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Porous Ge layers were fabricated by implanting Cu+ ions of various acceleration energies into c‐Ge substrate. This made it possible to form amorphous porous Ge layers of thicknesses from 18.6 to 50.5 nm. The distribution depth profiles of implanted Cu+ ions in Ge were simulated by SRIM‐2013 program. The formed layers were studied by Raman spectroscopy. The excitation was carried out by a laser with a wavelength of 488 nm, which has a small penetration depth of ∼20 nm. In the Raman spectra, there is a possibility to distinguish the contribution from the amorphous Ge film, the crystalline c‐Ge substrate, and Ge nanocrystals, which appear under intense laser excitation due to local crystallization. The decomposition of the spectra into individual components makes it possible to subtract the contribution of the substrate and estimate the crystalline volume fraction in the layers. The results obtained confirm the hypothesis of low thermal conductivity of the porous layer, due to which local crystallization occurs. [ABSTRACT FROM AUTHOR]

Porous Ge layers consisting of nanowires were formed by low‐energy high‐dose implantation of monocrystalline c‐Ge substrate with Ag+ and Cu+ ions. The obtained layers were studied by Raman spectroscopy using solid‐state and He‐Ne exciting lasers with wavelength of 532 and 633 nm, respectively. The crystalline volume fraction and local temperature of porous layers at the surface sites of laser probing were determined. To interpret the change in the shape of the spectra under the action of laser radiation, deconvolution into amorphous and nanocrystalline components was carried out. Analysis of the spectral line shape made it possible to estimate the crystalline and amorphous volume fractions. The quantum confinement model for Ge nanocrystallites was taken into account for accurate estimations of volume fractions. These estimates showed that the implanted amorphous layers of all samples were locally crystallized with a solid‐state laser. He‐Ne laser excitation resulted in partial crystallization only for layers obtained by Cu+ ion implantation. The measured ratio of the Stokes to anti‐Stokes components demonstrated that the porous layers obtained by implanting Ag+ ion were not heated by a He‐Ne laser and according to the analysis of spectral lines, the crystalline volume fraction did not appear in these layers during probing. The results obtained are explained by the difference in the penetration depth for various samples of the exciting radiation. [ABSTRACT FROM AUTHOR]

Performance of the material depends directly on the electronic and energy band structure, to improve the photoactivity of TiO2 and decrease carrier recombination centers induced by monodoping, the TiO2 thin film has been modified with V and N codopants by ion implantation for tailing and controlling the electronic structure and energy band structure. Compared to monodopant, codopants of V and N exhibit a synergistic effect in the photoactivity enhancement of TiO2. X-ray photoelectron spectroscopy (XPS) studies demonstrate that the implanted V and N ions are introduced into the lattice of TiO2 through V and N substituting Ti and O, respectively. The electronic structure of V/N codoped TiO2 was calculated by First-principles calculations based on density-functional theory, the results show the band edges of TiO2 can be tailored by V and N codopants. UV-vis spectra consistently show the absorption edge of V/N codoped TiO2 film is widen to visible light region. More importantly, the photoactivity of TiO2 film has been significantly improved after V/N codoping. The enhanced photocatalytic performance is believed to be due to the V and N codopants induced synergistic effect that not only enhances the absorption of visible light but also promotes the separation of photogenerated electrons and holes in TiO2. Besides, there exists an optimum for V/N ions implantation fluence. The capability of improving TiO2 photoactivity by V/N codoping could open up new opportunities in the development of highly efficient photocatalysts and photoelectrodes for solar energy and environmental applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The paper shows a new method of forming substrates (devices) with periodic micron surface grids for statistical analysis and visual characterization of ultra-small biological objects and microorganisms. When using implantation with Ar+ of silicate glasses through surface masks in the form of wire meshes, surface periodic structures in the form of gratings with cell sizes of 25×25 μm and a depth of 100 nm were fabricated. Testing of new types of devices was carried out using scanning electron and atomic force microscopy, as well as applying EDX analysis using the example of substrates with deposited bacteria as Bacillus subtilis. [ABSTRACT FROM AUTHOR]

