| 1. |
- Ignatova, V.A., et al.
(författare)
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Quantification problems in depth profiling of PWR steels using Ar+ ion sputtering and XPS analysis
- 2006
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Ingår i: Microscopy and Microanalysis. ; 12:5, s. 432-437
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Tidskriftsartikel (refereegranskat)abstract
- The oxide scales of AISI 304 formed in boric acid solutions at 300°C and pH = 4.5 have been studied using X-ray photoelectron spectroscopy (XPS) depth profiling. The present focus is depth profile quantification both in depth and chemical composition on a molecular level. The roughness of the samples is studied by atomic force microscopy before and after sputtering, and the erosion rate is determined by measuring the crater depth with a surface profilometer and vertical scanning interferometry. The resulting roughness (20–30 nm), being an order of magnitude lower than the crater depth (0.2–0.5 [mu]m), allows layer-by-layer profiling, although the ion-induced effects result in an uncertainty of the depth calibration of a factor of 2. The XPS spectrum deconvolution and data evaluation applying target factor analysis allows chemical speciation on a molecular level. The elemental distribution as a function of the sputtering time is obtained, and the formation of two layers is observed—one hydroxide (mainly iron–nickel based) on top and a second one deeper, mainly consisting of iron–chromium oxides.
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| 2. |
- Kalaboukhov, Alexei, 1975, et al.
(författare)
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Cationic Disorder and Phase Segregation in LaAlO3/SrTiO3 Heterointerfaces Evidenced by Medium-Energy Ion Spectroscopy
- 2009
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 103:14, s. 146101-
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Tidskriftsartikel (refereegranskat)abstract
- Medium-energy ion spectroscopy (MEIS) has been used to study the depth profile and deduce the distribution of possible cationic substitutions in LaAlO3/SrTiO3 (LAO/STO) heterointerfaces. Analysis of La and Sr peaks in aligned and random MEIS spectra indicates that the surface layers of LAO on an STO substrate are not homogeneous and stoichiometric if the film thickness is less than 4 unit cell layers. This is possibly caused by a redistribution of La and Sr at the interface. Kelvin probe force microscopy reveals an inhomogeneous distribution of the surface potential in a 4 unit cell LAO film, indicating micrometer-sized regions of different compositions. Our findings provide a novel view on the microstructural origin of the electrically conductive interfaces.
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| 3. |
- Khaibullin, R.I., et al.
(författare)
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An influence of the viscosity of polymer substrate on ion beam synthesis of iron granular films
- 2003
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Ingår i: Nuclear Instruments and Methods in Physics Research B. ; 206, s. 1115-1119
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Tidskriftsartikel (refereegranskat)abstract
- Iron granular films were synthesized in silicone polymers by implantation of 40 keV Fe ions with a fluence of1.25x10**17 ion/cm2 into viscous polymer substrates with various viscosity of 20–1000 Pa s. After the implantation the iron-implanted silicone substrates have been cured in the solid rubber-like state on the expiration of 72 h. The influenceof the substrate viscosity on the magnetic properties of the synthesized iron films was studied by ferromagnetic resonance(FMR) spectroscopy. It was shown that magnetic anisotropy and magnetization of the iron granular films is strongly and non-monotonically depended on the viscosity of silicone polymer under irradiation. Particularly, themaximal value of magnetization, 610 G, is observed for iron granular film synthesized at substrate viscosity on order of 70 Pa s. This value is higher than the magnetization of films obtained in silicone substrate implanted with iron ions in fully cured state.
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| 4. |
- Khaibullin, R.I., et al.
(författare)
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Formation of anisotropic ferromagnetic response in rutile (TiO2) implanted with cobalt ions
- 2007
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. ; 257:1-2, s. 369-373
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Tidskriftsartikel (refereegranskat)abstract
- The (1 0 0)- and (0 0 1)-monocrystalline plates of rutile (TiO2) were implanted by 40 keV Co+ ions with fluences in wide range of 0.15–1.5 × 1017 ion/cm2 to study the development of ferromagnetism in the diamagnetic TiO2. With increase of fluence the implanted rutile plates reveal sequentially paramagnetic, superparamagnetic, weak ferromagnetic and, eventually, strong anisotropic ferromagnetic response at room temperature. The thermo-magnetic analysis shows that the ferromagnetic samples exhibit two magnetic transitions with temperatures of the ferromagnetic ordering TC1 not, vert, similar 700 K and TC2 not, vert, similar 850 K, correspondingly. Heating of the samples in air strongly suppresses the ferromagnetic phases if the temperature of heating exceeds the corresponding transition temperature. Subsequent high-vacuum annealing restores only the low-temperature ferromagnetic phase. The origin of the two magnetic phases and anisotropy of the ferromagnetism in the Co-implanted rutile are discussed in the model of two cobalt-rich layers with different concentration and valence states of the implanted cobalt.
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| 5. |
- Kondyurin, A.V., et al.
(författare)
-
Pulse and continuous ion beam treatment of polyethylene
- 2003
-
Ingår i: Vacuum. ; 68, s. 341-347
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Tidskriftsartikel (refereegranskat)abstract
- Polyethylene (PE) films were treated by a nitrogen ion beam with an energy of 20 keV at a quasicontinuous regimewith low current density and at a pulse-periodical regime with high current density. IR ATR spectra and UV spectrashowed significant differences in structural changes of PE treated by pulse and continuous treatment at the sameaverage current density. The changes in the molecular structure that are induced by ion beams, i.e. the appearance ofaromatic cycles, unsaturated bonds and carbonyl groups in PE, have a similar qualitative character for all types of ionbeam regimes. However, the same degree of structural changes is achieved at lower dose in the pulse regime than in thecontinuous regime. At equal treatment parameters (ion energy, dose treatment, average current density) the pulseregime leads to a higher concentration of unsaturated and oxygen-containing groups then the continuous regime. Thiseffect at the pulse regime can be explained by the high current density in the single pulse, at which a high localtemperature is generated in the ion track field of the polymer. Probably this leads to a wave of internal stress, and theseeffects additionally stimulate structural changes in the polymer at pulsed ion beam treatment.
