ABSTRACT
We report on long-range electronic effects caused by hydrogen-carbon interaction at the graphite surface. Two types of defects could be distinguished with a combined mode of scanning tunneling microscopy and atomic force microscopy: chemisorption of hydrogen on the basal plane of graphite and atomic vacancy formation. Both types show a (sqrt[3]xsqrt[3])R30 degrees superlattice in the local density of states but have a different topographic structure. The range of modifications in the electronic structure, of fundamental importance for electronic devices based on carbon nanostructures, has been found to be of the order of 20-25 lattice constants.
ABSTRACT
Even though friction is one of the oldest problems in physics many aspects of friction processes are not clear today. We present an experimental setup, which permits the study of tribological systems by measuring the dissipated heat at the interface of two surfaces during a friction process with a time resolution of 1 ms. The apparatus is based on a standard ultrasonic wire-bond machine used in semiconductor industries to connect the internal semiconductor die to the external leads, but the standard bond wire is replaced by a thermocouple. To demonstrate the ability of the apparatus it will be shown that bond substrates used in semiconductor industries can be unequivocally characterized.
ABSTRACT
Submillimeter wave gas lasers are characterized by low Fresnel numbers and by gain widths smaller than the mode separations. This allows interferometry of laser emissions and resonator modes with the aid of the laser resonator. The theory of Bergstein and Schachter on modes occurring in resonators with low Fresnel numbers is compared with the experimental data obtained by laser resonator interferometry. The influence of the tilt of a resonator mirror on the intensity of the laser emission is measured for different modes.
