Unique Physical Mechanism Research Articles

Monte Carlo simulation of real-space electron transfer in GaAs-AlGaAs heterostructures

The Monte Carlo method has been used to simulate electron transport in GaAs/AlGaAs heterostructures with an electric field applied parallel to the heterojunction interface. The simulations indicate that a unique physical mechanism for negative differential conductivity is provided by such layered heterostructures, which is analogous in many respects to the Gunn effect. This mechanism has been termed ’’real-space electron transfer’’ since it involves the transfer of electrons from a high-mobility GaAs region to an adjacent low-mobility AlGaAs region as the applied electric field intensity is increased. The simulations further indicate that the important details of the resulting velocity-field characteristics for these layered heterostructures can be controlled primarily through material doping densities, layer thicknesses, and the material properties of the individual layers. Thus, the phenomenon of real-space electron transfer potentially provides the ability to ’’engineer’’ those basic material properties which influence the performance of negative resistance devices.

On the catalytic activity of certain synthetic organic polymers

1. Data were obtained on the catalytic activity of synthetic polymers with conjugated bondspolymethyl vinyl ketone and polyparadiethynylbenzene in reactions of ortho-para and para-ortho conversion of hydrogen and isotopic exchange of hydrogen with deuterium. 2. The indicated polymers manifest catalytic activity in the reaction of para-ortho conversion of hydrogen at high temperatures and in the reaction of ortho-para conversion of hydrogen at the temperature of liquid nitrogen. The kinetic principles correspond to a first-order reaction rate equation (according to the change in pressure). The reaction of isotopic exchange of hydrogen with deuterium practically does not occur in the presence of these polymers. 3. A comparison of the results obtained with the physical properties of the polymers shows that the reaction of para-ortho conversion evidently proceeds according to a unique physical mechanism, on account of the influence of the surface paramagnetic centers, the appearance of which is related to the presence of complexes with charge transfer.