Evaluation of secondary ion yield enhancement from polymer material by using TOF-SIMS equipped with a gold cluster ion source

We investigated the enhancement of the secondary ion intensity in the TOF-SIMS spectra obtained by Au⁺ and Au₃⁺ bombardment in comparison with Ga⁺ excitation using polymer samples with different molecular weight distributions. Since the polymer samples used in this experiment have a wide molecular weight distribution, the advantages of the gold cluster primary ion source over monoatomic ion could accurately be evaluated. It was observed that the degree of fragmentation decreased by the usage of cluster primary ion beam compared with monoatomic ion beam, which was observed as a shift of the intensity distribution in the spectra. It was also found out that the mass effect of Au⁺ and Ga⁺ as monoatomic primary ion, resulted in about 10-60 times of enhancement for both samples with different molecular distributions. On the other hand, the Au₃⁺ bombardment caused intensity enhancement about 100-2600 compared with Ga⁺ bombardment, depending on the mass range of the detected secondary ion species. The cluster primary ion effect of Au₃⁺, compared with Au⁺, therefore, was estimated to be about 10-45.     

Study of the Influence of Implanted Atoms on the Coefficients of the Sputtering of Silicon and Silicon with a Thin Oxide Film

The results of theoretical and experimental studies of the influence of Ba-atom implantation and the presence of an oxide film on the Si-surface sputtering coefficient under ion bombardment are presented. It is shown that, in the dose range of D = 10¹⁴–5 × 10¹⁵ cm^—2, the Si sputtering coefficient increases linearly, then this increase decelerates, and is almost constant, starting from 10¹⁶ cm^–2. In the range of D = 5 × 10¹⁵–5 × 10¹⁶ cm^—2, the Ba sputtering coefficient increases sharply, which is explained by an increase in the Ba concentration in the surface layer during the ion bombardment process.     

Self-oscillating mode of electron beam generation in a source with a grid plasma emitter

Plasma processes and electron beam generation in an electron source with a grid plasma cathode are investigated. Experiments are conducted under the conditions of efficient electron extraction and an intense counter ion flux, which break grid stabilization. It is shown that a rise in the gas pressure and in the emitting plasma potential leads to the plasma potential modulation in the frequency range 10⁴–10⁵ Hz. Under the self-oscillation conditions, an electron beam is obtained with a constant current of up to 16 A and an electron energy modulated up to 100% of the accelerating voltage level (100–300 V). An explanation is given for relaxation self-oscillations arising when the plasma potential grows and for the system’s inertial non-linearity arising when the plasma potential induced by the space charge of the counter ion flux lags behind the current of electron-beam-generated ions.     

Effect of high doses on the Si <Emphasis Type="Italic">L</Emphasis><Subscript>2,3</Subscript> x-ray emission spectra of silicon implanted with iron ions under steady-state conditions

The effect of high doses on p-and n-type silicon samples implanted with Fe⁺ ions under steady-state conditions (implantation energy, 100 keV; ion current density, 0.6–0.8 μA/cm²; irradiation dose, 10¹⁴–10¹⁶ ions/cm²) is investigated using Si L _{2, 3} x-ray emission spectroscopy (the 3d3s → 2p electronic transition). An analysis of the Si L x-ray emission spectra of the silicon samples is performed by comparison with the spectra of reference materials and the spectra of silicon samples implanted with Fe⁺ ions in a pulsed mode. The Si L x-ray emission spectra are simulated by the molecular dynamics and full-potential linearized augmented-plane-wave (FLAPW) methods. It is revealed that the effect of high doses under steady-state conditions of Fe⁺ ion implantation into the semiconductor crystal matrix exhibits specific features: the disordering of the structure and partial amorphization of the sample from the surface deep into the bulk are more pronounced than those observed under conditions of pulsed ion implantation, although virtually no recrystallization of the sample at the threshold dose occurs. The most probable origins and mechanisms of the effect of high doses on the samples under investigation are discussed.     

