Polyelectrolytes in thin liquid films

The review addresses the influence of polyelectrolytes on the statics and dynamics of thin liquid films. Both, changes of interfacial and bulk properties, contribute to the overall behaviour of thin films formed from aqueous polyelectrolyte solutions. Therefore, the chapter is separated into two parts: polyelectrolytes at film interfaces and polymers in film bulk.     

Oxygen incorporation in polyethylene and polypropylene implanted with F+, As+ and I+ ions at high dose

Samples of PolyPropylene (PP) and PolyEthylene (PE) implanted with 150 keV F⁺, As⁺ and I⁺ ions with a dose of 1×10¹⁵ cm^–2 were studied using standard Rutherford Back Scattering (RBS) technique. No fluorine atoms above the present RBS detection limit were observed in the ion-implanted polymers. The measured depth profiles of As and I atoms are significantly broader than those predicted by the TRIM code for pristine polymers. The differences can be explained by stepwise polymer degradation due to ion bombardment. Massive oxidation of the ion-implanted polymers is observed. The oxidation rate and the resulting oxygen depth profile depend strongly on the polymer type and implanted ion mass. In the samples implanted with F⁺ ions, an uniformly oxidized layer is built up with a mean oxygen concentration of 15 at.%. In the samples implanted with As⁺ and I⁺ ions, a non-uniform oxygen depth distribution is observed with two concentration maxima on the sample surface and in a depth correlated with implanted ion range.     

Probing the coherent transport through coupled quantum dots

We investigate the photoconductance through a double quantum dot or ‘artificial molecule’ induced by a broadband millimeter wave source. This source functions as a heterodyne interferometer, consisting of two nonlinear transmission lines generating harmonic output in the range of 2–400 GHz, and, being coherent, allows tracking of the induced current of the sample in both magnitude and phase. This enables us to monitor effects related to coherent electronic transport through these ‘artificial molecules’.     

Realization of dual,tunable, ordinary- and quantized-Hall resistances in doubly connected GaAs/AlGaAs heterostructures

An experimental configuration based on gated, double boundary GaAs/AlGaAs devices provides the first demonstration of dual distinct, tunable Hall resistances in the same sample over the weak- and strongmagnetic field limits, including the simultaneous observability of dual quantized Hall effects of dissimilar filling factors. These experiments suggest that the ordinary Hall resistance examined in experiment is essentially a topological resistance determined by connectivity, which need not reflect all “local” values of the off-diagonal resistivity, θ _M ρ _xy .     

Hole-density dependence of the cyclotron mass of 2D holes in a GaAs(001) quantum well

The dependence of the heavy-hole cyclotron mass in GaAs(001) quantum wells on the 2D-hole density has been measured by the optical detection method for resonance microwave by-absorption. A significant increase (almost doubling) has been observed in the cyclotron mass of heavy holes with an increase in the charge carrier density from 1.2 × 10¹⁰ cm^?2 to 1.3 × 10¹¹ cm^?2.     

An observation by photoconductivity of strain splitting of shallow bulk donors located near to the surface in silicon mos devices

Photoconductivity is observed in n-channel inversion Si MOSFETS at 4.2 K at infrared frequencies up to 700 cm^?1. Two groups of sharp lines of opposite sign are observed in the regions of 300 and 650 cm^?1 together with a continuum of transitions starting at ～ 350 cm^?1. The sharp lines are interpreted as bound transitions from shallow neutral phosphorous donors and boron acceptors on either side of the depletion layer. The angular dependence of the Zeeman splitting of the sharp lines demonstrates that the normal 90° symmetry of the 100 surface is lifted for devices with thin metal gates due to the presence of a strong unixial stress component.