Ultrafast Scanning Tunneling Microscopy PDF Download
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Author: David Aaron Botkin
Publisher:
ISBN:
Category :
Languages : en
Pages : 320
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Book Description
Author: David Aaron Botkin
Publisher:
ISBN:
Category :
Languages : en
Pages : 320
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 74
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Book Description
I have developed an ultrafast scanning tunneling microscope (USTM) based on uniting stroboscopic methods of ultrafast optics and scanned probe microscopy to obtain nanometer spatial resolution and sub-picosecond temporal resolution. USTM increases the achievable time resolution of a STM by more than 6 orders of magnitude; this should enable exploration of mesoscopic and nanometer size systems on time scales corresponding to the period or decay of fundamental excitations. USTM consists of a photoconductive switch with subpicosecond response time in series with the tip of a STM. An optical pulse from a modelocked laser activates the switch to create a gate for the tunneling current, while a second laser pulse on the sample initiates a dynamic process which affects the tunneling current. By sending a large sequence of identical pulse pairs and measuring the average tunnel current as a function of the relative time delay between the pulses in each pair, one can map the time evolution of the surface process. USTM was used to measure the broadband response of the STM's atomic size tunnel barrier in frequencies from tens to hundreds of GHz. The USTM signal amplitude decays linearly with the tunnel junction conductance, so the spatial resolution of the time-resolved signal is comparable to that of a conventional STM. Geometrical capacitance of the junction does not appear to play an important role in the measurement, but a capacitive effect intimately related to tunneling contributes to the measured signals and may limit the ultimate resolution of the USTM.
Author: Dzmitry Yarotski
Publisher:
ISBN:
Category : Picosecond pulses
Languages : en
Pages : 306
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Author:
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Category :
Languages : en
Pages : 10
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Book Description
The invention of the scanning tunneling microscope (STM) revolutionized the field of surface science, enabling the first images of surface structure on an atomic length scale. In the quest for both atomic spatial and temporal resolution several groups have integrated an ultrafast optoelectronic switch which gates the current from the tip, achieving picosecond time resolution. In this paper, the authors describe a novel STM tip consisting of a cleaved GaAs substrate with a 1-[mu]m thick epilayer of low-temperature-grown GaAs (LT-GaAs) deposited on the face. Since the LT-GaAs has a carrier lifetime of 1 ps, photoexcitation of the tip with an ultrafast, above-bandgap pulse both provides carriers for the tunneling current and photoconductively gates (with ps resolution) the current from the tip. They use this tip to detect picosecond transients on a coplanar stripline and demonstrate a temporal resolution of 1.2 ps in tunneling mode.
Author:
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Category :
Languages : en
Pages : 7
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Book Description
The author has merged the techniques of ultrafast laser spectroscopy with those of scanning probe microscopy to develop an ultrafast scanning tunneling microscope. The response of a tunneling gap to a 650 fs voltage pulse was measured.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 7
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Book Description
The authors have developed a general technique which combines the temporal resolution of ultrafast laser spectroscopy with the spatial resolution of scanned probe microscopy (SPM). Using this technique with scanning tunneling microscopy (STM), they have obtained simultaneous 2 ps time resolution and 50 Å spatial resolution. This improves the time resolution currently attainable with STM by nine orders of magnitude. The potential of this powerful technique for studying ultrafast dynamical phenomena on surfaces with atomic resolution is discussed.
Author:
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Category :
Languages : en
Pages : 4
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Book Description
In the quest for atomic spatial and picosecond temporal resolutions, several groups have integrated an STM tip with an ultrafast optoelectronic switch that gates the tunneling current from the tip. The authors report a novel ultrafast STM tip consisting of a cleaved GaAs substrate with a 1-?m thick epilayer of low-temperature-grown GaAs (LT-GaAs) deposited on the face. since LT-GaAs has a carrier lifetime of 1 ps, the photo-excitatin of the tip with an ultrafast above-bandgap pulse provides carriers for the tunneling current and photoconductively gates the current from the tip with picoseconds time resolution. The authors use this tip to detect picosecond voltage transients on a coplanar stripline.
Author:
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Category :
Languages : en
Pages : 5
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Book Description
We review the development of the ultrafast scanning tunneling microscope. Experimental results on the tunneling gap response to a short voltage pulse excitation are presented.
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Category :
Languages : en
Pages : 0
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Book Description
At the end of three years, we have met the majority of the project goals and made significant progress on the few remaining issues. As outlined in more detail below, we have designed and built a UHV system and incorporated a commercially made, custom designed STM. The microscope has demonstrated atomic resolution. We have a femtosecond laser system, optics for delivering ultrafast laser pulses to the STM, and a computer controlled delay line for time-resolved measurements. This project also has funding from the National Science Foundation, and work continues with that funding while we actively seek additional funds for continued work. We are actively working to develop the instrument as a probe-station for molecular electronics. To that end, we are collaborating with Prof. David Glueck in the Chemistry department on time-domain investigations of Coulomb-blockade effects in Au nanoparticles.
Author:
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ISBN:
Category :
Languages : en
Pages : 24
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Book Description
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). By combining scanning tunneling microscopy with ultrafast optical techniques we have developed a novel tool to probe phenomena on atomic time and length scales. We have built and characterized an ultrafast scanning tunneling microscope in terms of temporal resolution, sensitivity and dynamic range. Using a novel photoconductive low-temperature-grown GaAs tip, we have achieved a temporal resolution of 1.5 picoseconds and a spatial resolution of 10 nanometers. This scanning tunneling microscope has both cryogenic and ultra-high vacuum capabilities, enabling the study of a wide range of important scientific problems.