Structural and photoelectric properties of composite Ag:Si layers formed in the near-surface area of a single-crystal c-Si substrate by a high-dose implantation of Ag+ ions with subsequent pulsed laser annealing (PLA) have been studied. It has been established that, as a result of ion implantation, a maximal concentration of Ag impurity (NAg ~ 4 × 1022 at/cm3) is concentrated near the surface and drops to a level of ~1019 at/cm3 at a depth of ~60 nm. Meanwhile, Ag nanoparticles and silver oxide (Ag2O) inclusions are contained in a formed thin layer of amorphized Si (a-Si). Melting of a near-surface area and diffusion redistribution of the implanted impurity have been achieved in conditions of PLA, which increases Ag concentration near the surface and at a depth of 60 nm. Dark current–voltage characteristics of a junction between a Ag:Si layer and a p-Si substrate showed formation of a diode structure as a result of PLA. Photoconductivity measurements on formed samples demonstrate the presence of a photoresponse (photo-EMF) in the range of wavelengths of 500–1200 nm, which intensity increased for samples that are subjected to PLA when increasing energy density in the pulse. The obtained results demonstrate the potential use of composite Ag:Si layers and the method of their formation in the technology of photodetectors. [ABSTRACT FROM AUTHOR]

We propose a method for the formation of porous germanium (P-Ge) layers containing silver nanoparticles by means of high-dose implantation of low-energy Ag+ ions into single-crystalline germanium (c-Ge). This is demonstrated by implantation of 30-keV Ag+ ions into a polished c-Ge plate to a dose of 1.5 × 1017 ion/cm2 at an ion beam-current density of 5 μA/cm2. Examination by high-resolution scanning electron microscopy (SEM), atomic-force microscopy (AFM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX) microanalysis, and reflection high-energy electron diffraction (RHEED) showed that the implantation of silver ions into c-Ge surface led to the formation of a P-Ge layer with spongy structure comprising a network of interwoven nanofibers with an average diameter of ∼10-20 nm Ag nanoparticles on the ends of fibers. It is also established that the formation of pores during Ag+ ion implantation is accompanied by effective sputtering of the Ge surface. [ABSTRACT FROM AUTHOR]

The new results on the optical reflection of the Si surface layers implanted by silver ions at low energies of 30 keV over a wide dose range from 5.0 × 1014to 1.5 × 1017ion/cm2are presented. As the ion dose of irradiation was increased, a monotonic decrease in the reflection intensity in the ultraviolet region of the spectrum was observed, due to amorphization and macrostructuring of the Si surface. On the other hand, in the long-wavelength region, a selective reflection band appears with a maximum near 830 nm due to plasmon resonance of Ag nanoparticles synthesized during implantation. [ABSTRACT FROM PUBLISHER]

Low-energy high-current ion implantation in silica at a well-controlled substrate temperature has been used to produce composites containing a large concentration of spherical Cu clusters with an average diameter of 4 nm and a very narrow size distribution. A very large value for the third-order optical susceptibility, χ[sup (3)]=10[sup -7] esu, has been measured in the vicinity of the surface plasmon resonance by degenerate four-wave mixing at 585 nm. This value is among the largest values ever reported for Cu nanocomposites. Additionally, the response time of the nonlinearity has been found to be shorter than 2 ps. The superior nonlinear optical response of these implants is discussed in terms of the implantation conditions. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Porous silicon (PSi) have attracted remarkable concerns and found tremendous importance widespread in both fundamental research and industrial applications. At modern time PSi is considering as a key material in many industrial sectors such as electronics, sensors and photonics. Additionally, the interest to PSi nanostructures containing noble metal nanoparticles was recently found. Silver nanoparticles are the subject of specific increasing features due to their strongest plasmon resonance in the visible spectrum. Such materials could be widely used for variety applications as solar cells, absorbents, lightings, catalysts, and for biological sensors. At the present report a novel technological approach based on low-energy ion implantation is suggested and realized to create PSi layers with silver nanoparticles on the crystalline surface of Si wafers. It is demonstrated that using high-dose Ag-ion implantation of silicon with the energy of 30-60 keV the surface PSi structures with silver nanoparticles can be successfully fabricated. Also the fabricated plasmonic material - Ag:PSi is tested for Surface Enhanced Raman Scattering - SERS sensor application. [ABSTRACT FROM AUTHOR]

The results of Raman spectroscopy and electrical measurements of 40 keV boron-ion-implanted polymethylmethacrylate with ion doses from 6.25 × 1014to 5.0 × 1016ions/cm2are reported for the first time. The Raman spectra recorded in the 400–3800 cm−1range, showing the formation of new carbon–carbon bands for the as-implanted samples at higher ion doses (>1016ions/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 × 1016and 5.0 × 1016ions/cm2) have created a very thin conductive layer or conductive joints due to carbonization. [ABSTRACT FROM PUBLISHER]

