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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]

Abstract: Even at low fluences doping of quartz by ion implantation results in amorphization. Here we report on the measurement of cathodoluminescence and surface structures during solid phase epitaxy in Na-implanted α-quartz annealed in 18O2 atmosphere. Complete epitaxy was achieved under appropriate conditions of ion fluence, annealing temperature and time. The crystalline structure of the samples was studied by Rutherford backscattering channelling spectroscopy and the 18O–16O exchange between the matrix and 18O2 annealing gas by elastic recoil detection analysis. In the cathodoluminescence spectra taken at room temperature, five bands were identified and assigned to various defect centres. Two of the bands in the violet region at 3.25 and 3.65eV strongly vary in intensity at 843–1173K annealing temperature and appear to be intimately correlated with the presence of Na-ions in the implanted region of the matrix. Finally, atomic force microscopy enabled, for the first time, the observation of the correlation of surface structures and epitaxy. [Copyright &y& Elsevier]

Abstract: The luminescence properties of ion-beam doped silica and quartz sensitively depend on the ion species and fluence and the thermal processing during or after ion implantation. While no epitaxy, but a high cathodoluminescence (CL) output can be reached after dynamic Ge-ion implantation in quartz, full planar epitaxy is achieved after alkali-ion implantation (Na, Rb, Cs) under appropriate ion and annealing conditions. Now for the first time we achieved high luminescence intensity and (partial) recrystallization of α-quartz by double Ge/Rb-ion implantation. Pure synthetic α-quartz samples were irradiated with 175keV Rb-ions and subsequently with 120keV Ge-ions and post-annealed at 1170K in vacuo, air or 18O2 gas. A comparative analysis of the epitaxy (via RBS-Channeling) and cathodoluminescence was carried out, the latter showing three dominant emission bands in the blue/violet region at 2.95, 3.25 and 3.53eV, which were assigned to Rb- or Ge-implantation. For increasing CL temperature, a shift of the predominant peak from 2.95 to 3.25eV was noted after air-annealing, accompanying partial chemical epitaxy. [Copyright &y& Elsevier]

Abstract: Ion implantation and recrystallization of quartz may be a very important process for photonic applications. We have investigated how laser irradiation can be used to epitaxially recrystallize layers of α-quartz, which were amorphized by 175keV Rb+ or 250keV Cs+ ion implantation at a fluence of 2.5×1016 cm−2. The samples were irradiated with pulses of a XeCl excimer laser (wavelength 308nm, pulse length 55ns, energy density 3.2–5J/cm2). The thickness of the amorphous layer and the quality of the recrystallized layer were analyzed by Rutherford Backscattering Channeling Spectroscopy. Partial epitaxial recrystallization was found for all laser-irradiated samples that proceeded faster for higher laser energy density, however no full epitaxy was achieved up to the maximum laser energy of 5J/cm2. The degree of epitaxy was more or less the same for 20 or 200 laser shots. [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]

In order to investigate the swift heavy-ion-induced mixing of nitride coatings we have irradiated Ni3N films on SiO2-, Si3N4-, SiC- and Si-substrates with Ar, Kr, Xe and Au ions of energies ranging from 90 to 350 MeV, for which electronic energy loss dominates. The Ni-concentration profiles at the interfaces before and after irradiation were determined by means of Rutherford backscattering spectrometry with 900 keV He2+ ions. In all the cases, strong mixing occurred as soon as a material-dependent threshold Sec in the electronic stopping power Se was exceeded. The mixing rate exhibits a squared scaling k=Δσ2/Φ=η2 (Se−Sec)2 and estimation of the effective diffusion constant indicates interdiffusion in molten ion tracks. The threshold value Sec depends on the substrate material and seems to be determined by its melting point and specific heat. [Copyright &y& Elsevier]

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]

Rectangular 75 nm thick Co films were irradiated with 200 keV Xe-ions, to fluences of 2.5×1013–8×1015 ions/cm2. The film thickness and the implanted Xe profiles, the phase structure and ion-induced lattice dilations as well as the magnetic hysteresis patterns were measured. For lower fluences up to 4×1014 Xe/cm2, we found predominantly the HCP phase with an in-plane magnetization. The transition to the four-fold in-plane magnetization typical of the FCC phase occurred at a fluence range between 4×1014/cm2 and 2×1015/cm2. [Copyright &y& Elsevier]

Highlights: [•] Silicide phases formation in Co/Si system during annealing was investigated. [•] Thin Co films were deposited on crystalline or pre-amorphized Si wafers. [•] Argon ions generate damage region which represents diffusion barrier. [•] The phase sequence depends on the concentration of the reacting species. [•] The observed phase transitions are consistent with predictions of EHF model. [ABSTRACT FROM AUTHOR]

