High energy ion beam irradiation of polymers for electronic applications (original) (raw)
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1991
The keV-MeV ion irradiation of polymers produces deep changes in their physical and chemical properties associated with the breaking and rearrangement of original bonds. The modification of chain structure occurs within a well defined ion fluence range which depends on the ion linear energy transfer as well as on the target parameters. At low ion fluences (≈1014 ions/cm2) crosslinks between chains and chain-scissions are detected with a chemical yield in the range 0.05–0.3, depending on the ion mass. With increasing ion fluence (1015 ions/cm 2) the original polymer structure is heavily modified and the irradiated films exhibit properties close to those of hydrogenated amorphous carbon. At very high fluences (≈1016 ions/cm 2) graphitization of the material occurs.
HEAVY ION TRACKS IN POLYMERS AND THEIR APPLICATIONS
Heavy ion tracks in polymers offers a tremendous number of interesting applications in various fields of science and technology. The ion track filters produced by these irradiated polymers have advantage over conventional filters due to its simplicity, small geometry, permanent maintenance of the nuclear records and well-defined pore size. We report here some applications of ion track filters, in micro hydro dynamical flow studies, conduction of bacteria and blood cells, development of metal and metal–semiconductor microstructures and nanostructures. These micro/ nano wires have huge potential for their use as biosensors, field emission studies etc. Nano wires based sensors can detect diseases in blood samples.
Ion irradiation induced chemical changes of polymers used for optical applications
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1997
Polymers are a class of materials widely used in different fields of applications. In the field of optical telecommunication, polymers are discussed as a new class of materials for the fabrication of passive optical devices. Ion irradiation is a promising method to generate structures with a modified index of refraction, which is necessary for the guidance of light with different wavelengths in an optical device. The behaviour of different polymers which fulfil the requirements of high transparency has been studied during and after ion irradiation. Mass spectroscopy measurements of the reaction products outgassing during ion irradiation were performed as well as infrared (IR) measurements after irradiation. Ion induced chemical changes will be discussed in relation to modified macroscopic properties such as the index of refraction.
Infrared analysis of ion beam irradiated polymers
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2009
Irradiation with heavy ions can produce several modifications in the chain structure of polymers. These modifications can be related to scissioning and cross-linking of chemical bonds, which depend on the ion fluence and the density of energy deposited in the material. Stacked thin film Makrofol-KG Ò samples were irradiated with 350 MeV Au 26+ ions and FTIR absorption spectroscopy was used to determine the bond changes in the samples. Data on the absorption bands as a function of the fluence indicated a higher probability for simple-bonds scissioning than for double-bonds scissioning and no dependence on the number of double bonds breaking with ion fluence. Since sample irradiation was done in a non-trackoverlapping regime, a novel process for double bonds formation is suggested: the excitation of a site in the material by only one incident ion followed by a double bond formation during the de-excitation process.
Ion beam effects in polymer films: Structure evolution of the implanted layer
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1997
Thin films of polyethylene, polyamide-6 and cellulose implanted with 100 keV B+, Nf and Sb+ ions to the fluences of 10'3-10'7 cmv2 were investigated using RBS and NDP techniques as well as IR, UV-visible and EPR spectroscopies. The peculiarities of the depth distribution of implanted species and the origin of the processes responsible for modification of the structural, optical and paramagnetic properties of polymers are discussed with consideration for two major reactions occurring in the implanted layer: (i) oxidation of the radiation-damaged polymer that predominates at moderate doses; (ii) clusterization of radiation defects with the formation of carbon-enriched domains ("drops") which can overlap at high ion fluences yielding the network of conjugated carbon structures.
