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Abstract: Heavy-ion irradiation of ferromagnetic thin layers changes their micromagnetic and microstructural properties, due to the production of defects, relaxation or build-up of stress, or changes of grain size. When the ion range exceeds the layer thickness, ion mixing processes take place, leading to the formation of silicide phases. The present study deals with Co(30 or 55nm)/Si bilayers irradiated at room temperature with 100- or 200keV Xe ions to fluences of up to 15×1015/cm2. The Si(100) wafers were either crystalline or pre-amorphized by 1keV Ar+ implantation. Rutherford backscattering spectroscopy, in-plane magneto-optical Kerr effect, and X-ray diffraction served to analyse the samples before and after irradiation. The results will be compared with those obtained for other heavy-ions for Co/Si bilayers and in similar studies on Fe/Si bilayers. [Copyright &y& Elsevier]

Abstract: Ion-irradiation of ferromagnetic films induces pronounced changes of their microstructure and micromagnetism. The present study is devoted to the changes in the domain structure in 65–75nm electron-evaporated polycrystalline Ni films due to 200-keV Xe+ or 100-keV Ni+ implantation. For magnetic analysis, we combined magnetic force microscopy (MFM) and magneto-optical Kerr effect (MOKE); X-ray diffraction and Rutherford back-scattering spectroscopy served to characterize the microstructure of the films. After deposition, MFM indicated a pattern of magnetic ripples (with in-plane and perpendicular components of the magnetization). After ion irradiation, MOKE showed almost total in-plane remanence, and MFM confirmed the disappearance of the ripples at room temperature. The magnetic properties were correlated with the ion-induced changes in the strain in the as-deposited and ion-irradiated films. [Copyright &y& Elsevier]

Abstract: Ion implantation is a promising route for doping quartz with luminescent impurity atoms and growing photoactive nanoparticles of them. The present work focuses on cathodoluminescence (CL) and epitaxy during or after Na, Rb, Cs, Ge, and Ba ion implantation as well as Rb/Ge double implantation in crystalline α-quartz, under the conditions of dynamic, chemical or laser epitaxy. In addition to the known intrinsic sub-bands in the CL spectra, which have been associated with specific defects in the silica matrix, very intense blue or violet bands were found. They are correlated with the implanted ion species and follow their thermal behaviour. The quantum efficiency and possible origins of the blue/violet CL emission for various ions and processing treatments will be discussed. The case of double Rb/Ge implantation appears to be very promising with respect to a combination of a high CL output and full chemical epitaxy. [Copyright &y& Elsevier]

Abstract: [Co(7 nm)/Fe(7 nm)]6 multilayers were electron-beam evaporated onto Si(100) substrates in ultrahigh vacuum and irradiated at room temperature with 200-keV Xe ions, leading to ion beam mixing within the Co/Fe multilayer, but not with the Si substrate. Irradiation-induced changes in structural and magnetic properties were characterized by means of Rutherford backscattering spectroscopy, X-ray diffraction and in-plane magneto-optical Kerr effect. Irradiation with 1×1016 Xe ions/cm2 induced Co/Fe intermixing to a 1:1 atomic concentration ratio (RBS) and the formation of the Fe50Co50 permendur phase in the intermixed zone (XRD). For lower ion fluences, the coercivity decreased strongly, but then increased slowly for higher fluences. The angular pattern of the relative remanence showed a perfect uniaxial anisotropy. The magnetic energy density was parametrized with the expression E s / M s ∝(K u1 / M s) sin2(φ − φ 0)+(K u2 / M s) sin4(φ − φ 0), M s being the saturation magnetization and φ 0 the symmetry angle. The second-order term K u2 / M s was found to decrease strongly with increasing Xe fluence. [Copyright &y& Elsevier]

Abstract: We report on heavy-ion-induced modifications of 65–75nm thick Ni/Si bilayers in the regime of electronic stopping (350MeV 197Au26+-ions) and nuclear stopping (400keV Xe+-ions). The samples were analyzed by means of Rutherford back-scattering spectroscopy, X-ray diffraction and magneto-optical Kerr effect. For both types of ions, interface mixing was observed, correlated with full relaxation of the as-deposited stress and uniaxial magnetic anisotropy. For the higher fluences, full intermixing, rebuild-up of stress and loss in magnetic texture occurred. It can be concluded that for both types of ion beam stopping, interface mixing and changes of magnetization occur for similar reasons. [Copyright &y& Elsevier]

