Optical properties of MgH2 measured in situ in a novel gas cell for ellipsometry/spectrophotometry

The dielectric properties of alpha-MgH2 are investigated in the photon energy range between 1 and 6.5 eV. For this purpose, a novel sample configuration and experimental setup are developed that allow both optical transmission and ellipsometric measurements of a transparent thin film in equilibrium with hydrogen. We show that alpha-MgH2 is a transparent, colour neutral insulator with a band gap of 5.6 +/- 0.1 eV. It has an intrinsic transparency of about 80% over the whole visible spectrum. The dielectric function found in this work confirms very recent band structure calculations using the GW approximation by Alford and Chou [J.A. Alford and M.Y. Chou (unpublished)]. As Pd is used as a cap layer we report also the optical properties of PdHx thin films.Comment: REVTeX4, 15 pages, 12 figures, 5 table

Thin crystalline functional group copolymer poly(vinylidene fluoride–trifluoroethylene) film patterning using synchrotron radiation

The photodegradation mechanism due to synchrotron radiation exposure of crystalline poly[vinylidene fluoride–trifluoroetylene, P(VDF–TrFE)] copolymer thin films has been studied with ultraviolet photoemission spectroscopy (UPS) and mass spectroscopy. Upon increasing exposure to x-ray white light (h ν≤1000 eV), UPS measurements reveal that substantial chemical modifications occur in P(VDF–TrFE) 5 monolayer films, including the emergence of new valence band features near the Fermi level, indicating a semimetallic photodegradeted product. The photodetached fragments of the copolymer consist mainly of H2, HF, CHF, CH2. This x-ray exposure study demonstrates that P(VDF–TrFE) films, possessing unique technologically important properties, can be directly patterned by x-ray lithographic processes. ©2000 American Institute of Physics

Probing environmentally significant surface radicals: Crystallographic and temperature dependent adsorption of phenol on ZnO

Environmentally persistent free radicals (EPFRs) are toxic organic/metal oxide composite particles that have been discovered to form from substituted benzenes chemisorbed to metal oxides. Here, we perform photoelectron spectroscopy, electron energy loss spectroscopy, and low energy electron diffraction of phenol chemisorbed to ZnO(1 0 1̱ 0) and (0 0 0 1̱)-Zn to observe electronic structure changes and charge transfer as a function adsorption temperature. We show direct evidence of charge transfer from the ZnO surfaces to the phenol. This evidence can help gain a better understanding of EPFRs and be used to develop possible future remediation strategies