Search results for "electron emission"
showing 10 items of 36 documents
SURFACE AND VOLUME CRYSTALLIZATION OF METALLIC GLASS (Ni50Zr50)99.9P0.1 AS INVESTIGATED BY EXOELECTRON EMISSION (EEE) AND DIFFERENTIAL THERMAL ANALYS…
2002
Surface and volume crystallization of amorphous, melt-quenched (Ni50Zr50)99.9P0.1 alloy has been investigated by measurements of the temperature dependencies of the intensity of photostimulated exoelectron emission (EEE) and by differential scanning calorimetry (DSC). A comparison of these dependencies enables one to assess the tendency of the investigated materials to premature surface crystallization. For the (Ni50Zr50)99.9P0.1 alloy the surface crystallization occurs at temperatures distinctly lower than that for the crystallization in bulk. The activation energy for the surface crystallization, determined by the Ozawa method, i.e. from the shift of EEE peak corresponding to the surface…
Cathodoluminescence characterization of ZnO/ZnS nanostructures anodized under hydrodynamic conditions
2018
[EN] ZnO/ZnS nanostructures were successfully synthesized by a simple electrochemical anodization of zinc in a glycerol based electrolyte containing sulfide-ammonium fluoride. The influence of different hydrodynamic conditions and anodization potentials during anodization on the morphological and electronic properties of the obtained ZnO/ZnS nanostructures was studied. The anodized samples were characterized using confocal Raman microscopy, X-Ray Diffraction (XRD), Field Emission Scanning Electronic Microscopy (FE-SEM), cathodoluminescence (CL), and photoelectrochemical water splitting tests under standard AM 1.5 conditions. The results showed that hydrodynamic conditions and higher potenti…
Transition from direct to Fowler-Nordheim tunneling in chemically reduced graphene oxide film.
2014
We investigate charge transport in a chemically reduced graphene oxide (RGO) film of sub-micron thickness. The I-V curve of RGO film shows current switching of the order of ∼10(5) above the threshold voltage. We found that the observed I-V curve is consistent with quantum tunnelling based charge transport. The quantum tunnelling based Simmons generalized theory was used to interpret the charge transport mechanism which shows that the current switching phenomenon is associated with transition from direct to Fowler-Nordheim (F-N) tunneling. The absence of current switching in the I-V curve after stripping away the oxygen functional groups from chemically RGO film confirms that the presence of…
ZnO/ZnS heterostructures for hydrogen production by photoelectrochemical water splitting
2016
This work studies the photoelectrochemical behavior of novel ZnO/ZnS heterostructures obtained by means of anodization in water and glycerol/water/NH4F electrolytes with different Na2S additions under controlled hydrodynamic conditions. For this purpose different techniques such as Field Emission Scanning Electronic Microscopy (FE-SEM) with EDX, Raman spectroscopy and photoelectrochemical water splitting tests under standard AM 1.5 conditions have been carried out. The obtained results showed that the hydrodynamic conditions promoted an ordered nanotubular morphology which facilitates electron-hole separation and consequently, the photoelectrochemical activity for water splitting is enhance…
Photoelectron emission induced by low temperature hydrogen plasmas
2018
Experimental results of low temperature hydrogen plasma induced photoelectron emission measurements comparing two different plasma heating methods are summarized. By exposing the samples to the vacuum ultraviolet radiation of a filament-driven multi-cusp arc discharge ion source and a 2.45 GHz microwave-driven ion source, it has been measured that the total photoelectron emission from various metal surfaces is on the order of 1 A per kW of plasma heating power, which can be increased by a factor of 2–3.5 with a thin layer of alkali metal. The possible effects of the photoelectrons on the plasma sheath structure are studied with a 1D collisionless model extended to include the contribution o…
Novel tree-like WO3 nanoplatelets with very high surface area synthesized by anodization under controlled hydrodynamic conditions
2016
In the present work, a new WO3 nanostructure has been obtained by anodization in a H2SO4/NaF electrolyte under controlled hydrodynamic conditions using a Rotating Disk Electrode (RDE) configuration. Anodized samples were analyzed by means of Field Emission Scanning Electronic Microscopy (FESEM), Confocal Raman Microscopy and photoelectrochemical measurements. The new nanostructure, which consists of nanoplatelets clusters growing in a tree-like manner, presents a very high surface area exposed to the electrolyte, leading to an outstanding enhancement of its photoelectrochemical activity. Obtained results show that the size of nanostructures and the percentage of electrode surface covered by…
Electron beam induced optical and electronical properties of SiO 2
2000
Abstract Ionizing radiation in dielectric and optically transparent silica as well as thin SiO 2 layers produces defect luminescence as well as charge storage. A comparison of different excitation–relaxation processes like cathodoluminescence, charge injection and trapping, secondary electron field emission, and exoelectron emission leads to a generally similar excitation dose behaviour described by an electron beam saturation dose of 0.01–0.1 C/cm 2 . This suggests a correlation of these four electron excitation mechanisms likely related to the same kind of defect in glassy SiO 2 , the 2-fold-coordinated silicon Si: centre with typical electronic singlet–singlet and singlet–triplet transit…
Carbon nanotube bags: catalytic formation, physical properties, two-dimensional alignment and geometric structuring of densely filled carbon tubes.
2001
The catalytic CVD synthesis, using propyne as carbon precursor and Fe(NO3)3 as catalyst precursor inside porous alumina, gives carbon nanotube (CNT) bags in a well-arranged two-dimensional order. The tubes have the morphology of bags or fibers, since they are completely filled with smaller helicoidal CNTs. This morphology has so far not been reported for CNTs. Owing to the dense filling of the outer mother CNTs with small helicoidal CNTs, the resulting CNT fibers appear to be stiff and show no sign of inflation, as sometimes observed with hollow CNTs. The fiber morphology was observed by raster electron microscopy (REM), transmission electron microscopy (TEM), and atomic force microscopy (A…
Untersuchung der Feldelektronenemission und ihrer Temperaturabh�ngigkeit bei Stromst�rken zwischen 10?14 und 10?19 A
1964
The field emission of a tungsten point cathode at very low emission currents was investigated by means of a secondary emission multiplier. The validity of the Fowler-Nordheim equation was experimentally confirmed within the range from 10−8 to 10−19 A. The dependence of the total emission current on temperature and electrical field strength was measured in the transition region between thermionic and field emission. A comparison is drawn with the theory ofMurphy andGood.
Asymmetric tungsten oxide nanobrushes via oriented attachment and Ostwald ripening
2011
Tungsten oxide nanobrushes were synthesized using a solvothermal approach that lead to self-branching in the presence of citric acid and hexadecylamine as surfactants. Our synthetic approach yielded branched nanorods of tungsten oxide in a single synthetic step. Based on our results, we propose a phenomenological pathway for the formation, branching, and assembly of these tungsten oxide brushes. The formation of tungsten oxide brushes proceeds by thermal decomposition of ammonium tungstate in the presence of citric acid and hexadecylamine. The pale blue powder obtained after solvothermal reaction was analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolu…