Carbon ion beam induced modifications of optical,structural and chemical properties in PADC and PET polymers

We report a study on the carbon ion beam induced modifications on optical, structural and chemical properties of polyallyl diglycol carbonate (PADC) commercially named as CR-39 and Polyethyleneterepthalate (PET) polymer films. These films were then irradiated by 55 MeV C⁵⁺ ion beam at various fluences ranging from 1×10¹¹ to 1×10¹³ ions/cm². The pristine as well as irradiated samples were subjected to UV–Visible spectral study (UV–Vis), Photoluminescence (PL), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. It has been found that ion irradiation may induce a sort of defects in the polymers due to chain scission and cross linking as observed from PL spectral study. It is revealed from UV–Vis spectra absorption edge shifted towards longer wavelength region after irradiation with increasing ion fluence. This shift clearly reflects decrease in optical band gap. The XRD study indicates the gradual decrease in intensity in case of PADC with increasing ion fluence. However, the intensity pattern increased in case of PET at fluence of 10¹¹ ion/cm² then decreased with further increase in fluence. Crystalline size of PADC was found to be decreasing gradually with increase of ion fluence. Whereas, the crystalline size of PET films found to increase with lower fluence and decreases with higher ion fluence. FTIR spectrum also shows the change in intensity of the typical bands after irradiation in the both the polymers. The results so obtained can be used successfully in heavy ions dosimetry using well reported techniques.     

Dielectric properties and surface morphology of swift heavy ion beam irradiated polycarbonate films

Swift heavy ion beam irradiation induces modification in the dielectric properties and surface morphologies of polycarbonate (PC) films. The PC films were irradiated by 55 MeV energy of C⁵⁺ beam at various ions fluences ranging from 1 × 10¹¹ to 1 × 10¹³ ions cm^?2. The dielectric properties (i.e., dielectric constant, dielectric loss, and AC conductivity) and surface morphologies of pristine and SHI beam irradiated PC films were investigated by dielectric measurements, atomic force microscopy (AFM), and optical microscopy. The dielectric measurements show that the dielectric constant, dielectric loss, and AC conductivity increase with ion fluences and temperature, however, the dielectric constant and AC conductivity decrease while dielectric loss increases with frequency. AFM shows the increase in average roughness values with ion fluences. The change of color in PC films has been observed from colorless to yellowish and then dark brown with increases of ion fluence by using optical microscopy.     

100 keV H+ ion irradiation of as‐deposited Al‐doped ZnO thin films: An interest in tailoring surface morphology for sensor applications

We report the influence of 100 keV H⁺ ion beam irradiation on the surface morphology, crystalline structure, and transport properties of as‐deposited Al‐doped ZnO (Al:ZnO) thin films. The films were deposited on silicon (Si) substrate by using DC sputtering technique. The ion irradiation was carried out at various fluences ranging from 1.0 × 10¹² to 3.0 × 10¹⁴ ions/cm². The virgin and ion‐irradiated films were characterized by X‐ray diffraction, Raman spectroscopy, atomic force microscopy, and Hall probe measurements. Using X‐ray diffraction spectra, 5 points Williamson‐Hall plots were drawn to deduce the crystallite site and strain in Al:ZnO films. The analysis of the measurements shows that the films are almost radiation resistant in the structural deformation under chosen irradiation conditions. With beam irradiation, the transport properties of the films are also preserved (do not vary orders of magnitude). However, the surface roughness and the crystallite size, which are crucial parameters of the ZnO film as a gas sensor, are at variation with the ion fluence. As ion fluence increases, the root‐mean‐square surface roughness oscillates and the surface undergoes for smoothening with irradiation at chosen highest fluence. The crystallite size decreases initially, increases for intermediate fluences, and drops almost to the value of the pristine film at highest fluence. In the paper, these interesting experimental results are discussed in correlations with ion‐matter interactions especially energy losses by the ion beam in the material.     

