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18 Nov 1996

Volume 69, Issue 21, pp. 3117-3282

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Nanoscale investigation of fatigue effects in Pb(Zr,Ti)O3 films

A. Gruverman, O. Auciello, and H. Tokumoto

Appl. Phys. Lett. 69, 3191 (1996); http://dx.doi.org/10.1063/1.117957 (3 pages) | Cited 122 times

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Scanning force microscopy has been used to perform a comparative nanoscale study of domain structures and switching behavior of Pb(ZrxTi1−x)O3 (PZT) thin films integrated into heterostructures with different electrodes. The study revealed a significant difference between polarization state of as‐deposited PZT films on RuO2 and Pt electrodes. The PZT/RuO2 films exhibit polydomain crystallites and show almost symmetric switching behavior, while the PZT/Pt films are mainly in a single polarity state and exhibit highly asymmetric piezoelectric hysteresis loops. Formation of unswitchable polarization within the grains of submicron size as a result of fatigue process was directly observed. © 1996 American Institute of Physics.
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77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.60.Bs Mechanical and acoustical properties

X‐ray diffraction and nuclear magnetic resonance studies of Y2Fe17

N. X. Shen, Y. D. Zhang, J. I. Budnick, W. A. Hines, R. Lyver, and K. H. J. Buschow

Appl. Phys. Lett. 69, 3194 (1996); http://dx.doi.org/10.1063/1.117958 (3 pages) | Cited 2 times

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X‐ray structure analysis and 89Y nuclear magnetic resonance (NMR) measurements are presented for the hexagonal and rhombohedral phases of Y2Fe17. The rhombohedral structure has one Y site (designated 6c) and the hexagonal structure has two Y sites (designated 2b and 2d). By combining the x‐ray and NMR results, the hyperfine fields corresponding to the three Y sites in these two phases are obtained. Furthermore, a deconvolution of the NMR spectrum for 89Y in the hexagonal Y2Fe17 phase shows that a disordering exists, resulting in an occupancy for the Y 2b sites of approximately 71%. © 1996 American Institute of Physics.
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61.05.cp X-ray diffraction
76.60.-k Nuclear magnetic resonance and relaxation
61.66.Fn Inorganic compounds

Evidence for electron trapping by Sm dimer and trimer centers in Sm doped CaF2

W. Beck, D. Ricard, and C. Flytzanis

Appl. Phys. Lett. 69, 3197 (1996); http://dx.doi.org/10.1063/1.117959 (3 pages) | Cited 6 times

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Using coherent anti‐Stokes Raman and linear absorption spectroscopy we present experimental evidence for a novel electron trapping mechanism in Sm doped CaF2. The appearance of additional Raman lines after ionization of the Sm2+ ions, their dependence on the Sm3+ concentration and their behavior due to an enhancement by the lowest 4f→5d transition of Sm2+, support strongly that electrons can be trapped by dimers or trimers of Sm3+ ions in a CaF2 lattice. The resulting color change is reversible due to a possible reionization of the traps, rendering this material photochromic. © 1996 American Institute of Physics.
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71.55.Ht Other nonmetals
78.30.Hv Other nonmetallic inorganics
42.70.Hj Laser materials

Kohlrausch exponent of amorphous Zr65Al7.5Cu27.5 determined by anelastic relaxation measurements

M. Weiss, M. Moske, and K. Samwer

Appl. Phys. Lett. 69, 3200 (1996); http://dx.doi.org/10.1063/1.117960 (3 pages) | Cited 15 times

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Anelastic relaxations of amorphous Zr65Al7.5Cu27.5 have been studied in the range of the glass transition and in the supercooled liquid. Applying a force step function, an anelastic aftereffect of the form exp(t/τ)β (Kohlrausch–Williams–Watts function) is expected with an exponent β<1. From the measurement a value of β=0.67±0.03 is determined at Tg which confirms the empirical correlation between the fragility index m (36.4 for Zr65Al7.5Cu27.5) and β, established by Böhmer et al. This result is another indication for the metallic glass Zr65Al7.5Cu27.5 being a rather strong glass former. Furthermore, a strong increase in β just above Tg is found and is interpreted in the framework of a cluster model. © 1996 American Institute of Physics.
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81.05.Kf Glasses (including metallic glasses)
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
83.10.Gr Constitutive relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Composites with extremal thermal expansion coefficients

