Rosa Young

In-plane epitaxial alignment of YBa2Cu3O7-x films grown on silver crystals and buffer layers

Superconducting YBa2Cu3O7−x (YBCO) films were grown by laser ablation on Ag(001), Ag(110), and Ag(111) single‐crystal surfaces. X‐ray diffraction measurements showed that, in all cases, the films were aligned with specific in‐plane epitaxial orientation with respect to the crystallographic axes of the substrate. The observed orientations were consistent with predictions of near‐coincident site lattice models of the YBCO‐Ag interface. This technique for achieving three‐dimensional film alignment was extended to include a Ag epitaxial buffer layer on mica in place of a bulk Ag crystal. In‐plane epitaxial alignment on metal substrates and buffer layers has important consequences in practical applications for inhibiting weak‐link behavior caused by high‐angle grain boundaries.

EFFECTS OF TRANSITION-METAL ELEMENTS ON TELLURIUM ALLOYS FOR REVERSIBLE OPTICAL-DATA STORAGE

Tellurium‐based alloys are being applied to phase‐change, reversible optical‐data storage. In order to improve the disk performances, research efforts have been concentrated on increasing the erase speed (crystallization rate) while maintaining good film stability. We report, for the first time, that certain transition‐metal elements added to Te‐alloy films can substantially improve the rate of crystallization without any reduction of the amorphous‐phase stability.

Continuous roll‐to‐roll amorphous silicon photovoltaic manufacturing technology

Energy Conversion Devices, Inc. (ECD) has designed and constructed a 2 Megawatt (mW) manufacturing line that produces triple‐junction spectrum‐splitting a‐Si alloy solar cells in a continuous roll‐to‐roll process. This manufacturing line has reliably and consistently produced high efficiency solar cells. We have demonstrated the production of 4ft 2 triple‐junction two band‐gap a‐Si alloy PV production modules with 8% stable aperture area efficiency. The production line has successfully incorporated: 1) a band‐gap profiled a‐Si‐Ge narrow band‐gap solar cell deposited in a continuous roll‐to‐roll process using a proprietary gas distribution manifold and cathode configuration; and 2) a textured Ag/ZnO back‐reflector deposited in a continuous roll‐to‐roll sputtering machine with production subcell yields greater than 99%.

Ion and neutral argon temperatures in electron cyclotron resonance plasmas by Doppler broadened emission spectroscopy

Neutral and ionic gas temperatures (Tn and Ti) are crucial parameters in the plasma processing of materials (etching and film deposition). Here we evaluate a method used for obtaining the temperatures, i.e., the Doppler broadening, of emission lines. We focus on Ar lines from microwave electron cyclotron resonance plasmas. We use the same technique for both ions and neutrals. Three factors are important in achieving accuracy: (1) knowing the correct instrument width at the central wavelength of each ion and neutral line, (2) understanding the noise‐dependent variation in the measured widths, and (3) knowing how the magnetic field affects the spectra. We find that T can be determined to within ∼100 °C. Ti and Tn are typically found to be ∼0.5 and <0.1 eV, respectively for 0.5 mTorr Ar.

CO2 laser processing of diffusion induced lattice imperfections in silicon: Experiment and theory

The high‐temperature diffusion of phosphorus into crystalline silicon causes the formation of electrically inactive phosphorus‐rich precipitates near the surface. These precipitates decrease the carrier lifetime and mobility in the diffused layer, and thus lead to less than optimal diode characteristics of electrical junctions formed by diffusion of phosphorus into a p‐type substrate. We show that the free‐carrier absorption of a CO2 laser pulse can be used to completely dissolve the precipitates and remove dislocations in the diffused layer. Furthermore, we find that there are distinct advantages in depositing the pulse energy by way of free‐carrier transitions, since the energy can be preferentially deposited in either confined doped layers or diffusion wells that are surrounded by lightly doped material. Our transmission electron microscopy results show that the annealing of the extended lattice defects is caused by melting of the near‐surface region and subsequent liquid‐phase epitaxial regrowth. Van ...