Generation of a fast-ion beam upon the interaction of a multiterawatt picosecond laser pulse with a solid target

The parameters of fast particles generated upon the interaction of 10¹⁹ W/cm² laser pulses with solid targets are studied. The spatial and energy parameters of fast ions are investigated. It is found that approximately 1–3% of the laser energy is transformed to the energy of mega-and submegaelectronvolt ions at laser pulse intensities ≥10¹⁸ W/cm². It is shown experimentally that an ion beam is directed perpendicular to the target surface. The analytic and numerical simulations agree with experimental results and predict the propagation of fast electrons in the mirror direction with respect to the incident laser beam and of ions perpendicular to the target. The theoretical calculations are compared with the experimental output and spectra of fast electrons and ions.     

Optical properties of ZnO and Al2O3 implanted with silver ions

ZnO and Al₂O₃ samples implanted with 30-keV silver ions with fluences in the interval (0.25–1.00) × 10¹⁷ ions/cm² are studied by the method of optical photometry in the visible part of the spectrum. The optical transmission spectra of the implanted samples exhibit a selective band associated with surface plasmon resonance absorption of silver nanoparticles. The intensity of this band nonmonotonically depends on the implantation fluence. The silver ion depth distribution in the samples is calculated. It is shown that the non-monotonicity observed in experiments is due to an increase in the substrate sputtering ratio with increasing implantation fluence. It is found that vacuum thermal annealing of the implanted Al₂O₃ layers up to 700°C causes a considerable narrowing of the plasmon absorption bandwidth without a tangible change in its intensity. At higher annealing temperatures, the plasmon absorption band broadens and its intensity drops. Annealing of the ZnO films under such conditions causes their complete vaporization.     

Ion beam synthesis and investigation of nanocomposite multiferroics based on barium titanate with 3d metal nanoparticles

Samples of nanocomposite multiferroics have been synthesized by implantation of Co⁺, Fe⁺, and Ni⁺ ions with an energy of 40 keV into ferroelectric barium titanate plates to doses in the range (0.5–1.5) × 10¹⁷ ions/cm². It has been found that nanoparticles of metallic iron, cobalt, or nickel are formed in the barium titanate layer subjected to ion bombardment. With an increase in the implantation dose, the implanted samples sequentially exhibit superparamagnetic, soft magnetic, and, finally, strong ferromagnetic properties at room temperature. The average sizes of ion-synthesized 3d-metal nanoparticles vary in the range from 5 to 10 nm depending on the implantation dose. Investigation of the orientation dependence of the magnetic hysteresis loops has demonstrated that the samples show a uniaxial (“easy plane”) magnetic anisotropy typical of thin granular magnetic films. Ferromagnetic BaTiO₃: 3d metal samples are characterized by a significant shift of the ferromagnetic resonance signal in an external electric field, as well as by a large (in magnitude) magnetodielectric effect at room temperature. These results indicate that there is a strong magnetoelectric coupling between the ferroelectric barium titanate matrix and ion-synthesized nanoparticles of magnetic metals.     

Analysis of a tungsten surface irradiated by fast ions and deuterium plasma

The effects occurring on the surface of tungsten under irradiation with fast ions with an energy in the megaelectrolvolt range and with high fluxes of hydrogen (deuterium) plasma are considered. These effects are radiation damage of the surface layer of the material, its erosion and deuterium retention in it. Irradiation with helium ⁴He²⁺ (3.2–4.0 MeV) and carbon ¹²C³⁺ (10 MeV) ions is performed using a cyclotron at the National Research Center Kurchatov Institute. The thickness of the damaged layer is 3.5–6 μm. The irradiated samples are exposed to steady-state deuterium plasma using a LENTA linear plasma facility to reach a plasma ion fluence of 10²¹–10²² cm^?2. Tungsten erosion and modification of the structure of the damaged layer are analyzed at a plasma-ion energy of 250 eV. Deuterium retention in the damaged layer is studied by elastic recoil detection analysis. The deuterium concentration and its penetration depth into the material are measured. The data obtained for different kinds of fast ions used in the work are compared.     

