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24 Jul 2000

Volume 77, Issue 4, pp. 463-603

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Analysis of a photon assisted field emission device

K. L. Jensen, Y. Y. Lau, and D. S. McGregor

Appl. Phys. Lett. 77, 585 (2000); http://dx.doi.org/10.1063/1.127052 (3 pages) | Cited 13 times

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A field emitter array held at the threshold of emission by a dc gate potential from which current pulses are triggered by the application of a laser pulse on the backside of the semiconductor may produce electron bunches (“density modulation”) at gigahertz frequencies. We develop an analytical model of such optically controlled emission from a silicon tip using a modified Wentzel–Kramers–Brillouin and Airy function approach to solving Schrödinger’s equation. Band bending and an approximation to the exchange-correlation effects on the image charge potential are included for an array of hyperbolic emitters with a distribution in tip radii and work function. For a simple relationship between the incident photon flux and the resultant electron density at the emission site, an estimation of the tunneling current is made. An example of the operation and design of such a photon-assisted field emission device is given. © 2000 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
73.30.+y Surface double layers, Schottky barriers, and work functions

Significant improvement of the emission property of Spindt-type platinum field emitters by operation in carbon monoxide ambient

Y. Gotoh, D. Nozaki, H. Tsuji, J. Ishikawa, T. Nakatani, T. Sakashita, and K. Betsui

Appl. Phys. Lett. 77, 588 (2000); http://dx.doi.org/10.1063/1.127053 (3 pages) | Cited 9 times

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The emission property of a Spindt-type platinum field emitter was greatly improved by operating in carbon monoxide ambient with appropriate operating parameters. After sufficient aging, the emitter was operated in carbon monoxide ambient up to 10−3 Pa, at the emission current of 1 μA. The emission current first decreased in accordance with the gas introduction, but turned to show rapid increase when the gas pressure was increased to 10−3 Pa. The current stability, as well as the operating voltage, was improved by this treatment. The apex of the emitter was examined with the Seppen–Katamuki analysis technique, in which detailed information on the emission area and effective work function can be read from the diagram plotted with the intercept and slope of a Fowler–Nordheim plot. The analysis suggested reduction of the effective work function is a major reason for the improvement of the emission property. © 2000 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.05.Bx Metals, semimetals, and alloys
73.30.+y Surface double layers, Schottky barriers, and work functions

Near-field microscope probe for far infrared time domain measurements

O. Mitrofanov, I. Brener, M. C. Wanke, R. R. Ruel, J. D. Wynn, A. J. Bruce, and J. Federici

Appl. Phys. Lett. 77, 591 (2000); http://dx.doi.org/10.1063/1.127054 (3 pages) | Cited 27 times

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A near-field probe fabrication technique for far-infrared frequencies based on photoconducting antennas is developed. A subwavelength-size field source is accomplished by means of an aperture and protruding high refractive index tip. The near-field probe is tested by using free space traveling electromagnetic pulses with a broadband spectrum in the range of 0.3–1.5 THz. A spatial resolution of 60 μm is achieved for a 50 μm aperture. The described probe may be used for near-field transmission microscopy in illumination and collection modes. Resolution may be further improved by means of a smaller aperture. © 2000 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.60.Hv Refractometers and reflectometers

Cathodoluminescent properties at nanometer resolution through Z-contrast scanning transmission electron microscopy

H.-J. Gao, G. Duscher, M. Kim, S. J. Pennycook, D. Kumar, K. G. Cho, and R. K. Singh

Appl. Phys. Lett. 77, 594 (2000); http://dx.doi.org/10.1063/1.127055 (3 pages) | Cited 3 times

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We report the observation of porous structures in laser-ablation-deposited Y2O3:Eu thin films and their correlation with luminescent properties by a combination of transmission electron microscopy and Z-contrast scanning transmission electron microscopy (Z-STEM). Depending on growth conditions, a large density of voids is incorporated into the films, which leads to a much increased surface area. Cathodoluminescence imaging in the STEM directly reveals a 5 nm “dead layer” around each void, which is responsible for the observed reduction in luminescence efficiency. © 2000 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Nk Insulators
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
61.43.Gt Powders, porous materials
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Ultrafast dynamics microscopy

M. Dyba, T. A. Klar, S. Jakobs, and S. W. Hell

Appl. Phys. Lett. 77, 597 (2000); http://dx.doi.org/10.1063/1.127056 (3 pages) | Cited 16 times

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We report the three-dimensional imaging of the vibrational, solvent, orientational, and electronic relaxation in organic fluorescent samples at 200–500 nm spatial resolution. This is achieved in steady-state recordings by exciting the fluorophore with a femtosecond pulse and subsequent quenching with a time-delayed, redshifted femtosecond pulse through stimulated emission. Temporal resolution of 380 fs is solely determined by the pulse widths and is further reducible. Images of submicron structures revealing vibrational and solvent relaxation gradients are shown. Furthermore, we introduce contrast modes based on stimulated emission depletion and apply them to cellular imaging. © 2000 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
78.55.Bq Liquids
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
07.60.Pb Conventional optical microscopes
63.50.-x Vibrational states in disordered systems
78.45.+h Stimulated emission
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