The optical properties of hydrogen exposed palladium (Pd) and palladium oxide (PdO) thin films are calculated from reflectance and transmittance measurements in the visible and near infrared range (400–900nm). The time evolution of the films’ optical constants when exposed to hydrogen is shown. The real part of palladium’s refractive index increases about 5%, whereas the imaginary part decreases nearly 15% after hydrogen absorption. The Pd films’ resistance also increased upon hydrogen absorption, as expected. Pd oxide reduces to metallic palladium upon hydrogenation, showing a dramatic change in all the properties. The palladium films’ resistance initially decreases after a first exposure to 5Torr of hydrogen, and this is tentatively explained by the reaction of hydrogen with impurities trapped in the films.
Growth of pure phase delafossite CuFeO2 thin films on Al2O3 (00.1) substrates by pulsed laser deposition was systematically investigated as a function of growth temperature and oxygen pressure. X-ray diffraction, transmission electron microscopy, Raman scattering, and x-ray absorption spectroscopy confirmed the existence of the delafossite phase. Infrared reflectivity spectra determined a band edge at 1.15 eV, in agreement with the bulk delafossite data. Magnetization measurements on CuFeO2 films demonstrated a phase transition at TC ≈ 15 ± 1 K, which agrees with the first antiferromagnetic transition at 14 K in the bulk CuFeO2. Low temperature magnetic phase is best described by commensurate, weak ferromagnetic spin ordering along the c-axis.
Improved one-tier and two-tier designs for a high pressure-low pressure (HPLP) apparatus are described together with some of their recent applications. These instruments are used for surface analysis and in situ monitoring of catalytic reactions on small samples with a geometrical surface area of '-1 cm2. Catalytic reactions are studied over a wide range of pressures (10'8_105 torr) and temperatures (273-1273 K). The apparatus incorporates surface analysis methods such as Electron Spectroscopy for Chemical Analysis (ESCA), High Resolution Electron Energy Loss Spectrometry (HREELS) and 14 C-radiotracer labeling in addition to Low Energy Electron Diffraction (LEED), Auger Electron Spectroscopy (AES) and mass spectrometry. Facilities are also available for argon sputter-ion cleaning, deposition of adsorbates by evaporation and coverage calibration by means of a thickness monitor.
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