O. Sigmund and S. Torquato

Appl. Phys. Lett. 69, 3203 (1996); http://dx.doi.org/10.1063/1.117961 (3 pages) | Cited 58 times

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We design three‐phase composites having maximum thermal expansion, zero thermal expansion, or negative thermal expansion using a numerical topology optimization method. It is shown that composites with effective negative thermal expansion can be obtained by mixing two phases of positive thermal expansions with a void phase. We also show that there is no mechanistic relationship between negative thermal expansion and negative Poisson’s ratio. © 1996 American Institute of Physics.
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81.05.Zx New materials: theory, design, and fabrication
65.40.De Thermal expansion; thermomechanical effects

Control of structure and optical anisotropy in porous Si by magnetic‐field assisted anodization

Takashi Nakagawa, Hideki Koyama, and Nobuyoshi Koshida

Appl. Phys. Lett. 69, 3206 (1996); http://dx.doi.org/10.1063/1.117962 (3 pages) | Cited 8 times

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The effects of an applied magnetic field during anodization on the structural and optical isotropy of luminescent porous silicon (PS) are investigated. The PS layers are prepared by anodizing p‐type Si wafers in HF solutions with an external magnetic field of 0–1.7 T applied perpendicular to the Si surface. It is shown that the photoluminescence intensity of PS significantly increases with increasing magnetic field. This effect is accompanied by an increase in both the porosity and the optical isotropy without affecting the surface chemical composition. The structural uniformity in the PS layer and at the PS‐substrate interface are also improved. These results suggest that an external magnetic field during anodization regulates the supply of holes from the substrate and produces well‐controlled optical and structural properties of PS. © 1996 American Institute of Physics.
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78.55.Mb Porous materials
61.43.Gt Powders, porous materials
82.45.-h Electrochemistry and electrophoresis

p‐type InGaAs/InP quantum well infrared photodetector with peak response at 4.55 μm

D. K. Sengupta, S. L. Jackson, D. Ahmari, H. C. Kuo, J. I. Malin, S. Thomas, M. Feng, G. E. Stillman, Y. C. Chang, L. Li, and H. C. Liu

Appl. Phys. Lett. 69, 3209 (1996); http://dx.doi.org/10.1063/1.117963 (3 pages) | Cited 8 times

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Lattice‐matched InGaAs/InP quantum well intersubband photodetectors (QWIPs) have been grown on an InP substrate by gas source molecular beam epitaxy. Detection at 4.55 μm was observed for a narrow well p‐type InGaAs QWIP which, when complimented by a high responsivity 8.93 μm n‐type InGaAs/InP QWIP, demonstrates the possibility of dual band, monolithically integrated QWIPs on the same InP substrate. Theoretical calculations of the photocurrent spectra are in excellent agreement with the experimental data. © 1996 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Pw Imaging detectors and sensors
78.66.Fd III-V semiconductors

Nature of native oxide on GaN surface and its reaction with Al

K. Prabhakaran, T. G. Andersson, and K. Nozawa

Appl. Phys. Lett. 69, 3212 (1996); http://dx.doi.org/10.1063/1.117964 (3 pages) | Cited 49 times

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In this letter, we describe the surface properties of GaN thin films grown on sapphire substrate by molecular beam epitaxy, as revealed by ultraviolet and x‐ray photoelectron spectroscopic and Auger electron spectroscopic studies. The samples are seen to contain overlayer of native oxides, which are predominantly in the Ga2O3 form. Ammonia is shown to be a good etchant for these native oxides. Furthermore, we investigated the early stages of the reaction of monolayer Al with a GaN surface covered with native oxide. Aluminum reacts preferentially with the surface oxygen and leads to the formation of a mixture of oxides at the interface. © 1996 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Optical excitation of paramagnetic nitrogen in chemical vapor deposited diamond