Abstract: Polycrystalline titanium nitride (TiN) layers of 240nm thickness and columnar microstructure were deposited at 150°C by d.c. reactive sputtering on Si(100) wafers and then irradiated at room temperature with either 80keV V+ ions (at fluences of up to 2×1017 ions/cm2) or 200keV Ar+ ions (at fluences of 5×1015–2×1016 ions/cm2). Rutherford backscattering spectroscopy, cross-sectional (high-resolution) transmission electron microscopy and X-ray diffraction were used to characterize ion-induced changes in the structural properties of the films. Their optical and electric properties were analyzed by infrared reflectance (IR) and electric resistivity measurements. After deposition, the stoichiometric TiN films had a (111) texture. Ion implantation generated a damaged surface layer of nanocrystalline structure, which extended beyond the implantation profile, but left an undamaged bottom zone of (111) orientation. This layer geometry determined from transmission electron microscopy was inferred in the analysis of IR reflectance data using the Drude model, and the variation of the electric and optical resistivity with the irradiation was deduced. The results were compared to those recently gained for ion-implanted reactively sputtered chromium nitride films. [Copyright &y& Elsevier]

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: Ion implantation is a promising route for doping quartz with luminescent impurity atoms and nanoparticles at moderate fluences. The present work focuses on the comparison of epitaxy and cathodoluminescence (CL) after Ba, Ge, Na and Rb ion implantation as well as Rb/Ge double implantation in α-quartz, under the conditions of either dynamic or chemical epitaxy. In addition to the known intrinsic sub-bands in the CL spectra, due to the silica matrix or electron irradiation, we were able to line up several new blue or violet bands with the implanted ion species and follow their thermal behaviour. In the case of Na and Rb ions, complete chemical epitaxy has been achieved, but only rather weak CL output. For Ba ions, almost complete dynamic epitaxy and fairly high CL efficiency have been realized, but no epitaxy for Ge implantation. The case of dual Rb/Ge ion implantation appears as the most promising route to gain a high CL light output and full epitaxy. [Copyright &y& Elsevier]

Abstract: In the course of a systematic investigation of dynamic, chemical, and laser-induced solid phase epitaxy of α-quartz after ion implantation, we have studied epitaxy and cathodoluminescence emission after 250keV Cs-ion implantation and subsequent pulsed excimer laser treatment in air. Rutherford backscattering channelling analysis showed partial epitaxy for all the laser-irradiated samples; however, no full epitaxy was achieved. The optical properties of these samples were analyzed using cathodoluminescence spectroscopy, giving evidence of five emission bands at 2.42, 2.79, 3.25, 3.65, and 4.30eV photon energy. Their intensity relation to the laser power and retained Cs-ion fraction are discussed and the present results will be compared with those obtained after chemical and dynamic epitaxy of quartz after alkali-ion, Ge, and Ba implantation. [Copyright &y& Elsevier]

Abstract: ZrPt intermetallic compound was studied by perturbed angular correlation (PAC) method. The hyperfine interaction parameters and their temperature dependences for 181Hf/181Ta and 111In/111Cd radioactive probes were determined. An unusual temperature dependence of hyperfine interaction parameters for 181Ta probe atoms points to the appearance of a monoclinic variant of CrB-type phase below 573K and confirms the existence of the orthorhombic Bf-type phase at temperatures up to 1023K. [Copyright &y& Elsevier]

The intermetallic compound TiPd2 has been investigated with the perturbed angular correlation technique using radioactive 181Hf/181Ta and 111In/111Cd probes. The measurements confirmed an orthorhombic distortion of the C11b structure in the temperature range from 24 to 1023 K. However, the temperature dependence of the 111Cd quadrupole parameters demonstrated that above 650 K the indium ions reach the lattice site of high symmetry characterized by an axially symmetric electric field gradient (EFG). The situation for the 181Hf/181Ta probes is more complex: we observed two electric field gradients, whose fractions interchange near 700 K, possibly due to 181Hf probes switching their positions but still occupying a low-symmetry site. [Copyright &y& Elsevier]

In the course of a systematic investigation of heavy ion-irradiated Fe/Si layers, we have studied atomic transport and phase formation induced by 22-keV14N2+ ion implantation in57Fe(30 nm)/Si bilayers at high fluences. We report here results obtained by Rutherford backscattering spectroscopy, X-ray diffraction, and conversion electron Mössbauer spectroscopy after implantation and post-implantation annealing treatments. The irradiations caused little sputtering, but significant interface mixing. During implantation, iron nitrides, but no silicides were formed, even at the highest nitrogen fluence of 2×1017 ions/cm2. When heating these samples in vacuo up to 700 °C, the iron-rich phases e-Fe3N and ?'-Fe4N were produced. Starting at 600 °C the silicide phase ß-FeSi2 was also identified. [ABSTRACT FROM AUTHOR]

