Swift heavy ion irradiation induced nanoparticle formation in CeO2 thin films

Nanoparticle formation in the, rf-sputtering grown, polycrystalline CeO₂ thin films is achieved by the swift heavy ion (SHI) irradiation. Crystal structure and phases present in the as-grown and irradiated thin films are investigated by the X-ray diffraction (XRD) measurements. Irradiation induced formation of spherically shaped nanostructures, on the film surface, is confirmed by the atomic force microscopy (AFM). The Raman spectra of the irradiated samples show increased line-width and peak position shifting in the Raman active mode (F_2g) of CeO₂, indicative of the nanocrystallization in the irradiated CeO₂ thin films. Formation of nanostructures in the irradiated samples is also briefly discussed in the light of ion energy and energy loss mechanisms.     

CrN films deposited by ion source-assisted magnetron sputtering

CrN coatings were deposited on Si(100) and piston rings by ion source assisted 40 kHz magnetron sputtering.Structure and composition of the coatings were characterized by X-ray diffraction,atomic force microscopy,scanning electron microscopy and transmission electron microscopy.Mechanical and tribological properties were assessed by microhardness and pin-on-disc testing.The ion source-assisted system has a deposition rate of 3.88 μm/h,against 2.2 μm/h without ion-source assistance.The CrN coatings prepared with ion source assistance exhibited an increase in microhardness(up to 16.3 GPa) and decrease in friction coefficient(down to 0.48) at the optimized cathode source-to-substrate distance.Under optimized conditions,CrN coatings were deposited on piston rings,with a thickness of 25 μm and hardness of 17.85 GPa.     

Ion irradiation effects on the optical properties of tungsten oxide films

The optical changes in amorphous WO₃ film prepared by reactive RF sputtering and irradiated by 200-800 keV oxygen ions were measured to study the relationship between coloration and energy deposition. The color centers were effectively created by ion irradiation with contributions from nuclear collisions and electronic energy loss. The increase in the absorption coefficient was reasonably explained by a first order reaction, whose production rate depended roughly on the total deposited energy. During heat treatment in air atmosphere, transmittance recovery started at 400 K and completed at 550 K. No significant difference was found among films irradiated by different incident energies; therefore indicating that the ion-induced damage structure is not strongly influenced by the type of energy loss.     

Effects of O swift heavy ion irradiation on indium oxide thin films

Indium oxide thin films deposited by spray pyrolysis were irradiated by 100 MeV O⁷⁺ ions with different fluences of 5 × 10¹¹, 1 × 10¹² and 1 × 10¹³ ions/cm². X-ray diffraction analysis confirmed the structure of indium oxide with cubic bixbyite. The strongest (2 2 2) orientation observed from the as-deposited films was shifted to (4 0 0) after irradiation. Furthermore, the intensity of the (4 0 0) orientation was decreased with increasing fluence together with an increase in (2 2 2) intensity. Films irradiated with maximum fluence exhibited an amorphous component. The mobility of the as-deposited indium oxide films was decreased from ∼78.9 to 43.0 cm²/V s, following irradiation. Films irradiated with a fluence of 5 × 10¹¹ ions/cm² showed a better combination of electrical properties, with a resistivity of 4.57 × 10⁻³ Ω cm, carrier concentration of 2.2 × 10¹⁹ cm⁻³ and mobility of 61.0 cm²/V s. The average transmittance obtained from the as-deposited films decreased from ∼81% to 72%, when irradiated with a fluence of 5 × 10¹¹ ions/cm². The surface microstructures confirmed that the irregularly shaped grains seen on the surface of the as-deposited films is modified as “radish-like” morphology when irradiated with a fluence of 5 × 10¹¹ ions/cm².     

Heavy ion irradiation effects in the rare-earth sesquioxide Dy2O3

Polycrystalline pellets of the rare-earth sesquioxide Dy₂O₃ with cubic C-type rare-earth structure were irradiated with 300 keV Kr²⁺ ions at fluences up to 5 × 10²⁰ Kr/m² at cryogenic temperature. Irradiation-induced microstructural evolution is characterized using grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). In previous work, we found a phase transformation from a cubic, C-type to a monoclinic, B-type (C2/m) rare-earth structure in Dy₂O₃ during Kr²⁺ ion irradiation at a fluence of less than 1 × 10²⁰ Kr/m². In this study, we find that the crystal structure of the top and middle regions of the implanted layer transform to a hexagonal, H-type (P6₃/mmc) rare-earth structure when the irradiation fluence is increased to 5 × 10²⁰ Kr/m²; the bottom of the implanted layer, on the other hand, remains in a monoclinic phase. The irradiation dose dependence of the C-to-B-to-H phase transformation observed in Dy₂O₃ appears to be closely related to the temperature and pressure dependence of the phases observed in the phase diagram. These transformations are also accompanied by a decrease in molecular volume (or density increase) of approximately 9% and 8%, respectively, which is an unusual radiation damage behavior.     

