Previous work has shown that it is possible to image whole uncoated chloroplasts using scanning tunneling microscopy (STM), provided this is done in solution using tunnelling currents below about 100 pA. More recent images include some which suggest that the STM is sensitive to dynamic processes occ...

Mainsbridge and Thundat [J. Vac. Sci. Technol. B 9 (1991) 1259] recently reported STM images of chloroplast components. The goal of our work was to investigate the effects of sample preparation and imaging conditions, and to more clearly identify some of the structures that appear in chloroplast ima...

Oxides of the type La1.85Sr0.15Cu(1-x)V(x)O4-partial were prepared with vanadium contents, x, ranging from 0 to 0.10 in increments of 0.01. Vanadium entered into solid solution in the tetragonal K-phase structure at concentrations up to x = 0.05. Further additions of vanadium resulted in the formati...

Electrical deactivation of arsenic in highly doped silicon has been studied using the positron-beam technique. Direct experimental evidence linking the formation of arsenic-vacancy complexes (i.e., As-n-v) to the deactivation process is reported. The average number of arsenic atoms per complex, (n) ...

Doppler-broadening positron-annihilation-spectroscopy experiment that utilizes an in situ Cu-64 source for the study of Cu and Cu-containing materials is described. This technique is particularly useful for the investigation of defect structure at elevated temperatures, and the present instrumentati...

Using a low-temperature stage X-ray diffractometer, we have investigated the temperature dependence of the lattice parameters of single crystal superconductors Bi2.2Sr1.8CaCu2Ox. The experimental results show that (i) the lattice constants increase linearly with increasing temperature above about 10...

Room temperature Fe-57 Mossbauer effect measurements of the one- and two-dimensional quasicrystalline phases of Al75Pd15Fe10 are reported. Both materials show Mossbauer spectra with asymmetric doublets which have been analyzed in terms of a distribution of quadrupole splittings, and in terms of a di...

The positron beam technique is shown to be a sensitive indicator of the presence of arsenic within the grain boundaries of poly-silicon. Variable-energy positron beam and secondary-ion mass spectrometry studies have been performed on As+-implanted pre-amorphized Si samples as a function of dose and ...

In situ Doppler-broadening temperature scans and room temperature positron-lifetime measurements are reported for Al63CU25Fe12, Al62.5CU25Fe12.5, Al62CU25.5Fe12.5, and Al62Cu22.8Fe15.2 face-centered-icosahedral (FCI) quasicrystalline samples. Quenched-in disorder has been observed and found to annea...

Amorphous Al-Y-Ni alloys, prepared by rapid solidification from the melt, have shown a unique combination of low density and high tensile strength. In the present work amorphous alloys of the composition Al87Y8Ni5-xFex (2 less-than-or-equal-to x less-than-or-equal-to 5) have been studied using room ...

Amorphous alloys of the composition Al65Gd15Cu20 and Al1Gd1Fe1 have been prepared by rapid quenching from the melt. The alloys have been studied by X-ray diffraction, thermal analysis and SQUID magnetization methods. Thermal analysis results show crystallization temperatures of 647 and 945 K for Al-...

Al-Cu-Fe alloys of several different stoichiometries have been prepared using a variety of sample preparation methods and have been studied using Fe-57 Mossbauer effect spectroscopy. Well ordered icosahedral, phason disordered icosahedral and rhombohedral crystalline phases were investigated. The re...

Samples of the stable Al75Pd15Fe10 decagonal quasicrystal have been studied both in the as-cast state and after annealing. Structural properties were investigated using X-ray diffraction and Fe-57 Mossbauer effect studies. X-ray patterns show that annealing improves the degree of order in the decago...