C. F. O. Graeff, E. Rohrer, C. E. Nebel, M. Stutzmann, H. Güttler, and R. Zachai

Appl. Phys. Lett. 69, 3215 (1996); http://dx.doi.org/10.1063/1.117965 (3 pages) | Cited 23 times

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Investigations of polycrystalline chemical vapor deposited diamond films by electron‐spin‐resonance (ESR), light‐induced (L)ESR, and the constant photoconductivity method have identified dispersed substitutional nitrogen (P1 center) as the main paramagnetic form of N incorporated in the CVD diamond. The density of N‐related paramagnetic states is strongly affected by illumination and heat treatment. It is found that the P1 center in CVD diamond gives rise to a deep donor state about 1.5 eV below the conduction band. © 1996 American Institute of Physics.
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76.30.Da Ions and impurities: general
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Cn Elemental semiconductors
71.20.Nr Semiconductor compounds

InAs/GaSb(001) valence‐band offset: Independence of interface composition and strain

Barbara Montanari, Maria Peressi, Stefano Baroni, and Elisa Molinari

Appl. Phys. Lett. 69, 3218 (1996); http://dx.doi.org/10.1063/1.118015 (3 pages) | Cited 8 times

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The InAs/GaSb(001) valence‐band offset is calculated for the two inequivalent GaAs‐like and InSb‐like interfaces and found to coincide to within ≊30 meV. This result is rationalized and generalized to arbitrary composition profiles and induced strain by using a simple model, based on the linear response theory, which is validated by a number of accurate first‐principles calculations for intermixed interfaces. © 1996 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.35.Dv Composition, segregation; defects and impurities
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Molecular‐beam epitaxy of high‐quality ZnSe homo‐epitaxial layers on solid‐phase recrystallized substrates

E. Tournié, P. Brunet, J.‐P. Faurie, R. Triboulet, and J. O. Ndap

Appl. Phys. Lett. 69, 3221 (1996); http://dx.doi.org/10.1063/1.118016 (3 pages) | Cited 2 times

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We study through reflection high‐energy electron diffraction (RHEED) and low‐temperature photoluminescence (PL) spectroscopy the molecular‐beam epitaxy of ZnSe homoepitaxial layers on solid‐phase recrystallized substrates. We show that with a proper ex situ substrate polishing a two‐dimensional (2D) RHEED pattern is readily observed when introducing the substrate into the growth chamber at low temperature. We demonstrate that the in situ pre‐growth treatment has a dramatic influence on ZnSe nucleation and that a suitable preparation leads to direct 2D growth of ZnSe layers which exhibit superior optical properties. The PL spectra are dominated by the near‐band edge emission, with no deep‐level and defect‐related lines. © 1996 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
78.55.Et II-VI semiconductors

Room temperature optical gain in sol‐gel derived CdS quantum dots

J. Butty, N. Peyghambarian, Y. H. Kao, and J. D. Mackenzie

Appl. Phys. Lett. 69, 3224 (1996); http://dx.doi.org/10.1063/1.118017 (3 pages) | Cited 57 times

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Under strong nanosecond excitation, we demonstrate that II–VI semiconductor quantum dots exhibit optical gain up to room temperature. The CdS nanocrystallites, fabricated by sol‐gel process, are embedded in a sodium borosilicate glass matrix. The gain is spectrally broad and the crossing between absorption and gain is well above the bulk absorption band edge energy, since our nanocrystallites are in the intermediate quantum confinement regime. The gain has a long tail extending to the low energy side of the absorption edge. This tail was shown theoretically to originate from the multiple excited states involved in the recombination between two and one electron‐hole pairs. © 1996 American Institute of Physics.
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78.66.Hf II-VI semiconductors
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Nucleation of cubic GaN/GaAs (001) grown by gas source molecular beam epitaxy with hydrazine

S. A. Nikishin, V. G. Antipov, S. S. Ruvimov, G. A. Seryogin, and H. Temkin

Appl. Phys. Lett. 69, 3227 (1996); http://dx.doi.org/10.1063/1.118018 (3 pages) | Cited 9 times

