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1 Oct 1999

Volume 86, Issue 7, pp. 3497-4057

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Coatings for optical pumping cells and extending the lifetime of hyperpolarized xenon

Steven R. Breeze, Stephen Lang, Igor Moudrakovski, Chris I. Ratcliffe, John A. Ripmeester, Benoit Simard, and Giles Santyr

J. Appl. Phys. 86, 4040 (1999); http://dx.doi.org/10.1063/1.371325 (3 pages) | Cited 9 times

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We propose evaporative induction heating as a method for the reliable production of coatings for glass cells suitable for the optical pumping and storage of hyperpolarized xenon. The long spin-lattice relaxation times of hyperpolarized xenon-129 contained in cells coated with polyethylene or dotriacontane showed that high quality coatings could be prepared this way. Measurements on cells coated with deuteriated versions of these compounds showed that the expected improvement in performance with isotopic substitution did not occur. This leads to some questions about the level of understanding of wall-induced relaxation in polarization cells. © 1999 American Institute of Physics.
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32.30.-r Atomic spectra
32.80.Xx Level crossing and optical pumping
32.30.Dx Magnetic resonance spectra
07.77.-n Atomic, molecular, and charged-particle sources and detectors

Measuring interactions between tunnel-coupled quantum dots in the quantum Hall regime

C. Livermore, D. S. Duncan, R. M. Westervelt, K. D. Maranowski, and A. C. Gossard

J. Appl. Phys. 86, 4043 (1999); http://dx.doi.org/10.1063/1.371326 (3 pages) | Cited 4 times

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We present measurements of the relaxation of frustrated charge configurations via tunneling in a double quantum dot in the quantum Hall regime. We studied transport through two quantum dots in series at each of three Landau level filling factors: ν = 2, 3, and 4. The double dot conductance was measured as a function of the induced charge on each dot and of the interdot tunnel conductance to demonstrate the evolution of the charging diagram with increasing interdot electron tunneling. At all three filling factors, we find that the evolution from well separated to joined dots is complete at an interdot tunnel conductance Gint ≅ e2/h, in contrast with the zero magnetic field case. We also observe that the residual interaction energy relative to the charging energy increases above the zero field value. © 1999 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.43.-f Quantum Hall effects
73.40.Gk Tunneling
73.23.Hk Coulomb blockade; single-electron tunneling

Effect of working on the aligning capability of liquid crystals on the rubbed polymer surfaces

Dae-Shik Seo and Shunsuke Kobayashi

J. Appl. Phys. 86, 4046 (1999); http://dx.doi.org/10.1063/1.371327 (3 pages) | Cited 5 times

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The washing effects on the liquid crystal (LC) alignment capability on the rubbed polyimide PI surface were investigated. The induced optical retardation from the nonwashing process on the rubbed PI surface is larger when compared with the washing processes; it is attributed to the removal of dust in the washing process. The generated pretilt angles in 4-n-pentyl-4′-cyanobiphenyl (5CB) from the nonwashing process on the rubbed PI surface are almost the same as that of the rubbed PI surface after washing process. The polar anchoring energy of the weakly rubbed PI surfaces is increased by the washing process; the washing effects are clearly observed. The surface order parameter SS of 5CB for all washing processes is larger than that with the nonwashing process; it is attributed to the washing process. Consequently, we suggest that the LC aligning capability is largely attributed to the washing effects. © 1999 American Institute of Physics.
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61.30.-v Liquid crystals
81.65.Cf Surface cleaning, etching, patterning

Electron ejection from MgO thin films by low energy noble gas ions: Energy dependence and initial instability of the secondary electron emission coefficient

Kyoung Sup Moon, Jihwa Lee, and Ki-Woong Whang

J. Appl. Phys. 86, 4049 (1999); http://dx.doi.org/10.1063/1.371328 (3 pages) | Cited 45 times

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Low energy ion-induced secondary electron emission from the surface of thin (500–5000 Å) polycrystalline MgO films has been investigated with various noble gas ions at energies ranging from 45 to 300 eV. The dependence of secondary electron emission coefficient γi on the type and energy of ions is reported and interpreted in terms of electron ejection mechanisms. As-deposited MgO films showed an initial fluctuation in the secondary emission current, which upon annealing or after a certain ion bombardment time irreversibly disappeared. © 1999 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Leakage currents in high-quality pulsed-laser deposited aluminum nitride on 6H silicon carbide from 25 to 450 °C

C. J. Scozzie, A. J. Lelis, F. B. McLean, R. D. Vispute, S. Choopun, A. Patel, R. P. Sharma, and T. Venkatesan

J. Appl. Phys. 86, 4052 (1999); http://dx.doi.org/10.1063/1.371329 (3 pages) | Cited 6 times

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The high-temperature dielectric properties of thin-film AlN that were pulsed-laser deposited on a heavily doped n-type 6H–SiC substrate are investigated from 25 to 450 °C. Capacitor leakage current densities of low 10−8 A/cm2 at 25 °C and mid 10−3 A/cm2 at 450 °C are reported for a 1.7 MV/cm dielectric field. The primary high-temperature leakage mechanism appears to be Schottky emission with a zero-field barrier height of 1.76 eV. A dielectric strength in excess of 1.7 MV/cm at 450 °C is reported. © 1999 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
81.15.Fg Pulsed laser ablation deposition
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
73.30.+y Surface double layers, Schottky barriers, and work functions
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Microwave intermodulation of a superconducting disk resonator

T. Dahm, D. J. Scalapino, and Balam A. Willemsen

J. Appl. Phys. 86, 4055 (1999); http://dx.doi.org/10.1063/1.371330 (3 pages) | Cited 21 times

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We calculate the third order intermodulation products for the TM010 mode of a thin film disk resonator and discuss the particular case of a 1 GHz resonator in order to obtain a quantitative idea of the performance that can be obtained. The linear and nonlinear microwave responses of a TM010 disk resonator are then compared to that of an equivalent half wavelength microstrip resonator. This analysis allows one to independently quantify the contributions to the nonlinear device performance from the material properties, device size and field configuration. © 1999 American Institute of Physics.
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85.25.-j Superconducting devices
84.40.Az Waveguides, transmission lines, striplines
84.40.Dc Microwave circuits
74.72.-h Cuprate superconductors
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