On the relation between the Feynman paradox and Aharonov-Bohm effects

The magnetic Aharonov-Bohm (A-B) effect occurs when a point charge interacts with a line of magnetic flux, while its dual, the Aharonov-Casher (A-C) effect, occurs when a magnetic moment interacts with a line of charge. For the two interacting parts of these physical systems, the equations of motion are discussed in this paper. The generally accepted claim is that both parts of these systems do not accelerate, while Boyer has claimed that both parts of these systems do accelerate. Using the Euler-Lagrange equations we predict that in the case of unconstrained motion only one part of each system accelerates, while momentum remains conserved. This prediction requires a time dependent electromagnetic momentum. For our analysis of unconstrained motion the A-B effects are then examples of the Feynman paradox. In the case of constrained motion, the Euler-Lagrange equations give no forces in agreement with the generally accepted analysis. The quantum mechanical A-B and A-C phase shifts are independent of the treatment of constraint. Nevertheless, experimental testing of the above ideas and further understanding of A-B effects which is central to both quantum mechanics and electromagnetism may be possible.Comment: 21 pages, 5 figures, recently submitted to New Journal of Physic

Flexible n-i-p thin film silicon solar cells on polyimide foils with textured ZnO:Ga back reflector

In thin film silicon solar cells on opaque substrates in n-i-p deposition sequence where the textured transparent conductive oxide (TCO) layer serves as a back reflector, one can independently optimize the morphology of the TCO layer without compromise on transparency and conductivity of this layer and further adjust the electro-optical properties of the back contact by using additional layers on top of the textured TCO. In the present work, we use this strategy to obtain textured back reflectors for solar cells in n-i-p deposition sequence on non-transparent flexible plastic foils. Gallium doped ZnO (ZnO:Ga) films were deposited on polyimide substrates by DC magnetron sputtering at a temperature of 200 °C. A wet-chemical etching step was performed by dipping the ZnO:Ga covered foil into a diluted HCl solution. The textured ZnO:Ga is then coated with a highly reflective Ag/ZnO double layer. On this back reflector, we develop thin film silicon solar cells with a microcrystalline silicon absorber layer. The current density for the cell with the textured ZnO:Ga layer is ~ 23 mA/cm2, 4 mA/cm2 higher than the one without such layer, and a maximum efficiency of 7.5% is obtained for a 1 cm2 cell.Fundação para a Ciência e a Tecnologia (FCT

High mobility annealing of Transparent Conductive Oxides

To improve electrical properties a high temperature annealing treatment was applied to several transparent conductive oxides TCO , namely tin doped indium oxide ITO , Ga or Al doped ZnO ZnO Al Ga , ion beam assisted deposited IBAD ZnO Ga and Ga doped zinc magnesium oxide ZnMgO Ga . All these films were grown by magnetron sputtering. During the annealing process all TCO films were capped with 50 nm of amorphous silicon in order to protect the films from environmental impact. Increase in mobility up to 72 cm2 Vs and low resistivity of 1.6 10 amp; 8722;4 amp; 937;cm was achieved for ZnO Al after annealing at 650 C for 24 h. Independent of the deposition conditions and doping or alloying material almost all ZnO based films show a consistent improvement in mobility. Also for ITO films a decrease in resistivity with partially improved mobility was found after annealing. However, not all ITO films show consistent improvement, but carrier density above 1021 cm amp; 8722;3 while ZnO films show no clear trend for carrier density but a remarkable increase in mobility. Thus we propose the healing of defects and the activation of donors to be most significant effects for ZnO and ITO films, respectivel