Enhanced radiation hardness of ZnO nanorods versus bulk layers

It is shown that ZnO nanorods grown by MOCVD exhibit enhanced radiation hardness against high energy heavy ion irradiation as compared to bulk layers. The decrease of the luminescence intensity induced by 130 MeV Xe⁺²³ irradiation at a dose of 1.5 × 10¹⁴ cm^–2 in ZnO nanorods is nearly identical to that induced by a dose of 6 × 10¹² cm^–2 in bulk layers. The change in the nature of electronic transitions responsible for luminescence occurs at an irradiation dose around 1 × 10¹⁴ cm^–2 and 5 × 10¹² cm^–2 in nanorods and bulk layers, respectively. High energy heavy ion irradiation followed by thermal annealing is also effective on the quality of ZnO nanorods grown by electrodeposition. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Resonance Raman study of He+ ion implanted nanostructured ZnS

ZnS nanocrytsals of size ∼2.5 nm were prepared by chemical precipitation technique. Pressed pellets of nanostructured ZnS were implanted with He⁺ ions at doses of 5 × 10¹⁴, 1 × 10¹⁵ and 5 × 10¹⁵ ions/cm². Raman spectra of both unimplanted and He⁺ ion implanted samples were recorded with ultraviolet (UV) excitation. LO, 2LO, 2TO, (LO + TA) and (2TO − TA) modes of ZnS were observed in the resonance Raman spectra of the unimplanted nanostructured ZnS samples. In addition, a surface mode was observed at 294 cm⁻¹. With the implantation of He⁺ ions, the 2TO mode disappeared and 2LO mode became prominent and this observation was attributed to the decrease in band gap of ZnS nanocrytsals due to ion implantation. The exciton–LO phonon coupling strength was determined from the intensity ratio of 2LO to LO modes and it was observed that the exciton–LO phonon coupling strength increases with increase in implantation dose. In the present work, we report for the first time the observation of 2TO mode in the resonance Raman spectrum of nanostructured ZnS and also the modification of exciton–LO phonon coupling strength of semiconductor nanoparticles by ion implantation. Copyright © 2008 John Wiley & Sons, Ltd.     

Sputtering of highly oriented pyrolytic graphite with 30 keV Argon ions

The influence of the incidence angle of 30 keV Ar⁺ ions, ion fluence and target temperature on the sputtering yield and surface microgeometry of highly oriented pyrolytic graphite (UPV-1T) samples was experimentally studied. It was found that at fluences more than 5 × 10¹⁹ ion cm^?2 the sputtering yield at room temperature in the range of the ion incidence angle from 0° to 80° is twice as small as the corresponding experimental data for both polycrystalline graphite and glassy carbon. The analysis of ion-induced relief permits us to suppose the topographical suppression mechanism of highly oriented pyrolytic graphite sputtering.     

Carbonization in boron-ion-implanted polymethylmethacrylate as revealed from Raman spectroscopy and electrical measurements

ABSTRACT

The results of Raman spectroscopy and electrical measurements of 40 keV boron-ion-implanted polymethylmethacrylate with ion doses from 6.25 × 10¹⁴ to 5.0 × 10¹⁶ ions/cm² are reported for the first time. The Raman spectra recorded in the 400–3800 cm^?1 range, showing the formation of new carbon–carbon bands for the as-implanted samples at higher ion doses (>10¹⁶ ions/cm²), are found to be an additional support for carbonization processes earlier revealed by slow positrons. The current–voltage dependences at 360 K testify also that the as-implanted samples examined with higher fluences (3.75 × 10¹⁶ and 5.0 × 10¹⁶ ions/cm²) have created a very thin conductive layer or conductive joints due to carbonization.     

