Ion-molecule reactions in mixtures of methane with carbon tetrafluoride

Ion-molecule reactions have been measured for methane-carbon tetrafluoride mixtures of different composition using a quadrupole mass spectrometer with a high-pressure ion source. Concentration of methane in these mixtures ranged from 10% to 90% (at 10% increment). Primary ions , , F⁺, CF⁺ and were produced by electrons with energy of 300 eV. Secondary ions , , , , and were observed as the result of ion-molecule reactions. Relative current intensities for primary and secondary ions are presented as a function of both total mixture pressure and concentration of methane in the mixture. Potential of repeller electrode inside the ion source collision chamber was fixed at 5 V for all measurements. Total mixture pressure was changed from 0.7 to 33.3 Pa. Schemes of ion-molecule reactions were proposed.     

Formation and desorption of SiI2 molecules

The chemical etching of Si(100)−(2×1) in I₂ ambient is considered. The desorption activation energy of SiI₂ molecules is evaluated from experimental data. It is found that the desorption activation energy of SiI₂ molecules is equal to . This corresponds to a value of the mean lifetime of adsorbed molecules on the surface of at temperature .     

Reactivity of Pd doped Ag surfaces

We have performed first principles pseudopotential calculations for catalytic CO oxidation on Pd doped surface. We discuss the effect of the change in the atomic geometry and surface electronic structure on the adsorption and reaction mechanism when alloying Ag with Pd. Pd doped works as a better catalyst for CO oxidation than the pure elemental Ag surface since Pd acts as an electronic promoter for the oxidation process.     

Curvature-based residual stress measurement for ion-implanted stainless-steel sheet

Residual stress in ion-implanted stainless-steel sheet and the effects of ion species and implantation dose on the residual stress were investigated by using curvature technique based on the Stoney equation. Six species of ions of Au, Ag, Fe, Ni, Ti and Si were implanted into the stainless steel sheet with an energy of at the dose of 1.0×10¹⁶ to . The depth profile of the ion implantation in the ion-implanted layer was examined by using transmission electron microscopy equipped with an energy-dispersive X-ray spectroscopy. The level of the residual stress evaluated by the Stoney equation was compared with the results of X-ray diffraction.     

Photoinduced non-linear optics diagnostic of the InBr films doped by Al, In and Sn

Photoinduced and second-order optical effects in the interfaces separating InBr (IB) films doped by Al, In, Sn and bare glass substrates were investigated using the photoinduced optical second harmonic generation. The second-order optical susceptibilities (at ) show a good correlation with the shift of the absorption edge. The maximal response of the photoinduced response signal was observed for the pump-probe delaying times equal about . The measurements indicate that the observed effects are caused by two cases: by interface potential gradients on the border glass-IB and by polarization of the medium due to impurities. The observed phenomenon may be proposed as a sensitive tool for investigations of thin nanointerfaces appearing between the glass substrate and crystallite layers.     

Study of lithium behaviour in Si(Li) detectors

In this paper we describe the fabrication of a conventional lithium compensated silicon detector (Si(Li)) realized on Topsil silicon with bulk resistivity 0.9 to , using the process of ion drift introduced by Pell. Preliminary results of electrical and nuclear characterization are shown. A leakage current value of 4 pA is obtained under reverse bias voltage of , at pressure of and 113 K. An alpha test using triple source ²⁴¹Am, ²³⁹Pu, ²³³U was carried and a resolution on ²⁴¹Am peak around 42 keV was obtained with this type of detector. The fabricated detector present a good electrical and nuclear characteristics that can be used in X-ray spectrometry and widespread applications in research science, environment monitoring and natural radioactivity. The main contribution of this work is the demonstration of an easy-to-implement, low cost detector set that can be achieved with an inexpensive n⁺p diode.     

Growth and photoluminescence of ZnO thin films on Si(1 1 1) by PLD in oxygen adequate ambient

Polycrystalline ZnO thin films were synthesized on Si(1 1 1) substrates by pulsed laser deposition (PLD) under oxygen sufficient condition at temperatures ranging from 550 to . The results of in situ reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) show that the (0 0 2) orientation of ZnO thin films is deteriorated, but the full-width at half-maximum (FWHM) of (0 0 2) peak decreases as the substrate temperature (T_s) increases. In photoluminescence (PL) spectra at room temperature (RT), all the ZnO thin films show small ultraviolet (UV) peak FWHMs in the range of 83-95 meV. The thin film prepared at exhibits the narrowest UV peak FWHM of 83 meV and the biggest intensity ratio (122) of UV emission (UVE) to deep-level emission (DLE). When the T_s increases to , a low-energy peak in the UV region at around 381 nm (3.25 eV) appears, which maybe result from a donor-acceptor-pair (DAP) transition and be a signal of excess incorporation of oxygen in the thin film.