Angle-resolved photoemission study on hole-concentration dependence in Bi2Sr2CaCu2O8 high-Tc superconductor has been reported. The result clearly shows that (1) there exist two large Fermi surfaces as predicted from the band structure calculation, (2) the Fermi liquid states giving such large Fermi surfaces are formed by hole-doping, and (3) the hole-doping does not necessarily cause a rigid shift of the Fermi level but creats new electronic states in the charge-transfer gap.
The noise and signal parameters of several types of the RF amplifiers based on the different SQUIDs with integrated and hybrid input coils were studied. A new type of the multiloop dc SQUID with integrated input coil and extremely low stray capacitances was designed. The inductance of a 4-loop SQUID was 100pH, the input coil inductance 1.3nH and mutual inductance 300pH. The noise temperature of untuned SQUID amplifier with hybrid input coil at 100MHz was 1.2±1K and the power gain exceeds 20dB. The tuned integrated 4-loop amplifier at 300MHz has nearly 20dB gain in 25MHz band. For the noise calibration of such amplifiers we used SIS junctions as a shot noise source, or cooled attenuator and a room-temperature semiconductor noise source.
The results of experimental investigation of the integrated superconducting microcircuits for mm wave receivers and digital devices are presented. The high quality Nb-AlOx-Nb tunnel junctions have been successfully used to develop the low noise superconductor-insulator-superconductor mixer and to elaborate the SQUIDs and single flux quantum logic devices. The proposed mixing elements avoid the influence of the junction nonuniformity in the array, provide the optimal matching on both rf input and IF output, tune out junction capacitance. All-refractory material 11-layer 5μm integrated technology has been employed for fabrication of superconducting circuits with parameters spreading less then 10%. A new A/D converter which includes a comparator, reversible binary counter with do outputs have been fabricated and tested. The Josephson counter type A/D converter is very promising for high-accuracy measurement of a medium-bandwidth signal.
An interactive system and software for processing images of the side looking radar (SLR) was designed. With the help of this system the digital Antarctic map was synthesized from SLR images measured by satellite series “Ocean”. A part of this map and values of backscattering cross sections for different Antarctic regions are presented.
The behavior of lithium ion beams in a periodic wavy magnetic field is investigated experimentally to prove the spatial cyclotron resonance of selected isotope. Surface-ionized lithium ion beam source, which is collisionless and charge-neutralized, has been developed to perform the experiment. The wavy magnetic field is produced by setting arrays of magnets face to face in a homogeneous magnetic field. The spatial cyclotron resonance is clearly observed at the resonance condition. This resonance can be used to perform the lithium mass separation.
The reflection and scattering of surface-acoustic-waves from a single localized nonpiezoelectric ridge, made on a metallized surface are studied. The rigorous solution of wave propagation inside the ridge and in the piezoelectric semispace was performed. It was found that through the substrate all modes of the same symmetry are coupled one with other, but at given frequencies only one mode can be exited resonantly. The amplitudes and scattering diagrams for waves scattered into bulk of the substrate were found using asymptotic technique. The frequency dependences of the energy reflection coefficient and a surface to bulk wave conversion coefficient for a ridge with rectangular square profile were calculated. It is supposed that such resonating elements can found an application for local reflectors, semitransparent mirrors, etc.
The paper describes the results of investigation of internal photo-amplification mechanism in planar surface-barrier structures on GaAs. The experimental results of epitaxial n-GaAs layers on semi-isolating substrates with Al films obtained at low frequencies are presented. The frequency response of the surface-barrier structures have been investigated in frequency range from 0 to 1.2GHz in dark conditions and at illumination by laser radiation in visible optical range. The mechanisms of photosensitivity dependence on the barrier height are discussed. It is concluded that diodes of investigated structures with internal photo-amplification can be successfully used in optical systems of superfast information transmission.
Rayleigh wave scattering on a resonant element is discussed. As a resonator model a small load supported by a spring was chosen. It is shown, that near the eigenfrequency of resonator the reflection coefficient may reach 0.5, which allows to design wide-band local mirrors for the Rayleigh waves.
The Disk-Method has been used in measuring rolls' residual stress due to ease of handling. Though it has been said the Disk-Method is superior to the well known Sachs-Method, it still has had several problems to be solved such as undetermined disk thickness and roll size limitation. As a result of study on the effect of disk thickness and roll size on residual stress, an improved Disk-Method which solves those problems and which is widely applicable to common rolls has been developed.
The experimental results of the X-ray emission spectroscopic investigation of thin Au1-xSix (x≤0.3 and x=1.5×10-3) films and layered Au/Si/Au structures with intermediate Si layer are presented. The thin films have been deposited on different substrates at 80 and 300K. Three chemical states of Si atoms have been observed: 1) the state corresponding to the Si state in pure single crystal silicon, 2) the state bonded chemically with Au atoms, 3) the peculiar state that corresponds to the dilute solid solution of Si atoms in gold. It have been shown that chemical states of Si had different influence to the oxidation process. The most active system with respect to the oxidation have been found Si state, bonded chemically.