Optical reflectance of germanium surface modified by implanted silver ions

© 2020 Elsevier B.V. The article focuses on the optical reflection from the surface of the Ge substrates implanted with Ag+ ions at the low energy of 30 keV and the dose range from 5.0⋅1014 to 1.5⋅1017 ion/cm2. The optical findings were compared with the electron microscopy observations. The study showed that if the ion radiation dose increases, the reflection intensity monotonously decreases in the ultraviolet and visible spectral regions from virgin Ge surface. This occurs due to amorphization if the doses are low and due to formation of nanoporous structure of interwoven nanowires in the near-surface implanted Ge layer for the higher doses. According to the Mie theory modeling of optical scattering by nanostructured Ge shows a qualitative agreement between the calculated and experimental spectra

Raman study of germanium nanowires formed by low energy Ag⁺ ion implantation

Porous Ge layers of nanowires were formed by low energy (30 keV) Ag+ ion implantation of crystalline c-Ge substrate. Different radiation doses resulted in the formation of nanowires with various mean diameters. The obtained layers were studied by Raman spectroscopy using helium-neon and argon exciting lasers at wavelength of 633 and 488 nm respectively. It was demonstrated that implanted amorphous layers were locally crystallized by the lasers. The crystallization thresholds were found to be 3 kW/cm2 for helium-neon exciting laser and 1 kW/cm2 for argon exciting laser. The variation of thresholds is suggested to be due to the different light penetration depths at these wavelengths in Ge. The crystalline volume fraction was determined and reached maximum value of 6–7%, the divergence of which can be explained by the difference in the distribution of Ge nanowire diameters

Formation of Cu nanoparticles and Cu<inf>3</inf>Si phase in Si by ion implantation

© 2020 Elsevier Ltd The results of low-energy high-dose implantation of single-crystal c-Si by Cu+ ions at energy 40 keV, current density 8 μA/cm2 and doses of 3.1·1016 and 1.25·1017 ion/cm2 are presented. It was shown that if the dose is low Cu nanoparticles with average diameter of 10 nm are formed in a near-surface implanted Si layer. When the dose is higher Cu ions chemically interact with the Si atoms and the synthesis of the η″-phase Cu3Si instead of Cu nanoparticles is observed. Cu nanoparticles transformation to Cu3Si phase in the sample heated by long time implantation is discussed

Pulse ion annealing of silicon layers with silver nanoparticles formed by ion implantation

© 2020 Elsevier Ltd The paper presents the results of Si surface modification created by implantation with Ag+ ions at energy of 30 keV, current density of 8 μA/cm2 for various doses from 6.0·1015 to 7.5·1016 ion/cm2 and annealed by powerful beam pulses (C+, H+) of nanosecond duration. Scanning electron microscopy and optical reflection measurements showed that after ion implantation an amorphous a-Si layer on the surface of c-Si substrates with Ag nanoparticles was formed. Followed pulse ion beam annealing of sample obtained at lowest dose of 6.0·1015 ion/cm2 leads to melting and recrystallization of the Si surface layer with segregation of Ag nanoparticles. For samples implanted with doses higher than 2.5·1016 ion/cm2 after annealing an epitaxial cellular breakdown structures are fabricated on the Si surface decorated at the cell boundaries by Ag nanoparticles

Impedimetric DNA Sensor Based on Poly(proflavine) for Determination of Anthracycline Drugs

© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electropolymerization is often used as a tool for immobilization of charged biopolymers and their electric wiring in the biosensor assembly. In this work, electropolymerization of proflavine has been for the first time used for the physical adsorption of DNA and measurement of anthracycline drugs (doxorubicin and daunorubicin) able to intercalate DNA. Redox properties of the proflavine polymers on the glassy carbon electrode and DNA deposition were characterized with cyclic voltammetry, scanning electron microscopy and electrochemical impedance spectroscopy. It was shown that DNA decreased the peak currents on voltammogram but increased the charge transfer resistance. The latter effect is pronounced with the following drug application. The impedimetric response regularly increased with the drugs concentration in the range 1 nM to 0.1 μM for doxorubicin and 1 pM–10 nM for daunorubicin (limit of detections 0.3 and 0.001 nM, respectively). The biosensor was tested on pharmaceutical preparations and spiked solution simulating the plasma electrolytes and possible interference of serum proteins

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

Synthesis of Thin Niobium Films on Silicon and Study of Their Superconducting Properties in the Dimensional Crossover Region

Abstract: Niobium films with a thickness of 4–100 nm are synthesized on a silicon substrate under ultrahigh vacuum conditions. Measurements of the electrical resistance show a high superconducting transition temperature Tc in the range of 4.7–9.1 K and record-breaking small transition widths ΔTc in the range of 260–11 m. The dependences of Tc and ΔTc on the magnetic field are investigated, and the superconducting coherence lengths and mean free paths of conduction electrons for different thicknesses of the synthesized films are determined. A significant influence of the magnetic field on ΔTc is found, which reveals the transition from three- to two-dimensional superconductivity at thicknesses below 10 nm. The dependences of Tc and ΔTc on the thickness of the films and the magnitude of the magnetic field are discussed within the framework of existing theories of superconductivity in thin films of superconducting metals

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

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