There have been several recent reports of apparently nonbolometric optical responses in superconducting thin films. The photoresponse of 10 nm thin superconducting NbN meander lines on Si is measured at 670 nm using a diode laser... more
There have been several recent reports of apparently nonbolometric optical responses in superconducting thin films. The photoresponse of 10 nm thin superconducting NbN meander lines on Si is measured at 670 nm using a diode laser modulated to more than 100 kHz. Several types of photoresponse are identified, some apparently due to the Si substrate. A fast photoresponse due to
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Thin films of lanthanum-modified lead zirconate-titanate (PLZT) were prepared by rf magnetron sputtering from a single oxide target onto a heated substrate. The target consisted of Pbl-xLaxZryTi1-yO3 with composition close to x=8% and y=... more
Thin films of lanthanum-modified lead zirconate-titanate (PLZT) were prepared by rf magnetron sputtering from a single oxide target onto a heated substrate. The target consisted of Pbl-xLaxZryTi1-yO3 with composition close to x=8% and y= 65%, either as a loose powder or a solid sintered disk. Under appropriate conditions, the desired perovskite phase formed in situ without any subsequent post-anneal. Film composition and structure were correlated with deposition parameters, including substrate temperature, target composition, gas pressures, and target aging. For deposition onto MgO or A12O3 crystalline substrates, perovskite PLZT films formed if there was sufficient Pb at the target surface, sufficient oxygen in the sputter gas (≈ 50%), and a substrate temperature >≈600°C. Target heating led to excessive Pb loss from the loose powder target; this was much less significant for the solid target. In addition, it was found that deposition onto an epitaxial perovskite substrate promot...
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The deposition of thin films of superconducting YBa2Cu3O7-x onto substrates of up to 3-in diameter by an integrated off-axis sputtering is reported. The substrate is located above the center of an 8-in-diameter YBCO planar target, and, in... more
The deposition of thin films of superconducting YBa2Cu3O7-x onto substrates of up to 3-in diameter by an integrated off-axis sputtering is reported. The substrate is located above the center of an 8-in-diameter YBCO planar target, and, in conjunction with a negative ion shield, negative ion effects are avoided. A large radiant heater provides backside, noncontact heating of the bare substrates.
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YBa2Cu3O7 (YBCO) thin films with improved properties have been recently reported by post‐annealing in a low partial pressure of oxygen, similar to that used by in situ methods, compared to the usual post‐annealing in 1 atm of oxygen. Here... more
YBa2Cu3O7 (YBCO) thin films with improved properties have been recently reported by post‐annealing in a low partial pressure of oxygen, similar to that used by in situ methods, compared to the usual post‐annealing in 1 atm of oxygen. Here it is shown that the improvements extend to the microwave surface resistance. The surface resistance was measured at close to 10 GHz; the scaled value at 10 GHz and at 77 K is 240 μΩ. This value is as low as has been reported for YBCO thin films measured around 10 GHz made by any method, and is two orders of magnitude lower than the surface resistance of copper at the same temperature and frequency.
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It is generally believed that no simple real-space semiclassical picture can consistently explain both a quantum wave and its spin. However, it is shown here [1] that a rotating vector field carrying angular momentum leads directly to the... more
It is generally believed that no simple real-space semiclassical picture can consistently explain both a quantum wave and its spin. However, it is shown here [1] that a rotating vector field carrying angular momentum leads directly to the Einstein-de Broglie relations (E = hnu and p = h/lambda, the heart of quantum mechanics), assuming only quantization of spin and Lorentz invariance of the phase angle. For electromagnetism, such a circularly polarized wave packet defines the photon. A very similar picture of a massive rotating vector field maps onto a complex wavefunction obeying the time-dependent Schrödinger equation for a particle such as the electron, with m>0 and v<<c. This real vector field rotates about the spin axis at mc^2/h ˜ 10^20 Hz. This suggests a unified picture whereby all fundamental quantum particles consist of such coherent wave packets of rotating spin fields, with composite particles deriving their quantum properties from the coherent rotations of thei...
