Formation and Electric Properties of Disordered Yb Layers on Si(111)7×7 Surface

2003 ◽  
Vol 770 ◽  
Author(s):  
Nickolay G. Galkin ◽  
Dmitrii L. Goroshko ◽  
Alexander S. Gouralnik ◽  
Sergei A. Dotsenko ◽  
Andrei N. Boulatov
Keyword(s):  
Room Temperature ◽  
Hole Concentration ◽  
Hole Mobility ◽  
Growth Stages ◽  
Two Dimensional ◽  
Interface Formation ◽  
Dimensional Growth ◽  
2D And 3D ◽  
Semiconductor Type

AbstractInterface formation in Yb/Si(111) system has been investigated by AES and EELS spectroscopy and in situ Hall measurements at room temperature. It was found that interface formation process may be divided into five stages: 1) two-dimensional growth of Yb, 2) intermixing and formation of two-dimensional Yb silicide, 3) formation of 3D silicide islands, 4) growth of Yb on 3D silicide islands, 5) coalescence of 3D Yb – Yb silicide islands and formation of continuos Yb film. We attribute the observed character of conductivity in Yb/Si(111) system to the evolution of morphological and electrical properties of the growing Yb layer (2D Yb, silicide, metal) rather than to the changes within the space charge layer under the surface. Some amplitude oscillations have been observed in sheet conductivity, hole mobility and surface hole concentration within the coverage range below 6 ML where formation of a continuos Yb silicide film completes. Conductivity oscillations are explained by transition from semiconductor-type conductivity at the first growth stages (two-dimensional Yb growth) to metal-like conductivity of 2D and 3D Yb silicide films.

scholarly journals Transformation Between 2D and 3D Covalent Organic Frameworks via Reversible [2+2] Cycloaddition

2020 ◽  
Author(s):  
Thaksen Jadhav ◽  
Yuan Fang ◽  
Cheng-Hao Liu ◽  
Afshin Dadvand ◽  
Ehsan Hamzehpoor ◽  
...  
Keyword(s):  
Band Structure ◽  
Absorption Edge ◽  
Room Temperature ◽  
Three Dimensional ◽  
Cross Linking ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Doping Behavior ◽  
2D Polymers ◽  
2D And 3D

We report the first transformation between crystalline vinylene-linked two-dimensional (2D) polymers and crystalline cyclobutane-linked three-dimensional (3D) polymers. Specifically, absorption-edge irradiation of the 2D poly(arylenevinylene) covalent organic frameworks (COFs) results in topological [2+2] cycloaddition cross-linking the π-stacked layers in 3D COFs. The reaction is reversible and heating to 200°C leads to a cycloreversion while retaining the COF crystallinity. The resulting difference in connectivity is manifested in the change of mechanical and electronic properties, including exfoliation, blue-shifted UV-Vis absorption, altered luminescence, modified band structure and different acid-doping behavior. The Li-impregnated 2D and 3D COFs show a significant ion conductivity of 1.8×10<sup>−4</sup> S/cm and 3.5×10<sup>−5</sup> S/cm, respectively. Even higher room temperature proton conductivity of 1.7×10<sup>-2</sup> S/cm and 2.2×10<sup>-3</sup> S/cm was found for H<sub>2</sub>SO<sub>4</sub>-treated 2D and 3D COFs, respectively.

scholarly journals Thin, Flexible Supercapacitors Made from Carbon Nanofiber Electrodes Decorated at Room Temperature with Manganese Oxide Nanosheets

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
S. K. Nataraj ◽  
Q. Song ◽  
S. A. Al-Muhtaseb ◽  
S. E. Dutton ◽  
Q. Zhang ◽  
...  
Keyword(s):  
Thin Film ◽  
Electrochemical Performance ◽  
Specific Capacitance ◽  
Carbon Nanofibers ◽  
Room Temperature ◽  
Composite Electrode ◽  
Carbon Nanofiber ◽  
Two Dimensional ◽  
Nanostructured Composite

We report the fabrication and electrochemical performance of a flexible thin film supercapacitor with a novel nanostructured composite electrode. The electrode was prepared byin situcoprecipitation of two-dimensional (2D) MnO2nanosheets at room temperature in the presence of carbon nanofibers (CNFs). The highest specific capacitance of 142 F/g was achieved for CNFs-MnO2electrodes in sandwiched assembly with PVA-H4SiW12O40·nH2O polyelectrolyte separator.

