W. H. Schreiner
Universidade Federal do Rio Grande do Sul
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Featured researches published by W. H. Schreiner.
Solid State Communications | 1991
R.S. Lima; P.H. Dionisio; W. H. Schreiner; C.A. Achete
Tin Nitride obtained by magnetron sputtering has been studied with Conversion Electron Mossbauer Spectroscopy, X-ray diffraction, Auger Electron Spectroscopy and Rutherford Backscattering Spectroscopy. The results indicate a stable and well crystallized compound.
Journal of Applied Physics | 1990
D.H. Mosca; P.H. Dionisio; W. H. Schreiner; I.J.R. Baumvol; C.A. Achete
The compositional and magnetic properties of iron‐nitride thin films deposited by dc reactive magnetron sputtering under various nitrogen partial pressure conditions have been investigated by x‐ray diffraction, Mossbauer and Auger electron spectroscopy as well as magnetic measurements. The x‐ray diffraction patterns indicate a mixed phase composition. 57Fe Mossbauer spectroscopy shows that part of the nitrogen atoms are randomly distributed on interstitial sites with the formation of nonstoichiometric compounds. The excessive width of the Mossbauer lines indicates the degree of disorder of the different iron nitride precipitates. The nitrogen concentration as a function of depth is obtained by sputter‐etched Auger electron spectroscopy. Furthermore, the ferromagnetic films show moderate saturation magnetization and coercivities at room temperature as compared with pure iron thin films.
Thin Solid Films | 1992
M.R. Soares; P.H. Dionisio; I.J.R. Baumvol; W. H. Schreiner
Abstract Tin oxide thin films were obtained by reactive magnetron sputtering and analysed by X-ray diffraction and conversion electron Mossbauer spectroscopy. The main sputtering parameters employed were the relative Arue5f8O 2 gas composition and the deposition temperature. The evolution of thin films on thermal treatment in air was also studied.
Journal of Physics and Chemistry of Solids | 1982
W. H. Schreiner; D. E. Brandao; F. Ogiba; J. V. Kunzler
Abstract The electrical resistivity of eight different Heusler alloys is discussed in terms of electron phonon and spin-disorder scattering. The systematics common to the alloys can be explained in the intermediate to high temperature range while the low temperature range still presents interpretation difficulties.
Journal of Applied Physics | 1991
D.H. Mosca; Sérgio R. Teixeira; P.H. Dionisio; I.J.R. Baumvol; W. H. Schreiner; W. A. Monteiro
The thermal evolution of reactively sputtered iron nitride thin films has been investigated by x‐ray diffraction, Mossbauer conversion electron spectroscopy, transmission electron microscopy, and magnetic measurements. The results show that, independently of the original nitrogen content of the films, a similar composition of the end products after the 500u2009°C annealings is reached, being all composed of α‐Fe plus γ’‐Fe4N in a wide range of relative proportions. The magnetic characteristics, however, are different depending on the nitrogen content of the as‐deposited films.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment | 1989
M.A.Z. Vasconcellos; S.R. Teixeira; P.H. Dionisio; W. H. Schreiner; I.J.R. Baumvol
Abstract Conversion electron Mossbauer spectroscopy is presented here as a useful technique to investigate interdiffusion and reaction in thin solid films as induced by thermal annealing, ion mixing or a simultaneous combination of these two processes. As an illustrative example, the experimental results of the particular iron-aluminum bilayer system are reviewed. Some X-ray diffraction patterns are also shown for the sake of comparison.
Journal of Physics and Chemistry of Solids | 1980
J. V. Kunzler; T.A. Grandi; W. H. Schreiner; P. Pureur; D.E. Brandāo
Abstract Electrical resistivity measurements have been performed on the Cu 2 Mn(Al 1− x Sn x ) Heusler alloys, where x = 0; 0.05; 0.10; 0.15, in the temperature range of 4–800 K. The experimental curves clearly show the importance of the ferromagnetic character on the resistivities of the alloys. The results obtained are in agreement with an interpretation in terms of a spin-disorder model.
Thin Solid Films | 1990
Fernanda Chiarello Stedile; C.V.Barros Leite; W. H. Schreiner; I.J.R. Baumvol
Abstract Tin oxide thin films obtained by reactive sputtering were submitted to different thermal annealings and then implanted with Fe+, Cu+, Zn+, Ga+ or As+. Subsequent air annealing was performed after implantation. The system was characterized by sheet resistance measurements, Rutherford backscattering spectroscopy and nuclear resonant scattering. The sheet resistance measurements showed that the doping of the films in general leads to an increase in the electrical conductivity. From the Rutherford backscattering spectroscopy and nuclear resonant scattering analyses, correlations between the depth distribution of the implanted species and the oxygen-to-tin ratios as a function of depth were also found.
Journal of Applied Physics | 1995
N. Mattoso; D. H. Mosca; I. Mazzaro; Sérgio R. Teixeira; W. H. Schreiner
Successful and unexpected epitaxial growth of Cu/CaF2 bilayers on hydrogen terminated Si(111) wafers by thermal evaporation is reported. The bilayers were characterized with conventional x‐ray diffraction experiments, grazing angle incidence x‐ray diffraction experiments, rocking curves, and χ scans. The growth mode of Cu films on CaF2 epitaxially grown on Si(111) is completely different from that of the Cu film grown directly on Si(111).
Hyperfine Interactions | 1994
R.S. Lima; P.H. Dionisio; J. T. Moro; W. H. Schreiner; C. Achete
Tin nitride obtained by reactive magnetron sputtering was annealed at several temperatures to study the thermal evolution and stability of the compound. X-ray diffraction, thermal effusion and conversion electron Mössbauer spectrometry were used to characterize the events. The nitride has different stabilities, depending on the ambient conditions under which the annealings are performed. Apparently only one crystallographic phase of the nitride is present before it disproportionates.