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| 6. |
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| 7. |
- Lukashevich, M.G., et al.
(författare)
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Magnetoresistive effect in PET films with iron nanoparticles synthesised by ion implantation
- 2010
-
Ingår i: The Open Applied Physics Journal. - 1874-1835. ; 3, s. 1-5
-
Tidskriftsartikel (refereegranskat)abstract
- Thin polyethyleneterephthalate (PET) layers with Fe nanoparticles (NPs) were synthesised by high-fluence ion implantation. Temperature dependence of conductance and magnetoresitance were studied as a function of ion fluence. It is found that the implantation with fluences of about 1.0×1017 cm-2 causes high enough concentration of metal inclusions to provide conditions for electrical percolation that leads to an insulator-to-metal transition (IMT) in charge carrier transport mechanisms. The magnetoresistance measurements indicate that the magnetic percolation takes place at metal concentrations (fluences) lower than those needed for the electrical percolation. For the samples on insulating side of the IMT, a non-monotonous dependence of resistance in an increasing external magnetic field is observed due to anisotropic magnetoresistive effect and charge carrier scattering on magnetic inclusions. For the samples implanted with fluences > 1.0×1017 cm-2, the magnetoresistance becomes a monotonous decreasing function of the external magnetic field which is typical for ferromagnetic metals that indicates effective magnetic coupling of the iron inclusions.
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| 8. |
- Lukashevich, M.G., et al.
(författare)
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Modification of magnetic properties of polyethyleneterephthalate by iron ion implantation
- 2007
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. ; 257:1-2, s. 589-592
-
Tidskriftsartikel (refereegranskat)abstract
- Fe+ ions (40 keV) were implanted into polyethyleneterephthalate (PET) films with fluences of (0.25–1.5) × 1017 cm−2. Magnetic properties of the synthesised Fe:PET composites were studied using superconducting quantum interference device (SQUID) technique in temperature range of 2–300 K. For range of fluences (0.5–0.75) × 1017 cm−2 the samples reveal superparamagnetic behaviour at room temperature. At fluences above 0.75 × 1017 cm−2 the strong increase of magnetisation and transition to ferromagnetic properties are registered. Analysis of the magnetic hysteresis loops suggests an easy plane magnetic anisotropy similar to that found for thin magnetic films. Zero-field-cooled (ZFC) and field-cooled (FC) temperature measurements of magnetisation are found to be in agreement with earlier observed formation of Fe nanoparticles (NPs) in the implanted layers. The growth and agglomeration of the NPs forming the quasi-continuous labyrinth-like structure in the polymer film at the highest implantation fluence of 1.5 × 1017 cm−2 is an origin for the transition to the ferromagnetic properties.
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| 9. |
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| 10. |
- Okay, C., et al.
(författare)
-
Ferromagnetic resonance study of iron implanted PET foils
- 2006
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Ingår i: Physica Status Solidi (a). ; 203:7, s. 1525-1532
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Tidskriftsartikel (refereegranskat)abstract
- Polyethylene terephthalate (PET) foils were implanted with 40 keV Fe+ ions to doses of (0.15-1.50) x 1017 ions/cm2 at ion current density of 4 uA/cm2. The iron-implanted PET composites were investigated using ferromagnetic resonance (FMR) technique supplemented by transmission electron microscopy (TEM), atomic force microscopy (AFM) and DC resistance measurements. TEM studies revealed formation of iron nanoparticles with size in the range of 5-100 nm depending on the implantation dose. AFM images showed depending on the implantation dose either small bumps or worm-like structures on the polymer surface that corresponded to the inclusions towered above the surface. The results of AFM studies were found to be in good agreement with the TEM measurements. FMR signal was observed for the foils implanted with the dose higher than 0.15 x 1017 ions/cm2. The effective magnetization of the metal-polymer composite was extracted from the angular dependencies of FMR resonance field. The percolation transition at the implantation dose of 1.0 x 1017 ions/cm2 was observed in the dose dependencies of the FMR absorption intensity and the effective magnetisation. The minimum in DC resistance found at the same dose indicates that a charge carrier mediated (exchange) interaction rather than the dipolar one is underlying mechanism for the percolation transition. Formation of a carbonized layer in the heavily implanted area of the polymer is supposed to be responsible for the exchange coupling of the magnetic granules.
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| 11. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Beams of atomic clusters: effects on impact with solids
- 2006
-
Ingår i: Reviews on Advanced Materials Science. ; 11:1, s. 19-45
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Forskningsöversikt (refereegranskat)abstract
- A state-of-the-art review in the field of cluster beams and energetic cluster-surface interaction is presented. Ionised cluster beams are considered to be a controllable and versatile tool for modification and processing of surfaces and near-surface layers on an atomic scale as an alternative to ion implantation, ion assisted deposition and some other methods. A brief introduction to the history of cluster beams is given as well as a discussion of the capabilities of cluster beams for a variety of applications in material science, electronics and optics. Techniques for producing atomic and molecular clusters are described. Energetic cluster deposition and cluster implantation as well as related physical effects are the main emphasis of the review. In the final part of the paper the attention is focused on the study of surface erosion (crater formation) under energetic cluster ion impact.
