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Using high-resolution angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy, the atomic and low energy electronic structure of the Sr-doped superconducting topological insulators (Srx Bi2Se3) was studied. Scanning tunneling microscopy shows that most of the Sr atoms are not in the van der Waals gap. After Sr doping, the Fermi level was found to move further upwards when compared with the parent compound Bi2Se3, which is consistent with the low carrier density in this system. The topological surface state was clearly observed, and the position of the Dirac point was determined in all doped samples. The surface state is well separated from the bulk conduction bands in the momentum space. The persistence of separated topological surface state combined with small Fermi energy makes this superconducting material a very promising candidate for the time reversal invariant topological superconductor. [ABSTRACT FROM AUTHOR]

Using high-resolution angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy, the atomic and low energy electronic structure of the Sr-doped superconducting topological insulators (Srx Bi2Se3) was studied. Scanning tunneling microscopy shows that most of the Sr atoms are not in the van der Waals gap. After Sr doping, the Fermi level was found to move further upwards when compared with the parent compound Bi2Se3, which is consistent with the low carrier density in this system. The topological surface state was clearly observed, and the position of the Dirac point was determined in all doped samples. The surface state is well separated from the bulk conduction bands in the momentum space. The persistence of separated topological surface state combined with small Fermi energy makes this superconducting material a very promising candidate for the time reversal invariant topological superconductor. [ABSTRACT FROM AUTHOR]

We have determined the structures of compounds nucleated in a series of sequentially sputtered thin bilayer films of Al and Ti on Si substrates for a range of metal thicknesses and for both (100) and (111) substrates. The compound structures were determined by transmission electron microscopy and diffraction, augmented by Auger electron spectroscopy. An annealing temperature of about 380 °C for 30 min was required to produce compound nucleation. For the Ti/Al/Si(100) system it was found that the phases which were nucleated for samples with 30-min, 380 °C anneals varied from TiAl3 to Ti8Al24 to an unknown compound of tetragonal structure (a=b=5.782 Å, c=6.713 Å) as the Al intermediate layer thickness is changed from 200 to 60 to 40 Å. TiAl3 was the compound nucleated at 380 °C for all other cases. Finally, 410 °C annealing of the Al/Ti/Si(100) samples for 30 min resulted in formation of an apparently Al-altered form of TiSi2. [ABSTRACT FROM AUTHOR]

We report on selected results of an extensive study of SiO2 nitridation in an NH3 ambient obtained primarily using Auger sputter profiling. By investigating a large matrix of samples, we have sorted out the discrepancies present in the literature concerning the kinetics of the nitridation process. Two major new results obtained are the quantitative observation of oxygen depletion in the nitroxide ‘‘bulk’’ region and, consistent with a recent report by R. Vasquez, M. Hecht, F. Grunthaner, and M. Naiman [Appl. Phys. Lett. 44, 969 (1984)], the reoxidation of the interface by oxygen presumably liberated by the bulk exchange reaction. [ABSTRACT FROM AUTHOR]

n-type GaAs samples coated with TaSi2 and Ta5 Si3 Schottky barrier contacts were heated in a flashlamp rapid thermal processing (RTP) system to temperatures between 600 and 950 °C. We have measured the evaporation of gallium and arsenic through the contact overlayers which results from the decomposition of the GaAs substrate. These decomposition measurements have been correlated with the Schottky barrier behavior as determined from forward-bias current-voltage characteristics and selected capacitance-voltage measurements. The high-temperature stability against decomposition and electrical degradation was superior for Ta5 Si3 contacts relative to TaSi2 contacts. We observed for both contact compositions that the onset temperature for decomposition of GaAs was slightly lower than the maximum temperature for electrical stability. Thus, we found that in some cases substantial decomposition occurred with no effect on the current-voltage characteristics. For example, Ta5 Si3 contacts maintained a stable barrier height of 0.78 eV through 10 s RTP treatments up to 900 °C, in spite of decomposition of at least ten equivalent monolayers of GaAs. [ABSTRACT FROM AUTHOR]