Radiation damage of material surfaces under prolonged irradiation with He+ and Ar+ ions with broad energy spectra

The results of studying the redistribution of Be, Al, Ti, Fe, Cu, Zr, Mo, and W atoms incorporated in polycrystalline metal samples under irradiation with He⁺, (He⁺ + Ar⁺), and Ar⁺ ion beams with a broad energy spectrum and an average energy of 10 keV at irradiation doses of 1 × 10²¹ ion/cm² are studied. It is discovered that irradiation at doses exceeding 1 × 10¹⁹ ion/cm² results in local small-crystal formations being produced in a near-surface substrate layer. Their typical dimensions are less than 1–5 μm, and their the density is up to 1–100. They contain incorporated atoms and impurity atoms with a concentration of 0.1–10 at %. Subsequent irradiation at a dose of 1 × 10²⁰ ions/cm² or more leads to disappearance of these formations, mainly because of sputtering processes.     

X-ray spectroscopy diagnostics of a recombining plasma in laboratory astrophysics studies

The investigation of a recombining laser plasma is topical primarily because it can be used to simulate the interaction between plasma jets in astrophysical objects. It has been shown that the relative intensities of transitions of a resonance series of He-like multicharged ions can be used for the diagnostics of the recombining plasma. It has been found that the intensities of the indicated transitions for ions with the nuclear charge number Z _n ~ 10 are sensitive to the plasma density in the range N _e ~ 10¹⁶–10²⁰ cm^–3 at temperatures of 10–100 eV. The calculations performed for the F VIII ion have determined the parameters of plasma jets created at the ELFIE nanosecond laser facility (Ecole Polytechnique, France) in order to simulate astrophysical phenomena. The resulting universal calculation dependences can be used to diagnose different recombining plasmas containing helium-like fluorine ions.     

Comparative emission characteristics of a negative hydrogen ion source with a reflex discharge with and without Cs

A theoretical and experimental investigation is made to determine how cesium in the volume and at the surfaces of an ion source influences its emission characteristics. It is shown that under the real conditions of an ion source, cesium in the volume makes an appreciable influence to the kinetic processes but barely affects the H⁻ ion current extracted from the source. However, cesium at the surface of the source increases the H⁻ ion current severalfold even when the H-H⁻ conversion efficiency is low (γ≈10⁻³). The theoretical conclusions show good agreement with the experimental data obtained in the present study. Zh. Tekh. Fiz. 69, 102–109 (April 1999)     

Mechanism of small variations in energy of ultracold neutrons interacting with a surface

The cause of the small heating of ultracold neutrons (UCNs) by ～10^?7 eV with a probability of 10^?8–10^?5 per collision with a surface was investigated. Neutrons heated in this way will be called vaporized UCNs (VUCNs). It was established that a preliminary heating of a sample in vacuum up to a temperature of 500–600 K can increase small-heating probability P _VUCN by a factor of at least ～100 and 10 on a stainless steel and a copper surface, respectively. For the first time, an extremely vigorous small heating of UCNs was observed on a powder of diamond nanoparticles. In this case, both the VUCN spectrum and the temperature dependence of probability P _VUCN were similar to those previously obtained for stainless steel, beryllium, and copper samples. On the surface of single crystal sapphire, neither the small heating of UCNs nor nanoparticles were found. All these facts indicate that VUCNs are likely produced by inelastic scattering of UCNs on weakly bound surface nanoparticles being in permanent thermal motion.     

