Photodetachment microscopy is carried out on a beam of 127I− ions with a nanosecond pulsed laser. The photoelectron interferograms are recorded by means of a digital camera that images the light spots produced by the amplified photoelectrons on a phosphor screen. This is the first implementation of such an optical imaging technique in photodetachment microscopy. Due to their sensitivity to the photoelectron energy, the recorded electron interferograms can be quantitatively analysed to produce a measure of the electron affinity of iodine eA(127I) with an accuracy improved by more than a factor of 2 with respect to the best previous measurement. The result is 2467 287.4(29) m−1 or 3.059 0463(38) eV.

In this paper, we present a review of experimental work on Stark broadening of singly ionized xenon lines. Eighty lines, from close UV to the red region of the spectrum, have been studied. Stark halfwidths were compared with experimental data from the literature and modified semi-empirical calculations. A pulsed arc with 95% of helium and 5% xenon was used as a plasma source for this study. Measured electron densities Ne and temperatures T were in the ranges of 0.2–1.6 × 1023 m−3 and 18 300–25 500 K, respectively.

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The aim of this work is to produce 2D plasmonic and diffractive structures in Ag films with sharp features for which both a deeper understanding of laser induced transformation upon modulated laser intensity and a correlation between structural and optical properties are required. We compare results obtained by exposing silver films to an excimer laser operating at 193 nm whose intensity is either modulated or homogeneous. In all cases, one laser exposure is enough to break the film into nanoparticles (NPs). The use of the modulated beam intensity leads to diffractive 2D patterns that are formed by rectangular regions of untransformed material surrounded by transformed regions covered by NPs. The former have sharp edges that are consistent with the absence of significant mass transport that is discussed in terms of the thermal gradient induced. The latter contain NPs whose diameter increases as the initial film effective thickness increases. The surface plasmons associated with the NPs in the transformed regions dominate the reflectivity spectrum and the 2D array formed by the untransformed regions is responsible for the diffractive properties. Evidence for spinodal dewetting is only observed in our case for the steep gradient conditions achieved at the border of the homogeneously irradiated regions.

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Pairs of samples containing Ag nanoparticles (NPs) of different dimensions have been produced under the same conditions but on different substrates, namely standard glass slides and a thin layer of amorphous aluminum oxide (a-Al₂O₃) on-glass. Upon storage in ambient conditions (air and room temperature) the color of samples changed and a blue-shift and damping of the surface plasmon resonance was observed. The changes are weaker for the samples on-glass and tend to saturate after 12 months. In contrast, the changes for the samples on a-Al₂O₃ appear to be still progressing after 25 months. While x-ray photoelectron spectroscopy shows a slight sulfurization and negligible oxidation of the Ag for the on-glass samples upon 25 months aging, it shows that Ag is strongly oxidized for the on a-Al₂O₃ samples and sulfurization is negligible. Both optical and chemical results are consistent with the production of a shell at the expense of a reduction of the metal core dimensions, the latter being responsible for the blue-shift and related to the small (<10 nm initial diameter) of the NPs. The enhanced reactivity of the Ag NPs on the a-Al₂O₃ supports goes along with specific morphological changes of the Ag NPs and the observation of nitrogen.

UV nanosecond laser pulses have been used to produce a unique surface nanostructuration of Ag@ZnO supported nanorods (NRs). The NRs were fabricated by plasma enhanced chemical vapor deposition (PECVD) at low temperature applying a silver layer as promoter. The irradiation of these structures with single nanosecond pulses of an ArF laser produces the melting and reshaping of the end of the NRs that aggregate in the form of bundles terminated by melted ZnO spherical particles. Well-defined silver nanoparticles (NPs), formed by phase separation at the surface of these melted ZnO particles, give rise to a broad plasmonic response consistent with their anisotropic shape. Surface enhanced Raman scattering (SERS) in the as-prepared Ag@ZnO NRs arrays was proved by using a Rhodamine 6G (Rh6G) chromophore as standard analyte. The surface modifications induced by laser treatment improve the stability of this system as SERS substrate while preserving its activity.

Room temperature conductance transients in the SiN x :H/Si interface are reported. Silicon nitride thin films were directly deposited on silicon by the low temperature electron-cyclotron-resonance plasma method. The shape of the conductance transients varies with the frequency at which they are obtained. This behavior is explained in terms of a disorder-induced gap-state continuum model for the interfacial defects. A perfect agreement between experiment and theory is obtained proving the validity of the model. © 1997 American Institute of Physics. ͓S0003-6951͑97͒03732-7͔Presently, ultrathin silicon dioxide gates ͑30-40 Å͒ are required as a consequence of the reduction in the ultralargescale-integration ͑ULSI͒ silicon device dimensions. On the other hand, silicon nitride, Si 3 N 4 , has been successfully used as an insulator with different III-V semiconductors. Two important properties of silicon nitride ͑Si 3 N 4 ͒ make it a candidate to substitute silicon dioxide, SiO 2 , in ultrathin dielectric structures: silicon nitride has a higher dielectric constant and exhibits a better performance as a diffusion barrier than silicon dioxide. Nevertheless, the interface between Si 3 N 4 and Si is not as well known as the SiO 2 /Si interface and significantly higher densities of interfacial states are always displayed by the silicon nitride/silicon structure.In this letter we report for the first time the existence of conductance transients in Al/Si 3 N 4 /Si structures. As we show later, this behavior is related to the existence of a spatial distribution of interface states. We use metal-insulatorsemiconductor ͑MIS͒ diodes in which a 550-Å-thick SiN x :H film was directly deposited on ͗100͘ n-type silicon by electron-cyclotron-resonance ͑ECR͒ plasma at 200°C. Silicon nitride films have been fabricated with a wide composition range 1 from Si-rich to near stoichiometric and N-rich films. For compositions far from the stoichiometry the hydrogen content increases and the number of electrically active defects in the film increases due to the distortion in bonds induced by hydrogen, 2 in spite of the dangling bond saturation that it produces. In a previous work 3 we have proved by capacitance-voltage ͑C-V͒ and deep-level transient spectroscopy ͑DLTS͒ studies that the electrical properties of these films are closely related to hydrogen content. We observed hysteresis phenomena in the C-V curves. This behavior has been previously reported by Lau et al. 4 and may be understood by the defect model suggested by Hasegawa et al. 5,6 These authors proposed that the interface states are distributed both in energy and in space. This distribution is called disorder-induced gap-state ͑DIGS͒ continuum. Emission and capture of free electrons by states located far from the interface can occur by mean of tunneling mechanisms.7 When bias varies from inversion to accumulation, electrons in the semiconductor conduction band are captured by emptied interface states, whereas when moving in the opposite direction electrons are emitted from filled ...