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Abstract: Charge-state equilibration of ions moving in matter occurs within femtoseconds and when penetrating nanometer depths. Ion-beam mixing in bilayers, tens of nm thick, should therefore not depend on the charge state of the projectiles. As the experimental situation for metal/silicon bilayers irradiated with noble-gas ions of different charge-states is ambiguous, we studied interface mixing of Fe/Si(100) bilayers, induced by 100keV 40Ar, 180keV 86Kr and 250keV 132Xe ions, either singly and multiply charged (Ar8+, Kr11+, Xe17+). No significant influence of the ionic charge-state was established for Kr and Xe ions; a slightly higher mixing rate was found for Ar8+ than for Ar1+ irradiation. [Copyright &y& Elsevier]

Silicide formation and ion beam mixing of Fe/Si bilayers due to Ar-, Xe- and Au-ion irradiations at room and liquid-nitrogen temperatures were investigated. For the study of silicide phase formation, the Fe/Si bilayers were irradiated with 100-keV Ar[SUP+], 250-keV Xe[SUP+], 700-keV Xe[SUP2+] or 400-keV Au[SUP+] ions at fluences of 1 × 10[SUP15] to 2 × 10[SUP16] ions/cm[SUP2]. The influence of the ion-charge state on the mixing process was studied in Fe/Si by 100-keV Ar[SUP8+]-ion implantation, in addition to the corresponding irradiations with singly charged ions at the same energy. Changes in the samples were analyzed by Rutherford backscattering spectroscopy, conversion electron Mössbauer spectroscopy, X-ray diffraction and atomic force microscopy. Pronounced structural changes and the intermixing of the components at the Fe/Si interfaces were measured as a function of the ion species, ion fluence and sample temperature. A linear correlation between the interface broadening and the fluence was observed for all the cases. Mössbauer analysis with enriched [SUP57]Fe layers revealed the onset of phase formation out of the solid solution. In order to interpret the mixing rates in this most general case, we considered mixing through thermal local or global spikes and compound formation. The highly charged Ar[SUP8+]-ion irradiation produced a higher athermal mixing rate compared to singly charged Ar[SUP+] ions, and this result could not be explained by the above models. [ABSTRACT FROM AUTHOR]

This study deals with structural and optical properties of β-FeSi2 layers produced by direct ion beam mixing of Fe/Si bilayers with Xe ions. By irradiation of 35 nm Fe on Si, at 600 °C with 205 keV Xe to 2×1016 ions/cm2, the formation of ∼105 nm single-phase β-FeSi2 layers was achieved. Their structures were analyzed by Rutherford backscattering spectroscopy, X-ray diffraction, conversion electron Mo¨ssbauer spectroscopy, high resolution transmission electron microscopy, and photo-absorption. The structural analyses revealed that the β-FeSi2 layers grow in the form of irregularly shaped crystal grains, with a pronounced surface morphology, but with a rather sharp silicide/silicon interface. The grains that originate from the interface are epitaxially oriented relative to the Si(100) substrate. Optical absorption, as compared with that in β-FeSi2 layers produced by ion beam synthesis or co-sputter deposition, indicates a direct band gap of 0.92 eV. A pronounced surface roughness of the ion beam mixed layers yielded photo-absorption approximately three times higher as compared with the other two sets of samples. The band gap stays nearly constant over the temperature range from 80 to 295 K. This is tentatively assigned to a high degree of structural disorder and stress induced in the ion beam mixed β-FeSi2 layers. [Copyright &y& Elsevier]

Ion beam mixing of Fe/Si bilayers, induced by 100 keV 40Arions at room temperature was investigated. Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for structural characterization. The main focus of this study was on the influence of the substrate structure on interface mixing. The influence of the substrate structure is due to the two classes of irradiated bilayers, Fe thin films deposited on crystalline or pre-amorphized Si substrates. An about 76% higher efficiency of atomic transport across the pre-amorphized Fe/a-Si interface as compared to that of Fe/c-Si bilayers was observed. [ABSTRACT FROM AUTHOR]

Abstract: Fluorinated ethylene propylene (FEP) and tetrafluoroethylene–perfluoro(alkoxy vinyl ether) (PFA) copolymer films were irradiated in vacuum with 60keV C4+ and N4+ ions to fluences ranging from 1.0×1012 to 5.0×1015 cm−2. Changes in optical and dielectric properties were analyzed by spectroscopic ellipsometry and ultraviolet–visible (UV–vis), Raman and dielectric relaxation spectroscopies. Direct and indirect energy band gap values were determined from the absorption edge in the 200–800nm region using Tauc''s relation. The values of the direct energy gap have been found to be greater than the corresponding values of the indirect energy gap. Significant changes in the index of refraction, and β and γ dielectric relaxations were observed in the case of N4+ irradiated FEP and PFA samples. [Copyright &y& Elsevier]