A comparison of modifications induced by Li<Superscript>3+</Superscript> and Ag<Superscript>8+</Superscript> ion beams irradiation in poly(lactide-<Emphasis Type="Italic">co</Emphasis>-glycolide) films

Poly(lactide-co-glycolide) (PLGA) films were irradiated by 180 MeV/amu Ag⁸⁺ ions and 50 MeV/amu Li³⁺ ions at different fluences of 5 × 10¹⁰, 5 × 10¹¹ and 1 × 10¹² ions/cm². Modifications of polymer films induced by the swift heavy ions (SHI) irradiation were studied by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and UV–Vis spectroscopy. The dominant effect of the SHI beam irradiation is proposed to be chain scission which leads to breakage of polymer chains, followed by hydrogen abstraction. The results from FTIR spectroscopy showed that the intensity of all peaks of the irradiated samples decreased at high fluence of SHI, suggesting PLGA samples significantly degraded at high SHI fluence. The variation in optical band gap energy and Urbach energy with increasing fluence was calculated from UV–Vis spectroscopy and explained in terms of changes occurring in the polymer matrix. X-ray diffraction patterns also show appreciable changes in PLGA at high fluence. FESEM results revealed that the hydrophilicity of the PLGA surface increased with an increase in ion fluence. In this paper the optical, chemical and structural changes with different fluence rates are discussed.     

Ion induced controlled modifications in structural and optical properties of indium oxide thin films – studies with 25‐keV Co− and N+ beam implantations

Two sets of indium oxide thin films (~150 nm) grown on quartz substrates using thermal evaporation technique were processed separately with 25‐keV Co^? and N⁺ ions with several fluences ranging from 1.0 × 10¹⁵ to 1.0 × 10¹⁶ ions/cm². The pristine and the ion implanted films were characterized by Rutherford backscattering spectroscopy (RBS), X‐ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–Vis spectrometry. The RBS spectra reveal signature of only cobalt and nitrogen in accordance to their fluences confirming absence of any contamination arising due to ion implantation. An increase in the average crystallite size (from 13.7 to 15.3 nm) of Co^? ions implanted films was confirmed by XRD. On the other hand, the films implanted with N⁺ ions showed a decrease in the average crystallite size from 20.1 to 13.7 nm. The XRD results were further verified by SEM micrographs. As seen in AFM images, the RMS surface roughness of the samples processed by both ion beams was found to decrease a bit (29.4 to 22.2 nm in Co^? implanted samples and 24.2 to 23.3 nm in N⁺ implanted samples) with increasing fluence. The Tauc's plot deduced from UV–visible spectroscopy showed that the band gap decreases from 3.54 to 3.27 eV in Co^? implanted films and increases from 3.38 to 3.58 eV for films implanted with N⁺ ions. The experimental results suggest that the modifications in structural and optical properties of indium oxide films can be controlled by optimizing the implantation conditions. Copyright © 2017 John Wiley & Sons, Ltd.     

Electrical and Optical Properties of O6+ Ion Beam–Irradiated Polymers

Variations in dielectric, optical, and structural properties of Lexan and Kapton-H irradiated to 80 MeV O⁶⁺ ion beam were analyzed at different fluences ranging from 10¹¹ to 10¹³ ions/cm² with a scanned beam current of 1 pnA. The structural modifications were characterized with the help of FT-IR and UV-vis spectroscopies. The electrical properties were investigated through capacitance and dielectric loss variations in ion-irradiated and pristine polymers at different frequencies. UV-vis absorption analysis indicates a decrease in the band gap energy in the two polymers. However, the decrease is much more prominent in Lexan (30%) than in Kapton-H (2.5%). The dielectric constant does not show appreciable variations after ion irradiation; however, a small increase has been noticed. An overall increase in the intensities of some typical bonds and stretching was observed in the FT-IR spectra of the pristine and ion-irradiated polymers.     

50 keV H+ ion beam irradiation of Al doped ZnO thin films: Studies of radiation stability for device applications

Thin films of Al doped ZnO (Al:ZnO) were deposited on two substrates (Si and glass) at room temperature and 300°C using DC magnetron sputtering. These films were bombarded with 50 keV H⁺ beam at several fluences. The pristine and ion beam irradiated films were analysed by X‐ray diffraction, Raman spectroscopy, scanning electron microscopy, and UV‐Vis spectroscopy. The X‐ray diffraction analysis, Hall measurements, Raman and UV‐Vis spectroscopy confirm that the structural and transport properties of Al:ZnO films do not change substantially with beam irradiation at chosen fluences. However, in comparison to film deposited at room temperature, the Al:ZnO thin film deposited at 300°C shows increased transmittance (from 70% to approximately 90%) with ion beam irradiation at highest fluence. The studies of surface morphology by scanning electron microscopy reveal that the ion irradiation yields smoothening of the films, which also increases with ion fluences. The films deposited at elevated temperature are smoother than those deposited at room temperature. In the paper, we discuss the interaction of 50 keV H⁺ ions with Al:ZnO films in terms of radiation stability in devices.     