In-situ UHV TEM study of the two-dimensional growth of Al2Au phase on Al(111) surface

1984 ◽  
Vol 15 (1-2) ◽  
pp. 101-107 ◽  
Author(s):  
Á. Barna ◽  
P.B. Barna ◽  
G. Radnóczi ◽  
G. Sáfrán
Keyword(s):  
Two Dimensional ◽  
Dimensional Growth

D.C. electrical and optical properties of vacuum-deposited organic semiconductor FePcCl thin films

2005 ◽  
Vol 83 (11) ◽  
pp. 1151-1159 ◽  
Author(s):  
K R Rajesh ◽  
C S Menon
Keyword(s):  
Thin Film ◽  
Room Temperature ◽  
Hole Concentration ◽  
Hole Mobility ◽  
Optical Parameters ◽  
Trap Level ◽  
72.80 Le ◽  
Planar Structures ◽  
Optical Dielectric Constant ◽  
Optical Dielectric

Sandwich and planar structures are fabricated by a vacuum deposition method using iron phthalocyanine chloride (FePcCl) as an active layer and gold (Au) as electrodes. The permittivity ε of FePcCl is determined from the dependence of capacitance on film thickness. The current density – voltage characteristics characteristics of the Au/FePcCl/Au structure at room temperature are found. Thermally generated hole concentration p0, hole mobility µp, total trap concentration Nt, and depth of the trap level are estimated. The activation energies of FePcCl films are determined from Arrhenious plots of ln σ versus 1000/T. The absorption and reflectance spectra of a FePcCl thin film deposited at room temperature are recorded in the spectral range 300–900 nm. The optical band gap of a FePcCl thin film is determined from the α2 versus hν graph. The optical constants n and k are found. The real and imaginary parts of the optical dielectric constant ε1 and ε2 are calculated. These optical parameters are plotted against photonenergy. PACS Nos.: 72.80.Le, 73., 78.20.–e

IN SITU HALL MEASUREMENTS OF MACROSCOPIC ELECTRICAL PROPERTIES OF CHROMIUM-COVERED Si(111) SURFACES

1999 ◽  
Vol 06 (01) ◽  
pp. 7-12 ◽  
Author(s):  
N. G. GALKIN ◽  
D. L. GOROSHKO ◽  
A. V. KONCHENKO ◽  
V. A. IVANOV ◽  
A. S. GOURALNIK
Keyword(s):  
Electrical Properties ◽  
Hole Concentration ◽  
Hole Mobility ◽  
Epitaxial Films ◽  
Surface Phase ◽  
Sheet Resistivity ◽  
Hall Measurements ◽  
Phase Layers ◽  
Surface Phases

The first in situ Hall measurements of the ordered chromium surface phases on Si(111) substrate and CrSi(111) epitaxial films after their formation are presented. Formation of Si (111)-(1× 1)- Cr (0.1 nm Cr) and Si(111)-[([Formula: see text])/30°]-Cr (0.3 nm Cr) surface phases results in an increase in the sheet resistivity of Si(111)-Cr surface phase samples. The conductivities along the surface phases at these chromium thicknesses are very low. The conductivity decrease is caused by a decrease in the electron mobility in the surface phase layers. Formation of an epitaxial CrSi(111) layer with averaged Hall parameters (hole mobility of 440 cm 2· V -1· s -1, sheet resistivity of 2.2·104 Ω-1 and sheet hole concentration of 0.65·1012 cm -2) has been observed at 1.5–1.8 nm of chromium thickness.