Abstract: The present study deals with CrN/Si bilayers irradiated at room temperature (RT) with 120keV Ar ions. The CrN layers were deposited by d.c. reactive sputtering on Si(100) wafers, at different nitrogen partial pressures (2×10−4, 3.5×10−4 and 5×10−4 mbar), to a total thickness of 240–280nm. The substrates were held at room temperature (RT) or 150°C during deposition. After deposition the CrN/Si bilayers were irradiated up to fluences of 1×1015 and 1×1016 ions/cm2. Structural characterization was performed with Rutherford backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM) and grazing angle X-ray diffraction (XRD). For the highest nitrogen pressure (5×10−4 mbar) a pure stoichiometric CrN phase was achieved. The results showed that Ar ion irradiation resulted in the variation of the lattice constants, micro-strain and mean grain size of the CrN layers. The observed microstructural changes are due to the formation of the high density damage region in the CrN thin film structure. [ABSTRACT FROM AUTHOR]

Abstract: Studies on ion-irradiated transition-metal/silicon bilayers demonstrate that interface mixing and silicide phase formation depend sensitively on the ion and film parameters, including the structure of the metal/Si interface. Thin Co layers e-gun evaporated to a thickness of 50nm on Si(100) wafers were bombarded at room temperature with 400-keV Xe+ ions at fluences of up to 3×1016 cm−2. We used either crystalline or pre-amorphized Si wafers the latter ones prepared by 1.0-keV Ar-ion implantation. The as-deposited or Xe-ion-irradiated samples were then isochronally annealed at temperatures up to 700°C. Changes of the bilayer structures induced by ion irradiation and/or annealing were investigated with RBS, XRD and HRTEM. The mixing rate for the Co/c-Si couples, Δσ 2/Φ =3.0(4)nm4, is higher than the value expected for ballistic mixing and about half the value typical for spike mixing. Mixing of pre-amorphized Si is much weaker relative to crystalline Si wafers, contrary to previous results obtained for Fe/Si bilayers. Annealing of irradiated samples produces very similar interdiffusion and phase formation patterns above 400°C as in the non-irradiated Co/Si bilayers: the phase evolution follows the sequence Co2Si→CoSi→CoSi2. [Copyright &y& Elsevier]

Abstract: We report a study of experimental possibilities to produce high purity stoichiometric SiO2 thin films by reactive ion beam sputtering. The films were deposited in a UHV chamber, 4×10−9 mbar, using a high purity silicon target and 1keV Ar+ ions for sputtering. The ion beam current was varied from 1.67 to 6.85mA, at a constant argon partial pressure of 1×10−3 mbar. Different values of the oxygen partial pressure (5×10−6–1×10−3 mbar) were applied for reactive deposition. The substrates were held at room temperature or at 550°C, and the films were deposited to 12.5–150nm, at 0.0018–0.035nms−1. Structural characterization was performed by Rutherford backscattering spectrometry (RBS), electron microprobe, X-ray diffraction (XRD) and Raman spectroscopy. The results show that reactive ion beam sputtering can be efficient for deposition of high quality silica films at 550°C, oxygen partial pressure of 2×10−4 mbar and ion beam current on the target from 5 to 5.5mA, or at a lower deposition rate, ion beam current of 1.67mA and oxygen partial pressure of 6×10−5 mbar. One aspect of these investigations was to study consumption of oxygen from the gas cylinder, which was found to be lower for higher deposition rates. [Copyright &y& Elsevier]

Thin Fe and Ta layers of 30–45 nm thickness, deposited via magnetron sputtering on Si (1 0 0) substrates, were bombarded at room temperature with 100 keV Ar1+ or Ar8+ or with 250 keV Xe1+ or Xe19+ ions in order to test the influence of the ion charge state on the surface sputtering and interface mixing. The samples were characterized by means of Rutherford backscattering at 0.9–3.0 MeV α-particle energy, time-of-flight elastic recoil detection analysis with a 53 MeV 127I10+ beam and atomic force microscopy. No influence of the charge state on the sputtering and athermal mixing rate was observed in the case of the Ta/Si system. However, in the case of the Fe/Si system, the ion charge was observed to have an influence on the mixing rate. [Copyright &y& Elsevier]