64 research outputs found
Field emission from single multi-wall carbon nanotubes
Electron field emission characteristics of individual multiwalled carbon
nanotubes have been investigated by a piezoelectric nanomanipulation system
operating inside a scanning electron microscopy chamber. The experimental setup
ensures a high control capability on the geometric parameters of the field
emission system (CNT length, diameter and anode-cathode distance). For several
multiwalled carbon nanotubes, reproducible and quite stable emission current
behaviour has been obtained with a dependence on the applied voltage well
described by a series resistance modified Fowler-Nordheim model. A turn-on
field of about 30 V/um and a field enhancement factor of around 100 at a
cathode-anode distance of the order of 1 um have been evaluated. Finally, the
effect of selective electron beam irradiation on the nanotube field emission
capabilities has been extensively investigated.Comment: 16 pages, 5 figure
The DAMA/LIBRA apparatus
The 250 kg highly radiopure NaI(Tl) DAMA/LIBRA apparatus, running at
the Gran Sasso National Laboratory (LNGS) of the I.N.F.N., is described.Comment: 37 pages, 27 figure
Metallic 1T Phase, 3d1 Electronic Configuration and Charge Density Wave Order in Molecular Beam Epitaxy Grown Monolayer Vanadium Ditelluride.
We present a combined experimental and theoretical study of monolayer vanadium ditelluride, VTe2, grown on highly oriented pyrolytic graphite by molecular-beam epitaxy. Using various in situ microscopic and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X-ray and angle-resolved photoemission, and X-ray absorption, together with theoretical analysis by density functional theory calculations, we demonstrate direct evidence of the metallic 1T phase and 3d1 electronic configuration in monolayer VTe2 that also features a (4 Ă 4) charge density wave order at low temperatures. In contrast to previous theoretical predictions, our element-specific characterization by X-ray magnetic circular dichroism rules out a ferromagnetic order intrinsic to the monolayer. Our findings provide essential knowledge necessary for understanding this interesting yet less explored metallic monolayer in the emerging family of van der Waals magnets
Correction to Metallic 1T Phase, 3d1 Electronic Configuration and Charge Density Wave Order in Molecular-Beam Epitaxy Grown Monolayer Vanadium Ditelluride.
It has been brought to our attention that a mistake exists in the author list. The author âJohnson Gohâ in the original article should be âKuan Eng Johnson Gohâ. His primary corresponding email is [email protected]
Further results from DAMA/LIBRA-phase2 and perspectives
The data collected by the DAMA/LIBRA-phase2 set-up during two additional annual cycles have been analyzed, further investigating the long-standing model-independent annual modulation effect pointed out by DAMA deep underground at the Gran Sasso National Laboratory of the I.N.F.N. by using various different experimental configurations. Including the new results, the total exposure of DAMA/LIBRA-phase2 over 8 annual cycles is 1.53 t·yr and the evidence for a signal that meets all the requirements of the model-independent Dark Matter annual modulation signature is 11.8 Ï C.L. in the energy region (1 - 6) keV. In the (2 - 6) keV energy interval, where data are also available from DAMA/NaI and DAMA/LIBRA-phase1, the achieved C.L. for the full exposure of 2.86 t·yr is 13.7 Ï. No systematics or side reaction able to mimic this signature (i.e., to account for the whole measured modulation amplitude and to simultaneously satisfy all the requirements of the signature) has been found or suggested by anyone throughout some decades thus far. A preliminary result on the further lowering of the software energy threshold and perspectives are also mentioned
Evidence for metallic 1T phase, 3d1 electronic configuration and charge density wave order in molecular-beam epitaxy grown monolayer VTe2
We present a combined experimental and theoretical study of monolayer VTe2
grown on highly oriented pyrolytic graphite by molecular-beam epitaxy. Using
various in-situ microscopic and spectroscopic techniques, including scanning
tunneling microscopy/spectroscopy, synchrotron X-ray and angle-resolved
photoemission, and X-ray absorption, together with theoretical analysis by
density functional theory calculations, we demonstrate direct evidence of the
metallic 1T phase and 3d1 electronic configuration in monolayer VTe2 that also
features a (4 x 4) charge density wave order at low temperatures. In contrast
to previous theoretical predictions, our element-specific characterization by
X-ray magnetic circular dichroism rules out a ferromagnetic order intrinsic to
the monolayer. Our findings provide essential knowledge necessary for
understanding this interesting yet less explored metallic monolayer in the
emerging family of van der Waals magnets.Comment: 21 pages, 5 figure
Anomalous coarsening driven by reversible charge transfer at metalâorganic interfaces
The unique electronic properties and functional tunability of polycyclic aromatic hydrocarbons have recently fostered high hopes for their use in flexible, green, portable, and cheap technologies. Most applications require the deposition of thin molecular films onto conductive electrodes. The growth of the first few molecular layers represents a crucial step in the device fabrication since it determines the structure of the molecular film and the energy level alignment of the metalâorganic interface. Here, we explore the formation of this interface by analyzing the interplay between reversible moleculeâsubstrate charge transfer, yielding intermolecular repulsion, and van der Waals attractions in driving the molecular assembly. Using a series of ad hoc designed molecules to balance the two effects, we combine scanning tunnelling microscopy with atomistic simulations to study the self-assembly behavior. Our systematic analysis identifies a growth mode characterized by anomalous coarsening that we anticipate to occur in a wide class of metalâorganic interfaces and which should thus be considered as integral part of the self-assembly process when depositing a molecule on a conducting surface
The calibration and the monitoring/alarm system
Two important parts of the DAMA/LIBRA setup are the calibration system and the monitoring/alarm system. The calibration system allows to perform detector calibrations without changing the running condition of the experiment; the monitoring/alarm system allows to record several parameters to control the running status and its stability. In this paper, we will describe the two system reporting some related obtained results
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