Abstract: We report here on changes in magnetism and microstructure when implanting, at 92 or 300K, up to 5×1015 Au26+-ionscm−2 of 350MeV into natFe(45nm)/57Fe(20nm)/Si trilayers. This choice of ions and energy allowed to test the irradiation effects in the regime of pure electronic stopping. The samples were analysed before and after irradiation by Rutherford back-scattering spectroscopy, X-ray diffraction, conversion electron Mössbauer spectroscopy, and magneto-optical Kerr effect. Up to 1×1015 ionscm−2, there was interface broadening at a mixing rate of Δσ 2/Φ =55(5)nm4, followed by full Fe–Si inter-diffusion. The Mössbauer spectra revealed fractions of α-Fe and amorphous ferromagnetic and paramagnetic iron silicides, but no crystalline Fe–Si phase. The magnetic remanence in the as-deposited Fe-layer showed small components of uniaxial and four-fold magnetization. For increasing ion fluence, the component with four-fold symmetry grew at the expense of the uniaxial component. For the highest fluences, an isotropic magnetization was found. [Copyright &y& Elsevier]

Abstract: Highly textured FeCo thin films have been prepared by pulsed laser deposition on Si(100) and MgO(100) single crystals. The influence of the microstructure on the magnetic properties has been studied using the magneto-optical Kerr effect and vibrating sample magnetometry. The in-plane coercivity of the films deposited on Si and MgO was 28Oe and 12Oe, respectively. A fourfold in-plane magnetic anisotropy has been observed for a film deposited on MgO(100), in contrast to the isotropic pattern of the film deposited on Si. The films have then been irradiated under an in-plane magnetic field of 104Oe by 40-keV Ne- and 200-keV Xe-ions, at a fluence of 1×1015 ions/cm2. For Xe-ions, the film deposited on Si(100) developed a twofold magnetic anisotropy, while the film on MgO exhibited only slight changes of the fourfold anisotropy. [Copyright &y& Elsevier]

Abstract: Modifications of Ni/Si and Fe/Si bilayers induced by swift heavy ions were studied in the regime of pure electronic stopping. Polycrystalline films, 65–75nm thick, were deposited via electron evaporation (Ni) or pulsed laser deposition (Fe) onto Si wafers and irradiated at ⩽300K with 350-MeV Au26+ ions to fluences of up to 5×1015 ions/cm2. The samples were analyzed by Rutherford backscattering spectroscopy, X-ray diffraction and the magneto-optical Kerr effect. In the Fe/Si samples, a 20nm 57Fe layer was interlayed between natFe and Si in order to monitor interface mixing and phase formation by means of Moessbauer spectroscopy. In both systems, a high mixing rate of ≈60nm4 was found, correlated with relaxation of the as-deposited stress and uniaxial magnetic anisotropy. At higher fluences, full interdiffusion gives rise to amorphous silicide phases, build-up of stress and loss of magnetic texture. [Copyright &y& Elsevier]

Abstract: Ion implantation used for doping quartz with photoactive impurity atoms amorphizes the matrix already at moderate fluences. Following our recent studies on dynamic, laser-induced or chemical epitaxy of ion-irradiated α-quartz, this paper focuses on the cathodoluminescence (CL) spectra obtained after Ge, Ba, Rb and double Rb/Ge ion implantation, under the conditions of dynamic or chemical epitaxy. In addition to “intrinsic” subbands in the CL-spectra, several blue and violet bands correlated with the particular implanted ion species were observed. In the case of Ba, nearly complete dynamic epitaxial growth was achieved, but not for Ge. In the case of Rb, full chemical epitaxy was obtained upon annealing in oxygen or air, but the CL output decreased above 1000K due to Rb outdiffusion. Double Rb/Ge implantation and annealing in air appears as a very promising novel route to achieve high CL light output and full recrystallization. [Copyright &y& Elsevier]

The neutron-deficient nucleus68As was populated at high spin in two experiments using the reaction40Ca(32S, 3pn) at beam energies of 105 and 95 MeV. A self-supporting and a gold-backed, highly enriched40Ca target were used. Gamma rays were detected with the EUROBALL array, combined with the charged-particle detector array EUCLIDES and the Neutron Wall. The68As level scheme was considerably extended, especially at negative parity and many previous spin-parity assignments were confirmed or rejected. The total-Routhian-surface (TRS) calculations find shape coexistence and ? softness for the negative- and positive-parity states, respectively. [ABSTRACT FROM AUTHOR]

Perturbed angular correlation of tracer nuclei is sensitive to the size and orientation of the hyperfine field(s) in ferromagnetic films. We report on PAC measurements for 111In nuclei in 75 nm Ni films irradiated with 200 keV Xe ions. In particular, we investigated the effects of magnetostriction when bending the samples and of the 111In tracer implantation itself. [Copyright &y& Elsevier]

Presents a study which examined the surface topology and nitrogen concentration profiles of iron irradiated with pulses of an excimer laser in a nitrogen atmosphere. Details on the experimental procedures used; Information on the experimental results of the study; Discussion on the simulation of the surface properties; Summary and conclusions drawn from the results of the study.

