DETECTION OF SPATIAL DISTRIBUTION OF THE TUNNELING CURRENT DISPERSION OF STM

Noise and fluctuations of tunneling current of STM can be analyzed for a surface investigation. The tunnel gap can behave as a passive element, which transforms the noise in the sample–tip-piezodriver system and as an active source of noise due to the stochastic character of polarization and relocation of adsorbed molecules in the near-tip region. A spatial distribution of dispersion of the tunneling current of STM operated in air was detected. The samples of Cu, Nb, C (graphite), Pb, Zn, SnO 2, Si were studied. The regions with a high dispersion value formed dots, spots and lines. During several sequence scannings of surface by tip some spots can vanish. The connection of the observed dispersion with relief features and with the picture of the barrier height distribution is discussed. The simple model of the noise source is proposed.

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SPATIAL DISTRIBUTION OF 1/f NOISE SOURCE

Le Journal de Physique Colloques ◽

10.1051/jphyscol:1988431 ◽

1988 ◽

Vol 49 (C4) ◽

pp. C4-157-C4-160 ◽

Cited By ~ 1

Author(s):

L.K.J. VANDAMME

Keyword(s):

Spatial Distribution ◽

Noise Source

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High Quality HfO2 Film and Its Applications in Novel Poly-Si Devices

MRS Proceedings ◽

10.1557/proc-716-b2.6 ◽

2002 ◽

Vol 716 ◽

Author(s):

K.L. Ng ◽

N. Zhan ◽

M.C. Poon ◽

C.W. Kok ◽

M. Chan ◽

...

Keyword(s):

Barrier Height ◽

Nonvolatile Memory ◽

Dielectric Material ◽

Tunneling Current ◽

Interface Layer ◽

Si Substrate ◽

Hfo2 Film ◽

Effective Barrier Height ◽

Effective Barrier ◽

Nonvolatile Memory Devices

AbstractHfO2 as a dielectric material in MOS capacitor by direct sputtering of Hf in an O2 ambient onto a Si substrate was studied. The results showed that the interface layer formed between HfO2 and the Si substrate was affected by the RTA time in the 500°C annealing temperature. Since the interface layer is mainly composed of hafnium silicate, and has high interface trap density, the effective barrier height is therefore lowered with increased RTA time. The change in the effective barrier height will affect the FN tunneling current and the operation of the MOS devices when it is applied for nonvolatile memory devices.

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Development of a Simple Model to Predict Spatial Distribution of Cycle-Averaged Wall Heat Flux Using Artificial Neural Networks

10.4271/2003-32-0018 ◽

2003 ◽

Cited By ~ 3

Author(s):

T. Kim ◽

J. B. Ghandhi

Keyword(s):

Neural Networks ◽

Heat Flux ◽

Spatial Distribution ◽

Artificial Neural Networks ◽

Simple Model ◽

Wall Heat Flux ◽

Artificial Neural

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Xenon in sodium Y zeolite. 2. Arrhenius relation, mechanism, and barrier height distribution for cage-to-cage diffusion

The Journal of Physical Chemistry ◽

10.1021/j100117a036 ◽

1993 ◽

Vol 97 (15) ◽

pp. 3849-3857 ◽

Cited By ~ 22

Author(s):

Subramanian Yashonath ◽

Prakriteswar Santikary

Keyword(s):

Barrier Height ◽

Height Distribution ◽

Y Zeolite ◽

Arrhenius Relation ◽

Cage Diffusion

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Similarities and differences in polar mesosphere summer echoes observed in the Arctic and Antarctica

Annales Geophysicae ◽

10.5194/angeo-26-2795-2008 ◽

2008 ◽

Vol 26 (9) ◽

pp. 2795-2806 ◽

Cited By ~ 29

Author(s):

R. Latteck ◽

W. Singer ◽

R. J. Morris ◽

W. K. Hocking ◽

D. J. Murphy ◽

...