Porous materials have attracted remarkable concerns and found tremendous importance widespread in both fundamental research and industrial applications. Such materials could be widely used for variety applications as absorbents, lightings, catalysts, and for biological molecular filtration and isolation. One quite known method for preparation of porous semiconductor structures is ion implantation, which was successfully used to create porous germanium layers by Ge+-, Bi+- and Sn+-ion irradiation of crystalline germanium substrates. It was also shown that ion implantation suited to produce porous structures in amorphous germanium and SiGe (90% of germanium) alloys thin films. Ion implantation is a well established and all over the world accessible technique, being mainly used for semiconductor microelectronic device fabrication. Unfortunately, a possibility about porous silicon (PSi) fabrication using ion implantation was not completely studied now. At the present report a novel technological approach based on low-energy ion implantation is suggested and realized to create PSi layers on the crystalline surface of Si wafers. It is demonstrated that using high-dose (more than 1.0×1016 ion/cm2) Ag-ion implantation of silicon with the energy of 30 keV the surface PSi structures with nanoparticles can be successfully fabricated. [ABSTRACT FROM AUTHOR]

Polymethylmethacrylate (PMMA) and polyimide (PI) samples are implanted by 40 keV Cu+ ions with high fluences to synthesize copper nanoparticles in shallow polymer layers. The produced metal/polymer nanocomposites are studied using atomic force and scanning electron microscopies as well as optical transmission spectroscopy. It is found that nucleation and growth of copper nanoparticles are strongly fluence-dependent as well as they are affected by the polymer properties, in particular, by radiation stability yielding different nanostructures for the implanted PI and PMMA. Shallow synthesized nanoparticles are observed to partly tower above the sample surface due to a side effect of high-fluence irradiation leading to considerable sputtering of polymers. Implantation and particle formation significantly change optical properties of both polymers reducing transmittance in the UV–visible range due to structural and compositional change as well as causing an absorption band related to localized surface plasmon resonance (LSPR) of the nanoparticles. The role of polymer type and its degradation under the implantation on LSPR is studied to optimize conditions for the formation of nanoplasmonic materials. [ABSTRACT FROM PUBLISHER]

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 ז3 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). [ABSTRACT FROM AUTHOR]

Nowadays, ion implantation is an extensively used technique for material modification. Using this method, we can tailor the properties of target materials, including morphological, mechanical, electronic, and optical properties. All of these modifications impel nanomaterials to be a more useful application to fabricate more high-performance nanomaterial-based devices. Ion implantation is an accurate and controlled doping method for one-dimensional nanomaterials. In this article, we review recent research on ion implantation-induced effects in one-dimensional nanostructure, such as nanowires, nanotubes, and nanobelts. In addition, the optical property of single cadmium sulfide nanobelt implanted by N+ ions has been researched. [ABSTRACT FROM AUTHOR]

TiO2-SiO2-Ag composites are fabricated by depositing TiO2 films on silica substrates embedded with Ag nanoparticles. Enhancement of light absorption of the nanostructural composites is observed. The light absorption enhancement of the synthesized structure in comparison to TiO2 originated from the near-field enhancement caused by the plasmonic effect of Ag nanoparticles, which can be demonstrated by the optical absorption spectra, Raman scattering investigation, and the increase of the photocatalytic activity. The embedded Ag nanoparticles are formed by ion implantation, which effectively prevents Ag to be oxidized through direct contact with TiO2. The suggested incorporation of plasmonic nanostructures shows a great potential application in a highly efficient photocatalyst and ultra-thin solar cell. [ABSTRACT FROM AUTHOR]

The effect of KrF excimer laser radiation on a composite layer consisting of sodium-potassium silicate glass with silver nanoparticles is studied as a function of the number of laser nanosecond pulses. The silver nanoparticles are synthesized by ion implantation. The measured optical absorption of the composite layer demonstrates that the silver nanoparticle size decreases monotonically as the number of laser pulses increases. Rutherford backscattering shows that laser annealing is accompanied by silver diffusion into the bulk of the glass and partial metal evaporation from the sample surface. The detected decrease in the silver nanoparticle size is discussed in terms of simultaneous melting of silver nanoparticles and the glass matrix due to the absorption of laser radiation. [ABSTRACT FROM AUTHOR]

The nonlinear optical characteristics of silver, copper, and gold nanoparticles synthesized in a sapphire matrix by ion implantation are studied. The measurements are performed by the RZ-scan method with optical reflection at the radiation wavelength of a picosecond Nd:YAG laser (λ = 1064 nm). The nonlinear refractive indices and the real parts of the third-order nonlinear susceptibility of the composites are determined. It is shown that the nonlinear refraction in the samples is caused by the Kerr effect. [ABSTRACT FROM AUTHOR]

