keV Xenon Ion Research Articles

Ion mixing effects on the electrochemical behavior of tin coated nickel

Nickel substrates were coated with a thin Sn layer and implanted with 100 keV xenon ions, leading to the formation of new surface phases, mainly Ni 3Sn. Electrochemical measurements were carried out on Ni samples submitted to each of the following surface modifications: Sn-deposition, Xe +-implantation, ion-mixing (combined treatment), and on untreated Ni. The test solution was 0.5 M NaCl. Both the potentiodynamic anodic and cathodic polarization curves show that the implantation on uncoated Ni improves the anodic passivation with respect to the Sn deposition on Ni; comparable results are obtained by surface alloying induced by ion-mixing. The cathodic behaviour is in agreement with the presence of both galvanic couples and active sites for H 2 evolution due to defect spreading. Only the alloyed surface shows a clearly different behaviour, i.e. a high hydrogen reduction overvoltage. The electrochemical measurements were repeated in the presence of sulphide ions.

Transmission sputtering of gold thin films by low-energy (<1 keV) xenon ions. I. The system and the measurement

A novel system for direct measurement of the transmission-sputtering yields of ion-irradiated thin films is described. The system was specifically designed for the study of the transmission sputtering caused by low-energy (<1 keV) xenon ions. The xenon ion beam employed is first mass-analyzed in a specially constructed corssed magnetic- and electric-field mass spectrometer; this analyzer eliminates all energetic neutral and singly charged ions of mass less than 40 amu; it is also expected that ≤2% of the xenon ions which actually reach a specimen are doubly charged. The analyzed xenon ion beam is made to impinge on a gold thin film (∼100–500 Å thick) which is mounted in a JEM 200 transmission electron-microscope holder. The temperature of the specimen can be varied between ∼25 and 300 K employing a continuous transfer liquid-helium cryostat. The particles (atoms or ions) ejected from the unirradiated surface of the gold thin film are detected by two channeltron electron-multiplier arrays (CEMA) in the Chevron configuration; the Chevron detector is able to detect individual transmission-sputtered particles when operated in the saturated mode. To further enhance resolution, the electron cascades (produced by the CEMA), are amplified and shaped electronically into uniform square pulses. The shaped signals are detected with an Ithaco 391A lock-in amplifier (LIA). With the aid of a ratiometer feature in the LIA, we are able to measure directly the ratio of the transmission-sputtered current It to the incident ion current Ib; for Ibn=1 μA cm−2, a ratio of It/Ib as small as 1×10−9 has been measured. A detailed discussion of the calibration procedure and the experimental errors, involved in this technique, are also presented.

Collection of Large Amounts of Xenon in Solid Targets

Targets containing a considerably higher dose of implanted atoms than earlier reported saturation values have been made with an isotope separator. The collected atoms seem however to be embedded in a carbon layer on the target surface rather than implanted in the target material in the usual sense. For 35 keV xenon ions impinging on iron we have measured concentrations as high as 85 μg/cm2. The targets have been used to determine nuclear magnetic moments and B(E2, 0+ → 2+)-values for even xenon isotopes.

Radiation damage and xenon release in quartz and fused silica following ion bombardment

AbstractSingle‐crystalline quartz and fused silica were bombarded with 40 keV xenon ions to give integrated ion doses of up to 2 × 1016 ions/cm2. At low dose (8 × 1010 ions/cm2) diffusional release processes dominated with activation enthalpies of 58 and 61 kcal/mol for quartz (diffusion along and perpendicular to the c‐axis respectively) and 72 kcal/mol for fused silica. Diffusion in the amorphous phase was markedly slower than diffusion in the crystalline phase. At doses ≧ 4 × 1013 ions/cm2 radiation damage in the form of a phase change to a quasi‐amorphous state occurred in quartz, as revealed by reflection electron diffraction. The annealing of this structural damage coincided with enhanced thermally activated gas release at temperatures below those of volume diffusion. Fused silica showed a similar enhanced release at high bombardment dose. Thus, the quasi‐amorphous phase produced by ion bombardment is different from that of fused silica. The present results indicate further, in agreement with the literature on neutron irradiated quartz and fused silica, that both materials approach a common state at a high level of radiation damage.