Swift heavy ion irradiation induced modification of the microstructure of NiO thin films

NiO nanoparticle films (200 nm thick) grown on Si substrates by pulsed laser deposition method were irradiated by 200 MeV Ag¹⁵⁺ ions. The films were characterized by glancing angle X-ray diffraction, atomic force microscopy and optical absorption spectroscopy. Though electronic energy loss of 200 MeV Ag ions in NiO matrix was higher than the threshold electronic energy loss for creation of columnar defects, films remained crystalline with the initial fcc structure even up to a fluence of 5 × 10¹³ ions cm⁻², where ion tracks are expected to overlap. Irradiation however modified the microstructure of the NiO films considerably. The grain size decreased with increasing ion fluence, which led to reduced surface roughness and increased optical band gap due to quantum confinement. These results correlate well with variation of the power spectral density exponent with ion fluence, which indicate that at high ion fluences, the evolution of surface morphology is governed by surface diffusion.     

Xenon-ion-induced and thermal mixing of Co/Si bilayers and their interplay

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 50 nm on Si(1 0 0) 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, Δσ²/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.     

Grain growth and crack formation in NiO thin films by swift heavy ion irradiation

NiO thin films grown on Si(1 0 0) substrates by electron beam evaporation and sintered at 700 °C, were irradiated by 120 MeV Au⁹⁺ ions. Though irradiation is known to induce lattice disorder and suppression of crystallinity, we observe grain growth at some fluences of irradiation. Associated with the growth of grains, the films develop cracks at a fluence of 3 × 10¹² ions cm⁻². The width of the cracks increased at higher fluences. Swift heavy ion irradiation induced atomic diffusion and strain relaxation in nanoparticle thin films, which are not in thermodynamic equilibrium, seem to be responsible for the observed grain growth. This phenomenon along with the tensile stress induced surface instability lead to crack formation in the NiO thin films.     

Study of 160 MeV Ni ion irradiation effects on electrodeposited polypyrrole films

Conducting polymer polypyrrole thin films doped with LiCF₃SO₃, [CH₃(CH₂)₃]₄NBF₄ and [CH₃(CH₂)₃]₄NPF₆ have been electrodeposited potentiodynamically on ITO coated glass substrate. The polymer films are irradiated with 160 MeV Ni¹²⁺ ions at three different fluences of 5 × 10¹⁰, 5 × 10¹¹ and 3 × 10¹² ions cm⁻². An increase in dc conductivity of polypyrrole films from 100 S/cm to 170 S/cm after irradiation with highest fluence is observed in four-probe measurement. X-ray diffractogram shows increase in the crystallinity of the polypyrrole films upon SHI irradiation, which goes on increasing with the increase in fluence. Absorption intensity increase in the higher wavelength region is observed in the UV–Vis spectra. The SEM studies show that the cauliflower like flaky microstructure of the surface of polypyrrole films turns globular upon SHI irradiation at fluence 5 × 10¹¹ ions cm⁻² and becomes smooth and dense at the highest fluence used. The cyclic voltammetry studies exhibit that the redox properties of the polypyrrole films do not change much on SHI irradiation.     

Impedance studies on high energy Li irradiated PZT thin films

The ferroelectric Pb(Zr_0.48Ti_0.52)O₃ (PZT) thin films prepared by the pulsed laser deposition technique were studied for their response to high energy lithium ion irradiation through impedance spectroscopy. The Debye peaks, observed in the impedance and modulus plots of irradiated films, shifts towards higher frequencies compared to those of unirradiated films. This is equivalent to the trend observed with increase in temperature in the unirradiated films due to the dielectric relaxation. The irradiated films showed a decrease in the grain resistance compared to the unirradiated films. The activation energy of dielectric relaxation increases from 1.25 eV of unirradiated film to 1.62 eV of irradiated film. The observed modifications in the irradiated film were ascribed to the modifications in the grain structure due to the high value of electronic energy loss.     

