R. V. Gainutdinov

Microhardness and fracture toughness of Y2O3-and Y3Al5O12-based nanocrystalline laser ceramics

The microhardness and fracture toughness of laser nanocrystalline ceramics based on the cubic oxides Y2O3 and Y3Al5O12 are determined experimentally. It is shown by comparative measurements that the fracture toughness and microhardness of Y2O3 ceramics exceed the corresponding parameters of Y2O3 single crystals by factors of 2.5 and 1.3, respectively. The fine morphology of grains and grain boundaries in fractures is investigated. It is ascertained that changes in the mechanical properties of the nanocrystalline ceramics under study are related to both the sizes and structure of grains and the structure of grain boundaries. It is suggested that twinning processes determine the mechanisms of formation of nanocrystalline ceramics.

Interfacial nanofabrication strategies in development of new functional nanomaterials and planar supramolecular nanostructures for nanoelectronics and nanotechnology

Clusters, nanoparticles, nanowires, long molecules as nanotubes and polynucleotides, and functional supramolecular nanostructures are currently considered as potential building blocks for nanotechnology and nanoelectronic devices and circuits, and development and introduction of new methods to control effectively their structure, composition and nanoscale organization are necessary. Here we describe a number of new nanofabrication methods which are based on the monolayer techniques, biomimetic principles, interfacial reactions and interactions. The methods allowed to produce new stable reproducible planar one-dimensional and two-dimensional arrays of ligand-stabilized nanoclusters and nanoparticles on solid substrates, ultrathin polymeric nanoscale-ordered mono- and multilayer quasi-crystalline and nanocomposite films, planar polymeric complex films with integrated DNA and inorganic building blocks as semiconductor and iron oxide nanoparticle quasi-linear arrays and nanowires. Transmission electron microscopy, STM and AFM techniques were used to characterize the fabricated nanostructures. Effects related to discrete electron tunneling were observed in the monolayers of nanoclusters and small gold nanoparticles at room temperature using STM.

Ferroelectric microdomains and microdomain arrays recorded in strontium–barium niobate crystals in the field of atomic force microscope

Microdomains and various one-dimensional (1D)- and two-dimensional (2D)-microdomain arrays were formed under dc-voltages applied to the tip of an atomic force microscope (AFM) in ferroelectric SrxBa1−xNb2O6 crystals. Detailed studies of the characteristics of the AFM—recording and decay kinetics of the written arrays have shown that the crucial factors of the stability of a domain array are its dimensionality and discreteness (described by a distance Δ between the recorded point domains forming the array). The dependence of the stability on the discreteness of domain ensembles is analyzed. With decreasing Δ, the decay times of the domain ensembles increases. The stability of 2D arrays (domain squares, complex-shaped arrays composed of the domain ensembles of opposite polarity) by orders of magnitude exceeds that of 1D-arrays (domain chains and lines) provided all factors of recording being the same. As an illustration, the decay time of individual (spatially separated) domains and quasicontinuous domain l...

Studies of nanoscale structural ordering in planar DNA complexes with amphiphilic mono- and polycations

Abstract Formation of DNA complexes with Langmuir monolayers of cationic lipid octadecylamine (ODA) and new amphiphilic polycation poly-4-vinylpyridine with 16% cetylpyridinium groups (PVP-16) on the surface of native DNA aqueous solution with low ionic strength has been studied. AFM topographic images of DNA/ODA and DNA/PVP-16 complex Langmuir–Blodgett films deposited on the mica substrates were obtained. The complex structures and individual DNA molecules on the amphiphile monolayer surface were observed. The characteristic extended net-like structures and quasi-circular toroidal condensed conformations of the planar DNA complexes were formed in dependence on the polycationic amphiphile monolayer state during the DNA binding. The data obtained give evidence for the effectiveness of monolayer techniques for investigation the mechanisms of DNA complexation with amphiphilic mono- and polycations and demonstrate its perspectives for creation of supramolecular planar DNA-based self-organized nanostructures with nanoscale structural ordering.

Nanostructure of optical fluoride ceramics

The real structure of samples of optical fluoride ceramics is studied by atomic force, scanning electron, and transmission electron microscopy. It is shown that the optical ceramic samples based on CaF2 have a lamellar structure, and the distance between lamellae is 25–50 nm. Most likely, lamellae have a twin nature. For BaF2 ceramic, lamellae are not typical, and they are concentrated near grain boundaries.

