V. A. Vdovin

An experimental study of millimeter wave absorption in thin metal films

Optical characteristics (R, T, A) of thin aluminum films with thicknesses from 1.7 to 15 nm were studied at a wavelength of 8 mm with allowance for a substrate material. The absorption exhibits a maximum for a film thickness of 2.5 nm. The experimental data are interpreted taking into account the dependence of electric conductivity on film thickness.

Use of High-Power Electromagnetic Pulses in Processes of Disintegration and Opening of Rebellious Gold-Containing Raw Material

Possible mechanisms of mineral particle disintegration under the action of high-power electromagnetic pulses on gold-containing sulfides and enrichment products are described theoretically for the first time. The results of experimental investigations are presented, and the theoretical substantiation is given for the effect of synergetic influence of high-power electromagnetic pulses with a wide range of their parameters and pore moisture on the opening of rebellious gold-containing raw material of different type and subsequent gold extraction.

A thermoacoustic sensor for recording high-power nanosecond microwave pulses

The operating principle and design of an uncooled noise-immune high-power microwave pulse sensor is described. The sensor operation is based on the effect of acoustic signal generation when microwave pulses are absorbed in a layer structure, in which a thin metal nanometer-thick film is used as an absorber. The sensor is placed in a free space and intended to detect microwave pulses with ∼10- to 100-ns durations in a 10- to 300-GHz frequency band with a pulse repetition rate of up to 5 kHz. For 10-ns-long pulses, the sensor sensitivity is 0.5 V/mJ.

Spectral characteristics of nanometer-thick chromium films in terahertz frequency range

The spectral characteristics (reflection, transmission, and absorption coefficients) of thin chromium films on silica substrates have been measured using a pulsed source of terahertz radiation. The spectra of optical coefficients were obtained in a frequency range of 0.25–1.1 THz. Dependences of the optical coefficients on the metal film thickness at 1 THz were constructed. The maximum absorption coefficient (43%) was observed at a film thickness of 10 nm.

Optical coefficients of nanometer-thick copper and gold films in microwave frequency range

Ultrathin (1–10 nm) Cu and Au films were prepared on the silicon and quartz substrates by magnetron sputtering at room temperature. We measured the transmission coefficient of the films at a wavelength of 3cm and analyzed a surface morphology of these films. It was shown that the films with thicknesses less than 7.5 nm (Au) and 3 nm (Cu) are almost transparent for microwaves. This effect is explained by quick oxidation of Cu and the complex surface morphology of nanometer thick films. The Au film morphology is evolved with increasing average Au thickness d from hemispherical islands initially (1.0 nm<d<5.0 nm) to partially coalesced worm-like island structures (d=10 nm).

Nonstationary fluid dynamics under exposure to nanosecond voltage pulses

A numerical analysis of the liquid motion in a spherical capacitor under the applied voltage pulse with a duration of several nanoseconds and a peak value to 300 kV is performed. A system of hydrodynamics equations written in the general form in the spherical coordinate system and the Tait equation of state are used to simulate the liquid motion. The electrostrictive pressure is calculated for a liquid in the form of a dipole dielectric.

Effect of Gold Nanorods on the Remote Decapsulation of Liposomal Capsules Using Ultrashort Electric Pulses

Decapsulation of nanocomposite liposomal capsules due to the effect of ultrashort electric pulses is obtained when the liposomal sheaths of the capsules are bound to significantly anisotropic gold nanoparticles (nanorods). Destruction of the liposomal sheath is interpreted using the rotational displacement of gold nanorods in the presence of the pulsed electric field. Such an interpretation is used to derive an expression for the critical electric field that determines the threshold level of the effect. The calculated critical field is in agreement with the experimental results. It is shown that the decapsulation is related to the presence of the gold nanorods in the sheath of liposomal capsules and is not obtained in the absence of the nanorods.

Effective optical constants of silver nanofilms calculated in wide frequency range

The optical properties of Ag ultrathin films in dependence of their thickness are studied theoretically in a wavelength range 0.3 - 10 μm. The extinction coefficient (k) and refractive index (n) for thin Ag films with smooth surface structure are calculated with software package VASP. It was found the effect of growth of extinction coefficient and shift of its peak into long wavelength range with the thickness increasing. The effect is explained by the significant increasing of the surface electron states. Refractive index n is increased with the wavelength growth and attains saturation value ns at the wavelength λs. The thicker the films the higher the magnitude of ns and the larger the wavelength λs. Our results of calculations of k(λ) are in a good agreement with experimental data from ref.[25]. The difference in magnitudes of n obtained experimentally and theoretically can be explained by the formation of Ag nanoclusters on the surface of sputtered film.

Mechanical properties of bimetallic one-dimensional structures

Mechanical properties of freestanding Au-Mn nanowires and Au-Mn nanowire on a Cu (110) substrate are studied with ab initio theoretical approach. The calculations were carried out using the software package Vienna Ab-initio Simulation Package (VASP), which is based on the density functional theory (DFT). It was shown that the breaking force (0.45nN) as well as the interatomic distance at a breaking point in bimetallic nanowire (3.0 Å) are higher than in one component Au wire (0.4 nN and 2.6Å respectively). Relative elongation of 15 % results in a fracture of bimetallic nanowire. We studied the mechanical response of the nanojunction in a form of three-atomic Au chain aligned vertically between two pyramidal gold electrodes and demonstrated that the breaking of nanocontact depends only the interaction between Au atoms in the chain and dependents slightly on the structure and properties of the atomic structure of the electrodes.

Remote decapsulation of nanocomposite liposomal capsules containing gold nanorods by ultrashort electric pulses

The decapsulation effect of nanocomposite liposomal capsules containing anisotropic gold nanoparticles (nanorods), which is caused by the action of ultrashort electric pulses on these capsules, is discovered. The mechanism of destruction of liposomal shells of the capsules near poles of conducting gold nanorods under the pulse electric action is described. An expression for the critical intensity of the pulse electric field, which determines the threshold of initiation of this effect, is obtained. Its numerical value is in agreement with the obtained experimental data. It is shown experimentally that the discovered decapsulation effect is caused by the presence of gold nanorods connected to the liposomal shell of the capsules and does not arise in the absence of nanorods.