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Research Interests: Electrical Engineering, Computer Science, Physics, Electronic Warfare, Josephson Junctions, and 15 moreRadio Frequency, Detectors, High performance, GNSS receivers, Converters, Sensor Array, Rsfq, Bandwidth, High Sensitivity, Mixed signal, Analog to Digital Conversion, Broadband Communication, Dynamic Range, Magnetic Flux, and Analog to Digital Converter
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Abstract We have examined the I-V characteristics of superconducting phase-slip centers (PSCs) located in the middle of narrow In channels. Features in dV/dI can be associated with resonances in charge imbalance waves driven by the PSC,... more
Abstract We have examined the I-V characteristics of superconducting phase-slip centers (PSCs) located in the middle of narrow In channels. Features in dV/dI can be associated with resonances in charge imbalance waves driven by the PSC, as suggested by the model of Kadin, Smith and Skocpol. The velocity and temperature dependence of the waves thus inferred are in rough accord with theoretical predictions.
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The concept of electrical duality is reviewed, with a focus on the symmetry between the motion of charge and the motion of magnetic flux. This approach is especially illuminating for the case of a superconductor, in which flux is... more
The concept of electrical duality is reviewed, with a focus on the symmetry between the motion of charge and the motion of magnetic flux. This approach is especially illuminating for the case of a superconductor, in which flux is quantized in units of Φ0=h/2e. In a two‐dimensional superconductor, a quantized vortex or fluxon can be viewed as the dual of an electron. Based on this analogy, new superconducting ‘‘fluxonic’’ device concepts are proposed, including optical detectors and transistors. Finally, the implications of this picture for low‐ and high‐temperature superconductors are evaluated.
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A simple real-space model for the free-electron wavefunction with spin is proposed, based on coherent vortices on the scale of h/mc, rotating at mc^2/h. This reproduces the proper values for electron spin and magnetic moment.... more
A simple real-space model for the free-electron wavefunction with spin is proposed, based on coherent vortices on the scale of h/mc, rotating at mc^2/h. This reproduces the proper values for electron spin and magnetic moment. Transformation to a moving reference frame turns this into a wave with the de Broglie wavelength. The mapping of the real two-dimensional vector phasor to the complex plane satisfies the Schrodinger equation. This suggests a fundamental role for spin in quantum mechanics.
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It is proposed that the paradox of wave-particle duality in quantum mechanics may be resolved using a physical picture analogous to magnetic domains. Within this picture, a quantum particle represents a coherent region of a quantum wave... more
It is proposed that the paradox of wave-particle duality in quantum mechanics may be resolved using a physical picture analogous to magnetic domains. Within this picture, a quantum particle represents a coherent region of a quantum wave with characteristic total energy, momentum, and spin. The dynamics of such a state are described by the usual linear quantum wave equations. But the coherence is maintained by a nonlinear self-interaction term that is evident only during transitions from one quantum state to another. This is analogous to the self-organizing property of domains in a ferromagnetic material, in which a single domain may appear as a stable macro-particle, but with rapid transitions between different domain configurations also possible. For the quantum case, this implies that the "collapse of the wave function" is a real dynamical physical process that occurs continuously in spacetime. This picture may also permit the resolution of apparent paradoxes associated ...
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Thin films of Y‐Ba‐Cu‐O have been fabricated using rf diode sputtering from a single mixed‐oxide powder target. The target consisted of about 200 grams of mixed reacted CuO, BaCO3, and Y2O3 powders spread over an 8‐inch Cu plate, and... more
Thin films of Y‐Ba‐Cu‐O have been fabricated using rf diode sputtering from a single mixed‐oxide powder target. The target consisted of about 200 grams of mixed reacted CuO, BaCO3, and Y2O3 powders spread over an 8‐inch Cu plate, and mounted horizontally in a standard‐model sputtering system. Such a target was used for repeated rf‐diode depositions in a ‘‘sputter‐up’’ mode to a substrate hanging face‐down, with deposition rate of order 50–100 A/minute. Substrates investigated include sapphire and yttria‐ stabilized zirconia. Well‐cooled substrates yielded films close to the composition of an YBa2Cu3O7 target. In contrast, uncooled or heated substrates yielded films dramatically deficient in Cu relative to the target. Sputtering for several hours in Ar plasma with 10% O2 yielded shiny, black films ≊1 μm thick. Subsequent processing of films on zirconia substrates up to 850 °C in pure O2 yielded an onset of superconductivity at ≊87 K, with a broad transition to zero resistance at ≊50 K. Improvements in this...