Influence of ion irradiation on internal residual stress in DLC films

The dependence of internal residual stress in thin diamond-like carbon films grown on Si substrate by PECVD technique on most important growth parameters, namely RF-power, DC bias voltage and substrate temperature, is described. Results show that compressive stress reaches the highest value of 2.7 GPa at low RF-power and DC bias. Increase of substrate temperature from 250 to 350 °C leads to nonlinear increase of stress value. Inhomogeneity of residual stress along the film surface disappears when film is deposited at temperatures above 275 °C. Post-growth film irradiation by P⁺ and In⁺ ions cause decrease of compressive stress followed by its inversion to tensile. For all ion energy combinations used residual stress changes linearly with normalized fluence up to 0.2 DPA with slope (8.7 ± 1.3) GPa/DPA.     

Radiation-induced luminescence of PET and PEN films under MeV ion and pulsed UV laser irradiation

Ion- and photo-induced luminescence of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) films was investigated during irradiation by MeV H and He ions and an ultraviolet pulsed laser. At the beginning of ion irradiation, the PEN film emitted blue luminescence, whose intensity was an order of magnitude higher than that emitted by the PET film. Successive ion irradiation effectively reduced the luminescence centers, and the rate of decease in luminescence intensity depended on the energy deposited along the trajectory of the ions. Optical absorption measurements in the infrared region revealed an irradiation-sensitive feature of the PEN film. Moreover, a photo-induced band grew remarkably at 470 nm in the PET film under 266 nm pulsed laser irradiation, while the PEN film showed a moderate decrease in luminescence intensity at 440 nm.     

Radiation damage effects in layered thin film MgO/HfO2 structures

In this report, we present a study of a thin film tri-layer structure, HfO₂/MgO/HfO₂, irradiated at room temperature with 10 MeV Au ions over a wide fluence range from 5 × 10¹³ to 3.7 × 10¹⁶ Au/cm². The tri-layer structure is a model representation for the microstructure in a composite dispersion nuclear fuel or waste form. Microstructural and chemical composition changes were examined by transmission and scanning transmission electron microscopy (TEM & STEM) combined with energy dispersive X-ray spectroscopy (EDXS), grazing incidence X-ray diffraction (GIXRD) and Rutherford backscattering spectroscopy (RBS) techniques. The microstructural evolution in the HfO₂/MgO/HfO₂ trilayer was similar to the radiation damage behavior of the individual HfO₂ and MgO constituents. For instance, we observed an absence of amorphization in both the MgO and HfO₂ layers and a phase transformation of HfO₂ from the monoclinic to the tetragonal HfO₂ polymorph. In addition, we observed the formation of void-type defects at one of the MgO/HfO₂ interfaces. Such voids are not characteristic to either bulk material (MgO or HfO₂) exposed to ion irradiation.     

Effects of ion irradiation on the mechanical properties of SiNawOxCyHz sol-gel derived thin films

A study of the effects of ion irradiation of hybrid organic/inorganic modified silicate thin films on their mechanical properties is presented. NaOH catalyzed SiNa_wO_xC_yH_z thin films were synthesized by sol-gel processing from tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto Si substrates. After drying at 300 °C, the films were irradiated with 125 keV H⁺ or 250 keV N²⁺ at fluences ranging from 1 × 10¹⁴ to 2.5 × 10¹⁶ ions/cm². Nanoindentation was used to characterize the films. Changes in hardness and reduced elastic modulus were examined as a function of ion fluence and irradiating species. The resulting increases in hardness and reduced elastic modulus are compared to similarly processed acid catalyzed silicate thin films.     

Ion beam induced formation of nanocrystalline silicon in pulsed laser deposited SiOX thin films

Synthesis and structural studies of nanocrystalline silicon grown in pulsed laser deposited SiO_X films is reported. The effect of high energy heavy ion beam irradiation on these films is studied using 100 MeV Ag ions. The structural studies were carried out using micro Raman spectroscopy, GAXRD, FTIR, TEM, HRTEM, SAED and EDX. The occurrence of phase separation in non-stoichiometric silicon oxide by means of ion beam irradiation leading to the formation of silicon nanocrystals in the films is confirmed by the results. HRTEM results reveal the structure of silicon phase formed after ion beam treatment and the particle size can be controlled up to 2-3 nm. A detailed analysis by micro Raman and HRTEM studies suggest the presence of crystallite size distribution. The results of GAXRD and SAED confirm the formation of cubic phase of silicon with two different lattice parameters. The studies conclude that the size of the nanocrystals can be controlled by varying deposition and ion irradiation parameters.     