Single crystal Al2O3 substrates have been implanted with 160-keV Au+ to a dose of 0.6 × 1017 or 1.0 × 1017cm–2, with a postimplantation annealing for 1 h at 800°C in air. The obtained composite layers were studied by the method of linear optical reflection; the nonlinear optical characteristics were determined by the RZ-scan technique using picosecond radiation pulses of an Nd:YAG laser operating at 1064 nm. The appearance of a characteristic surface optical plasmon resonance band in the linear reflection spectra was indicative of the formation of gold nanoparticles in a subsurface layer of ion-irradiated Al2O3 . It is shown that the synthesized particles are responsible for the observed manifestations of nonlinear refraction. The composite layers were characterized by the nonlinear refractive index (n2) and the real part of the third-order nonlinear susceptibility (Re χ(3)). © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

We have obtained a layered composite material by implantation of single crystal zinc oxide (ZnO) substrates with 160-keV Cu+ ions to a dose of 1016 or 1017cm–2. The composite was studied by linear optical absorption spectroscopy; the nonlinear optical characteristics were determined by means of Z-scanning at a laser radiation wavelength of 532 nm. The appearance of the optical plasmon resonance bands in the spectra indicated that ion implantation to the higher dose provides for the formation of copper nanoparticles in a subsurface layer of ZnO. The new nonlinear optical material comprising metal nanoparticles in a ZnO matrix exhibits the phenomenon of self-defocusing and possesses a high nonlinear absorption coefficient (β = 2.07 × 10–3 cm/W). © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Sapphire-based composite layers implanted with 40-keV Cu[sup +] ions to a total dose of 1.0 × 10[sup 17] cm[sup -2] at an ion beam current density varied from 2.5 to 10 µA/cm² were studied using Rutherford backscattering and optical reflectance methods. The appearance of optical plasma resonance lines in the reflectance spectra indicates that ion implantation allows copper nanoparticles to be synthesized in the subsurface region of the dielectric crystal studied. [ABSTRACT FROM AUTHOR]

Metal-dielectric composites have been fabricated by ion synthesis of silver nanoparticles in soda-lime silicate glass. Ion implantation has been performed with Ag[sup +] ions at 60keV to a dose of 4 10[sup 16]ionscm[sup -2]. The glass was annealed using pulses of a high-power KrF excimer laser (248nm) in an ambient atmosphere. This employed a single (25ns) pulse fluence of 0.25Jcm [sup -2] for implanted samples. From 1 to 250 pulses with the same energy densities and at a frequency of 1Hz were accumulated in the same area on the glass surface. The formation and modification of metal nanoparticles were assessed via optical reflectance, combined with Rutherford back-scattering analysis. Generally, changes induced by laser pulses suggest there are both reductions in the nanoparticles and some longer-range diffusion of metal atoms into the glass. However, before the total dissolution of metal nanoparticles occurs, increases in the substrate temperature during many-pulse treatments initiate the regrowth of new metal nanoparticles, which leads to a rise in the reflectance. These results are discussed on the basis of surface substrate melting. [ABSTRACT FROM AUTHOR]

Dielectric layers with silver nanoparticles, which are synthesized in a soda-silicate glass by implan- tation of 60-keV ions with a dose of 7.0 × 10[sup 16] Ag[sup +] /cm² at an ion current density of 10 µA/cm², are analyzed. The depth of silver distribution was measured by Rutherford backscattering. Data on optical characteristics of composite layers were obtained from the transmission spectra and from the reflection, which were measured both from the side of an implanted glass surface and from the unimplanted side. To calculate reflection spectra, a multilayer plane-parallel film structure was considered, which was modeled on the basis of the matrix method using complex Fresnel coefficients. Dielectric functions of separate layers were determined using the Maxwell- Garnet theory of an effective medium. A qualitative agreement between the experimental and the model optical spectra was obtained taking into account a nonuniform depth distribution of metal nanoparticles in a composite material. [ABSTRACT FROM AUTHOR]

Silver nanoparticles have been synthesized by ion implantation at 30 keV into polymethyl-methacrylate at doses from 3:1 x 10[sup 15] to 7:5 x 10[sup 16] ion cm[sup -2] and a beam current 4 muA cm[sup -2] at room temperature. Transmission electron microscopy was used to determine the structure of the silver-polymer systems obtained. It was observed that in the prepared samples, spherical metal particles with sizes smaller than 12 nm were fabricated. For characterization of the optical response of the composites, transmittance spectroscopy was employed. The formation of the silver nanoparticles leads to an increase of the optical absorption bends at the plasma wavelength in the visible range, where the spectral position of the transmittance minimum depends on the implantation conditions. It was observed that the intensity of the absorption is very weak in spite of the large quantity of silver particles existing in the polymer medium; the factors influencing the optical data are discussed. [ABSTRACT FROM AUTHOR]

