Low-temperature positron annihilation study of B⁺-ion implanted PMMA

Temperature dependent positron annihilation lifetime spectroscopy (PALS) measurements in the range of 50–300 K are carried out to study positronium formation in 40 keV B+-ion implanted polymethylmethacrylate (B:PMMA) with two ion doses of 3.13·10¹⁵ and 3.75·10¹⁶ ions/cm². The investigated samples show the various temperature trends of ortho-positronium (o-Ps) lifetime τ3 and intensity I3 in PMMA before and after ion implantation. Two transitions in the vicinity of ∼150 and ∼250 K, ascribed to γ and β transitions, respectively, are observed in the PMMA and B:PMMA samples in consistent with reference data for pristine sample. The obtained results are compared with room temperature PALS study of PMMA with different molecular weight (Mw) which known from literature. It is found that B⁺-ion implantation leads to decreasing Mw in PMMA at lower ion dose. At higher ion dose the local destruction of polymeric structure follows to broadening of lifetime distribution (hole size distribution)

Isothermal Pneumo-Forming of Hemispherical Parts Made Out of Anisotropic Materials In Short-Term Creep Mode

International audienceProvided here are results of theoretical and experimental research of strained and stressed state, force modes, geometrical sizes for the blanks, and limit possibilities of deformation during isothermal blow molding of hemispheric parts of anisotropic material in creeping mode .Determined is the effect for the researched parameters of the studied deformation process, produced by anisotropy of mechanical properties, loading conditions and blank's geometric dimensions. Comparison of the theoretical and experimental data regarding the relative blank thickness in the blank dome and base points, and of data regarding the relative height of the blank, point to their satisfactory agreement (up to 10 percent). Recommendations have been developed regarding calculation of scientifically-based technological parameters for operations of isothermal straining of semi-spherical components made out of highly strong anisotropic materials in the mode of short-time creeping. The recommendations were used during development of technological processes of manufacture-in the mode of short-time creeping and out of highly strong anisotropic materials-.of semispherical components conforming to the operational technical requirements. The technological processes provide for increasing specific strength by 1,5 – 1,7 times, for decreasing the mass by 1,5 times, for reducing labor content by 2-3 times, and for growth of capacity factor – from 0,3 to 0,9

Sputtering of Silicon Surface during Low-Energy High-Dose Implantation with Silver Ions

© 2020, Pleiades Publishing, Ltd. Abstract: We report on the results of first practical observations of sputtering of the Si surface during the implantation with Ag+ ions with an energy of 30 keV depending on irradiation dose D in the interval from 2.5 × 1016 to 1.5 × 1017 ion/cm2 for a fixed value of ion beam current density J = 8 μA/cm2, as well as for variation of J = 2, 5, 8, 15, and 20 μA/cm2 at constant D = 1.5 × 1017 ion/cm2. In the former case, the thickness of the porous Si (PSi) layer being sputtered increases monotonically to 50 nm at the maximum value of D; in this case, the effective sputtering ratio of the implanted Ag : PSi layer is 1.6. We have also established that the thickness of the sputtered layer increases with current density J

Microstructured Substrates for Counting Bacteria Formed by Ion Implantation

© 2020, Pleiades Publishing, Ltd. Abstract: A novel technological approach based on ion implantation for obtaining nanostructured substrates for the visual characterization of ultrasmall biological objects and microorganisms has been described. By means of argon-ion implantation of silicate glasses through surface masks made of copper wire mesh, periodic microstructures in the form of gratings with mesh sizes of 50 × 50 μm were formed. The novel substrates were tested by scanning electron microscopy and energy-dispersive X-ray analysis, as well as atomic force microscopy, using bacteria of the genera Bacillus and Staphylococcus deposited onto their surface

Formation of nanoporous Ge layers by ion implantation at different temperatures of c-Ge substrate

The flat monocrystalline c-Ge wafers implanted by 108Ag + ions with the energy E = 30 keV, dose D = 1.3·1016 ion/cm2 and at current density J = 5 μA/cm2 for various substrate temperatures from 25 to 400 °C were studied. By scanning electron microscopy and optical reflection spectroscopy it was found that as a result of ion implantation in the temperature range from 25 to 300 °C an amorphous porous Ag:PGe layers of a spongy structure consisting of Ge nanowires on the c-Ge substrate surface are formed. The diameter of Ge nanowires increases from 16 to 24 nm with a rising of substrate temperature. It is shown that at the highest temperature of 400 °C, the porous structure does not form and the Ge surface remains flat on which the formation of Ag nanoparticles can be observed. A change in the level of the sample surface in dependence on substrate temperature due to swelling up to 280 °C was replaced by effective ion sputtering at higher temperatures

SERS activity of Ag/ZnO nanocomposites produced by combined surface modification techniques