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| 12. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Charge carrier transport in polyimide with Co nanoparticles formed by ion implantation
- 2004
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 566-568:1-3 PART 1, s. 327-331
-
Tidskriftsartikel (refereegranskat)abstract
- Temperature dependence of resistance is studied for polyimide (PI) samples implanted by Co+ ions with fluences of 2.5x1016-1.25x1017 cm-2 at ion current densities of 4, 8 and 12 uA.cm-2. It is found that electron transport in the implanted samples originates from radiation-induced changes of the PI and Co nanoparticle formation and it depends dramatically on the ion current density. A variable range hopping mechanism dominates for all fluences at a low ion current density of 4 uA.cm-2 while a transition to a semimetallic type of conductance is observed with an increase in ion current density due to agglomeration of the Co nanoparticles forming a percolation way for the charge carriers. It is shown that both quantum effects of weak localisation and electron-electron interaction give a significant contribution to the transport mechanism.
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| 13. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Complex crater formation on silicon surfaces by low-energy Ar cluster ion implantation
- 2004
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 566-568, s. 1179-1184
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Tidskriftsartikel (refereegranskat)abstract
- Silicon samples were implanted by small mass-selected Ar cluster and Ar+ monomer ions with energies in the range of 1.5-18.0 keV/ion. Atomic force microscopy (AFM) shows simple and complex crater formation on the Si surface at the collision spots. A typical complex crater is surrounded by a low-height (0.5 nm) rim and it encloses a centre-positioned cone-shaped hillock with height of up to 3.5 nm depending on the implantation conditions. The morphology and dimensions of the craters and hillocks are studied as a function of the cluster size and implantation energy. A model explaining the hillock formation with relation to the thermal-transfer effect and local target melting at the collision spot is proposed.
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| 14. |
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| 15. |
- Popok, Vladimir, 1966
(författare)
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Compositional and structural alterations of polymers under low-to-medium-energy ion implantation
- 2005
-
Ingår i: Surface Science Research, Ed. Ch. P. Norris. - New York : Nova Science Publishers. - 1594541590 ; , s. 147-193
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Numerous studies of polymers modified by low-to-medium-energy ion beams are generalised. The accent is put on peculiarities of ion stopping in a polymer matrix, latent track formation and on complex process of polymer degradation. Main trends in the changes of the structure and composition of the polymers as a function of implantation conditions are discussed. In particular, the effects of radiothermolysis, degassing and carbonisation are under examination. Recent results on the high fluence and high ion current density implantation are reviewed. Post-implantation oxidation phenomenon of the radiation-damaged polymers is described in connection to the structural alteration. Depth distribution of various implanted species in polymers is one of the significant items under consideration. Main aspects of nucleation and growth of the metal nanoparticles (NPs) under the implantation conditions leading to the exceeding the metal solubility limit in the dielectric matrix are described as a special case of ion-beam treatment. The implantation-induced polymer modification is found to be originating a spectrum of new properties, i.e. significant changes in conductance, optical and magnetic characteristics, surface hardness, adhesion and other parameters that is reviewed with relation to practical applications.
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| 16. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Conductance and EPR study of the endohedral fullerene Li@C60
- 2005
-
Ingår i: Solid State Communications. ; 133:8, s. 499-503
-
Tidskriftsartikel (refereegranskat)abstract
- Thin films and bulk samples of endohedral fullerenes Li@C60 are studied using current-voltage (I-V) measurements and electron paramagnetic resonance (EPR). Electrical measurements show a linear behaviour for the I-V curves and give an average resistivity of ca. 1.5 kOhmcm for thin Li@C60 films deposited in vacuum, four orders of magnitude lower than C60 samples. A drastic effect on the conductance, lowering it to the values typical for C60, is observed when the Li@C60 samples are exposed to ambient atmosphere. No additional paramagnetic centres (PCs) are found for the Li@C60 compared to C60 that can be related to the formation of dimers or trimers of the endohedral fullerene molecules. However, the presence of the Li atoms in the fullerene cages contributes to a change of the spin-spin and spin-lattice relaxation times. The spin-lattice relaxation time becomes 4 orders of magnitude longer compared to the spin-spin relaxation time.
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| 17. |
- Popok, Vladimir, 1966, et al.
(författare)
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Conductance and polarisability of C60 films
- 2007
-
Ingår i: Journal of Nanoscience and Nanotechnology. ; 7:4-5, s. 1434-1438
-
Tidskriftsartikel (refereegranskat)abstract
- Thin films of C60 deposited in vacuum are studied using current-voltage (I-V) measurements and atomic force microscopy (AFM). In situ electrical measurements give an average resistivity of ca. 30 MΩcm for the as-deposited films at room temperature. The I-V dependences are found to correspond to ohmic behaviour but they have a hysteresis shape attributed to remnant polarisation due to the domain structure of the films. AFM images show a grainy surface morphology for the deposited C60. Temperature dependent measurements in the range 290-365 K provide evidence for a variable range hopping mechanism of conductance with an activation energy of 0.8-1.0 eV. With further temperature increase the C60 films restructure leading to an increase in grain size and a change of the electrical properties with I-V dependences showing Schottky barrier formation. The effect of oxygen on the conductance of the C60 films under their exposure to an ambient atmosphere is considered and discussed.