scholarly journals Anisotropic ultrahigh hole mobility in two-dimensional penta-SiC2 by strain-engineering: electronic structure and chemical bonding analysis

RSC Advances ◽  
2017 ◽  
Vol 7 (72) ◽  
pp. 45705-45713 ◽  
Author(s):  
Yuanfeng Xu ◽  
Zeyu Ning ◽  
Hao Zhang ◽  
Gang Ni ◽  
Hezhu Shao ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Chemical Bonding ◽  
Room Temperature ◽  
Hole Mobility ◽  
Strain Engineering ◽  
Uniaxial Strain ◽  
Two Dimensional ◽  
Bonding Analysis

At room temperature, the uniaxial strain (εx = −8%) can enhance the hole mobility of monolayer penta-SiC2 along the b-direction by almost three orders of magnitude up to 1.14 × 106 cm2 V−1 s−1, which is much larger than that of graphene.

CHROMATOGRAPHIC AND MICROSCOPIC DETECTION OF GLUCOSINOLATES IN RAPESEED USING N,2,6-TRICHLORO-p- BENZOQUINONEIMINE

1984 ◽  
Vol 64 (4) ◽  
pp. 869-878 ◽  
Author(s):  
S. H. YIU ◽  
F. W. COLLINS ◽  
R. G. FULCHER ◽  
I. ALTOSAAR
Keyword(s):  
Gas Chromatography ◽  
Room Temperature ◽  
Brassica Campestris ◽  
Protein Bodies ◽  
Distilled Water ◽  
Two Dimensional ◽  
Brassica Napus L ◽  
Methanolic Extracts ◽  
Microscopic Studies

A new histochemical method for detecting glucosinolates in rapeseed (Brassica napus L. ’Midas’) methanolic extracts and rapeseed (Brassica campestris L. ’Candle’) hand-cut sections has been developed using N,2,6-trichloro-p-benzoquinoneimine (TCQ) as the staining reagent. The specificity of TCQ was established by the following experiments. (1) TCQ was used as a spray reagent for detecting thio sugars separated from (a) crude and (b) partially purified rapeseed extracts on silica gel coated chromatograms. By comparison, the reaction of TCQ was relatively more selective than that of alkaline silver nitrate as it detected fewer spots on the chromatogram. (2) Rapeseed extracts and glucosinolate (GS) standards were analyzed on the same plate by one- and two-dimensional chromatography. After spraying with TCQ two of the three spots originated from the extract had the same color (yellow) reaction and similar Rf values as those of 3-butenyl GS and 2-hydroxy-3-butenyl GS. (3) Gas chromatography was used to identify the TCQ-reactive compounds present in the rapeseed extract. 3-butenyl GS and 2-hydroxy-3-butenyl GS were present as major constituents while 4-pentenyl GS, 2-hydroxy-4-pentenyl GS and an hydroxyindolylmethyl GS formed the minor entity. The use of TCQ for detecting glucosinolates in situ was established by the following microscopic studies. Hand-cut sections were prepared, stained with TCQ and examined microscopically. Protein bodies found inside cells of the cotyledon were the only stained (yellow in color) structures. The number of yellow-colored protein bodies decreased if the sections were left untreated at room temperature for more than 10 min prior to staining. Treatment of the sections with distilled water, 70% methanol or myrosinase before staining diminished the stainability of the protein bodies.Key words: Rapeseed structure, glucosinolates, chromatographic analyses, N,2,6-trichloro-p-benzoquinoneimine

scholarly journals Transformation Between 2D and 3D Covalent Organic Frameworks via Reversible [2+2] Cycloaddition

2020 ◽  
Author(s):  
Thaksen Jadhav ◽  
Yuan Fang ◽  
Cheng-Hao Liu ◽  
Afshin Dadvand ◽  
Ehsan Hamzehpoor ◽  
...  
Keyword(s):  
Band Structure ◽  
Absorption Edge ◽  
Room Temperature ◽  
Three Dimensional ◽  
Cross Linking ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Doping Behavior ◽  
2D Polymers ◽  
2D And 3D

