5,013 research outputs found
Pair tunneling through single molecules
By a polaronic energy shift, the effective charging energy of molecules can
become negative, favoring ground states with even numbers of electrons. Here,
we show that charge transport through such molecules near ground-state
degeneracies is dominated by tunneling of electron pairs which coexists with
(featureless) single-electron cotunneling. Due to the restricted phase space
for pair tunneling, the current-voltage characteristics exhibits striking
differences from the conventional Coulomb blockade. In asymmetric junctions,
pair tunneling can be used for gate-controlled current rectification and
switching.Comment: 4+ pages, 4 figures; minor changes, version published in Phys. Rev.
Let
Symplectic integrators for index one constraints
We show that symplectic Runge-Kutta methods provide effective symplectic
integrators for Hamiltonian systems with index one constraints. These include
the Hamiltonian description of variational problems subject to position and
velocity constraints nondegenerate in the velocities, such as those arising in
sub-Riemannian geometry and control theory.Comment: 13 pages, accepted in SIAM J Sci Compu
Life inside black holes
We consider test planet and photon orbits of the third kind inside a black
hole, which are stable, periodic and neither come out of the black hole nor
terminate at the singularity. Interiors of supermassive black holes may be
inhabited by advanced civilizations living on planets with the third-kind
orbits. In principle, one can get information from the interiors of black holes
by observing their white hole counterparts.Comment: 4 pages, 2 figure
Multilayer composite AZO/AGZO thin films for transparent conductive electrodes
Transparent electronics are an essential ingredient in many new technologies which are emerging in the 21st century - high efficiency solar cells[ll, interactive and transparent displays, energy efficient windows, and photonics for communications and computing[2J. The development of functionalised transparent conductive oxide materials (TCOs), in terms of abundant, cheap and environmentally friendly, is critical for materials science in such applications. Specifically, an impmiant research goal is to find substitutes for the dominant TCO material indium tin oxide (ITO), made from indium which is scarce, expensive and toxic. Zinc oxides doped with small amounts of aluminium (AZO), are promising candidates for such a substitute but generally don't perform as well as IT0[2l. Gallium co-doping with aluminium improves AZO performance significantly, but raises similar concerns to ITO, in terms of the scarcity and high cost of gallium.
This project aims to enhance the conductivity of AZO thin films-by adding a thin 'seed' layer co-doped with AI and minimum Ga concentration (AGZO). The project employed solution based sol-gel technique for synthesising AZO/GZO nanoparticles and then deposited on glass substrates through a spin coating process, followed by thermal annealing treatment. The optical properties, crystal structure and surface morphology of the films were characterised using UV-vis spectroscopy, X-ray diffraction and scanning electron microscopy. Composite multilayer films, with thickness around 400nm, exhibit transmittance above 90% across the visible range and resistivity approximately 10 O•cm.
Preliminary results indicate significant improvement in AZO films with the co-doped AGZO layer, compared with AZO films alone. Compared to uniformly doped AGZO films, the composite multilayer films exhibited similar performance, but with only 20% of the gallium consumed
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