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Thin films of superconducting Y1Ba2Cu3O7 have been used as the active element in an optically triggered fast opening switch. Both granular and highly c-axis oriented films, ranging in thickness from 2000 A to 7000 A, were subject to 150... more
Thin films of superconducting Y1Ba2Cu3O7 have been used as the active element in an optically triggered fast opening switch. Both granular and highly c-axis oriented films, ranging in thickness from 2000 A to 7000 A, were subject to 150 psec pulses from a Nd:YAG laser and exhibited switching from the superconducting to the normal state in times ranging from 1 nsec to 10 nsec, followed by a much slower decay over 100 nsec to 1 µsec. The magnitude of the voltage response and the slow decay can be explained in terms of a simple bolometric effect, while the rapid switching of even the thicker films is indicative of nonequilibrium hot electron transport from the absorbing surface layer to the remaining film thickness. At higher temperatures the response time is slower than 10 nsec, indicating a more diffusive behavior to the electron heat transport. These results give some indication of the electron-phonon collision time and help set limits to the maximum film thickness useable for laser triggered fast opening switches.
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The response to short infrared pulses of some epitaxial YBCO films prepared by sputter deposition and by electron-beam evaporation is reported. The response is found to be essentially bolometric on the ns timescale, with some indirect... more
The response to short infrared pulses of some epitaxial YBCO films prepared by sputter deposition and by electron-beam evaporation is reported. The response is found to be essentially bolometric on the ns timescale, with some indirect hints of nonequilibrium electron transport on the ps scale. Fast switching could be obtained either by biasing the switch close to the critical current or by cooling the film below about 20 K. These results are encouraging for potential application to a high-current optically-triggered opening switch.
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The authors have used RF magnetron sputtering from a large near-stoichiometric YBCO target onto heated substrates to produce c-axis oriented films with Tc=87 K in situ, without a subsequent post-anneal. Effects of negative ion bombardment... more
The authors have used RF magnetron sputtering from a large near-stoichiometric YBCO target onto heated substrates to produce c-axis oriented films with Tc=87 K in situ, without a subsequent post-anneal. Effects of negative ion bombardment were avoided by placing substrates above the center of the target, directly above a grounded ion shield. Film properties are rather sensitive to small changes in target composition. At 66 K, critical currents of optimum films are greater than 1MA/cm2, and microwave surface resistance at 2 GHz is less than 10 m Omega .
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... ez-Regueiro,a) D. Gupta, and AM Kadin Department of Electrical Engineering, University of Rochester, Rochester, New York 14627 Magnetoresistance and Hall coefficient have been investigated as a function of temperature in patterned... more
... ez-Regueiro,a) D. Gupta, and AM Kadin Department of Electrical Engineering, University of Rochester, Rochester, New York 14627 Magnetoresistance and Hall coefficient have been investigated as a function of temperature in patterned thin films of LaCaMnO. Our data on ...