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| 18. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Design and capabilities of a cluster implantation and deposition apparatus: First results on hillock formation under energetic cluster ion bombardment
- 2002
-
Ingår i: Review of Scientific Instruments. ; 73:12, s. 4283-4287
-
Tidskriftsartikel (refereegranskat)abstract
- A description, advantages, and capabilities of a cluster implantation and deposition apparatus supplied by a pulsed cluster source from gaseous precursors are presented. A number of possible in situ and ex situ experimental methods to study clustersurface collisions and modified substrate surfaces are discussed. Test experiments on cluster production show formation of Ar, N2, and O2 clusters with size up to 150 atoms for Ar and 6070 molecules for the other gases. The possibility of cluster mass selection and acceleration up to 25 keV is reported. Nanosize hillock formation was found as a result of clustersurface collisions with pyrolytic graphite and indiumtinoxide. It is suggested that the hillocks' parameters such as size and density per surface area can be controlled by varying the implantation parameters and substrate material and thus provide a promising technique for nanoscale surface modification.
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| 19. |
- Popok, Vladimir, 1966, et al.
(författare)
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Electronic Properties of thin films sublimed from La@C82 and Li@C60
- 2008
-
Ingår i: Nano. ; 3:3, s. 155-160
-
Tidskriftsartikel (refereegranskat)abstract
- La@C82 and Li@C60 thin films obtained by sublimation in vacuum are studied using four-probe current-voltage measurements and atomic force microscopy. In situ electrical measurements show semiconducting behavior of both films with room-temperature resistivity of 21+-8 and 1230+-50 Ohm.cm for the La@C82 and Li@C60, respectively. A variable range hopping mechanism of conductance is suggested from the temperature dependences of resistance. The activation energies for electron transport are calculated for both metallofullerenes. Irreversible changes to the Li@C60 film structure increasing the film resistivity to values typical for C60 are found at elevated temperatures. The effect of exposure to ambient atmosphere on the conductance of the films is discussed.
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| 20. |
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| 21. |
- Popok, Vladimir, 1966
(författare)
-
Energetic cluster-surface collisions
- 2010
-
Ingår i: Handbook of nanophysics, Vol. 2 Clusters and Fullerenes (edited by Klaus D. Sattler). - New York : Taylor&Francis. - 9781420075557
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 22. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Formation of surface nanostructures on rutile (TiO2): comparative study of low-energy cluster ion and high-energy monoatomic ion impact
- 2009
-
Ingår i: Journal of Physics D. - : Institute of Physics. - 0022-3727 .- 1361-6463. ; 42:20, s. 205303-
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Tidskriftsartikel (refereegranskat)abstract
- The formation of nanostructures on rutile (TiO2) surfaces formed after the implantation of kiloelectronvolt-energy Ar+n cluster ions and megaelectronvolt- to gigaelectronvolt-energy multiply charged heavy ions (Iq+, Taq+ and Uq+) is studied. Despite the differences in stopping and energy transfer mechanisms between the kiloelectronvolt-energy cluster ions and megaelectronvolt-energy monoatomic ions, their impacts lead to a similar type of surface damage, namely craters. For the cluster ion implantation the craters are caused by the multiple-collision effect (dominated by nuclear stopping) and the high density of energy and momentum transferred to the target, while for the case of megaelectronvolt multiply charged ions the craters are probably formed due to the Coulomb explosion and fast energy transfer caused by the electronic stopping. At ion energies in the gigaelectronvolt range, nanosize protrusions, so-called hillocks, are observed on the surface. It is suggested that electronic stopping leads to the formation of continuous tracks and the transferred energy is high enough to melt the material along the whole projectile path. Elastic rebound of the tension between the molten and solid state phases leads to liquid flow, expansion and quenching of the melt, thus forming the hillocks. Atomic force microscopy measurements carried out under different environmental conditions (temperature and atmosphere) suggest that the damaged material at the nanosize impact spots has very different water affinity properties (higher hydrophilicity or water adsorption) compared with the non-irradiated rutile surface.
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| 23. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Kelvin Probe Force Microscopy Study of LaAlO3/SrTiO3 Heterointerfaces
- 2010
-
Ingår i: Journal of Advanced Microscopy Research. - : American Scientific Publishers. - 2156-7581 .- 2156-7573. ; 5:1, s. 26-30
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Tidskriftsartikel (refereegranskat)abstract
- Surface potential distributions in ultra-thin (0.8-3.9 nm) LaAlO3 layers deposited on SrTiO3 substrates are studied. It is found that the potential distribution evolves from island-like to a homogeneous one with increasing LaAlO3 thickness. It is suggested that the observed islands are caused by a locally enhanced concentration of mobile charge carriers at the interface that is, in turn, related to non-stoichiometry of the layers with thickness bellow 4 unit cells. Transition to a homogeneous potential distribution with increasing LAO thickness (≥4 unit cells) corresponds to the formation of a quasi-2-dimensional electron gas. The results agree with a percolation model explaining the insulator-to-metal transition that occurs at the LaAlO3/SrTiO3 heterointerface.
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| 24. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Magnetoresistive effect and impedance spectroscopy of Co-implanted polyimide
- 2006
-
Ingår i: Physica Status Solidi (a). ; 203:7, s. 1545-1549
-
Tidskriftsartikel (refereegranskat)abstract
- Electronic properties and magnetoresistance of polyimide (PI) films implanted by 40 keV Co+ ions with high fluences at various ion current densities are studied. Insulator-to-metal transition (IMT) is found for the highest implantation fluence (1.25 x 1017 cm-2) at ion current densities of 8 and 12 uA/cm2. The IMT is caused by the radiation-induced alteration of the implanted PI and agglomeration of the Co nanoparticles (NPs) providing an efficient percolation way for the charge carriers. Impedance spectroscopy shows the increase in capacitance with fluence for the samples on the dielectric side of the IMT, which is caused by formation of the conductive metal NPs and carbonised clusters separated by insulating polymer media. The percolation of the conductive phase for the samples on the metallic side of the IMT results in an inductive character of the impedance. The magnotoresistive effect is found to be positive for the samples on the dielectric side of the IMT and negative for the samples on the metallic side.
