Oxide electronics

Abstract:

A high frequency oscillating Au (111) surface was measured with atomic resolution using a modified scanning tunneling microscope. On the atomic scale propagating surface acoustic waves lead to oscillations of atoms on elliptical trajectories, with the axes being determined by the material parameters of the surface. Since those oscillation frequencies are much higher than the scan frequencies the topography contrast is reduced. This basic problem is solved by measuring a stroboscopic snapshot seeing a defined state of oscillation. The atomic resolution of the phase and the amplitude contrast is explained by the superposition of the surface topography and the oscillation trajectory. © 1996 American Institute of Physics.

Abstract:

By using the high-pressure high-temperature technique, we succeeded in substituting in the mercury cuprate superconductors up to about 40% of mercury by gold. The samples were studied by X-ray and neutron powder diffraction, electron microscopy, energy dispersive spectroscopy. AC suceptibility measurements were also performed. The experimental data obtained for the Au substituted Hg-1223 compound indicate that the substitution leads to overdoping of the CuO2 layers, with a progressive decrease of cell parameters and Tc with increasing gold content. Taking into account these results, we used gold substitution to increase Tc of a Hg-1245 sample up to 110 K. The corresponding unsubstituted samples are normally obtained by the high-pressure high-temperature technique in an underdoped state with a Tc around 100 K.