K. Havancsák

Swift heavy ion-induced modification of Al2O3 and MgO surfaces

Abstract Surface topography changes in single-crystal alumina and magnesium oxide samples irradiated with 245 MeV Kr and 128–710 MeV Bi ions have been studied by atomic force microscopy. The surface response consists of nanoscale hillock-like defects associated with single ion impact. These defects are observed on the surfaces of Al 2 O 3 and MgO targets at ionizing energy loss values of about 25 and 15.8 keV/nm, respectively, which is less than the expected threshold values of amorphous latent track formation in these materials. Corresponding electron diffraction and high-resolution transmission electron microscopy studies show no evidence of an amorphous core of the ion track in sapphire irradiated with Bi ions at surface electronic stopping power of 41 keV/nm. Possible mechanisms of hillocks formation, alternative to crystalline–amorphous phase transition are discussed.

Application of the thermal spike model to latent tracks induced in polymers

Abstract Polyethylene terephtalat (PET) foils were irradiated by 246 MeV Kr and 595 MeV Xe ions and the irradiated samples were studied by wide angle X-ray diffraction. A simple exponential law describes the variation of the integral X-ray intensity I int with the fluence. By applying the Poisson law 12.3 nm and 16 nm were deduced for the mean diameters of tracks induced by Kr and Xe ions, respectively. We did not observe considerable beam heating effect. The analysis of the irradiation experiments on polyvinylidene fluoride and on PET foils shows that the predictions of the thermal spike model of Szenes are in quantitative agreement with the experimental results.

AFM and STM investigation of carbon nanotubes produced by high energy ion irradiation of graphite

Carbon nanotubes (CNT) were produced by high energy, heavy ion irradiation (215 MeV Ne, 246 MeV Kr, 156 MeV Xe) of graphite. On samples irradiated with Kr and Xe ions large craters were found by atomic force microscopy, these are attributed to sputtering. Frequently one or several CNTs emerge from the craters. Some of the observed CNTs showed a regular vibration pattern. No other carbon based materials, like amorphous carbon or fullerenes were evidenced. Focused ion beam cuts were used to compare CNTs with surface folds on graphite. ” 1999 Elsevier Science B.V. All rights reserved.

Carbon nanotubes produced by high energy (E > 100 MeV), heavy ion irradiation of graphite

Abstract Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) were used to investigate the surface of highly oriented pyrolytic graphite (HOPG) irradiated with 209 MeV Kr or 830 MeV U ions. The density of hillocks found on samples irradiated by Kr and U ions indicates synergism of electronic and nuclear stopping processes. Carbon nanotubes (CNTs) were found on all of the investigated samples, STM images show an atomic arrangement identical with that of graphite. AFM revealed sputtering craters from which emerge CNTs, the vibration of some CNTs was observed.

Scanning probe microscopy investigation of nanometer structures produced by irradiation with 200 MeV ions

Abstract Nanometer size structures created by irradiation with 215 MeV Ne, and 209 MeV Kr ions on the surface of muscovite mica (MM), highly oriented pyrolitic graphite (HOPG), and single crystal Si were investigated by scanning tunnelling microscopy (STM), and atomic force microscopy (AFM). The comparison of the structures observed on these three materials shows that : (i) high energy heavy ions are suitable to produce well individualised, nanometer size structures without any further developing process being needed ; and (ii) the character of the structures can be ‘‘tailored’’ to a certain extent by using different target-ion combinations, and different angles of incidence.The layered nature of MM and HOPG make these materials particularly suitable for the creation of various nanometer size structures, their behaviour being more close to each other than to the covalent Si

Combination of electrochemical hydrogenation and Mossbauer spectroscopy as a tool to show the radiation effect of energetic heavy ions in Fe-Zr amorphous alloys

Abstract Radiation effects of energetic heavy ion irradiation in Fe–Zr amorphous alloys were investigated by the help of Mossbauer spectroscopy, X-ray diffraction and electrolytical hydrogenation. The electrolytical hydrogenation of non-irradiated and irradiated samples was carried out by a unique cathodic potential (−1000 mV versus SHE). The combination of electrolytical hydrogenation and Mossbauer analysis gives a very sensitive method for detecting structural changes of these amorphous alloys. It was found that the structural changes in the amorphous state, which are undetectable without hydrogenation by Mossbauer spectroscopy, modify the localization and the concentration of introduced hydrogen, and are reflected in a significant change of magnetic hyperfine interaction. The results can be associated with structural changes due to the effect of energetic heavy ion irradiation.