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Thin films of Y-Ba-Cu-O have been prepared by RF diode sputtering from a single mixed-oxide powder target. The films were deposited on sapphire and cubic zirconia substrates, with the substrates either cooled, heated, or left to establish... more
Thin films of Y-Ba-Cu-O have been prepared by RF diode sputtering from a single mixed-oxide powder target. The films were deposited on sapphire and cubic zirconia substrates, with the substrates either cooled, heated, or left to establish thermal equilibrium. The Cu content in the films decreased with increasing substrate temperature. Films having a composition close to the desired 1-2-3 stoichiometry were fabricated either by enriching the target with CuO or by cooling the substrate. Using the latter approach, a single target was used for over 20 depositions yielding films that were uniform in composition (although slightly Cu-rich), and consistent from run to run. These films had as-deposited room temperature sheet resistances on the order of 100 k ohms. Subsequent annealing at temperatures up to 850 C resulted in films that were superconducting with an onset around 90 K and zero resistance at 50 K. The critical current was found to exceed 2000 A/sq cm at 4.2 K.
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The development of a commercial-scale sputtering process for deposition of superconducitng YBa2Cu3O7 (YBCO) thin films is described. YBCO films are sputter deposited from a single 20 cm diameter powder target onto 2 inch substrates of MgO... more
The development of a commercial-scale sputtering process for deposition of superconducitng YBa2Cu3O7 (YBCO) thin films is described. YBCO films are sputter deposited from a single 20 cm diameter powder target onto 2 inch substrates of MgO and LaAlO3 using in-situ heating to produce high quality, c-axis oriented films without post annealing. By locating the substrate above the center of the magnetron erosion ring and by placing a ``negative ion shield'' between the target and the substrate, negative ion resputtering is avoided. Small shifts in composition are corrected by using a slightly Y- and Cu-rich target to produce films within 1% of stoichiometric composition. Films on LaAlO3 and MgO have critical temperatures up to 88 K and critical currents above 5×105 A/cm2 at 77 K. Uniformity is +/-5% in thickness and +/-7% in resistivity across at 2-inch diameter substrate. Microwave surface resistance meaurements at 1.2 GHz and 4 K show RS~=0.1 mOmega for YBCO ground planes and...
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Thin films of the new high temperature ceramic superconductors have the potential of being very fast opening switches. In the normal state, these films can have a surface resistivity of 40 n/O. Thus the change from the superconducting to... more
Thin films of the new high temperature ceramic superconductors have the potential of being very fast opening switches. In the normal state, these films can have a surface resistivity of 40 n/O. Thus the change from the superconducting to the normal state represents an enormous change in device impedance. Thin films of YBCO have been illuminated with 100 ps, 1 pm optical pulses and driven normal with energy densities as small as 2 mJ/cmZ. We have seen response times of under 2 ns. Such a fast transition indicates that the transition is not bolometric. The transition has been characterized as a function of bias current, temperature, and incident intensity.
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Rapid solidification onto a copper quench surface (melt-spinning) has been used to fabricate a high-performance permanent magnet alloy (Ovonic Hi-Rem™) based on the Nd-Fe-B class of materials. Crucial idditions of alloying elements are... more
Rapid solidification onto a copper quench surface (melt-spinning) has been used to fabricate a high-performance permanent magnet alloy (Ovonic Hi-Rem™) based on the Nd-Fe-B class of materials. Crucial idditions of alloying elements are combined with careful control over quench parameters to yield a random assembly of microcrystallites, with macrosconically isotropic magnetic properties including values of remanent induction that can exceed 10 kG and maximum energy products greater than 20 MGOe. These values exceed those expected from conventional randomly oriented magnets. The enhanced magnetic performance is related to results of x-ray diffraction and electron microscopy.