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Growth nucleation and evolution of morphology of GaN on (001) GaAs is investigated as a function of the N2H4/Ga flux ratio. The use of hydrazine allows us to reach high flux ratios without causing any damage to the epitaxial layer. Epitaxial GaN is purely cubic but shows growth anisotropy dependent on the flux ratio. GaN layers grown at low flux ratios show three‐dimensional nucleation and no preferential island orientation. With higher flux ratios, the nucleation rate increases, the surface becomes smoother, and the growth anisotropy markedly increases. The growth morphology reflects the surface anisotropy of the underlying GaAs substrate. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Synthesis of nanocrystalline gallium nitride in silica aerogels

T. J. Goodwin, V. J. Leppert, C. A. Smith, S. H. Risbud, M. Niemeyer, P. P. Power, H. W. H. Lee, and L. W. Hrubesh

Appl. Phys. Lett. 69, 3230 (1996); http://dx.doi.org/10.1063/1.118019 (3 pages) | Cited 12 times

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Nanocrystals of gallium nitride were synthesized in silica aerogel host matrices by pyrolysis of dimeric dimethylgallium‐diphenylamide precursor sequestered in the nanometer scale aerogel pores. Powder x‐ray diffraction (XRD) and selected area electron‐diffraction results verify the formation of hexagonal gallium nitride material in the aerogels, and Scherrer‐broadening analysis of the XRD data indicate the gallium nitride particle size is ∼20 nm. Transmission electron microscopy results show that the gallium nitride nanoparticles have diameters between 10 and 40 nm with an average diameter of 23 nm. The synthesis parameters for the gallium nitride nanocrystals in the aerogel hosts are discussed. © 1996 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Cy Elemental semiconductors
61.46.-w Structure of nanoscale materials
61.05.jm Convergent-beam electron diffraction, selected-area electron diffraction, nanodiffraction

Tuning of ZnSe–GaAs band discontinuities in heterojunction diodes

Vittorio Pellegrini, Marco Börger, Michele Lazzeri, Fabio Beltram, Jens J. Paggel, Lucia Sorba, Silvia Rubini, Marco Lazzarino, Alfonso Franciosi, Jean‐Marc Bonard, and Jean‐Daniel Ganiére

Appl. Phys. Lett. 69, 3233 (1996); http://dx.doi.org/10.1063/1.118020 (3 pages) | Cited 11 times

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The conduction band offset in ZnSe/GaAs n‐p heterodiodes was determined from measurements of the low‐temperature tunneling current of photoinjected carriers. We found widely different discontinuities for heterojunctions fabricated with different Zn/Se flux ratios, with conduction band offsets as high as 0.75 eV for Se‐rich interfaces, and as low as 0.26 eV for Zn‐rich interfaces. © 1996 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.60.Jv Interfaces; heterostructures; nanostructures

Site‐specific reaction kinetics for gallium arsenide metalorganic vapor‐phase epitaxy

S. D. Adamson, B. K. Han, and R. F. Hicks

Appl. Phys. Lett. 69, 3236 (1996); http://dx.doi.org/10.1063/1.118021 (3 pages) | Cited 6 times

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We have developed a kinetic model for arsine decomposition on GaAs(001) that accounts for the effect of the surface reconstructions on the rates of As4 and As2 desorption. The main assumption of the model is that As2 desorbs more slowly from Ga sites than from As sites. The model accurately simulates the temperature‐programmed desorption of arsenic from GaAs(001). In addition, it reveals how the As coverage and the As2 and As4 production rates depend on the conditions employed during GaAs metalorganic vapor‐phase epitaxy. © 1996 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
81.05.Ea III-V semiconductors

Structure of high resistivity GaAs film grown by low‐temperature metalorganic chemical vapor deposition

Wen‐Chung Chen, C.‐S. Chang, and S. H. Chan

Appl. Phys. Lett. 69, 3239 (1996); http://dx.doi.org/10.1063/1.118022 (3 pages)