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| 25. |
- Popok, Vladimir, 1966, et al.
(författare)
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Nanohillock formation by impact of small low-energy clusters with surfaces
- 2003
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Ingår i: Nuclear Instruments and Methods in Physics Research B. ; 207:2, s. 145-153
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Tidskriftsartikel (refereegranskat)abstract
- Results on nanoscale structuring of different substrates (silicon, pyrolytic graphite, indium-tin-oxide) using clusters from 20 to 100 atoms in size formed from gaseous precursors (O2, N2, Ar) at relatively low impact energy up to 15 keV are presented. Images of the substrate surfaces after cluster collisions obtained using atomic force microscopy (AFM) show the formation of hillocks from a few to 15 nm height with a basal diameter from 50 to 300 nm depending on implantation conditions. The shape and size of the structures are found to be a function of the cluster size and species, implantation energy, impact angle and the type of substrate. A model explaining the hillock formation is discussed.
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| 26. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Optical and AFM study of ion-synthesised silver nanoparticles in thin surface layers of SiO2 glass
- 2010
-
Ingår i: JOURNAL OF NON-CRYSTALLINE SOLIDS. - 0022-3093. ; 356:25-27, s. 1258-1261
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Tidskriftsartikel (refereegranskat)abstract
- Silver nanoparticles were synthesised in thin surface layers of SiO 2 glass by 30 keV implantation of Ag+ ions with various fluences. Properties of the composites were studied using optical spectroscopy and atomic force microscopy. Optical spectra reveal specific absorption bands assigned to the surface plasmon resonance of the nucleated Ag nanoparticles. The spectral positions of absorption maxima are found to be dependent on the ion fluence that corresponds to the difference in mean sizes of the nanoparticles. Microscopy study shows formation of hemispherical nanosize bumps on the glass surfaces which represent a near-surface fraction of the partly towered nanoparticles. Post-implantation annealing leads to a shift of the plasmon maxima and to a change of the band widths. The transformations of optical spectra are in good agreementwith the change of nanoparticle sizes found by atomic force microscopy. Possible mechanisms governing the redistribution of the nanoparticles in size under the thermal treatment are suggested and discussed. © 2010 Elsevier B.V. All rights reserved.
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| 27. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Radiation-induced change of polyimide properties under high-fluence and high ion current density implantation
- 2004
-
Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; A78:7, s. 1067-72
-
Tidskriftsartikel (refereegranskat)abstract
- Polyimide (PI) films were implanted with 40-keV Ar+ and 80-keV Ar(2+) ions in a fluence range of 5.0*10^14-1.5*10^17 cm-2 at ion-current densities of 1-16 uA*cm2. It is shown that the conductivity of the samples rises with the ion-current density at a fixed fluence. Electrophysical parameters of the polyimide change stepwise with the implantation fluence when it exceeds a certain value. The change of electrical parameters of the implanted PI correlates with that of the optical and paramagnetic characteristics. The phenomenon of complete volatilisation of argon implanted with an energy of 40 keV due to surface heating and disordering under the high-power beam is found. It is shown that the change of ion charge and energy at constant beam-power density causes only a quantitative change in the polymer characteristics. A model of PI alteration and carbonised phase formation, taking into account the action of the high-power ion beam and the peculiarities of PI chemical structure, is developed to explain the observed effects. Implantation at high ion-current density can be suggested as an efficient practical means to control polymer conductivity and other parameters
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| 28. |
- Popok, Vladimir, 1966, et al.
(författare)
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Stopping of energetic argon cluster ions in graphite: Role of cluster momentum and charge
- 2010
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Ingår i: PHYSICAL REVIEW B. - 1098-0121. ; 82:20
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Tidskriftsartikel (refereegranskat)abstract
- We show that the implantation depth for argon clusters in graphite scales linearly with cluster momentum. A plot of implantation depth versus the momentum scaled with the projected surface area of the cluster falls on the same universal plot as that shown for semiconductor and metallic clusters, thus providing a universal scaling law for cluster implantation. Molecular dynamics simulations provide some insight to the mechanisms behind the empirical observation.
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| 29. |
- Popok, Vladimir, 1966, et al.
(författare)
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Stopping of energetic cobalt clusters and formation of radiation damage in graphite
- 2009
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Ingår i: Physical Review B. ; 80:20
-
Tidskriftsartikel (refereegranskat)abstract
- The interaction of energetic (up to 200 eV/atom) size-selected Con clusters with HOPG is studied both experimentally and theoretically. Etching of the radiation damage areas introduced by cluster impacts provides a measure of the depth to which the collision cascades are developed and allowes a comparison of these data with the molecular dynamics simulations. Good agreement between the experimental results and modelling is obtained. It is shown that the projected range of the cluster constituents can be linearly scaled with the projected momentum (the cluster momentum divided by surface impact area). With decrease of cluster energies to ca. 10 eV/atom the transition from implantation to pinning is suggested. It is found that even after quite energetic impacts residual clusters remain intact in the shallow graphite layer. These clusters can catalyse reaction of atmospheric oxygen with damaged graphite areas under the thermal heating that leads to the formation of narrow (5-15 nm) random in shape surface channels (trenches) in the top few graphene layers. Thus, small imbedded Co nanoparticles can be used as a processing tool for graphene.
