Library

Notes: Following a method proposed by Divin and Modovets [Sov. Tech. Phys. Lett. 9, 108 (1983)], we have measured at millimeter waveband the intrinsic noise temperatures TN of YBa2Cu3O7−δ Josephson junctions or dc superconducting quantum interference devices (SQUIDs) fabricated on SrTiO3, yttria-stabilized ZrO2, or Si bicrystal substrates. Over wide ranges of physical temperatures TP and the junction's normal resistance RN, it was found that TN follows TP pretty well. This indicates that the intrinsic noise in the devices is dominated by Johnson noise. TN was also measured in cases where there is external magnetic field applied, or where there is another microwave radiation like the local oscillator in a mixer. The magnetic field or microwave radiation does not seem to affect TN in any appreciable way. To estimate the high frequency performance of the junctions on Si bicrystal substrates, direct irradiation by a far infrared laser at 1.81 THz is carried out and the clear first Shapiro step is observed. © 1996 American Institute of Physics.

Notes: Magneto-optical Kerr spectra of ultrathin Co films grown on Cu(001) surfaces have been measured in situ. The growth mode and the crystal structure have been investigating by reflection high-energy electron diffraction observation. A 20-A(ring)-thick fcc Co grown on Cu(001) had a lateral lattice constant of 3.59±0.01 A(ring), which was about 1.4% expanded compared with that of the bulk fcc Co. There was a remarkable difference above 4 eV in ωσyz spectra between 20- and 1000-A(ring)-thick films. ωσyz spectra for 20-A(ring)-thick Co film showed a resonance-type structure at around 5 eV. It is considered that the structure is caused by the lower energy shift of the 1→6 interband transitions due to the narrowing of the 3d bands. © 1996 American Institute of Physics.

Notes: We have studied low frequency (1/f) noise of YBa2Cu3O7−δ dc superconducting quantum interference devices (SQUIDs) on SrTiO3 bicrystal substrates. 1/f flux noise, either measured at different temperatures for optimized bias current or measured at 77 K for different bias currents, is almost constant. These facts imply that 1/f noise mainly comes from fluctuations of the critical current of the Josephson junction that form the SQUID. Also, we explain the critical current fluctuations in the junction by an equilibrium temperature fluctuation model.

Notes: Morphology and coefficient of friction associated with water content in the skin were investigated by a combination method of profilometry and measurement of friction using a newly developed instrument placed on the flexor aspect of the forearm. It was shown that the number of domains enclosed by lines (sulci cutis) on the skin surface per unit area initially decreased rapidly, but then more gradually, with the advancing age of the subjects. Electron micrographs showed that the skin surface exhibited a pattern formed by thick and fine lines, each of which differed both in length and depth from the superficial surface of the skin. The pattern of the skin surface in advanced age is mainly formed by thick lines. The number of domains on the skin surface caused changes in the friction coefficient; that is, the increase in the static coefficient of friction varies with the decrease in the number of domains. The results are discussed from the point of view of the change in the elastic modulus of skin with the advancing age of subjects. We found that the number of domains (i.e., areas enclosed by lines) varied inversely with the square of the coefficient of friction.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméLe coefficient de morphologie et de friction associé avec le contenu en eau de la peau a été analysé en combinant 1 méthode de profilométrie et la mesure de la friction à l'aide d'un nouvel instrument placé sur la partie flexible de l'avant bras. Il est apparu que le nombre de sillons par ligne (sulci cutis) sur la surface cutanée par unité d'aire à d'abord diminué rapidement puis graduellement avec le vieillissement des individus. Les micrographes à électrons ont montré que la peau était formée de ligne fines ou épaisses, chacune d'entre elles différent par la longueur et la profondeur sur la surface de la peau. La surface cutanée de personnes plus âgées est formée principalement de lignes épaisses. Le nombre de sillons sur la peau modifiait le coefficient de friction, le coefficient de friction statique correspondant à la diminution du nombre de sillons. Les résultats ont été discutés du point de vue du changement d'élasticité de la peau avec le vieillissement des sujets. Nous avons découvert que le nombre de sillons c'est à dire les aires par ligne variait inversément par rapport au coefficient de friction.

Notes: We present experimental results on elementary phase-mode Josephson circuits whose combinations enable us to construct a total data processing system which is expected to be superior to the ordinary voltage-mode Josephson computer in several respects. In the phase-mode system a device depends for its operation on the existence of many stable states differing from one another by integer multiples of 2π in the phase plane. The total system is considered to be a prototype of quantum computer systems where physical quantum states are employed as logic states of information processing. By using the fabricated elementary circuits composed of SQUIDs and two types of branching points we have experimentally confirmed and, fan-out, fan-in operations, etc. We have also proposed an inhibit circuit, and presented the experimental results on the inhibit circuit.

Notes: Admittance spectroscopy is applied to the analysis of the thermal properties of the Mn acceptor-doped InP grown by liquid-phase epitaxy. The thermal activation energy and capture cross section are determined as ΔET=183 meV and σp=1.8×10−13 cm2, respectively. The cutoff frequency of the emission of holes from the Mn acceptor is 1 GHz at 300 K. It is shown that the small signal frequency characteristic of a buried heterostructure laser is improved at frequencies f〉1 GHz by using the Mn-doped p-InP layer for the current blocking region.

Notes: The current waveforms of the self-resetting oscillation in a dc superconducting quantum interference device (SQUID) are observed by means of a Josephson sampling system. The frequency of the oscillation is around 60 GHz. The time period of the self-resetting oscillation is experimentally measured as a function of the bias current to the SQUID. Theoretical and numerical analyses are presented for the self-resetting oscillation in the dc SQUID.

Notes: Using c-axis-oriented oxygen-deficient YBa2Cu3O7−δ film deposited across a low-angle step on a SrTiO3 substrate, we successfully demonstrated intrinsic Josephson effects. In addition to several voltage jumps of large amplitudes (a few millivolts) and remarkable hysteresis on the dc current–voltage curves, we observed upturns on the current–voltage curves under microwave irradiation which appeared at increasingly high voltages with increasing microwave power. We proposed to explain this observation in terms of high-order microwave-induced Shapiro steps. © 1999 American Institute of Physics.