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The structure of a low‐temperature GaAs layer grown by low‐pressure metalorganic chemical vapor deposition with precursors of triethylgallium and arsine is reported. Dense particles containing Ga clusters are found in a high resistivity GaAs film grown at 420 °C. The size and concentration of particles are about 800–1000 nm and 7×1011 cm−3, respectively. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
73.61.Ey III-V semiconductors

Correlation between the valence‐ and conduction‐band‐tail energies in hydrogenated amorphous silicon

S. Sherman, S. Wagner, and R. A. Gottscho

Appl. Phys. Lett. 69, 3242 (1996); http://dx.doi.org/10.1063/1.118023 (3 pages) | Cited 20 times

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We provide experimental evidence for a correlation between the characteristic energies of the exponential conduction‐ and valence‐band tails of hydrogenated amorphous silicon (a‐Si:H). We measured subgap optical‐absorption spectra of isolated a‐Si:H films in order to extract their valence‐band‐tail energies. Also, we modeled the current–voltage characteristics of thin‐film transistors which had a‐Si:H layers deposited identically to the isolated films, in order to extract their conduction‐band‐tail energies. When the quality of the a‐Si:H was varied, the characteristic energies of the two tails scaled linearly with each other. © 1996 American Institute of Physics.
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71.23.Cq Amorphous semiconductors, metallic glasses, glasses
85.30.De Semiconductor-device characterization, design, and modeling
78.66.Jg Amorphous semiconductors; glasses
81.05.Gc Amorphous semiconductors

Strain field imaging on Si/SiGe(001)‐(2×1) surfaces by low‐energy electron microscopy and scanning tunneling microscopy

D. E. Jones, J. P. Pelz, Y. Hong, I. S. T. Tsong, Y.‐H. Xie, and P. J. Silverman

Appl. Phys. Lett. 69, 3245 (1996); http://dx.doi.org/10.1063/1.118024 (3 pages) | Cited 8 times

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We show that ultrahigh‐vacuum low‐energy electron microscopy and scanning tunneling microscopy can be used to image residual uniaxial strain fields on (001) surfaces of SiGe heterostructures. We find that the surface crosshatch morphology on these films is highly correlated with large spatial variations in the residual uniaxial strain fields, confirming the importance of local strain fields in the formation of crosshatch. © 1996 American Institute of Physics.
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61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.Gy Mechanical properties; surface strains
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Asymmetric GaAs/AlGaAs T wires with large confinement energies

H. Gislason, W. Langbein, and J. M. Hvam

Appl. Phys. Lett. 69, 3248 (1996); http://dx.doi.org/10.1063/1.118025 (3 pages) | Cited 14 times

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We report on the design and growth of asymmetric T‐shaped quantum wires with large one‐dimensional confinement energies. Prior to growth, the optimal structure for a given (110) well width is determined by a calculation. The structures are made by molecular beam epitaxy cleaved edge overgrowth. We demonstrate a confinement of 54 meV in an experimental structure consisting of a narrow (110) oriented GaAs/Al0.3Ga0.7As quantum well overgrown on much wider (001) oriented Al0.14Ga0.86As/Al0.3Ga0.7As wells. © 1996 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Fd III-V semiconductors

Hyperfine properties of bond‐center muonium and hydrogen in diamond

Sanjay Chawla and Richard P. Messmer

Appl. Phys. Lett. 69, 3251 (1996); http://dx.doi.org/10.1063/1.118026 (3 pages) | Cited 2 times

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The bond‐center (BC) hydrogen/muonium defect is of considerable interest both as a model for the theoretical description of defects in semiconductors, and because of its possible role in affecting the opto‐electronic properties of polycrystalline silicon and diamond. Its identification requires a reliable calculation of its hyperfine couplings (HFCs) both in the bulk and in strained bonds that occur at grain boundary sites. Using a novel multiconfigurational perturbative approach we have calculated the HFCs of BC muonium/hydrogen in diamond. To our knowledge the method provides the best compromise between accuracy and computational efficiency. Our results for the bulk BC muonium defect are in very good agreement with experiment. As an application of this method, we have obtained the HFCs for hydrogen in strained C‐C bonds. © 1996 American Institute of Physics.
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61.72.Bb Theories and models of crystal defects
31.15.xp Perturbation theory
36.10.Dr Positronium