Ion beam modification of surface properties of CR-39

The effects of ion-beam bombardment on the physical and chemical properties of poly(allyl diglycol carbonate) (CR-39) polymer have been investigated. CR-39 samples were bombarded with 320 keV Ar and 130 keV He ions at fluences ranging from 1 × 10¹³ to 2 × 10¹⁶ ions/cm². The nature and extent of radiation damage induced were studied by UV–VIS spectrometry, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, as well as Vickers' hardness measurements. In addition, the effect of ion fluence on the wetting properties of ion-beam bombarded CR-39 polymer was determined by measuring the contact angle for distilled water. UV–VIS spectra of bombarded samples reveal that the optical band gap decreases with increasing ion fluence for both Ar and He ions. In the FTIR spectra, changes in the intensity of the bands on irradiation relative to pristine samples occurred with the appearance of new bands. XRD analyses showed that the degree of ordering of the CR-39 polymer is dependent on the ion fluence. Changes of surface layer composition and an increase in the number of carbonaceous clusters produced important change in the energy gap and the surface wettability. The surface hardness increased from 10.54 MPa for pristine samples to 28.98 and 23.35 MPa for samples bombarded with Ar and He ions at the highest fluence, respectively.     

Electrical characteristics of etched ion-tracks in polyimide filled with silver nanoparticles

Silicon ions, of energy 150?MeV and fluence ～10¹²?ions/cm², were used to register latent tracks in 40?µm thick polyimide samples. Different sizes of tracks were obtained by etching the ion irradiated polyimide samples, in chemical solutions, by varying the temperature and etching period. Silver nanoparticles were diffused into the etched tracks by immersing the polyimide samples in silver solution and then irradiating with 6.5?MeV electrons at different fluences varying from 1?×?10¹⁵ to 5?×?10¹⁵?cm^?2. Results of morphological and elemental analysis, carried out by Scanning Electron Microscopy and Energy Dispersive X-ray. Analysis revealed that the conical tracks could be fully filled with silver nanoparticles at electron fluence of 5?×?10¹⁵?cm^?2. The minimum d. c. resistance of an array of tracks, filled with silver nanoparticles and measured across the polyimide film, was orders of magnitude higher as compared to that of silver wires of equivalent sizes connected in parallel. In addition, these silver nanoparticles filled tracks exhibited rectifying I–V behavior and frequency dependent a. c. resistance, characteristic of metal–polymer nano-composites. Possible mechanisms have been discussed, which can justify the asymmetric current–voltage characteristics in such nano-composites.     

Effects of silicon negative ion implantation in semi-insulating gallium arsenide

ABSTRACT

In the present work, effects of silicon negative ion implantation into semi-insulating gallium arsenide (GaAs) samples with fluences varying between 1?×?10¹⁵ and 4?×?10¹⁷?ions?cm^?2 at 100?keV have been described. Atomic force microscopic images obtained from samples implanted with fluence up to 1?×?10¹⁷?ion?cm^?2 showed the formation of GaAs clusters on the surface of the sample. The shape, size and density of these clusters were found to depend on ion fluence. Whereas sample implanted at higher fluence of 4?×?10¹⁷?ions?cm^?2 showed bump of arbitrary shapes due to cumulative effect of multiple silicon ion impact with GaAs on the same place. GXRD study revealed formation of silicon crystallites in the gallium arsenide sample after implantation. The silicon crystallite size estimated from the full width at half maxima of silicon (111) XRD peak using Debye-Scherrer formula was found to vary between 1.72 and 1.87?nm with respect to ion fluence. Hall measurement revealed the formation of n-type layer in gallium arsenide samples. The current–voltage measurement of the sample implanted with different fluences exhibited the diode like behavior.     

Modifications induced by swift heavy ions in rapidly solidified Sn–8.5Sb–5.5Cu alloy

Alloys of composition Sn–8.5Sb–5.5Cu (in atomic percent) were rapidly solidified by a melt-spinning technique. The samples were irradiated at room temperature with GeV uranium ions of fluences between 9×10⁸ and 9×10¹¹ ions cm^?2. X-ray diffraction analysis revealed the formation of a new-phase Cu₁₁Sb₃ as well as a reduction in the axial ratio (c/a) of the matrix (β -Sn) indicating the regular re-arrangement of atoms. Scanning force microscopy showed no surface topographic changes with the ion fluence. The mechanical properties (Young's modulus and hardness) of the irradiated alloys were studied as a function of ion fluence. The radiation-annealing process is discussed in terms of the evolution of both resistivity and hardness as a function of ion fluence.