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]

We have applied the technique of direct laser synthesis to the hydrogen–titanium system. Large amounts of hydrogen are incorporated into the sample surface by laser irradiating the samples in a hydrogen atmosphere at elevated gas pressures. The process of “laser hydriding” leads to the formation of TiH2 and the amount of incorporated hydrogen was found to be independent of the hydrogen gas pressure. Similarities to the laser nitriding process are briefly discussed and the results are interpreted with the help of thermodynamic simulations of the laser–material interaction. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Reports on the solid-phase epitaxial growth of thin amorphous silicon oxide films deposited by electron gun evaporation in single-crystalline alpha-quartz substrates achieved by high-dose Cs(supra +)-ion implantation. Thin amorphous layer produced by silicon-ion implantation on alpha-quartz epitaxially regrown.

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]

We report on modifications of 280-nm thin polycrystalline CrN layers caused by vanadium ion implantation. The CrN layers were deposited at 150°C by d.c. reactive sputtering on Si(100) wafers and then implanted at room temperature with 80-keV V+ ions to fluences of 1×1017 and 2×1017 ions/cm2. Rutherford backscattering spectroscopy, cross-sectional transmission electron microscopy, and X-ray diffraction were used to characterize changes in the structural properties of the films. Their optical and electrical properties were analyzed by infrared spectroscopy in reflection mode and electrical resistivity measurements. CrN was found to keep its cubic structure under the conditions of vanadium ion implantation used here. The initially partially non-metallic CrN layer displays metallic character under implantation, which may be related to the possible formation of Cr1−x V x N. [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: 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]

Implanting photoactive ions into quartz or silica is a simple and efficient way to tune the luminescence light used for various optoelectronic applications. However, such ion implantation damages or even destroys the crystalline order in quartz. We report here on cathodoluminescence of α-quartz after 175 keV Rb-ion implantation and epitaxial growth when annealing the samples in air or 18 O 2. In the cathodoluminescence spectra taken at room temperature, five bands were identified. In addition to three intrinsic bands at 2.40, 2.79, and 4.30 eV, which are related to the quartz and/or silica matrix, two strong violet sub-bands at 3.25 and 3.65 eV were observed, which appear to be strongly correlated with the presence of alkali ions and/or the degree of epitaxy of the matrix. Their properties and origin are discussed in relation to similar bands observed after Ba, Ge, and Na ion implantation. [ABSTRACT FROM AUTHOR]

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]

The perturbed angular correlation technique was applied to study the electric field gradients of 111In/111Cd and 181Hf/181Ta radioactive probe atoms in the compounds Zr2Al and Zr3Al. In both matrices 181Hf/181Ta was found to substitute into the Zr sites. The 111In/111Cd probes were assigned to the unique Al site in the Zr2Al compound, while in the Zr3Al compound they were distributed between the unique Zr and Al positions of this lattice, with a clear preference for the Al site. The temperature dependences of the various quadrupole frequencies were measured in the temperature range from 20 to 1100 K. [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]

Bilayers of polycrystalline Co(37 nm)/Fe(37 nm) were deposited onto Si wafers via electron-gun evaporation and irradiated at room temperature with 200 kev Xe+ ions to fluences of 5 × 1014-1 × 1016/cm². The magneto-optical Kerr effect, Rutherford backscattering spectroscopy and x-ray diffraction were used to characterize the magnetization and microstructure of the films. Xe fluences of up to 5 × 1015 ions/cm² were found to induce a four-fold magnetic anisotropy in the originally isotropic films, as a consequence of the phase transformation of hexagonal Co to face-centered-cubic Co caused by ion irradiation. Xe fluences exceeding 7 × 1015 ions/cm² produced a uniaxial magnetic texture, which is explained by strong Co/Fe interface mixing and possibly ion-induced formation of CoFe grains at the interface. [ABSTRACT FROM AUTHOR]

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]

The migration of oxygen in ion-beam-amorphized c-SiO[sub 2] (α-quartz) was investigated by means of nuclear reaction analysis using the resonant reaction [sup 18]O(p,α)[sup 15]N for oxygen depth profiling. Only very small amounts of oxygen were observed to diffuse in crystalline or in Xe[sup +]-ion beam-amorphized α-quartz after high-temperature annealing. However, a dramatic migration of oxygen occurs in Cs[sup +]-implanted α-quartz in the same temperature range (600-900 °C), where Cs diffuses out of the amorphized layer and epitaxial recrystallization occurs. These results point out to a strong correlation of all these processes. A mechanism to explain the observed indiffusion of [sup 18]O is proposed and is related to the Cs migration and the topological modification to achieve epitaxial regrowth of the SiO[sub 2] matrix. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]