Features of the profiles of silver ions implanted into a soda-lime silicate glass were studied depending on the substrate temperature varied in a narrow range from 20 to 100°C. The implant depth-concentration profiles were modeled with an allowance for a thermostimulated increase in the diffusion mobility of the implanted impurity in the sample volume. It is shown that an increase in the substrate temperature by several tens of degrees leads to a diffusion smearing of the implanted impurity profile and, hence, to a decrease in the local implant concentration hindering the metal silver nucleation. An analysis of the results of modeling points to the need in thoroughly controlling the substrate temperature in order to provide for the required conditions of the metal nanoparticle synthesis and to obtain the metal-glass composites with reproducible characteristics. [ABSTRACT FROM AUTHOR]

Performance of the material depends directly on the electronic and energy band structure, to improve the photoactivity of TiO2 and decrease carrier recombination centers induced by monodoping, the TiO2 thin film has been modified with V and N codopants by ion implantation for tailing and controlling the electronic structure and energy band structure. Compared to monodopant, codopants of V and N exhibit a synergistic effect in the photoactivity enhancement of TiO2. X-ray photoelectron spectroscopy (XPS) studies demonstrate that the implanted V and N ions are introduced into the lattice of TiO2 through V and N substituting Ti and O, respectively. The electronic structure of V/N codoped TiO2 was calculated by First-principles calculations based on density-functional theory, the results show the band edges of TiO2 can be tailored by V and N codopants. UV-vis spectra consistently show the absorption edge of V/N codoped TiO2 film is widen to visible light region. More importantly, the photoactivity of TiO2 film has been significantly improved after V/N codoping. The enhanced photocatalytic performance is believed to be due to the V and N codopants induced synergistic effect that not only enhances the absorption of visible light but also promotes the separation of photogenerated electrons and holes in TiO2. Besides, there exists an optimum for V/N ions implantation fluence. The capability of improving TiO2 photoactivity by V/N codoping could open up new opportunities in the development of highly efficient photocatalysts and photoelectrodes for solar energy and environmental applications. [ABSTRACT FROM AUTHOR]

A systematic study of ensembles of nickel nanoparticles fabricated by Ni+-ion implantation at a dose of (0.5-1.0)×1017 ions/cm2 in a thin near-surface layer of an amorphous SiO2 matrix by means of transmission electron microscopy (TEM), dc magnetic measurements, and magneto-optical technique is presented. TEM characterization of Ni nanoparticles proves the formation of isolated spherical nickel nanoparticles with diameters from 2 to 16 nm. The crystal structure and lattice constant of the nanoparticles correspond to face-centered-cubic Ni. The larger size nanoparticles are shown to have core-shell structure, which is unusual for the implantation conditions used. The shell of these nanoparticles consists of Ni, while the core has supposedly the composition coinciding with the matrix, i.e., SiO2. The core-shell nanoparticles in the investigated sample coexist with ordinary pure Ni nanoparticles, which strongly affects the magnetic and especially magneto-optic properties of the samples. For all three doses, the nanoparticles are in the superparamagnetic state at room temperature passing to the "frozen" state at lower temperatures. However, only the sample implanted with the lowest dose demonstrates the classic superparamagnetic behavior according to the shape of the experimental magnetization temperature dependencies for the zero-field-cooled (ZFC) and field-cooled regimes. This shape deviation from that characteristic of the pure superparamagnetic ensembles is ascribed mainly to the particle core-shell structure. The Ni nanoparticles' anisotropy constant estimated with the help of ZFC curves appears to exceed the bulk Ni anisotropy second constant approximately by two orders of magnitude. Magnetic circular dichroism (MCD) is characterized by spectral dependence modified strongly as compared to the MCD spectra of a continuous Ni film. In the spectral range 1.1-4.2 eV, the MCD spectrum consists of two broad maxima of opposite sign with the characteristics depending on the implantation dose and the measurement temperature. The MCD spectra analysis allows one to show that the higher-energy maximum (at 3.34-3.48 eV depending on the dose) is related to the surface plasmon resonance (SPR) excitation in pure Ni nanoparticles, while the lower-energy maximum (at 2.19-2.73 eV depending on the dose) should be associated with the SPR excitation in core-shell nanoparticles. [ABSTRACT FROM AUTHOR]