Individual tracks in ion bombarded poly(methyl methacrylate)
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1997
The paper presents a study aimed to extract information on individual tracks in nearly monodisperse poly(methy1 methacrylate) bombarded with 200 keV He* ions. The study of the molecular weight distribution of the polymer after low fluence irradiation shows that it is possible to identify the contribution of the individual tracks to the overall distribution. In particular it is shown that the extraction of useful information about the mechanism of scission of the macromolecules inside the ion tracks in the low fluence limit ("single track regime") is not obtainable by means of a simple data treatment of the experimental molecular weight distribution. Hence, a model simulation of the macromolecular scission has been developed that allows us to obtain the bond scission probability in the energy conditions studied here (200 keV He+). Comparison with experimental data indicates that only a negligible part of the macromolecules in the tracks undergo more than two scissions per macromolecule and that the most part of the macromolecules undergo only one scission event, in the energy condition used here (230 keV He+). 0 1997 Elsevier Science B.V.
1984
During heavy ion irradiation of polymer and condensed gas films large fluxes of ions, excited neutrals and ultraviolet radiation are liberated. Because the fluxes are so large, they can contribute secondary currents comparable to (or even larger than) the current of incident ions unless they are carefully suppressed. For polymer films the secondary fluxes vary with the polymers used and with the primary ion dose. While films like HPR-204, and polyimides like PIQ show a gradual decrease of the ionic species emission, poly(methy1 methacrylate), PMMA, shows a peak in the ionic species emission with increasing dose. These observations suggest that for typical ion implantations through polymer masks, the error in the charge integration at the target may be a function of the polymer as well as the dose if proper care is not exercised in the suppression of secondaries. For condensed gas solids, efficient ultraviolet emission can produce photoelectron currents which are a strong function of film thickness. Argon is a particularly striking example. We comment on secondary suppression techniques that can be used to minimize or eliminate beam integration errors in these cases or that alternatively can provide info~atioR about the secondary fluxes and the processes which produce them.
Structural modification of polymer films by ion irradiation
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1992
The atomic and electronic structure of polymer films undergoes deep modifications during high energy (keV-MeV) ion irradiation, from molecular solid to amorphous material. At low energy density (1022–1024) typical effects include chain scissions, crosslinks, molecular emission and double bonds formation. In hydrocarbon polymer (polystyrene, polyethylene) the main effect of irradiation is the formation of new bonds as detected by molecular weight distribution, solubility and optical measurements. Moreover the concentration of trigonal carbon (sp2) in the polymer changes with ion fluence (1011–1014) and stabilizes to a value of 20% independently on the initial chemical structure of the irradiated sample. Photoemission spectroscopy shows an evolution of valence band states from localized to extended states. At high energy density (1024–1026) the irradiated polymer continues to evolve showing spectroscopic characteristics close to those of hydrogenated amorphous carbon. Trigonal carbon concentration changes with ion fluence (1014–1016) reaching the steady state value of 60% and the hydrogen concentration decreases to 20%. Moreover the values of the optical gap (2.5–0.5 eV) suggest the presence of medium range order in the obtained hydrogenated amorphous carbon. These values are consistent with the formation of graphitic clusters, whose size goes from 5 Å to 20 Å by changing the ion fluence (or energy density).
Track size and track structure in polymer irradiated by heavy ions
The structure of latent tracks in polyethylene terephthalate (PET) was studied using chemical etching combined with a conductometric technique. Polymer samples were irradiated with Ar, Kr, Xe, Au, and U ions with energies in the range of 1 to 11.6 MeV/u. The etching kinetics of the tracks was investigated in the radii range 0±100 nm. The highly damaged track core manifests itself on the etching curves as a zone where the etch rate changes dramatically and reaches its minimum at a radius of a few nm. It was found that the track core radius is approximately proportional to (dE/ dx) 0X55 . The track core is surrounded by a halo. In the track halo the etching proceeds at a rate that slowly increases approaching a constant value. Cross linking of macromolecules causes reduction of the etch rate in the halo which extends up to distances exceeding 100 nm in the case of the heaviest ions. Measurable change of the etch rate at such large radii could not be predicted from the shape of the calculated spatial distributions of energy dissipated in tracks. Obviously, formation of the extended track halo is in¯uenced by the diusion of active intermediates from the track core to the polymer bulk. Ó 0168-583X/98/$ ± see front matter Ó 1998 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 -5 8 3 X ( 9 8 ) 0 0 4 4 5 -5