© 2020 SPIE. The present study is focused on the development of advanced technology for creation of plasmonic composite nanostructures for Surface Enhanced Raman Spectroscopy (SERS) detection of ammonium nitrate. The investigation of the interaction of nanostructured composite objects with electromagnetic field, the description of their optical properties as well as determination of mechanisms and conditions for their effective modification brings the information for potential application as SERS substrates. The ZnO thin films are deposited by pulsed lased deposition (PLD) in an oxygen environment at high substrate temperature. The laser grown ZnO films are modified by Ag-ion implantation. The produced nanocomposites are subsequently laser annealed at different laser wavelengths. The influence of the ion implantation doses and the laser annealing parameters on the SERS activity of produced nanostructures is investigated. The observation of morphology of the samples demonstrates the influence of the laser annealing wavelength on the size distribution of embedded silver nanoparticles on the ZnO matrix. The plasmonic behaviour of embedded metal nanoparticles is determined by studying the optical properties of the fabricated structures. The proposed combined method for synthesis has potential application in fabrication of reliable substrates for Raman spectroscopy analysis with high sensitivity. The design of appropriate structures by laser and ion implantation methods can increase the efficiency of the high resolution analyses

Features of Formation of Cr³⁺ Paramagnetic Centers in Strontium Titanate (SrTiO<inf>3</inf>) Implanted with Chromium Ions

© 2020, Pleiades Publishing, Ltd. Abstract: We present results of structural (XPS) and magnetic resonance (EPR) studies of single-crystal plates of strontium titanate (SrTiO3) heavily doped with chromium utilizing ion implantation technique. It was shown that the temperature of the oxide matrix during ion implantation (300 or 900 K) significantly affects the valence state of the implanted chromium impurity (Cr0 or Cr3+) and the depth profiles of its distribution in the SrTiO3 matrix. Using the EPR method, it was established that as a result of implantation of chromium impurity at an elevated substrate temperature during irradiation, the dominating color centers in the surface implanted oxide layer appear in the form of trivalent chromium ions in a cubic environment with a g-factor g = 1.976 and the value of the hyperfine coupling constant with the magnetic nucleus of 53Cr isotope, A = 16.2 × 10–4 cm–1. From a comparison of these data with parameters for the cubic Cr3+ impurity center in the SrTiO3 single crystal, it was concluded that this center is localized in the structural positions of titanium. Upon implantation of a chromium impurity in SrTiO3 at room temperature of the substrate, in addition to cubic Cr3+ centers, new signals were detected in the EPR spectra, apparently associated with the formation of oxygen vacancies in the implanted oxide. However, the number of these additional centers does not change significantly even after high-temperature heat treatment of samples in air at temperatures up to 900 K. It is noted that signals of this type also appear in the spectra of SrTiO3 samples obtained as a result of hot implantation and then subjected to high-temperature thermal annealing

The relationship between tunable optical absorption and SERS activity of Ag/ZnO nanocomposites

The optical characteristics of Ag/ZnO composite nanostructures have long been of particular interest and, thus, the subject of broad experimental and theoretical studies. This work is focused on the synthesis and properties of Ag/ZnO nanocomposites and demonstrates the possibility of their application as active substrates for surface-enhanced Raman spectroscopy (SERS) in detection of pesticides. The samples were synthesized by pulsed laser deposition (PLD) of ZnO thin films, followed by Ag+-ion implantation in the ZnO matrix and by laser annealing of the heterostructures produced. The morphology and properties of the samples were studied with respect to the processing parameters. The optical absorption studies revealed the existence of tunable surface plasmon resonance of silver nanoparticles in the ZnO matrix. Theoretical calculations of the optical properties, as extinction, absorption and scattering efficiencies, were performed based on a generalized multi-particle Mie (GMM) approach. The simulated system assumed in this comparative study consists of a surface-embedded ensemble of silver nanoparticles in a ZnO surrounding media and in air. The simulated structures were reproduced from the corresponding SEM images after laser annealing at 355 nm and 532 nm

Incoherent-light pulse annealing of nanoporous germanium layers formed by ion implantation

The study addresses the monocrystalline c-Ge substrates implanted by Ag+ ions with the energy of 30 keV, irradiation dose of 7.5·1016 ion/cm2 at current density of 8 μA/cm2 and annealed by incoherent-light pulse. By scanning electron microscopy and optical reflection spectroscopy measurements it was shown that after ion implantation an amorphous porous Ag:PGe layer of a spongy structure with nanowires on the c-Ge substrate were formed. Pulsed light annealing of the implanted samples leads to partial melting and recrystallization of the surface Ag:PGe layer. The spongy annealed structure of the Ag:PGe layer was not destroyed, however the diameters of nanowires increased by about 1,5 times