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)

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

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

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

Retraction notice to “Porous germanium with copper nanoparticles formed by ion implantation” [Vacuum 166 (2019) 84–87] (Vacuum (2019) 166 (84–87), (S0042207X19307195), (10.1016/j.vacuum.2019.04.062))

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor in Chief due to very significant similarity between it and another published article by the same corresponding author, which has copied Fig. 1 and results from Nanotechnologies in Russia 13 (2018) 487–495 [Rossiiskie Nanotekhnologii, 2018, Vol. 13, Nos. 9–10], DOI: 10.1134/S1995078018050129

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

Analysis of Surface Morphology and Chemical Composition of Silicon Implanted with Copper Ions

© 2020, Pleiades Publishing, Ltd. Abstract: We report on the results of analysis of the structure and chemical composition of the surface of c-Si single crystal substrates implanted with Cu+ ions with energy of 40 keV and doses in a range of 3.1 × 1015–1.25 × 1017 ions/cm2 for a current density of 8 μA/cm2 in the ion beam. It has been established using scanning electron microscopy and probe microscopy combined with X-ray photoelectron and Auger spectroscopy that at the initial stage, the implantation with Cu+ ions to a dose of 6.25 × 1016 ions/cm2 induces the formation of Cu nanoparticles with an average size of 10 nm in the Si surface layer. Upon a further increase in the implantation dose, beginning with 1.25 × 1017 ions/cm2 and higher, the nucleation of the η phase of copper silicide (η-Cu3Si) is observed. This is due to heating of the surface layer of the Si substrate during its irradiation to a temperature facilitating the formation of the η-Cu3Si phase

Hybrid Ag/ZnO nanostructures for SERS detection of ammonium nitrate

© 2020 IOP Publishing Ltd. All rights reserved. Ag/ZnO composite nanostructures are produced by combined laser and ion implantation techniques. The ZnO layers are grown on SiO2 (001) and Al2O3 (r-cut) substrates by pulsed laser deposition (PLD) in vacuum and in oxygen ambient using a third-harmonic Nd:YAG laser. The ion implantation allows the introduction of Ag nanoparticles (NPs) in the surface of the ZnO matrix. These NPs are incorporated into the ZnO matrices to fabricate metal-semiconductor nanocomposites with the aim of manipulating their functionalities, exploiting the characteristics of both the matrix and the metal NPs. The composite samples are modified by laser annealing at 355 nm and 532 nm. The changes are investigated in the plasmon resonance absorption of the nanostructures before and after the annealing. The influence is explored of the different substrates used and the deposition conditions of ZnO growth on the properties of Ag/ZnO. The nanostructures obtained are efficient as SERS substrates for detection of ammonium nitrate under laser excitation at 633 nm. The SERS enhancement is attributed to the synergistic interactions between the plasmonic coupling among the surface embedded AgNPs and the enhanced charge transfer properties of the ZnO