The design, fabrication and characterization of controlled-morphology nanomaterials and functional planar molecular nanocluster-based nanostructures

Abstract New nanofabrication methods based on the monolayer techniques, biomimetic principles, interface reactions and interactions have been developed. The formation and deposition of the mixed Langmuir monolayers composed of inert amphiphile matrix and guest ligand-stabilized metal-core nanocluster molecules allowed to obtain ordered stable reproducible planar monomolecular nanocluster-based nanostructures on solid substrates. The decomposition of similar metal–organic precursor compounds in the mixed Langmuir monolayers at the gas–liquid interface resulted in the initiation of two-dimensional growth of inorganic nanoparticles in the plain of monolayer. Gold and iron-containing nanoparticles were synthesized and characterized by scanning probe microscopy and transmission electron microscopy techniques. Effect of external applied field on the shape of two-dimensionally grown magnetic nanoparticles was observed. Effects related to discrete electron tunneling were observed in the monolayer structures of nanocluster molecules and gold nanoparticles at room temperature using STM.

Microdomain Patterns Recorded by an Electron Beam in He-Implanted Optical Waveguides on X-Cut LiNbO 3 Crystals

We present the results of studies in planar optical waveguides fabricated by He-ion implantation with the energy of 500 keV in X-cut LiNbO3 crystals. The thickness of the formed waveguide layer confined by the depth D of the implanted layer is of about 1.06 μm. The refractive indices as well as differences in refractive indices were evaluated for wavelengths λ = 445, 626.5, and 650 nm. Domain gratings with the period λ = 4 μm were recorded in these samples by electron beam irradiation with acceleration voltages U in the range from 5 to 25 kV. Gratings characteristics measured by the PFM method were obtained for different domain thicknesses Td determined by U. The optimum grating regularity is achieved when the domain growth occurs beyond the He-implanted damaged barrier, i.e., at Td ≤ D, which in the given case corresponds to U = 10 and 15 kV. Otherwise, (Td > D), the domain evolution is affected by the structurally damaged layer and the gratings become irregular.

Second harmonic generation in microdomain gratings fabricated in strontium-barium niobate crystals with an atomic force microscope

Regular surface domain gratings were created in strontium barium niobate crystals by local poling with an AFM-tip. Piezoresponse force microscopy was utilized to subsequently image the domain patterns and to investigate their temporal and thermal stability. The gratings were examined by means of nonlinear diffraction in reflection geometry using a Ti-sapphire laser (800 nm) as pump source. The well-resolved second harmonic diffraction patterns were recorded for various angles of incidence of the fundamental wave. The origin of the observed nonlinear diffraction is discussed.

Creation of domains and domain patterns on the nonpolar surface of SrxBa1 − xNb2O6 crystals by atomic force microscopy

Microdomains and microdomain patterns have been recorded by applying dc voltages to the probe of an atomic force microscope contacting the nonpolar surface in a barium-strontium niobate ferroelectric crystal. Processes of the formation of microdomains have been investigated. It has been shown that the frontal growth of domains on the nonpolar surface is described by a viscous-friction-type law. The features of the formation of stable domains associated with the back-switching effects have been revealed. Oppositely oriented domains (“head-to-head” and “tail-to-tail”) have been obtained in polydomain crystals. Domain gratings with the reciprocal vector G = 2Π/Λ (where Λ = 3.6 and 8 μm is the grating period), which is parallel and perpendicular to the polar Z axis, have been written by the vector lithography method. Gratings with G ‖ Z, which form a system of 180° linear domains of opposite signs (head to head and tail to tail), hold for no less than several days.

Characterization of electron-beam recorded microdomain patterns on the nonpolar surface of LiNbO3 crystal by nondestructive methods

We report on characterization of the electron-beam fabricated planar domain gratings on the nonpolar (Y-) surface of LiNbO3 crystals performed with the use of AFM and confocal second harmonic generation (SHG) microscopy. The dependence of domain formation on the irradiation conditions was investigated. The relation of domain thicknesses to the electron penetration depth is experimentally proved. In particular, the possibility of controlling the thickness of planar domains by varying acceleration electron-beam voltages is demonstrated. The observed specificity of SHG is analyzed in the framework of the Kleinman-Boyd theory [G. D. Boyd and D. A. Kleinman, J. Appl. Phys. 39, 3597 (1968)] and Uesu approach [Kaneshiro et al., J. Appl. Phys. 104, 054112 (2008); Kaneshiro et al., J. Opt. Soc. Am. B 27, 888 (2010)] extended in our case to reflection geometry. The calculations performed predict the dependence of SHG conversion efficiency η on the domain thickness, which is in a qualitative agreement with the exper...