Medium energy ion irradiation of Ge surface – search for a better understanding of the surface nano‐patterning

We report the morphological changes on Ge surfaces upon 50 keV Ar⁺ and 100 keV Kr⁺ beam irradiation at 60° angle of incidence. The Ge surfaces having three different amorphous–crystalline (a/c) interfaces achieved by the pre‐irradiation of 50 keV Ar⁺ beam at 0°, 30° and 60° with a constant fluence of 5 × 10¹⁶ ions/cm² were further processed by the same beam at higher fluences viz. 3 × 10¹⁷, 5 × 10¹⁷, 7 × 10¹⁷ and 9 × 10¹⁷ ions/cm² to understand the mechanism of nano‐scale surface patterning. The Kr⁺ beam irradiation was carried out only on three fresh Ge surfaces with ion fluences of 3 × 10¹⁷, 5 × 10¹⁷ and 9 × 10¹⁷ ions/cm² to compare the influence of projectile mass on surface patterning. Irrespective of the depth of a/c interface, the nanoscale surface patterning was completely missing on Ge surface with Ar⁺ beam irradiation. However, the surface patterning was evidenced upon Kr⁺ beam irradiation with similar ion fluences. The wavelength and the amplitude of the ripples were found to increase with increasing ion fluence. In the paper, the mass redistribution at a/c interface, the incompressible solid flow through amorphous layer, the angular distribution of sputtering/backscattering yields and the generation of non‐uniform stress across the amorphous layer are discussed, particularly in analogy with low energy experiments, to get better understanding of the mechanism of nanoscale surface patterning by the ion beams. Copyright © 2016 John Wiley & Sons, Ltd.     

Opto-structural characterization of proton (3 MeV) irradiated polycarbonate and polystyrene

Polycarbonate (Makrofol-N) and polystyrene thin films were irradiated with protons (3 MeV) under vacuum at room temperature with the fluence ranging from 1×10¹⁴ to 1×10¹⁵ protons cm⁻². The change in optical properties, degradation of the functional groups and crystallinity of the proton-irradiated polymers were investigated with UV–vis, Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) techniques, respectively. The UV–vis analysis revealed that the optical band gap of irradiated Makrofol-N is reduced by 30% as compared to 27.5% in polystyrene at highest fluence of 1×10¹⁵ protons cm⁻², owing to higher electronic energy loss of protons in Makrofol-N. The calculations of the number of carbon atoms per conjugation length, N and number of carbon atoms per clusters, M embedded in the network of polymers further revealed that Makrofol-N is more modified as compared to polystyrene on proton irradiation. FTIR results reveal the reduction in absorption intensity of the main characteristic bands of both the polymers after irradiation. The proton-irradiated Makrofol-N shows a strong decrease of almost all of its characteristic absorption bands at about 1×10¹⁴ protons cm⁻². Beyond a critical dose an increase of almost all its characteristic bands are noticed, however, no such effect had been observed in polystyrene at this particular fluence. Appearance of new –OH groups was observed at the higher fluences in the FTIR spectra of both proton-irradiated polymers. XRD measurements show the decrease of the main peak intensity and the crystallite size, confirming the increase of amorphization in polymers under irradiation.     

Investigation of O7+ swift heavy ion irradiation on molybdenum doped indium oxide thin films

Molybdenum (0.5 at%) doped indium oxide thin films deposited by spray pyrolysis technique were irradiated by 100 MeV O⁷⁺ ions with different fluences of 5×10¹¹, 1×10¹² and 1×10¹³ ions/cm². Intensity of (222) peak of the pristine film was decreased with increase in the ion fluence. Films irradiated with the maximum ion fluence of 1×10¹³ ions/cm² showed a fraction of amorphous nature. The surface microstructures on the surface of the film showed that increase in ion fluence decreases the grain size. Mobility of the pristine molybdenum doped indium oxide films was decreased from ～122 to 48 cm²/V s with increasing ion fluence. Among the irradiated films the film irradiated with the ion fluence of 5×10¹¹ ions/cm² showed relatively low resistivity of 6.7×10^?4 Ω cm with the mobility of 75 cm²/V s. The average transmittance of the as-deposited IMO film is decreased from 89% to 81% due to irradiation with the fluence of 5×10¹¹ ions/cm².     