We report the first transformation between crystalline vinylene-linked two-dimensional (2D) polymers and crystalline cyclobutane-linked three-dimensional (3D) polymers. Specifically, absorption-edge irradiation of the 2D poly(arylenevinylene) covalent organic frameworks (COFs) results in topological [2+2] cycloaddition cross-linking the π-stacked layers in 3D COFs. The reaction is reversible and heating to 200°C leads to a cycloreversion while retaining the COF crystallinity. The resulting difference in connectivity is manifested in the change of mechanical and electronic properties, including exfoliation, blue-shifted UV-Vis absorption, altered luminescence, modified band structure and different acid-doping behavior. The Li-impregnated 2D and 3D COFs show a significant ion conductivity of 1.8×10<sup>−4</sup> S/cm and 3.5×10<sup>−5</sup> S/cm, respectively. Even higher room temperature proton conductivity of 1.7×10<sup>-2</sup> S/cm and 2.2×10<sup>-3</sup> S/cm was found for H<sub>2</sub>SO<sub>4</sub>-treated 2D and 3D COFs, respectively.

scholarly journals Electrical properties of strained germanium nanofilm

2021 ◽  
Vol 22 (2) ◽  
pp. 313-320
Author(s):  
S.V. Luniov ◽  
P.F. Nazarchuk ◽  
O.V. Burban
Keyword(s):  
Electrical Properties ◽  
Band Structure ◽  
Crystallographic Orientation ◽  
Room Temperature ◽  
Specific Conductivity ◽  
Hole Mobility ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Dimensional Quantization ◽  
Different Temperatures

Dependences of the concentration of intrinsic current carriers, electron and hole mobilities and specific conductivity for strained germanium nanofilms grown on the Si, Ge(0,64)Si(0,36) and Ge(0,9)Si(0,1) substrates with crystallographic orientation (001), on their thickness at different temperatures were calculated on the basis of the statistics of non-degenerate two-dimensional electron and hole gas in semiconductors. The electrical properties of such nanofilms are determined by the peculiarities of their band structure. It is established that the effects of dimensional quantization, the probability of which increases with decreasing temperature, become significant for germanium nanofilms with the thickness of d<7 nm. The presence of such effects explains the significant increase in the specific conductivity and the decrease in the intrinsic concentration of current carriers for these nanofilms. The electron and hole mobility in the investigated germanium nanofilms is lower in relation to such unstrained nanofilms. Only for the strained germanium nanofilm with the thickness of d> 50 nm grown on the Ge(0,9)Si(0,1) substrate, an increase in the hole mobility at room temperature of more than 1.5 times was obtained. The obtained results of the electrical properties of strained germanium nanofilms can be used in producing on their basis new elements of nanoelectronic.

New BCT Iron Phase in (100) Felr Superlattices

1993 ◽  
Vol 313 ◽  
Author(s):  
S. Andrieu ◽  
J. Hübsch ◽  
M. Piecuch ◽  
L. Hennet ◽  
H. FISCHER
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Molecular Beam ◽  
Two Dimensional ◽  
X Ray ◽  
Bcc Lattice ◽  
Iron Phase ◽  
Dimensional Growth ◽  
Weak Ferromagnetic ◽  
Second Order Phase Transition

ABSTRACTIn this paper, the synthesis of a new structure of iron in (100) Felr superlattices grown by Molecular Beam Epitaxy is reported. Two-dimensional growth up to 4 planes at 400K occurs, as shown by RHEED oscillations. Electron diffraction also gives evidence that the Fe lattice is pseudomorphic to the Ir one during the 2D-growth, and relaxes to the bcc lattice for thicker deposits. An X-Ray analysis shows that the Fe structure is a body centered tetragonal one with a c/a ratio close to 1.25. This phase is observed to be non-Magnetic at room temperature, as a weak ferromagnetic behaviour is observed at low temperatures, except at small Ir thicknesses. This is the evidence of the existence of a low spin phase which seems to undergo a second order phase transition with the atomic volume of iron.

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