864 research outputs found
Focused Ion Beam Milling and Deposition of Tungsten Contacts on Exfoliated Graphene for Electronic Device Applications
We demonstrate a rapid-prototyping method for the fabrication of electrical structures from exfoliated graphene using focused ion beam (FIB) assisted deposition of tungsten and milling. Alignment accuracies of less than 250 nm are achieved without imaging of the graphene using the FIB beam. Parameters for the FIB assisted deposition on graphene have to be controlled exactly to avoid damage to the underlying graphene. Measured channel resistance of 58 k? shows a good electrical contact between deposited tungsten and graphene
Nitrogen Ion Microscopy
The gas field ion source (GFIS) can be used to generate beams of helium, neon, hydrogen, and nitrogen ions, among others. Due to the low energy spread and the atomically small virtual source size, highly focused ion beams (FIB) can be obtained. We discuss the history of the GFIS and explain the field ionization and field evaporation process in general. Then, the unique properties of the nitrogen ionization, originating from the molecular nature, are explained. We show how the nitrogen ion microscopy (N2IM) can be used to image and pattern samples. The unique contrast observed in samples with graphene or carbon is reported. Finally, we conclude with an outlook of the technology and possible key applications such as spatially localized nitrogen-vacancy center implantation
Silicon nanowires for advanced sensing: Electrical and electromechanical characteristics and functionalisation technology
541 HEMICALLOTASIS CAN MAINTAIN THE OPTIMAL CORRECTION ANGLE WITH LASTING LONG TIME IN THE PATIENTS WITH MEDIAL GONARTHROSIS
Large area plasma-enhanced chemical vapor deposition of nanocrystalline graphite on insulator for electronic device application
This paper reports on large area plasma-enhanced chemical vapor deposition (PECVD) of nanocrystalline graphite (NCG) on thermally grown SiO2 wafer, quartz and sapphire substrates. Grown films are evaluated using Raman spectroscopy, ellipsometry, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Electrical characterization and optical transmission measurementsindicate promising properties of this material for use as transparent electrodes and for electronic device application. A plasma-based etch process for NCG has been developed
Tailoring the thermal Casimir force with graphene
The Casimir interaction is omnipresent source of forces at small separations between bodies, which is difficult to change by varying external conditions. Here we show that graphene interacting with a metal can have the best known force contrast to the temperature and the Fermi level variations. In the distance range 50–300 nm the force is measurable and can vary a few times for graphene with a bandgap much larger than the temperature. In this distance range the main part of the force is due to the thermal fluctuations. We discuss also graphene on a dielectric membrane as a technologically robust configuration
Electrical control of ferromagnetism in Mn-doped semiconductor heterostructures
The interplay of tunneling transport and carrier-mediated ferromagnetism in
narrow semiconductor multi-quantum well structures containing layers of GaMnAs
is investigated within a self-consistent Green's function approach, accounting
for disorder in the Mn--doped regions and unwanted spin-flips at
heterointerfaces on phenomenological ground. We find that the magnetization in
GaMnAs layers can be controlled by an external electric bias. The underlying
mechanism is identified as spin-selective hole tunneling in and out of the
Mn-doped quantum wells, whereby the applied bias determines both hole
population and spin polarization in these layers. In particular we predict
that, near resonance, ferromagnetic order in the Mn doped quantum wells is
destroyed. The interplay of both magnetic and transport properties combined
with structural design potentially leads to several interrelated physical
phenomena, such as dynamic spin filtering, electrical control of magnetization
in individual magnetic layers, and, under specific bias conditions, to
self-sustained current and magnetization oscillations
(magneticmulti-stability). Relevance to recent experimental results is
discussed.Comment: 10 pages, 8 figure
Nucleon scattering with higgsino and wino cold dark matter
Neutralinos that are mostly wino or higgsino are shown to be compatible with
the recent DAMA annual modulation signal. The nucleon scattering rates for
these dark matter candidates are typically an order of magnitude above the
oft-considered bino. Although thermal evolution of higgsino and wino number
densities in the early universe implies that they are not viable dark matter
candidates, non-thermal sources, such as from gravitino or moduli decay in
anomaly mediated supersymmetry breaking, suggest that they can be the dominant
source of cold dark matter. Their stealthiness at high energy colliders gives
even more impetus to analyze nucleon scattering detection methods. We also
present calculations for their predicted scattering rate with Germanium
detectors, which have yet to see evidence of WIMP scattering.Comment: 16 pages, LaTex, 4 figures, uses feynMF, minor changes made for PRD
publicatio
Particle Dark Matter Physics: An Update
This write--up gives a rather elementary introduction into particle physics
aspects of the cosmological Dark Matter puzzle. A fairly comprehensive list of
possible candidates is given; in each case the production mechanism and
possible ways to detect them (if any) are described. I then describe detection
of the in my view most promising candidates, weakly interacting massive
particles or WIMPs, in slightly more detail. The main emphasis will be on
recent developments.Comment: Invited talk at the 5th Workshop on Particle Physics Phenomenology,
Pune, India, January 1998; 21 pages, LaTeX with equation.st
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