N. V. Vostokov

Observation of Laser-Induced Local Modification of Magnetic Order in Transition Metal Layers

Laser-induced local modifications of magnetic order in thin Fe-Cr layers were investigated. Local modification in the layers were induced by interfering laser beams. The results of the study give evidence for the formation of submicron-sized anisotropically shaped ferromagnetic regions with a well-defined direction of the easy magnetic axis in the interference maxima at the modification threshold. It was also found that the magnetic anisotropy of a medium is drastically reduced with changing the shapes of these local regions and distances between them. This may be due to the strengthening of the interaction between the regions through the paramagnetic matrix.

High-sensitivity accelerometer based on cold emission principle

A possibility for fabrication of a high-sensitivity accelerometer is considered. The linear acceleration of a sensor causes displacement of the proof mass electrode. The displacement detector is based on a strong dependence of the tunneling or cold emission current on the gap between the electrodes. The geometry of the electrodes that provides the best sensitivity is determined. The accelerometer with tunneling-emission electrodes is fabricated. At frequencies up to 5 kHz the resolution reaches 10/sup -4/ g/Hz/sup 1/2/ in the tunneling mode and 10/sup -3/ g/Hz/sup 1/2/ in the emission mode.

Application of low-barrier metal-semiconductor-metal structures for the detection of microwave signals

New structures of sensitive elements based on asymmetric low-barrier metal-semiconductormetal structures are proposed. The structures can be used for the detection of microwave or terahertz signals. A vertical structure with different barrier heights of two metal-semiconductor junctions and a planar structure with different areas of junctions are studied. It is demonstrated that the sensitive element based on the vertical structure is superior to a detecting low-barrier Mott diode. The sensitivity of the planar element is comparable with the sensitivity of the diode but the former is easier to produce. The characteristics of a detector based on the planar low-barrier structure integrated in a broadband antenna are calculated. Possible sensitivities in a band of 1 THz are determined.

Interference nanolithography with a UV laser

The sensitivity and resolution of a photoresist composed of a two-layer (polymer-metallic indium) film are measured. 2D masks used to create nanodimensional metallic and insulating islands on a silicon substrate are prepared by direct laser action. Conditions are found for preparing submicron periodic structures on TiO2 films that are applied on a glass substrate by the sol-gel technology. Optical properties of these arrays are measured, and it is shown that they can be used for exciting plane electromagnetic waves.

Method of the near-field optical nanolithography using tapered optical fiber

A method of contact scanning near-field optical lithography has been developed to enable fabrication of elements with characteristic dimensions of about 30 - 50 nanometres. The method involves deposition of a thin-layer polymer-metal coating, photothermal nonplastic deformation of top metal layer with a probe microscope, the transfer of the pattern through the polymer of dry etching and the formation of various nanoelements through this prepared mask. The method is applicable to any materials (metal, dielectric, light/heavy doped semiconductors) relevant to the formation of different nanometre objects (metal, dielectric, etched in surface or its combinations) on their surface.

Influence of the channel–gate barrier height on the detection properties of a field-effect transistor in the microwave and terahertz ranges

The detection properties of a field-effect transistor with a low Schottky barrier gate in the microwave and terahertz ranges has been studied theoretically. Different detector circuits have been considered. The voltage and current distributions along the channel, the input impedance of the transistor, sensitivity, and noise equivalent power have been found. The influence of the Schottky barrier height on the above characteristics has been analyzed.

Method of scanning near-field optical lithography

A contact scanning near-field optical lithography method has been developed to enable fabrication of different nanoelements; (metal, dielectric, etched in surface or its combinations) on the various surfaces (metal, dielectric, light- and heavy doped semiconductors). The method involves interaction of heated probe of scanning near-field optical microscope with two-layer coating, followed by pattern transfer onto sample surface. The software for creation of different nanoelements; is developed. The nanoelements; with characteristic dimensions of about 50 nm are fabricated.

Investigation of nanocontact electron properties to the semiconductor islands

Distribution of charge in semiconductor islands of InAs on GaAs surface and Ge/sub x/Si/sub 1-x/ on Si surface are investigated by atomic-force microscopy method with using conductor probes. Carriers of charge are concentrated on the islands perimeter that are shown in rough current peaks in this regions. Reason of this effect are indicated. Nanodimensional contact with /spl sim/10/sup -2/ mkm/sup 2/ area to single islands are fabricated, its current-voltage characteristics are investigated.

Fabrication of nanodimensional objects by atomic-force lithography methods

An atomic-force lithography method yielding individual elements of <100 nm size has been developed. It involves deformation of the masking layer with an atomic-force microscope probe, followed by plasma-chemical etching and deposition of metal contacts through the mask.