R. I. Khaibullin

Formation of metal-polymer composites by ion implantation

Abstract Silver nanoparticles have been synthesized by ion implantation at 30 keV into polymethyl-methacrylate at doses from 3.1 × 1015 to 7.5 × 1016 ion cm−2 and a beam current 4 μA cm−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.

Nonlinear optical properties of copper nanoparticles synthesized in indium tin oxide matrix by ion implantation

Copper nanoparticles were elaborated in an indium tin oxide matrix by ion implantation. The nonlinear refraction and absorption coefficients of the composite materials obtained were measured using the z-scan method with nanosecond pulses (τ=7 ns) at the wavelength of 532 nm. In addition to the conventional on-axis z-scan configuration, measurements were carried out in the off-axis scheme to get a better sensitivity. The mechanisms responsible for nonlinear refraction and absorption in these nanocomposite materials are discussed. By using the temporal trace of the signal in the off-axis configuration, we show the thermal lensing effect to be negligible as compared with pure electronic ones.

Application of ion implantation for synthesis of copper nanoparticles in a zinc oxide matrix for obtaining new nonlinear optical materials

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 1017 cm−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).

Ion synthesis of silver nanoparticles in viscous-fluid epoxy resin

A method is described for the ion synthesis of silver nanoparticles in epoxy resin that is in a viscousfluid state (viscosity 30 Pa s) during irradiation. The viscous-fluid or glassy polymer is implanted by 30-keV silver ions at a current density of 4 μA/cm2 in the ion beam in the dose range 2.2 × 1016–7.5 × 1016 ions/cm2. The epoxy layers thus synthesized contain silver nanoparticles, which are studied by transmission electron microscopy and optical absorption spectroscopy. The use of the viscous-fluid state increases the diffusion coefficient of the implanted impurity, which stimulates the nucleation and growth of nanoparticles at low implantation doses and allows a high factor of filling of the polymer with the metal to be achieved.

Synthesis and magnetic properties of nickel nanoparticles in magnesium fluoride matrix

A new composite material, comprising a diamagnetic matrix (magnesium fluoride) containing metal nanoparticles (nickel), has been synthesized in a high-vacuum laser-based universal cluster ablation system. The structure and magnetic properties of the composite were studied by transmission electron microscopy (TEM) and ferromagnetic resonance (FMR). According to TEM data, the nickel nanoparticles have a spherical shape and their dimensions are described by a narrow distribution function with an average value of 3.2 nm. An analysis of the FMR spectra reveals strong interaction between nickel nanoparticles in the composite, which accounts for an out-of-plane magnetic anisotropy and suggests the formation of granular magnetic films.

Mössbauer study of the magnetic phase composition of single-crystalline rutile (TiO2) implanted with iron ions

Depth-resolved Mössbauer measurements have been performed for four ferromagnetic samples obtained by the implantation of iron ions (enriched to ∼ 50% with 57Fe isotope) into single-crystalline rutile (TiO2) substrates with two crystallographic orientations [(100) and (001)] at different temperatures (300 and 900 K). It is established that the ferromagnetic properties of iron-implanted rutile samples at room temperature are determined by the presence of α-Fe and Fe3O4 phases. The phase composition of samples obtained by iron implantation into substrates heated to 900 K depends on the crystallographic orientation of the substrate, which is explained by a significant anisotropy of the diffusion of iron atoms in rutile.

Structure and optical properties of ZnO with silver nanoparticles

Textured nanocrystalline ZnO thin films are synthesized by ion beam assisted deposition. According to X-ray diffraction data, the crystallite size is ~25 nm. Thin (~15 nm) ZnO layers containing Ag nanoparticles are formed in a thin surface region of the films by the implantation of Ag ions with an energy of 30 keV and a dose in the range (0.25–1) × 1017 ion/cm2. The structure and optical properties of the layers are studied. Histograms of the size distribution of Ag nanoparticles are obtained. The average size of the Ag nanoparticles varies from 0.5 to 1.5–2 nm depending on the Ag-ion implantation dose. The optical transmittance of the samples in the visible and ultraviolet regions increases, as the implantation dose is increased. The spectra of the absorption coefficient of the implanted films are calculated in the context of the (absorbing film)/(transparent substrate) model. It is found that the main changes in the optical-density spectra occur in the region of ~380 nm, in which the major contribution to absorption is made by Ag nanoparticles smaller than 0.75 nm in diameter. In this spectral region, absorption gradually decreases, as the Ag-ion irradiation dose is increased. This is attributed to an increase in the average size of the Ag nanoparticles. It is established that the broad surface-plasmon-resonance absorption bands typical of nanocomposite ZnO films with Ag nanoparticles synthesized by ion implantation are defined by the fact that the size of the nanoparticles formed does not exceed 1.5–2 nm.

Effects of nickel ions implantation and subsequent thermal annealing on structural and magnetic properties of titanium dioxide

Wide bandgap semiconducting rutile (TiO2) doped with 3d-elements is a promising material for spintronic applications. In our work a composite material of TiO2:Ni has been formed by using implantation of Ni+ ions into single-crystalline (100)- and (001)- plates of TiO2. Sub-micron magnetic layers of TiO2 containing nickel dopant have been obtained at high implantation fluence of 1?1017 ion/cm2. A part of the implanted samples was then annealed in vacuum at different temperatures Tann = 450-1200 K for 30 min. The influence of the implantation fluence, crystalline orientation, as well as subsequent annealing on the structural and magnetic properties of the nickel-implanted TiO2 have been investigated by using X-ray photoelectron spectroscopy, scanning electron microscopy and coil magnetometry techniques.

Specific features of depth distribution profiles of implanted cobalt ions in rutile TiO2

This paper reports on the results of the calculation of the depth distribution profiles of the concentration of the impurity implanted into an anisotropic crystalline material. The sputtering of the irradiated material, fast one-dimensional diffusion of the impurity along structural channels, and accumulation of the implanted impurity at different depths have been taken into account. The results of the calculations have been compared with the experimental distribution profiles of cobalt ions implanted into the crystal structure of rutile TiO2 along and across structural channels at different temperatures of the irradiated substrate. A comparison of the model and experimental profiles has made it possible to evaluate the precipitation rate of cobalt in the TiO2 matrix on different precipitation centers. A model has been proposed for explaining the unusual shift in the peak of the concentration distribution of implanted ions deep into the sample with an increase in the temperature of the irradiated substrate. The model has allowed one to separate the contributions from different phases of the impurity (nanoparticles and solid solution) to the magnetism of the Co: TiO2 system.

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.