Investigation of 500 keV Si ion induced surface structuring of Ni and Ti for enhancement of field emission properties

The present paper reports the investigation of surface morphology, elemental composition, phase changes and field emission properties of Si ion irradiated nickel (Ni) and titanium (Ti). The Ni and Ti targets have been irradiated with 500 keV Si ions generated by Pelletron accelerator at various fluences ranging from 6.9 × 10¹³ to 77.1 × 10¹³ ions/cm². Stopping range of ions in matter analysis revealed higher values of electronic stopping and sputtering yield for Ni as compared with Ti. For both irradiated metals, electronic energy loss dominant over the nuclear stopping. The growth of induced surface structures have been analysed by using field emission scanning electron microscopy (FESEM) analysis. In case of Ni, as the ion fluence increases from 6.9 × 10¹³ to 65.8 × 10¹³ ions/cm², the formation of spherical particulates, agglomers and sputtering is observed. Although in the case of Ti, with the increase of Si ion fluence from 11.6 × 10¹³ to 77.1 × 10¹³ ions/cm², the formation of irregular-shaped particulates along with crater and sputtered channels is observed. X-ray diffraction (XRD) analysis shows that no new phase is identified. However, a significant increase in peak intensity is observed with increasing ion fluence. The variation in crystallite size and dislocation line density is also observed as a function of Si ion fluence. Fourier transform infrared spectroscopy analysis shows that no bands are formed after the Si ion irradiation. Field emission properties of ion-structured Ni and Ti are well correlated with the growth of surface structures observed by SEM and dislocation line density evaluated by XRD analysis.     

Ion Beam Modification of Polymethyl methacrylate (PMMA) Polymer Matrix Filled with Organometallic Complex

A Nickel Dimethylglyoxime (Ni‐DMG) compound was dispersed in polymethyl methacrylate (PMMA) films at different concentrations. PMMA was synthesized by a solution polymerization technique. These films were irradiated with 120 MeV Ni¹⁰⁺ ions at the fluences of 1×10¹¹ and 1×10¹² ions/cm². The radiation induced changes in dielectric properties and average surface roughness were investigated by using an LCR meter in the frequency range 50 Hz to 10 MHz and atomic force microscopy (AFM), respectively. The electrical properties of irradiated films are found to increase with the fluence and also with the concentration of Ni‐DMG. From the analysis of frequency, f, dependence of dielectric constant, ?, it has been found that the dielectric response in both pristine and irradiated samples obey the Universal law given by ? α f ^n?1. The dielectric constant/loss is observed to change significantly due to the irradiation. This suggests that ion beam irradiation promotes (i) the metal to polymer bonding (ii) convert the polymeric structure in to hydrogen depleted carbon network due to the emission of hydrogen gas and/or other volatile gases. Atomic force microscopy (AFM) shows that the average surface roughness and surface morphology of irradiated films are observed to change.     

Medium energy,heavy and inert ion irradiation of metallic thin films: studies of surface nano‐structuring and metal burrowing

In context to the ion induced surface nanostructuring of metals and their burrowing in the substrates, we report the influence of Xe and Kr ion‐irradiation on Pt:Si and Ag:Si thin films of ~5‐nm thickness. For the irradiation of thin films, several ion energies (275 and 350 keV of Kr; 450 and 700 keV of Xe) were chosen to maintain a constant ratio of the nuclear energy loss to the electronic energy loss (S_n/S_e) in Pt and Ag films (five in present studies). The ion‐fluence was varied from 1.0 × 10¹⁵ to 1.0 × 10¹⁷ ions/cm². The irradiated films were characterized using Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The AFM and SEM images show ion beam induced systematic surface nano‐structuring of thin films. The surface nano‐structures evolve with the ion fluence. The RBS spectra show fluence dependent burrowing of Pt and Ag in Si upon the irradiation of both ion beams. At highest fluence, the depth of metal burrowing in Si for all irradiation conditions remains almost constant confirming the synergistic effect of energy losses by the ion beams. The RBS analysis also shows quite large sputtering of thin films bombarded with ion beams. The sputtering yield varied from 54% to 62% by irradiating the thin films with Xe and Kr ions of chosen energies at highest ion fluence. In the paper, we present the experimental results and discuss the ion induced surface nano‐structuring of Pt and Ag and their burrowing in Si. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of N5+ ion implantation on optical and gas sensing properties of WO3 films