Pyroelectricity in gallium nitride thin films

A. D. Bykhovski, V. V. Kaminski, M. S. Shur, Q. C. Chen, and M. A. Khan

Appl. Phys. Lett. 69, 3254 (1996); http://dx.doi.org/10.1063/1.118027 (3 pages) | Cited 14 times

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We report on the measurements of the pyroeffect in wurtzite n‐type GaN films deposited over basal plane sapphire substrates. We measured the voltage drop between the contacts while the sample was subjected to the uniform heating or cooling. The pyroelectric voltage coefficient extracted from our data is comparable to that of the pyroelectric ceramics (∼104 V/m K). Our results show that the pyroelectric effect in GaN is a combination of a fast response to an initial heat flow and a slower response related to a change in the sample temperature. © 1996 American Institute of Physics.
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77.70.+a Pyroelectric and electrocaloric effects
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

High‐temperature superconducting Josephson fluxon–antifluxon transistors

S. J. Berkowitz, Y. M. Zhang, W. H. Mallison, K. Char, E. Terzioglu, and M. R. Beasley

Appl. Phys. Lett. 69, 3257 (1996); http://dx.doi.org/10.1063/1.118028 (3 pages) | Cited 6 times

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We have realized the Josephson fluxon–antifluxon transistor (JFAT) in high temperature superconductivity using an asymmetric control line on top of either bicrystal junctions or Co‐doped YBa2Cu3Ox superconductor–normal–superconductor (SNS) junctions. We have measured current gains as high as 6 for 30 μm‐wide bicrystal JFATs (30 K) and as high as 3 for Co‐doped SNS JFATs (50 K). An improvement in gain over the Josephson vortex flow transistor, due to improved coupling efficiency, is demonstrated. There is also a reduction of control line inductance that should lead to an improvement in gate speed. © 1996 American Institute of Physics.
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85.25.Cp Josephson devices
85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits
74.72.-h Cuprate superconductors

Infrared quenching of photoinduced persistent conductivity in YBa2Cu3O6+x

D. C. Chew, J. F. Federici, J. Gutierrez‐Solana, G. Molina, W. Savin, and W. Wilber

Appl. Phys. Lett. 69, 3260 (1996); http://dx.doi.org/10.1063/1.118029 (3 pages) | Cited 9 times

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Experimental evidence for infrared quenched photoinduced persistent conductivity in oxygen deficient YBa2Cu3O6+x films is presented. Results are interpreted in terms of both a charge transfer model, in which photogenerated electrons are trapped in oxygen vacancy defects, and a photoassisted oxygen ordering model. Infrared illumination of the photoinduced state results in detrapping of electrons, a recombination of photogenerated holes/electrons, and a partial quenching of the photoinduced state. Experimental results suggest the possibility of optically controlled superconducting devices in which the superconducting state is generated and quenched with different colors of light. © 1996 American Institute of Physics.
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74.25.Gz Optical properties
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors

Scanning magnetoresistance microscopy

S. Y. Yamamoto and S. Schultz

Appl. Phys. Lett. 69, 3263 (1996); http://dx.doi.org/10.1063/1.118030 (3 pages) | Cited 30 times

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We have developed a new scanning magnetic microscopy which uses commercial magnetoresistive (MR) record/playback heads as sense probes. Two‐dimensional magnetic images are constructed by bringing the MR head into physical contact with the sample, and then acquiring MR voltage while the head is raster scanned using a high resolution (∼1 nm), linearized positioning stage. With currently available MR heads, an upper bound on the spatial resolution is 0.1×2.0 μm. This technique has broad applications beyond the magnetic storage media for which these heads were designed. In addition to magnetic imaging, this instrument can also be used to evaluate contact record and playback processes. © 1996 American Institute of Physics.
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07.55.-w Magnetic instruments and components
07.79.-v Scanning probe microscopes and components
75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
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