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| 30. |
- Popok, Vladimir, 1966, et al.
(författare)
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Surface nanostructuring by implantation of cluster ions
- 2004
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Ingår i: Vacuum. - : Elsevier BV. - 0042-207X. ; 76:2-3, s. 265-272
-
Tidskriftsartikel (refereegranskat)abstract
- A brief state-of-the-art review in the field of cluster ion implantation is presented. Ionised cluster beams are considered as a controllable and versatile tool for modification and processing of surfaces and near-surface layers on an atomistic scale as an alternative to ion implantation and ion assisted deposition. The main effects occurring under cluster-surface collisions as well as advantages in the application of cluster ion beams are reviewed. The problem of surface erosion under impact of energetic cluster ions is emphasised in the paper. A model explaining crater and hillock formation on target surfaces with relation to the thermal-transfer effect and local target melting at the collision spot is discussed.
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| 31. |
- Popok, Vladimir, 1966, et al.
(författare)
-
Synthesis of Silver Nanoparticles by the Ion Implantation Method and Investigation of their Optical Properties
- 2005
-
Ingår i: Journal of Applied Spectroscopy. ; 72:2, s. 229-234
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the process of metal nanoparticle (NP) synthesis in SiO2 by implanting Ag+ ions with an energy of 30 keV depending on the dose ((2–8)·1016 cm−2) and the ionic current density (4–15 µA/cm2). Analysis of the composite materials formed was performed with the use of optical spectroscopy and atomic-force microscopy (AFM). The NPs synthesized in the glass demonstrate a characteristic absorption line associated with the surface plasma resonance effect. A correlation of the spectral shift of the lines caused by a change in the NP size with the diameter of the hemispherical asperities on the SiO2 surface registered by the AFM method has been revealed. It has been found that for the case of a fixed current density in the ion beam the silver NP sizes remain practically unaltered with increasing ion dose up to a certain value (6·1016 cm−2), and only an increase in the concentration of NPs is observed thereby. However, a further increase in the dose causes a decrease in both the NP density and size. On the other hand, at a fixed high dose an increase in the ionic current density leads to a gradual enlargement of the NPs. We have considered the mechanisms explaining the change in the NP sizes with increasing dose and ionic current density and evaluated the possibilities of carrying out controlled synthesis by varying the implantation conditions.
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| 32. |
- Prasalovich, Sergei, 1976, et al.
(författare)
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Experimental studies of complex crater formation under cluster implantation of solids
- 2005
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 36, s. 79-88
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Tidskriftsartikel (refereegranskat)abstract
- The results of a systematic study of surface defect formation after energetic Arn+ (n = 12, 22, 32, 54) and Xen+ (n = 4, 16) cluster ion implantation into silicon and sapphire are presented. Implantation energies vary from 3 to 18 keV/ion. Two cases of comparative studies are carried out: the same cluster species are implanted into two different substrates, i.e. Arn+ cluster ions into silicon and sapphire and two different cluster species Arn+ and Xen+ are implanted into the same kind of substrate (silicon). Atomic force, scanning electron and transmission electron microscopies (AFM, SEM and TEM) are used to study the implanted samples. The analysis reveals the formation of two types of surface erosion defects: simple and complex (with centrally positioned hillock) craters. It is found that the ratio of simple to complex crater formation as well as the hillock dimensions depend strongly on the cluster species, size and impact energy as well as on the type of substrate material. Qualitative models describing the two comparative cases of cluster implantation, the case of different cluster species and the case of different substrate materials, are proposed.
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| 33. |
- Prasalovich, Sergei, 1976, et al.
(författare)
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Surface entropy of rare-gas clusters
- 2005
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Ingår i: J. Chem. Phys.. - : AIP Publishing. - 0021-9606. ; 123
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Tidskriftsartikel (refereegranskat)abstract
- Abundances of Ar and Xe clusters produced in a supersonic expansion source are inverted to find relative dissociation energies. The values around the shell and subshell closings at N=55, 71, and 147 differ from theoretical values derived from ground-state energies of Lennard-Jones clusters. A significant part of the difference can be accounted for by the conformational entropies of surface atoms and vacancies.
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| 34. |
- Rameev, B., et al.
(författare)
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FERROMAGNETIC RESONANCE INVESTIGATIONS OF COBALT IMPLANTED POLYIMIDES
- 2004
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Ingår i: Journal of Magnetism and Magnetic Materials. ; 278:1-2, s. 164-171
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Tidskriftsartikel (refereegranskat)abstract
- 40 keV Co+ ions were implanted in thin polyimide foils with doses in range of (0.25-1.50)x1017 ions/cm2 at ion current densities of 4, 8 and 12 microA/cm2. The cobalt-implanted polymer foils were annealed at the temperature of 300 oC for 2 hours in vacuum. Both the as-implanted and post-annealed samples were investigated by the ferromagnetic resonance (FMR) technique supplemented by transmission electron microscopy (TEM). TEM investigations showed that the implantation results in formation of cobalt granules in the irradiated polymer layer with the thickness of about 70 nm. The mean lateral size of cobalt granules varied within 5-20 nm depending on the dose. The annealing of the implanted samples induced coalescence of the cobalt granules and increase of their lateral sizes. No FMR signals were found for the as-prepared polymer foils implanted by cobalt ions at low current density of 4 microA/cm2. FMR signals were observed for the as-prepared samples implanted at higher ion current densities of 8 and 12 microA/cm2 as well as for all annealed samples. The values of the effective magnetisation were extracted from the FMR spectra measured at different sample orientations in the applied magnetic field. Dose dependencies of the FMR absorption intensity and effective magnetisation were obtained for the annealed films. The magnetic properties of the synthesised cobalt-polymer composite materials and their modification due to the annealing treatment are discussed.