Irradiation effects with 100 MeV Xe ions on optical properties of Al-doped ZnO films

Al-doped ZnO (AZO) films are known as n-type transparent semiconductors. We have investigated the effects of 100 MeV Xe ion irradiation on the optical and structural properties of AZO films, which were prepared on SiO₂ glass at 400 °C by using a RF-magnetron sputtering deposition method. We discuss relationships between these property modifications and the recent observations of the conductivity increase by ion irradiation. It is suggested that the band-gap modification has more close relation with the conductivity increase than the structural modification.     

Effects of ion irradiation on cobalt nanocomposite

The effects of ion irradiation of 3-dimensional arrays of Co nanoparticles were investigated. Arrays were obtained by electron beam deposition of 15 Co/SiO₂ bilayers 0.5 and 20 nm thick, respectively. The Co layers consist of Co nanoparticles 3.2 nm in diameter with a standard deviation of 16%. Irradiation was carried out using combinations of 150 kV Ar²⁺ and 90 kV Ar⁺ ion bombardments with a Ar⁺:Ar²⁺ fluence ratio of 1:4. The effects of ion irradiation were followed by Rutherford backscattering, measurements of hysteresis loops at 5 K and of temperature-dependent field-cooled (FC) and zero-field-cooled (ZFC) measurements of the magnetic susceptibility. A decrease of the peak temperature in the ZFC curve for displacements per atom (DPA) up to 1.1 was observed. Irradiation also induces progressively lower coercivity values. The Co particles showed a remarkable high resistance to ion irradiation, surviving damage up to 33 DPA.     

Effects of 160 MeV Ni ion irradiation on polypyrrole conducting polymer electrode materials for all polymer redox supercapacitor

Electronically conducting polymers are suitable electrode materials for high performance supercapacitors, for their high specific capacitance and high dc conductivity in the charged state. Supercapacitors and batteries are energy storage and conversion systems which satisfies the requirements of high specific power and energy in a complementary way. Ion beam {energy > 1 MeV} irradiation on the polymer is a novel technique to enhance or alter the properties like conductivity, density, chain length and solubility.

Conducting polymer polypyrrole thin films doped with LiClO₄ are synthesized electrochemically on ITO coated glass substrate and are irradiated with 160 MeV Ni¹²⁺ ions at different fluence 5 × 10¹⁰, 5 × 10¹¹ and 3 × 10¹² ions cm⁻². Dc conductivity measurement of the irradiated films showed 50–60% increase in conductivity which is may be due to increase of carrier concentration in the polymer film as observed in UV–Vis spectroscopy and other effects like cross-linking of polymer chain, bond breaking and creation of defects sites. X-ray diffractogram study shows that the degree of crystallinity of polypyrrole increases in SHI irradiation and is proportionate to ion fluence. The capacitance of the irradiated films is lowered but the capacitance of the supercapacitors with irradiated films showed enhanced stability compared to the devices with unirradiated films while characterized for cycle life up to 10,000 cycles.     

Pb离子辐照注碳a-SiO2薄膜的光致发光性能

用湿氧化法在单晶硅表面生长了非晶态SiO2薄膜,进行120 keV C离子注入和950 MeV Pb离子辐照,用荧光光谱分析样品发光特性的改变.结果发现,C离子注入和高能Pb离子辐照均能显著影响样品的发光特性,且荧光光谱的改变强烈依赖于注入和辐照剂量,预示不同注入和辐照剂量将导致不同的发光结构形成.对注入和辐照造成薄膜...     

Effect of swift heavy ion irradiation on structural, optical and electrical properties of Cd2SnO4 thin films

Transparent conducting cadmium stannate thin films were prepared by spray pyrolysis method on Corning substrate at a temperature of 525 °C. The prepared films are irradiated using 120 MeV swift Ag⁹⁺ ions for the fluence in the range 1 × 10¹² to 1 × 10¹³ ions cm⁻² and the structural, optical and electrical properties were studied. The intensity of the film decreases with increasing ion fluence and amorphization takes place at higher fluence (1 × 10¹³ ions cm⁻²). The transmittance of the films decreases with increasing ion fluence and also the band gap value decreases with increasing ion fluence. The resistivity of the film increased from 2.66 × 10⁻³ Ω cm (pristine) to 5.57 × 10⁻³ Ω cm for the film irradiated with 1 × 10¹³ ions cm⁻². The mobility of the film decreased from 31 to 12 cm²/V s for the film irradiated with the fluence of 1 × 10¹³ ions cm⁻².