study involve time-resolved atomic high resolution transmission electron microscopy imaging and quantum conductance measurement using an ultra-high-vacuum mechanically controllable break junction combined with quantum transport calculations. We have observed drastic changes in conductance and structural properties of Ag NWs generated at different temperatures (150 and 300 K). By combining electron microscopy images, electronic transport measurements and theoretical modeling, we have been able to establish a consistent correlation between the conductance and structural properties of Ag NWs. In particular, our study has revealed the formation of metastable rectangular rod-like Ag wires along the [001] crystallographic direction.

Optical Second Harmonic Generation from Surface Segregants and Adsorbed Oxygen on an Fe-18Cr-3Mo (110) Surface

1986 ◽  
Vol 83 ◽  
Author(s):  
J. C. Hamilton ◽  
R. J. Anderson ◽  
G. W. Foltz
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Surface Segregation ◽  
Second Harmonic ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Harmonic Intensity ◽  
Single Crystal Surfaces ◽  
Optical Second Harmonic Generation ◽  
Solid Liquid

ABSTRACTOptical second harmonic generation is a new surface diagnostic applicable both in ultra-high vacuum and ambient environments and capable of examining gas-solid, liquid-solid and solid-solid interfaces. Studies of surface segregation of chromium and nitrogen on Fe-18Cr-3Mo(II0) single crystal surfaces in ultra-high vacuum are described. Major increases in second harmonic intensity generated by 700 nm excitation at the surface are seen upon heating to temperatures at which chromium and nitrogen cosegregate. Adsorption of oxygen has also been studied on this surface. Second harmonic generation shows promise in providing structural and electronic information for surfaces and interfaces in a wide variety of environments.

Thin Pyrolytic Graphite Films for Electron Microscope Substrates

1971 ◽  
Vol 29 ◽  
pp. 226-227 ◽  
Author(s):  
George H. N. Riddle ◽  
Benjamin M. Siegel
Keyword(s):  
Vacuum Chamber ◽  
Pyrolytic Graphite ◽  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Graphite Substrate ◽  
Nickel Substrate ◽  
Routine Procedure ◽  
Field Electron Microscopy ◽  
Dark Field Electron

A routine procedure for growing very thin graphite substrate films has been developed. The films are grown pyrolytically in an ultra-high vacuum chamber by exposing (111) epitaxial nickel films to carbon monoxide gas. The nickel serves as a catalyst for the disproportionation of CO through the reaction 2C0 → C + CO2. The nickel catalyst is prepared by evaporation onto artificial mica at 400°C and annealing for 1/2 hour at 600°C in vacuum. Exposure of the annealed nickel to 1 torr CO for 3 hours at 500°C results in the growth of very thin continuous graphite films. The graphite is stripped from its nickel substrate in acid and mounted on holey formvar support films for use as specimen substrates.The graphite films, self-supporting over formvar holes up to five microns in diameter, have been studied by bright and dark field electron microscopy, by electron diffraction, and have been shadowed to reveal their topography and thickness. The films consist of individual crystallites typically a micron across with their basal planes parallel to the surface but oriented in different, apparently random directions about the normal to the basal plane.

A High Voltage Electron Microscopy Study of Sub-Oxide Formation in Vanadium

1971 ◽  
Vol 29 ◽  
pp. 212-213
Author(s):  
R. H. Geiss ◽  
R. L. Ladd ◽  
K. R. Lawless
Keyword(s):  
High Vacuum ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Ultra High Vacuum ◽  
Pure Oxygen ◽  
Pressure Oxidation ◽  
High Voltage Electron Microscopy ◽  
Oxidation Study ◽  
Voltage Electron ◽  
Good Agreement

Detailed electron microscope and diffraction studies of the sub-oxides of vanadium have been reported by Cambini and co-workers, and an oxidation study, possibly complicated by carbon and/or nitrogen, has been published by Edington and Smallman. The results reported by these different authors are not in good agreement. For this study, high purity polycrystalline vanadium samples were electrochemically thinned in a dual jet polisher using a solution of 20% H2SO4, 80% CH3OH, and then oxidized in an ion-pumped ultra-high vacuum reactor system using spectroscopically pure oxygen. Samples were oxidized at 350°C and 100μ oxygen pressure for periods of 30,60,90 and 160 minutes. Since our primary interest is in the mechanism of the low pressure oxidation process, the oxidized samples were cooled rapidly and not homogenized. The specimens were then examined in the HVEM at voltages up to 500 kV, the higher voltages being necessary to examine thick sections for which the oxidation behavior was more characteristic of the bulk.

The High Resolution Scanning Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 316-317
Author(s):  
A. V. Crewe
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Vacuum ◽  
Scanning Transmission Electron Microscope ◽  
Ultra High Vacuum ◽  
Resolving Power ◽  
Imaging Characteristics ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Moment

The high resolution STEM is now a fact of life. I think that we have, in the last few years, demonstrated that this instrument is capable of the same resolving power as a CEM but is sufficiently different in its imaging characteristics to offer some real advantages.It seems possible to prove in a quite general way that only a field emission source can give adequate intensity for the highest resolution^ and at the moment this means operating at ultra high vacuum levels. Our experience, however, is that neither the source nor the vacuum are difficult to manage and indeed are simpler than many other systems and substantially trouble-free.

Structure of Palladium Single-Crystal Films Prepared by Flash Evaporation onto (001) NaCl Substrates

1970 ◽  
Vol 28 ◽  
pp. 456-457
Author(s):  
L. E. Murr ◽  
G. Wong
Keyword(s):  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Rate ◽  
Flash Evaporation ◽  
Optimum Load ◽  
Single Crystal Films ◽  
Crystal Films ◽  
A Current

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

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