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| 35. |
- Samela, J., et al.
(författare)
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Argon cluster impacts on layered silicon, silica, and graphite surfaces
- 2007
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Ingår i: European Physical Journal D. ; 43, s. 181-184
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Tidskriftsartikel (refereegranskat)abstract
- Seven structures of covalently bonded materials are used as targets of 6 keV Ar12 cluster bombardment in classical molecular dynamics simulations. Energy deposition, cratering and Ar ranges are compared and remarkable differences are found between the structures. In particular, bombardment of a thin 2 nm silica layer on top of the Si(111) surface is shown to behave quite differently from bombardment of pure Si.
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| 36. |
- Samela, J., et al.
(författare)
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Comparison of silicon potentials for cluster bombardment simulations
- 2007
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. ; 255:1, s. 253-258
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Tidskriftsartikel (refereegranskat)abstract
- We have compared three common silicon potentials for molecular dynamics simulations of cluster bombardment of silicon structures. The potentials tested are Stillinger–Weber, Tersoff III and EDIP. We have also tested one variation of Stillinger–Weber and a variation of Tersoff III potential to see how small modifications of parameter values affect collision cascade and crater geometries. Single ion sputtering yields are compared to experimental values. In simulations, Si(1 1 1) surfaces are bombarded with 1–60 keV Ar12 clusters. The potentials give almost similar overall description of collision cascades at different energies. However, measurable quantities like sputtering yields and crater sizes vary considerably between potentials and even between different parametrisations of the same potential.
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| 37. |
- Samela, J., et al.
(författare)
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Origin of complex impact craters on native oxide coated silicon surfaces
- 2008
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Ingår i: Physical Review B. ; 77
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Tidskriftsartikel (refereegranskat)abstract
- Crater structures induced by impact of keV-energy Ar cluster ions on silicon surfaces are measured with atomic force microscopy. Complex crater structures consisting of a central hillock and outer rim are observed more often on targets covered with a native silicon oxide layer than on targets without the oxide layer. To explain the formation of these complex crater structures, classical molecular dynamics simulations of Ar cluster impacts on oxide coated silicon surfaces, as well as on bulk amorphous silica, amorphous Si, and crystalline Si substrates, are carried out. The diameter of the simulated hillock structures in the silicon oxide layer is in agreement with the experimental results, but the simulations cannot directly explain the height of hillocks and the outer rim structures when the oxide coated silicon substrate is free of defects. However, in simulations of 5 keV/atom Ar12 cluster impacts, transient displacements of the amorphous silicon or silicon oxide substrate surfaces are induced in an approximately 50 nm wide area surrounding the impact point. In silicon oxide, the transient displacements induce small topographical changes on the surface in the vicinity of the central hillock. The comparison of cluster stopping mechanisms in the various silicon oxide and silicon structures shows that the largest lateral momentum is induced in the silicon oxide layer during the impact; thus, the transient displacements on the surface are stronger than in the other substrates. This can be a reason for the higher frequency of occurrence of the complex craters on oxide coated silicon.
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| 38. |
- Stepanov, A.L., et al.
(författare)
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Effect of the Ion Beam Current Density on the Formation of Implanted Metal Nanoparticles in a Dielectric Matrix
- 2003
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Ingår i: Technical Physics Letters. ; 29:12, s. 977-979
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the ion beam current density, varied within 4–15 uA/cm2, on the formation of metal nanoparticles in a subsurface layer of SiO2 substrates implanted with 30-keV Ag ions to a dose of 5x10**16 cm–2 was studied by optical spectroscopy and atomic force microscopy techniques. An increase in the ion beam current density leads to the formation of nanoparticles of a greater size as a result of the glass substrate heating and due to an increase in the diffusion mobility of implanted silver atoms. These results suggest the possibility of controlling the dimensions of implanted nanoparticles in dielectrics by means of variation of the ion beam current density during the process.
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| 39. |
- Stepanov, A.L., et al.
(författare)
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Nanostructuring of silicate glass under low energy Ag-ion implantation
- 2004
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 566-568:1-3 PART 2, s. 1250-1254
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Tidskriftsartikel (refereegranskat)abstract
- Silicate glasses implanted by 30 keV Ag+ ions with a dose of 5x1016 ion/cm2 at ion current densities from 4 to 15 uA/cm2 were investigated using optical spectroscopy and atomic force microscopy (AFM). Optical spectroscopy measurements show a characteristic absorption band of surface plasmon resonance that is associated with nanosize Ag particles formed in the implanted glasses. Observed both the shift of transmittance band minimum to long wavelengths and the intensity change with rise of ion current density are caused by increase of the nanoparticle sizes. AFM images of the implanted glass surfaces show a formation of semispherical hills. These hills are tops of the spherical nanoparticles towering above the surface due to sputtering of the glass surface layer under the implantation. The increase of ion current density leads to enlarge of the hill size, i.e. nanoparticles. The nanoparticle enlargement is explained in terms of enhanced thermal diffusion of the implanted Ag atoms. Increase of the ion current density leads to temperature rise in the glass matrix that elevates atoms mobility and causes effective collection of the silver atoms into nucleated particles and their growth.
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| 40. |
- Stepanov, A.L., et al.
