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The syntheses of new nitroimidazole compounds using silicon-[(18)F]fluorine chemistry for the potential detection of tumor hypoxia are described. [(18)F]silicon-based compounds were synthesized by coupling 2-nitroimidazole with silyldinaphtyl or silylphenyldi-tert-butyl groups and labeled by fluorolysis or isotopic exchange. Dinaphtyl compounds (6, 10) were labeled in 56-71% yield with a specific activity of 45 GBq/μmol, however these compounds ([(18)F]7 and [(18)F]11) were not stable in plasma. Phenyldi-tert-butyl compounds were labeled in 70% yield with a specific activity of 3 GBq/μmol by isotopic exchange, or in 81% yield by fluorolysis of siloxanes with a specific activity of 45 GBq/μmol. The labeled compound [(18)F]18 was stable in plasma and excreted by the liver and kidneys in vivo. In conclusion, the fluorosilylphenyldi-tert-butyl (SiFA) group is more stable in plasma than fluorosilyldiphenyl moiety. Thus, compound [(18)F]18 is suitable for further in vivo assessments., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Focused silicon beams are useful for direct write applications, e.g., lithography on silicon without the undesirable effect of substrate contamination. However, since pure silicon is not amenable to liquid metal ion source (LMIS) manufacture, a suitable alloy containing silicon has to be produced. This paper covers almost all fundamental aspects of a Au82Si18 eutectic, including the most detailed beam mass spectra reported to date of a AuSi source. A finding worthy of note in this investigation, manifested in the behaviour of the ion extraction voltage with temperature, is the abnormal behaviour of the surface tension coefficient of the alloy with temperature. An important deduction from this work, however, concerns the mechanisms responsible for the creation of doubly charged ions: reasons of self-consistency indicate that while Si2+ is directly field evaporated, Au2+ must form by the post-ionization of Au+. Finally, two different mechanisms seem to co-exist, as far as the production of cluster ions is concerned. While for cluster ions containing only a few atoms some sort of surface field-ionization mechanism might be responsible for their creation, for larger clusters, a droplet break-up mechanism, possibly by ion capture, seems very likely., (Copyright 2004 Elsevier B.V.)

Four different liquid metal ion sources (LMIS), working with pure Bi as well as with Bi containing alloys (Au13Bi87, Ga38Bi62, Ga35Bi60Li5) were investigated with respect to the emission behavior as a function of current and temperature, the mass spectra and the energy distribution of the individual ion species. Additionally, for the pure Bi-LMIS the sputtering rates for Bi ions and clusters on Si, SiO2 and Ge substrates were compared with that of Ga projectile ions using a mass separating focused ion beam system. [ABSTRACT FROM AUTHOR]

Abstract: In this work the defect induced formation of CoSi2 nanoparticles and nanowires is investigated and discussed. The results show that defects created in silicon by FIB irradiation can getter solved Co atoms from the Si bulk during subsequent thermal treatment. Consequently, CoSi2 nanoparticles and nanowires are formed in the defect regions by CoSi2 precipitation and by following Ostwald ripening stabilizing the further growth of nanowires due to diffusion of the Co atoms during annealing. The nanowires are oriented in the 〈110〉 crystalline directions, which are energetically favored for CoSi2 growth. Presumably this self-aligned growing process is initiated by the formation of well known {311}-extended rod-like defects elongated in these 〈110〉 directions. [Copyright &y& Elsevier]

The study of AuSi liquid metal alloy ion sources (LMAIs) for the production of Si ions is not new. However, the present work encompasses in a concise form almost all fundamental aspects of source behaviour, in particular of a Au82Si18 source. A key finding, manifested in the behaviour of the ion extraction voltage with temperature, is the abnormal behaviour of the surface tension coefficient of the alloy with temperature. An important deduction, however, concerns the mechanisms responsible for the creation of doubly charged ions: reasons of self-consistency suggest that while Si++ is directly field-evaporated, Au++ must form by the post-ionization of Au+. [Copyright &y& Elsevier]

The interaction of a pulsed ion beam with a solid leads to a small temperature variation in the near subsurface region. Due to the local heating of the target thermal elastic waves were generated. The measurement of these waves gives information about the internal structure and properties of the sample. Experiments were carried out using an intensity modulated beam of high energy ions from a TANDETRON accelerator for the investigation of elastic waves in aluminum, steel, copper and silicon samples as well as for a pulsed low energy focused ion beam (FIB) for acoustic imaging from structures on different targets. The detection of the acoustic signal was provided by piezoelectric transducers based on lead zirconium titanium (PZT) ceramic or on polyvinylidene fluoride (PVDF) films which can be applied in the scanning ion acoustic microscopy. In this case the modulation frequency was varied in the range from 60 kHz to 2 MHz. A lateral resolution of the ion acoustic images near the samples surface of a few micrometers could be obtained. [Copyright &y& Elsevier]

Abstract. The lattice damage of silicon produced by ion implantation at extremely high current density of 0.8 A/cm[sup 2] (2.5 x 10[sup 18] cm[sup -2] s[sup -1]) was investigated. In a focused ion beam system, implantation was carried out with 70 kev Co ions, fluences of 1.2 x l0[sup 16]cm[sup -2] and 6.7 x 10[sup 15]cm[sup -2] into Si (111) at room temperature and elevated temperatures between 355 Celsius and 400 Celsius. Radiation damage measurements were performed by Rutherford backscattering/channeling spectroscopy and micro-Raman analysis. The radiation damage was studied as a function of pixel dwell-time and implantation temperature. The critical temperature for amorphization increases with current density. Although the fluence of the focused ion implantation was constant, crystalline layers were obtained for short and amorphous layers for long pixel dwell-times. The critical dwell-time of crystalline/amorphous transition increases with implantation temperature. From the results a typical time for deflect annealing of 10[sup-5] s at 400 Celsius and an activation energy of (2.5 +/- 0.6) eV were deduced. [ABSTRACT FROM AUTHOR]