This article reports on the formation of iron nitrides during nitrogen ion irradiation of Fe/Si bilayers at room temperature. The 30 nm 57Fe/Si bilayers were prepared by pulsed laser ablation and irradiated with 22 keV N2+ ions at fluences of (0.6–2)×1017 ions/cm2. The structural changes and phases formed by irradiation were analyzed by Rutherford backscattering spectroscopy (RBS), X-ray diffraction analysis (XRD) and conversion electron Mössbauer spectroscopy (CEMS). The results clearly show the formation of several iron nitrides. At the lower fluences, the samples contain a mixture of #x03B5;-Fe2+x N and α-Fe with nitrogen interstitials. For the highest fluence, the paramagnetic #x03B5;-Fe2 N (61%) phase predominated. It can be concluded that the elemental iron almost fully transforms to an iron–nitride layer, but that no iron silicides are formed. [Copyright &y& Elsevier]

LixIn2S3 was electrochemically prepared with different small amounts x of lithium (0⩽x⩽0.13) in order to maintain the initial crystallographic structure of the thiospinel In2S3. About 1012 radioactive 111In ions have been implanted into these samples at 400 keV to perform PAC experiments in the temperature range from 10 to 773 K. The results are compared to previous experiments with undoped In2S3 samples. According to the structure of In2S3 in the β-phase, which belongs to the I41/amd space group having a unit cell with 32 In and 48 S atoms and the cell parameters α=7.61 A˚ and c=32.28 A˚, three different electric field gradients were observed. Within two different temperature ranges dynamical EFGs occur, which are clearly influenced by the insertion of Lithium. The strong dependence of one EFG on the Li concentration x can be correlated to the effective charge of the In ions. This correlation is discussed with respect to XRD analyses of the LixIn2S3 samples and to XANES measurements on a similar sample. [Copyright &y& Elsevier]

Crystalline and ion-beam-amorphized silicon samples were irradiated with a pulsed nanosecond excimer laser in a pure hydrogen atmosphere. The hydrogen concentration was determined via the [SUP1] H([SUP15]N,αβ)[SUP12]C nuclear reaction. In the case of crystalline silicon, hydrogen incorporation into the sample surface was found to be well above the hydrogen solubility limit at thermodynamic equilibrium. The hydrogen depth profiles perfectly matched the damage profiles measured via Rutherford backscattering channeling spectroscopy. For the preamorphized silicon samples, the laser treatment resulted in epitaxial recrystallization of the amorphous top layer, but the hydrogen uptake was found to be negligible in that case. The experimental data were compared with the results of thermodynamic simulations of the laser-gas-material interaction. [ABSTRACT FROM AUTHOR]

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]

The hyperfine quadrupole interaction parameters and their temperature dependences for 181Hf/181Ta and for 111In/111Cd probes in the polycrystalline HfAl and ZrAl isostructural compounds were determined. Strong preference of 111In solute for the Zr2Al3 phase occurring as a contamination fraction in ZrAl sample was observed. [Copyright &y& Elsevier]

MINIBALL a highly efficient, position sensitive γ-spectrometer is under construction for upcoming radioactive-beam experiments. In contrast to high spin arrays the total full energy peak efficiency and not the resolving power is optimized with a factor of two larger efficiency for γ-ray energies up to 10 MeV and for low to medium γ-ray multiplicity events. Cluster detectors, incorporating three or four Ge crystals, will be employed to provide high flexibility and to accomodate the various demands of the experiments. [Copyright &y& Elsevier]

Using perturbed angular correlation (PAC) spectroscopy and 181Hf/181Ta and 111In/111Cd radioactive probes, the electric field gradients (EFGs) in the ZrAl2 and HfAl2 Laves phases were measured in the temperature range 20–1100 K. In both matrices, 181Hf was found to substitute at the unique Hf/Zr site. In the ZrAl2 compound, the 111In probes were assigned to the two Al sites. The relative fractions of the corresponding EFGs indicate a strong preference of these impurities in favor of the 2(a) Al site over the 6(h) Al site. In the HfAl2 compound, the 111In impurities substitute for Hf up to 370 K and reach the Al sites only above 420 K. In both compounds and for both radioactive probes, the temperature dependence of the quadrupole interaction frequencies was measured. It is interesting to note that, for 181Ta in both compounds, they increase with temperature. [Copyright &y& Elsevier]