Gas atomization processing of designed dual-phase intermetallic hydrogen storage alloys ☆

Abstract Two dual-phase nickel–metal hydride (Ni–MH) battery powders for battery applications were produced by gas atomization. They are characterized by a fine and uniform dispersion of rare-earth (RE)-containing second phase in the Zr-containing base alloy, achieved from gas atomizing molten mixtures of AB2 and AB5 alloys. The dual-phase alloy formulations were (AB2)100−x(AB5)x, where x is 1 and 5. The new dual-phase alloys were found to have high C-rate discharge capacities. Crushing and annealing the dual-phase powders improved the discharge capacity of as-gas atomized powder. C- and C/8-rate discharge capacities of 383 and 425 mAh g−1 (or power density of 134 and 148 Wh kg−1), respectively, were measured for the crushed and annealed dual-phase MmZr05 alloy powder. The possible commercial powder production of the Ni–MH battery powder using a gas atomization process was demonstrated. Four 500 lbs lots of a Zr-based AB2 alloy were successfully gas atomized in a pilot gas atomizer unit. The discharge capacities of this powder after processing exhibited 349 and 414 mAh g−1 at C- and C/8-rate discharges, respectively.

High quality epitaxial YBCO(F) films directly deposited on sapphire

Abstract High-quality epitaxial YBa 2 Cu 3 O 7−δ (F) films were grown directly on r-plane (1 1 02) sapphire by a pulsed laser deposition technique using a multiphase fluorinated target. X-ray diffraction data showed that the film is highly c -axis oriented and in-plane aligned. The c -axis and in-plane mosaic spread are 1.1° and 2.4°, respectively. The microwave surface resistance measured by a con-focal resonator configuration is 56 mΩ at 94.1 GHz at 77 K which is the best reported value for a YBCO film on sapphire. The improved film quality is attributed to the fluorine which is transported from the target to the growing surface of the film where it acts as an etching and/or catalytic agent to preferentially remove defects and second phase impurities and to promote better in-plane epitaxy.

Superconductivity in Fluorinated Copper Oxide Ceramics

It is difficult to do justice to the scientific and technological impact of the recent discoveries in high Tc superconducting ceramic oxides. It is now clear that the oxides that were the basis of the lanthanum copper oxide ceramics which moved the superconducting temperature from 23 to 30 to 40K (1) have been around for some time.(2,3)

Epitaxial YBCO(F) films directly deposited on sapphire and its microwave properties

Abstract High quality epitaxial YBa 2 Cu 3 O 7-δ (F) films were grown directly on r -plane (1102) sapphire by a pulsed laser deposition technique using a multiphase fluorinated target. X-ray diffraction data showed that the film is highly c -axis oriented and in-plane aligned. The c -axis and in-plane mosaic spread are 1.1° and 2.4°, respectively. The film has a Tc(R=) of 89K with a transition width less than 0.25K. The microwave surface resistance R s measured by a con-focal resonator configuration is 56mΩ at 94.1 GHz at 77K which is the best reported value for a YBCO film on sapphire. The magnetization critical current density is as high as 3x10 7 A/cm 2 at 5K and 2x10 6 A/cm 2 at 77K. A bandpass filter which is centered at 8.1 GHz is fabricated. A very low insertion loss (

Proplriies of Post-Hydrogenated Amorphous and Microcrystalline Germanium Films

Amorphous and microcrystalline germanium films prepared by glowdischarge and molecular beam deposition were hydrogenated after deposition, using a 3cm Kaufman ion source. The hydrogen profiles were determined using the N 15 p nuclear resonance reaction. We found that the surface region hydrogen concentration depended on ion beam modification of the material, and the bulk concentration was determined by the hydrogenation conditions and deposition conditions. The light and dark conductivities wee measured before and after hydrogenation. Several orders of magnitude change in the ratios of the conductivities were measured under optimum hydrogenation conditions. The aclivation energy for electrical conductivity was measured and found to be dependent on film structure thickness and hydrogenation conditions.