(författare)
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Synthesis of Cu Nanoparticles in Al2O3 by Ion Implantation and Subsequent Laser Annealing
- 2003
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Ingår i: AIP Conference Proceedings. ; 680, s. 601-604
-
Konferensbidrag (refereegranskat)abstract
- Al2O3 samples with Cu nanoparticles synthesised by ion implantation at 40 keV, with a dose of 1x10**17 ion/cm2 and a current density from 2.5 to 12.5 μA/cm2 were annealed using several pulses from a KrF excimer laser witha single pulse fluence of 0.3 J/cm2. The copper depth distribution, formation and modification of metal nanoparticles under the ion implantation and laser treatment were studied by Rutherford backscattering (RBS), energy dispersive X-ray(EDX) analysis, atomic force microscopy (AFM) and optical spectroscopy. The metal nucleation, the change in particle size and the possibility for oxidation of the copper particles are examined in the framework of Mie theory.
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| 41. |
- Stepanov, Andrei, et al.
(författare)
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Nanosecond pulse laser and furnace annealing of silver nanoparticles formed by implantation in silicate glass
- 2004
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Ingår i: Surface and Coatings Technology. ; 185:1, s. 30-37
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Tidskriftsartikel (refereegranskat)abstract
- Soda-lime silicate glasses implanted with 60 keV Ag+ ions with a dose of 3x1016 ion/cm2 at an ion current density of 10 μA/cm2 were investigated. As a result of the ion implantation, a composite layer with silver nanoparticles is synthesised in the near-surface region. This layer is characterised by high non-uniformity in the size distribution of these particles over the depth of the layer. Subsequent pulsed laser irradiation in combination with furnace annealing makes it possible to modify this composite layer, improving the uniformity in the size distribution of the nanoparticles. This is particularly promising for development of the technology for fabrication of non-linear optical materials. To control the parameters of the obtained layers a method based on the analysis of the optical reflection spectra measured on the implanted side and on the rear side of a glass substrate is applied. In addition, factors influencing the experimental data are discussed and the optical extinction spectra of the nanoparticles in the glass are modelled using Mie theory.
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| 42. |
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| 43. |
- Vilensky, A.I., et al.
(författare)
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THERMAL REGRESSION OF LATENT TRACKS IN THE POLYMER IRRADIATED BY HIGH ENERGY HEAVY IONS
- 2004
-
Ingår i: Nuclear Instruments and Methods in Physics Research B. ; 218, s. 294-299
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Tidskriftsartikel (refereegranskat)abstract
- Influence of heat treatment (85-180 oC) on latent tracks (LTs) in poly(ethylene terephthalate) (PET) films irradiated by Xe ions with energy of 1 MeV/nucleon was studied. Kinetics of the alkaline etching (layer-by-layer technique) was investigated. Thermal annealing rises the time of through-pore formation. The etching of through pores, investigated by Hagen-Poiseuille and atomic force microscopy (AFM) methods, was found to be non-linear: steps were discovered at the etching diagram. They were associated with earlier detected zones of high chemical stability around the track (with the diameters of approximately 10 and 20 nm). Using AFM method an appearance of surface craters after the irradiation was found. After the annealing the shape of these defects changed to the hillock form. From analysis of the Raman and electron paramagnetic resonance (EPR) spectra it is supposed that polymer structure in LT area was changed towards carbonaceous phase with graphite-like inclusions, which is evolving under the annealing and effecting the sequential etching process.
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| 44. |
- Vuckovic, Sasa, 1974, et al.
(författare)
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Laser ablation source for formation and deposition of size-selected metal clusters
- 2008
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 79:7
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Tidskriftsartikel (refereegranskat)abstract
- This work describes construction of a source and optimisation of its parameters for production of cluster ion beams using material ablation by the second harmonic of a Nd:YAG laser (532 nm). The influence of different source parameters such as carrier gas pressure, laser power, delay time between gas, and laser pulses as well as nozzle configuration on the cluster formation are studied. For the current experiments the laser ablation cluster source was optimized for production of Co cluster ions. Clusters with n up to 150 atoms are registered by a time-of-flight mass spectrometer. Deposition of size-selected Co50 clusters with kinetic energies in the interval of 250–4850 eV/cluster on highly ordered pyrolytic graphite is studied. At the highest impact energies the clusters are implanted. Craters and well-like structures can be seen by scanning tunneling microscopy at impact spots. A decrease in cluster kinetic energy leads to formation of bumplike structures which probably represent damaged graphite areas with incorporated Co atoms. Further decrease in the cluster impact energy to the level of 450–250 eV/cluster creates condition for so-called cluster pinning when the cluster constituents are intact but the energy transferred to the graphite is still enough to produce radiation defects to which the cluster is bound.
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| 45. |
- Vuckovic, Sasa, 1974, et al.
(författare)
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Pinning of size-selected Co clusters on highly ordered pyrolytic graphite
- 2009
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Ingår i: European Physical Journal D. ; 52:1-3, s. 107-110
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Tidskriftsartikel (refereegranskat)abstract
- Deposition and implantation of size-selected Co50±5 cluster ions on/in highly ordered pyrolytic graphite (HOPG) have been performed. Cobalt clusters were produced by laser ablation using the second harmonic (532 nm) of a Nd:YAG laser. They were deposited/implanted with energies of 250-4850 eV/cluster and examined using scanning tunneling microscopy (STM). For the highest energies the clusters created craters and wells with residual clusters at the bottom of the wells. Decrease of the impact energy led to formation of bumps which consist of damaged graphite areas mixed with fragmented cobalt clusters. Further decrease of the impact energy to 250-450 eV/cluster probably corresponds to the so-called pinning regime, when the impacting cluster creates defects in the surface layer and becomes bound to them. The transition from implantation to pinning with a decrease of impact energy was confirmed by etching experiments showing the depth of the damage introduced by the cluster collisions with HOPG.
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