Keyword(s):

Noise Source ◽

Late Summer ◽

The Arctic ◽

Occurrence Rate ◽

Height Distribution ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes ◽

The Mean ◽

Resolute Bay ◽

Highly Correlated

Abstract. Polar Mesosphere Summer Echoes (PMSE) have been observed in the high latitudes of the Northern and Southern Hemisphere for several years using VHF radars located at Andenes/Norway (69° N, 16° E), Resolute Bay/Canada (75° N, 95° W), and Davis/Antarctica (69° S, 78° E). The VHF radars at the three sites were calibrated using the same methods (noise source and delayed transmitting signal) and identical equipment. Volume reflectivity was derived from the calibrated echo power and the characteristics of the seasonal variation of PMSE were estimated at the sites for the years 2004 to 2007. The largest peak volume reflectivity of about 2×10−9 m−1 was observed at Andenes compared with their counterparts at Davis (~4×10−11 m−1) and Resolute Bay (~6×10−12 m−1). The peak of the PMSE height distribution is 85.6 km at Davis which is about 1 km higher than at Andenes. At Resolute Bay the height distribution peaks at about 85 km but only a few layers were found below 84 km. The mean PMSE occurrence rate is 83% at Andenes, 38% at Davis with larger variability and only 18% at Resolute Bay (in late summer). The duration of the PMSE season varies at Andenes from 104 to 113 days and at Davis from 88 to 93 days. In general the PMSE seasons starts about 5 days later at Davis and ends about 10 days earlier compared to Andenes. In all three seasons the PMSE occurrence suddenly drops to a much lower level at Davis about 32 days after solstice whereas the PMSE season decays smoothly at Andenes. The duration of the PMSE season at Andenes and Davis is highly correlated with the presence of equatorward directed winds, the observed differences in PMSE occurrence are related to the mesospheric temperatures at both sites.

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Which Galaxy Property Best Predicts Quiescence?

Proceedings of the International Astronomical Union ◽

10.1017/s174392131300464x ◽

2012 ◽

Vol 8 (S295) ◽

pp. 177-177

Author(s):

Joel Leja ◽

Pieter van Dokkum ◽

Keyword(s):

Spatial Distribution ◽

Star Formation ◽

Velocity Dispersion ◽

High Redshift ◽

Line Emission ◽

Elliptical Galaxies ◽

High Dispersion ◽

Quenching Mechanism ◽

Line Flux ◽

Line Equivalent Width

AbstractIt is generally accepted that local elliptical galaxies assembled most of their mass in a burst of star formation between 1 < z < 3, yet today, their star formation has been almost entirely quenched. In order to constrain this quenching mechanism, we measure Hα line emission in galaxies sorted by multiple galaxy properties as a function of redshift to what galaxy parameter best predicts quiescence. This is done for samples of the most massive, most luminous, and galaxies with the highest velocity dispersion both locally (0.05 < z < 0.07 in the SDSS) and at high redshift (0.7 < z < 1.5 in 3D-HST). It is demonstrated through spectral stacking that velocity dispersion results in the lowest Hα line equivalent width both locally and at high redshift. The spatial distribution of the emission line flux is available from grism spectroscopy: the line flux from the high dispersion stack is centrally peaked and thus likely associated with AGN activity rather than star formation, strengthening this conclusion. Since velocity dispersion may also be the best predictor of halo mass (Wake et al. 2012), this may imply that the quenching mechanism is directly related to halo mass.

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Chromospheric Surface Structures on EI Eridani and HD 199178

International Astronomical Union Colloquium ◽

10.1017/s0252921100079859 ◽

1991 ◽

Vol 130 ◽

pp. 330-332

Author(s):

James E. Neff

Keyword(s):

Spatial Distribution ◽

Effective Temperature ◽

Three Dimensional ◽

Stellar Atmospheres ◽

Surface Structures ◽

High Dispersion ◽

The Sun ◽

Late Type ◽

Magnetic Topology ◽

Radial Dimension

Several groups at this meeting are presenting maps of the spatial distribution of either brightness or effective temperature in the photospheres of rapidly-rotating, late-type stars. It is generally believed that structure seen in these maps traces the magnetic topology, in analogy with the Sun. We expect the structure of the outer atmospheres (i.e., chromosphere and corona) of these stars to be even more directly tied to the magnetic topology; the magnetic structure is three-dimensional. In order to probe the radial dimension of stellar atmospheres, we need to combine maps of the spatial distribution of emission from chromospheres and coronae with these detailed photospheric maps.Along with collaborators at Armagh, Catania, Boulder, Paris, Helsinki, and Stony Brook, I have been obtaining high-dispersion ultraviolet spectra of several rapidly-rotating, late-type stars using the IUE spacecraft. I discuss results for two stars, El Eridani and HD 199178, for which photospheric maps are presented elsewhere at this conference.

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