In this paper we report the optical and gas sensing behaviours of tungsten oxide (WO₃) films, implanted with 45‐keV N^{5 +} ions of different fluences in the range 1 × 10¹⁵ to 1 × 10¹⁷ cm^–2. The film with fluence 1 × 10¹⁵ cm^–2 shows the most intense PL spectrum with two prominent peaks near UV and blue regions. The morphological changes because of ion implantation are also investigated by atomic force microscopy. Because of implantation the gas sensitivity of the film, in exposure of methane, is found to increase with reasonably fast response and recovery times. With the increase of the concentration of methane, the sensors show better result. Present work also includes the effect of N^{5 +} ion implantation on the structural property of WO₃ films. Copyright © 2015 John Wiley & Sons, Ltd.     

Dielectric and conductivity studies of 90 MeV O7+ ion irradiated poly(ethylene oxide)/montmorillonite based ion conductor

In the present work effect of 90 MeV O⁷⁺ ions with five different fluences on poly(ethylene oxide) (PEO)/Na⁺-montmorillonite (MMT) nanocomposites has been investigated. PEO/MMT nanocomposites were synthesized by solution intercalation technique. With the increase in irradiation fluence, gallery spacing of MMT increases in the composite and an exfoliated nanostructure is obtained at the fluence of 5?×?10¹² ions/cm² as revealed by X-ray diffraction results. Highest room temperature ionic conductivity of 4.2?×?10^?6?S?cm^?1 was found for the fluence 5?×?10¹² ions/cm², while the conductivity for unirradiated polymer electrolyte was found to be 7.5?×?10^-8?S?cm^?1. The increase in intercalation of PEO chains inside the galleries of MMT results in the increase in interaction between Na⁺ cation and oxygen heteroatom leading to the increase in ionic conductivity of the composites. Surface morphology and interactions among the various constituents in the nanocomposites at different fluence have been examined by scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. The appearance of peak for each fluence in the loss tangent suggests the presence of relaxing dipoles in the polymer nanocomposite electrolyte films. With the increase in ion fluence the peak shifts towards higher frequency side, suggesting decrease in the relaxation time.     

Ion implant-induced change in polyimide films monitored by variable energy positron annihilation spectroscopy

6FDA-pMDA polyimide membranes were implanted with 140 keV N⁺ ions to fluences between 2 × 10¹⁴ and 5 × 10¹⁵ cm⁻². Variable energy positron annihilation spectra were taken and spectral features compared to previously reported changes in gas permeability and permselectivity of these membranes as a function of ion fluence. Positron data corroborate the explanation of these changes in terms of molecular damage caused by the implant: for fluences up to about 1 × 10¹⁵ cm⁻², the concentration of irradiation-induced defects merely increases with implant fluence; while fluences exceeding this threshold value create a second type of positron annihilation site, thereby marking a distinct change in the structure of the polymer, which is responsible for the vast improvement of gas permselectivity data found at the same threshold fluence. PACS codes: 78.70.Bj—positron annihilation; 61.82.Pv—polymers, organic compounds; 61.72.Ww—doping and impurity implantation. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2413–2421, 1998     

Ion‐beam‐induced morphology on the surface of thin polymer films at low current density and high ion fluence

The effect of Xe⁺ bombardment on the surface morphology of four different polymers, polystyrene (PS), poly(phenylene oxide), polyisobutylene, and polydimethylsiloxane, was investigated in ion energy and fluence ranges of interest for secondary ion mass spectrometry depth‐profiling analysis. Atomic force microscopy (AFM) was applied to analyze the surface topography of pristine and irradiated polymers. AFM analyses of nonirradiated polymer films showed a feature‐free surface with different smoothness. We studied the influence of different Xe⁺ beam parameters, including the incidence angle, ion energy (660–4000 eV), current density (0.5 × 10² to 8.7 × 10² nA/cm²), and ion fluence (4 × 10¹⁴ to 2 × 10¹⁷ ion/cm²). Xe⁺ bombardment of PS with 3–4 keV at a high current density did not induce any change in the surface morphology. Similarly, for ion irradiation with lower energy, no surface morphology change was found with a current density higher than 2.6 × 10² nA/cm² and an ion fluence up to 4 × 10¹⁶ ion/cm². However, Xe⁺ irradiation with a lower current density and a higher ion fluence led to topography development for all of the polymers. The roughness of the polymer surface increased, and well‐defined patterns appeared. The surface roughness increased with ion irradiation fluence and with the decrease of the current density. A pattern orientation along the beam direction was visible for inclined incidence between 15° and 45° with respect to the surface normal. Orientation was not seen at normal incidence. The surface topography development could be explained on the basis of the balance between surface damage and sputtering induced by the primary ion beam and redeposition–adsorption from the gas phase. Time‐of‐flight secondary ion mass spectrometry analyses of irradiated PS showed strong surface modifications of the molecular structure and the presence of new material. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 314–325, 2001     