Nanotechnology at Present and its Promise for the Future

Nanotechnology is a future manufacturing technology giving thorough, inexpens ive control of the structure of matter. Nanotechnology, as a comprehensive t echnological system, does not exist today, although it is believed to make the technology of the 21 st century. Nevertheless nanoscience, as the cradle of the future nanotechnology, already exists , pre enting several scientific results in the field of nanophysics, nanomedicine and biotechnology. The headwa y of nanoscience has been demonstrated by several facts. The scientific and technologi cal tendencies, as well as the demands from the society enforcing the development of nanotechnology are pr esented. A short overview will be given of scientific results considered as contribut ion o nanoscience. The first results of the borning nanotechnology are presented as well.

COMPARISON OF DAMAGE PRODUCED BY 209 MEV KR IRRADIATION IN MUSCOVITE MICA,GRAPHITE AND SILICON

Abstract A new irradiation geometry and atomic force microscopy (AFM) were used to investigate and compare damage produced in Si, highly oriented pyrolythic graphite (HOPG), and muscovite mica (MM). Although the value of electronic stopping for 209 MeV Kr ions is in the range of 104 keV/μm for all three of the investigated materials, very different damage structures were found. The layered materials showed cleavage; in the case of mica, 100 nm deep “channels” and 1 μm in width were imaged. In HOPG, both individual ion tracks of apparent width of 100 nm, and dense nuclear cascades of 500 nm in width were found. In the isotropic silicon with covalent bonding, it was possible to separate four different regions, with different type of damage, but no cleavage was present.

Mössbauer study of metastable phase formation in vacuum deposited FeNiCr multilayers due to swift heavy ion irradiation

Abstract Conversion electron Mossbauer spectroscopy (CEMS) and X-ray diffraction (XRD) were used to study multilayers, consisting of a few atomic layers of iron, nickel and chromium with a composition 50%Fe–25%Ni–25%Cr, prepared by high vacuum deposition and subsequently irradiated by 246 MeV 86 Kr 8+ ions at room temperature. Metastable highly disordered microcrystalline ferromagnetic and paramagnetic phases have been detected in the Fe–Ni–Cr multilayers as a result of the swift heavy ion irradiation. These metastable phases never occur with thermally prepared alloys but are similar to those observed previously in the case of Fe–Ni–Cr alloys prepared by other non-equilibrium techniques as electrochemical deposition. The relative amount of these metastable phases increases with the irradiation fluence. It was shown that transformation of metastable phases into the stable ones occurs in high vacuum evaporated and ion beam mixed Fe–Ni–Cr films due to appropriate heat treatment in vacuum.

Electrodeposited, Ion Beam Mixed and Ball Milled FeCrNi Alloys

Conversion electron and transmission Mossbauer spectroscopy, X-ray diffractometry and electron microprobe analysis were used to perform comparative study of Fe-Cr-Ni electrodeposited, ion beam mixed vacuum deposited and ball milled alloys of same composition around 50%Fe-25%Cr-25%Ni. The main phase of the electroformed Fe-CrNi microcrystalline samples is ferromagnetic contrary to the paramagnetic character of thermally prepared alloys of equivalent composition. Metastable phases have been shown in Fe-Cr-Ni multilayers, consisting of a few atomic layers of iron and nickel as well as chromium, prepared by high vacuum deposition and ion beam or laser irradiation. The main phase of evaporated and ion beam mixed Fe-Cr-Ni films has been found to be ferromagnetic similarly to that observed in the case of electrodeposited alloys. It was shown that transformation of metastable phases into the stable one occurs in high vacuum evaporated and ion beam mixed or laser irradiated Fe-Cr-Ni films due to appropriate heat treatment in vacuum. Transformation of metastable phases in electrodeposited Fe-Cr-Ni alloys was achieved by irradiation with energetic heavy ions at room temperature. Metastable phases, including the ferromagnetic one, were found in Fe-Cr-Ni alloys prepared by ball milling method, too.