Cobalt implantation with a focused ion beam (FIB) was applied to study ion beam synthesis of cobalt disilicide nanowires in silicon. Two mechanisms of CoSi2 nanowire formation were investigated: (a) conventional synthesis by Co++ FIB implantation at elevated temperatures into silicon along in-plane <110> Si crystal direction and subsequent annealing and (b) self-aligned CoSi2 nanowire growth in cobalt supersaturated silicon on FIB-induced defects at room temperature during subsequent annealing. The obtained CoSi2 nanowires are 20–100 nm in diameter and several micrometers long. [ABSTRACT FROM AUTHOR]

Channeling implantation of Ga into Ge is performed at two very different ion fluxes (1012 and 1019 cm-2 s-1), at two temperatures (room temperature and 250 °C), and at five different fluences. The fluence dependence of the range profiles and of the implantation damage is strongly influenced by defect accumulation and dynamic annealing. At 250 °C, the maximum lifetime of the defects is less than 10 s. On the other hand, at room temperature no significant annealing is found within the first 10 s after ion impact. The measured Ga depth profiles are reproduced very well by atomistic computer simulations. [ABSTRACT FROM AUTHOR]

A focused ion beam system is applied to study the dose dependence of the shape of Ge channeling implantation profiles at two very different dose rates (10[sup 18] and 10[sup 11] cm[sup -2] s[sup -1]), and for implantation temperatures of 250 °C and room temperature (RT). A simple model for the buildup of radiation damage is developed to describe the dechanneling effect of defects formed during ion bombardment. The use of this model in atomistic computer simulations yields Ge depth profiles which agree well with measured data. The lifetime of ion-beam-induced defects at 250 °C was estimated to be in the order of 100 s. At RT, some defect relaxation was found between 10 μs and 100 s after ion impact. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Parallel stripes of nanostructures on an n-type Si substrate have been fabricated by implanting 30keV Ga+ ions from a focused ion beam (FIB) source at three different fluences: 1×1015, 2×1015 and 5×1015 ions/cm2. Two sets of implantation were carried out. In one case, during implantation the substrate was held at room temperature and in the other case at 400°C. Photoemission electron microscopy (PEEM) measurements were carried out on these samples. The implanted parallel stripes, each with a nominal dimension of 4000×100nm2, appear as bright regions in the PEEM image. Line scans of the intensities from PEEM images were recorded along and across these stripes. Intensity profile at the edges of a line scan is broader for the implantation carried out at 400°C compared to room temperature. From the analysis of this intensity profile lateral diffusion coefficient of Ga in silicon was estimated assuming that the PEEM intensity is proportional to Ga concentration. The diffusion coefficient at 400°C has been estimated to be ∼10−15 m2/s. No significant dependence of diffusion coefficient on ion fluence was observed in the fluence range investigated here. Radiation enhanced diffusion has been discussed in the light of the associated defect distribution due to lateral straggling of the implanted ions. [Copyright &y& Elsevier]

Abstract: We have fabricated parallel stripes of nanostructures in an n-type Si substrate by implanting 30keV Ga+ ions from a focused ion beam (FIB) source. Two sets of implantation were carried out. In one case, during implantation the substrate was held at room temperature and in the other case at 400°C. Photoemission electron microscopy (PEEM) was carried out on these samples. The implanted parallel stripes, each with a nominal dimension of 4000nm×100nm, appear as bright regions in the PEEM image. Line scans of the intensities from the PEEM image were recorded along and across these stripes. The intensity profile at the edges of a line scan is broader for the implantation carried out at 400°C compared to room temperature. From the analysis of this intensity profile, the lateral diffusion coefficient of Ga in silicon was estimated assuming that the PEEM intensity is proportional to Ga concentration. The diffusion coefficient at 400°C has been estimated to be ∼1.3×10−15 m2/s. Across the stripes an asymmetric diffusion profile has been observed, which has been related to the sequence of implantation of these stripes and the associated defect distribution due to lateral straggling of the implanted ions. [Copyright &y& Elsevier]

Thin films (d∼200 nm) of hydrogenated amorphous silicon carbide (a-SiC:H), deposited by RF reactive magnetron sputtering, have been ion implanted with high doses (D=1016–1017 cm−2) of Ga+ as the implant species. The increased disorder and additional structural modification of a-SiC:H, induced by the implantation of Ga+, results in a considerable change of the optical properties, best manifested by a significant shift of the optical absorption edge to lower photon energies in the results obtained by optical transmission and reflection measurements and as derived from photo-thermal-deflection spectroscopy results. This shift may be attributed both to additional defect introduction and to accompanying structural modification effects, as confirmed by optical absorption measurements in the infra-red region and by Raman spectroscopy results. [Copyright &y& Elsevier]

Abstract: Silicon ion implantation effects on the optical and photoluminescence (PL) properties of polymethyl–methacrylate (PMMA) have been studied. Low-energy ion implantation (E =30–50keV) was carried out over a range of different ion fluences (D =1013–1017 cm−2). Visible PL and optical transmission spectra in the range (330–800nm) have been measured. The existing visible range PL emission in the unimplanted PMMA samples is clearly affected by the Si+ ion implantation and the observed modification effect of photoluminescence enhancement (PLE) is essentially dependent on the implantation fluence. For certain fluences, dependent on the ion energy, the overall amplitude of the PL emission has a several times (∼5 times) increase. Optical absorption also gradually increases with the fluence. [Copyright &y& Elsevier]