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High-temperature superconducting thin films of YBaâCuâOâ are deposited on 2 in. MgO and LaAlOâ substrates by radio frequency magnetron sputtering from an 8 in. diam powder target. By locating the substrate above the center of the... more
High-temperature superconducting thin films of YBaâCuâOâ are deposited on 2 in. MgO and LaAlOâ substrates by radio frequency magnetron sputtering from an 8 in. diam powder target. By locating the substrate above the center of the magnetron erosion ring and by placing a negative ion shield&#39;&#39; between the target and the substrate, negative ion resputtering is avoided and high quality
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A parametric study of titanium silicide formation by rapid thermal processing was conducted to determine the effects of annealing temperature (650 °C, 750 °C), annealing time (30 s, 60 s), wet etching (no HF dip, with HF dip), sputter... more
A parametric study of titanium silicide formation by rapid thermal processing was conducted to determine the effects of annealing temperature (650 °C, 750 °C), annealing time (30 s, 60 s), wet etching (no HF dip, with HF dip), sputter etching (no sputter etch, with sputter etch), and annealing ambient (Ar, N2) on the completeness of conversion of 60 nm Ti on (111)-Si to C54–TiSi2 based on sheet resistance and the uniformity of the sheet resistance measurements across the entire wafer. Statistical analysis of the results showed that temperature, annealing ambient, and sputter etching had the greatest influence. Increasing the temperature and using argon gas instead of nitrogen promoted conversion of the film to C54–TiSi2. On the other hand, sputter etching retarded it. The results also indicated significant interactions among these factors. The best uniformity in sheet resistance was obtained by annealing at 750 °C without sputter etching. The different sheet resistance profiles show...
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We have fabricated a macroscopically isotropic permanent magnet material (Ovonic Hi-RemTM) which significantly exceeds conventionally understood performance limits for a material with saturation magnetization Ms =16 kG. Enhanced magnetic... more
We have fabricated a macroscopically isotropic permanent magnet material (Ovonic Hi-RemTM) which significantly exceeds conventionally understood performance limits for a material with saturation magnetization Ms =16 kG. Enhanced magnetic properties, including a remanent magnetization Mr =9–10 kG or more, and a maximum energy product in excess of 20 MGOe, are observed without preferred orientation. This material has been fabricated by
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... A. Mop-Campero, LG Turner, AM Kadin, and DS Mallory, "Superior microwave properties by post-annealing YBa2Cu3e thin films at low oxygen ... SM Anlage, H. Sze, SJ Snortland, S. Tahara, B. Langley, C.-B. Eom, and MR Beasley,... more
... A. Mop-Campero, LG Turner, AM Kadin, and DS Mallory, "Superior microwave properties by post-annealing YBa2Cu3e thin films at low oxygen ... SM Anlage, H. Sze, SJ Snortland, S. Tahara, B. Langley, C.-B. Eom, and MR Beasley, "Measurements of the magnetic penetration ...
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ABSTRACT Market applications of digital and mixed-signal superconducting electronics require the inte- gration of a robust, long life, highly efficient 4 K cryocooler with an equally robust cryopackage including superconducting integrated... more
ABSTRACT Market applications of digital and mixed-signal superconducting electronics require the inte- gration of a robust, long life, highly efficient 4 K cryocooler with an equally robust cryopackage including superconducting integrated circuits (ICs). The ideal 4 K cryocooler, with full reliability, power and cost efficiency, and manufacturability, is not yet commercially available. Recently, a custom-designed laboratory prototype of a 4 K 4-stage Stirling-type pulse-tube cryocooler was produced by Lockheed-Martin and delivered to HYPRES. We have adapted the system with a cryopackage which we used to mount and successfully test a superconducting IC with a variety of Nb circuits including an RSFQ binary counter. For 600 W total compressor power and a package with broadband input-output lines, extended stable operation of the counter at T=4.5 K was demon- strated with a clock frequency up to 46 GHz clock speed, with 25 mW of excess cooling capacity on the coldest stage (4.5 K). The thermodynamic and mechanical performance is promising for the development of an improved compact cryocooler for superconducting electronic applications such as wireless communications.
... PH Ballentine, AM Kadin, and DS Mallory, "In-situ sputtering of YBCO films for microwave applications", IEEE Trans. Mag., Vol. ... P. Rosenthal, K. Shinohara, AF Marshall, RH Hammond, and MR Beasley, "Reactive... more
... PH Ballentine, AM Kadin, and DS Mallory, "In-situ sputtering of YBCO films for microwave applications", IEEE Trans. Mag., Vol. ... P. Rosenthal, K. Shinohara, AF Marshall, RH Hammond, and MR Beasley, "Reactive coevaporation of YBaCuO superconducting films", J. Mater. ...