Reversal of sign of the Hall coefficient in n-InSb in the magnetic freeze out regime

Change in sign of the Hall coefficient has been observed in n-InSb with carrier concentrations ranging from 2 × 10¹⁴ cm^?3 to 6 × 10¹⁴ cm^?3, which occurs at liquid helium temperatures and magnetic fields above 30 kG. The influence of the compensation ratio, temperature, and geometry has been investigated.     

Increased imaging speed and force sensitivity for bio-applications with small cantilevers using a conventional AFM setup

In this study, we demonstrate the increased performance in speed and sensitivity achieved by the use of small AFM cantilevers on a standard AFM system. For this, small rectangular silicon oxynitride cantilevers were utilized to arrive at faster atomic force microscopy (AFM) imaging times and more sensitive molecular recognition force spectroscopy (MRFS) experiments. The cantilevers we used had lengths between 13 and 46μm, a width of about 11μm, and a thickness between 150 and 600nm. They were coated with chromium and gold on the backside for a better laser reflection. We characterized these small cantilevers through their frequency spectrum and with electron microscopy. Due to their small size and high resonance frequency we were able to increase the imaging speed by a factor of 10 without any loss in resolution for images from several μm scansize down to the nanometer scale. This was shown on bacterial surface layers (s-layer) with tapping mode under aqueous, near physiological conditions and on nuclear membranes in contact mode in ambient environment. In addition, we showed that single molecular forces can be measured with an up to 5 times higher force sensitivity in comparison to conventional cantilevers with similar spring constants.     

Magnetooptical investigation of PbTe/Pb1−xSnxTe superlattices

Intra- and interband magnetooptical experiments were carried out on PbTe/Pb_1?xSn_xTe superlattices (x=0.135) with layer thicknesses ranging from 13 – 225 nm. For the magnetic field parallel to the [111] growth direction, the Landau levels for the superlattice band structure are calculated within the framework of the envelope function approach for the [111] and the three obliquely oriented valleys. The experimental intra- and interband data agree qualitatively with the results of the model calculation and are consistent with the predictions of a LCAO calculation according to which the electrons or holes are confined in the Pb_1?xSn_xTe layers.