The Effect of O6+ and Si7+ ion beam irradiations on poly(lactide-co-glycolide) (50: 50) copolymer

Sterilization by ion beam radiations unfortunately also has a significant effect on the degradation of many polymers. The aim of present study is to examine the effect of heavy ion beam irradiation on poly(lactide-co-glycolide) (PLGA) (50: 50). The radiation effect is manifested through its degradation behavior and changes in the morphological, optical and structural properties. PLGA films are prepared by solvent casting method and subsequently irradiated with swift heavy ions O⁶⁺ and Si⁷⁺ ion with fluence in the range of 5 × 10¹⁰?1 × 10¹² ions/cm². The dominant effect on PLGA films is chain scission as evidenced by change in surface modification. Changes in optical and structural properties were analyzed by UV-Vis, XRD and FTIR spectrometric techniques. XRD technique is not responsive to degradation occurring in samples. Surface modifications caused by ion irradiations have been observed with SEM.     

Focused ion beam implantation of Ga in Si and Ge: fluence‐dependent retention and surface morphology

Focused ion beam implantation of 30‐keV Ga⁺ ions in single‐crystalline Si and Ge was investigated by SIMS, using Cs⁺ primary ions for sputtering. Nine different implantation fluences ranging from 1 × 10¹³ to 1 × 10¹⁷ Ga⁺‐ions/cm² were used, with implanted areas of 40 × 40 µm². The Ga concentration distributions of these implants were determined by SIMS depth profiling. Such 30‐keV Ga implantations were also simulated by a dynamic Monte‐Carlo code that takes into account the gradual change of the near‐surface composition due to the Ga incorporation. In both approaches, an essentially linear increase of the Ga peak concentrations with fluence is found up to ～1 × 10¹⁶cm^?2; for higher fluences, the Ga content approaches a saturation level which is reached at about (1–2) × 10¹⁷cm^?2. The measured and simulated peak concentrations of the Ga distributions are in good agreement. The most probable ranges obtained from the experiments correspond closely with the respective values from the simulations. The surface morphology caused by Ga⁺ implantation was investigated by atomic force microscopy (AFM). The AFM data indicate that for low fluences (<3 × 10¹⁵cm^?2) the surface within the implanted areas is growing outward (i.e. is swelling). For increasingly higher fluences, sputter‐induced erosion of the surface becomes dominant and distinct craters are formed for fluences above ～1 × 10¹⁶cm^?2. At the boundary of the implanted region a wall‐like structure is found to form upon Ga implantation; its height is growing with increasing fluence, reaching a value of ～15 nm at 1 × 10¹⁷ Ga⁺‐ions/cm². Copyright © 2008 John Wiley & Sons, Ltd.     

ESR study for ion beam induced phenomena in poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP)

Trapped radicals induced in poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP) were observed by X-band electron spin resonance (ESR) spectroscopy at room temperature (RT) under atmospheric field after an irradiation with various kinds of high energy ion beams (6 MeV/u). The irradiation was carried out to a stacked FEP films under vacuum (<4E?4 Pa) at RT with various fluences from 1.0×10⁹ to 1.0×10¹¹ ions/cm². All ESR spectra indicated an existence of peroxy radicals in each of the FEP films without any relation to a kind of ion and a penetration depth. Obtained depth profiles of radical concentrations induced with each ion beam almost correspond to those of stopping power. The trapped radical concentrations were strongly dependent on stopping power. It was found that G-value of trapped radicals by ion beam irradiation was decreased with increasing a stopping power, and was less than the case of gamma-rays irradiation.