We report on the first measurements carried out with the new accelerator facility MaRPel (Materials Research Pelletron) in Go¨ttingen. Samples of pure tantalum were irradiated with a pulsed nanosecond excimer laser in the UV wavelength range in a nitrogen atmosphere. The laser-nitrided tantalum samples were perfectly suited for testing a low-level set-up for resonant nuclear reactions analysis. The samples also allowed for a recalibration of the mass separator magnet, which was necessary after moving the 3 MV NEC-Pelletron from the Max Planck Institut fu¨r Kernphysik in Heidelberg to the University of Go¨ttingen. In addition, it is shown that the low-level set-up allows high resolution hydrogen depth profiling. [Copyright &y& Elsevier]

Surface coatings and thin films can be easily produced by irradiation of materials with short laser pulses in (reactive) gas atmospheres, e.g. nitrided iron and steel or AlN films on Al and its alloys by irradiation with an excimer laser in nitrogen atmosphere. For these treatments, various lasers with different wavelengths and time structures can be used. In addition to the experiments with excimer laser (pulse duration: 55 ns; wavelength: 308 nm), also the results of irradiations with Nd:YAG laser (pulse duration: 8 ns; wavelength: 1060 nm), free electron laser (FEL) (pulse duration: 2 ps; wavelength: 3 μm) and Ti:sapphire laser (pulse duration: 150 fs; wavelength: 750 nm) will be presented. The pulse duration varies from nanoseconds to femtoseconds and thus includes different laser interaction regimes. The results of the surface modifications and coating formation for the irradiation of different types of materials (Fe, Al, Si, and Ti) in pure nitrogen atmosphere will be presented. [Copyright &y& Elsevier]

Abstract: Cathodoluminescence measurements were performed on swift heavy ion irradiated and annealed Au/SiO2/p-Si structures. 5 nm thick Au film was deposited on 500 nm SiO2 thermally grown on [100] oriented p-type Si wafers. The Au/SiO2/p-Si structures were irradiated using 350 MeV Au ions at fluences of 1–4×1013 cm−2 and annealed in vacuum at 1050 K for 8 h. The structures were characterised via Rutherford backscattering spectrometry and CL before and after annealing. The CL spectra mainly consist of an ultraviolet peak (4.3 eV) arising from Neutral Oxygen Vacancies (NOVs) and a blue-violet peak (2.7 eV) due to E′ centres as well as NOVs, both of which are oxygen-deficient centres. It is concluded that swift heavy ion irradiations create E′ centres in SiO2 and annealing transforms E′ centres into NOVs. As NOVs are thought to be precursors to the formation of Si-nanoclusters (Si-nc), the present study leads to the knowledge of a possible synthesis route to form Si-nc. [Copyright &y& Elsevier]

Abstract: Swift heavy ions are used to study the effects of electronic energy loss on Cu cluster formation in fused silica after post-irradiation annealing. Fused silica substrates covered with 10nm thin Cu-films were irradiated using beams of either 120MeV Ag9+ ions or 350MeV Au26+ ions at fluences ranging from 2×1013 to 1×1014 cm−2. After irradiation, the samples were annealed for 30min in argon, at temperatures of 773–1200K and characterized by UV–VIS absorption spectroscopy. The swift ion irradiations created E′ and B2 defects in silica, which were partially eliminated during annealing. In addition, Cu cluster formation in silica was observed after annealing. Irradiation fluences exceeding 4×1013 cm−2 and annealing temperatures above 1100K are more effective in forming larger nanoclusters. [Copyright &y& Elsevier]

Solid phase epitaxial regrowth of α-quartz amorphized by ion implantation of dopants appears to be an attractive method for processing this optoelectronically important material. In an attempt to optimize solid phase epitaxy of α-quartz, we have studied the case of 50 keV 23Na ion implantation and annealing in an 18O atmosphere at 500–850 °C. The damage profiles were monitored by means of Rutherford backscattering-channeling, while the out-diffusion of the implanted 23Na and the 16O⇔18O exchange in the near-surface layers were investigated using the time-of-flight Elastic Recoil Detection analysis technique. As in the case of Cs-irradiated quartz, full epitaxial recrystallization was observed to occur for Na-irradiated quartz, however, at the lower temperature of approximately 650 °C (vs. 875 °C for Cs). Based on these observations, Na appears to offer a good compromise between a low recrystallization temperature (required to avoid oxidation of the dopants) and full recrystallization of the matrix. [Copyright &y& Elsevier]

Abstract: Hysteresis and coercivity in ferromagnetic thin films strongly depend on the extent of the domain nucleation and wall motion. Ion irradiation can affect both the number of domain walls existing for a given field history and their mobility. To address these factors, we present a micromagnetic study of magnetisation reversal for non-irradiated and Xe-irradiated 185nm Ni films at 8.3K. It is shown that irradiation facilitates reversal domain nucleation and increases the number of pinning centres at least 10-fold, although this does not augment hysteresis. In field magnetic force microscopy (MFM) reveals this to be due to a domain size no larger than the average distance between pinning centres. [Copyright &y& Elsevier]