Highly homogeneous, ultrathin films of copper nitride ͑Cu 3 N͒ have been grown on Fe͑001͒ at room temperature using a Cu evaporator and a radio-frequency plasma source to obtain atomic nitrogen in a UHV environment. Cu 3 N is a semiconductor with the valence band edge at −0.65± 0.05 eV below the Fermi Level. The formation of copper nitride can be detected spectroscopically by the shape of the Cu LVV-Auger electron transition, which changes sensibly in shape and position compared to metallic Cu. Cu 3 N grows epitaxially with the substrate forming flat disklike mosaic blocks, ͑001͒ oriented. Both x-ray core level photoelectron spectroscopy and ultraviolet photoelectron spectroscopy photoemission experiments have been used to study the electronic structure. A first-principles calculation has been performed and compared with the measured spectra.

The aim of this work is to obtain amorphous thin films of poly(3-hydroxybutyrate) (PHB) at room temperature. The PHB thin films were obtained by spin-coating of chloroform−polymer solutions on glass substrate. The films were extensively characterized by X-ray diffraction and AFM. In this work it has been shown that the local interaction of the polar groups of the polymer with the glass substrate reduces the chain mobility, precluding the crystallization within a tens of nanometers thick region close to the polymer−substrate interface. That makes possible to obtain stable amorphous PHB nanofilms at room temperature, opening a new insight into the technological applications of this polymer. Above this critical film thickness the polymer is able to crystallize, but the polymer chains tends to lie down parallel to the air−polymer interface. This crystal growth anisotropy is reduced with the increasing of the film thickness.

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The electronic structure of ultrathin films of ␥Ј-Fe 4 N͑100͒ deposited on Cu͑100͒ has been characterized by a combination of photoelectron spectroscopies, scanning tunneling microscopy, and diffraction techniques. The comparison of the data with first-principles simulations sheds light on magnetic moments, type of bonding, and charge transfer. N atoms residing in the bulk or at the surface are found to be distinguishable. The ␥Ј-Fe 4 N͑100͒ surface is laterally heterogeneous and contains both areas reconstructed with a p4gm͑2 ϫ 2͒ symmetry and bulklike terminated. The densities of states of the reconstructed and unreconstructed areas of the surface are obtained and compared with the experiment. Comparison with c͑2 ϫ 2͒N/Fe͑100͒ provides spectroscopic evidence that a subsurface excess of N drives the p4gm͑2 ϫ 2͒ reconstruction.