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31 Dec 2001

Volume 79, Issue 27, pp. 4479-4603

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Actively induced transmission via a quadratic nonlinear optical interaction in a potassium titanyl phosphate microcavity

Crina Cojocaru, R. Vilaseca, Jordi Martorell, J. Carvajal, J. Massons, and F. Diaz

Appl. Phys. Lett. 79, 4479 (2001); http://dx.doi.org/10.1063/1.1429295 (3 pages) | Cited 2 times

Online Publication Date: 13 March 2002

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We report an actively induced change in the transmission of a light pulse passing through a microcavity filled with a 40 μm thick nonlinear potassium titanyl phosphate crystal. This change was induced by an intense pulse at the frequency of the second harmonic of the original pulse. The magnitude of the change was measured to be 20%. The observed changes in transmission are shown to be in very good agreement with the numerical results from a model that considers the intrinsically fast second-order nonlinear interaction between both pulses within the nonlinear microcavity. © 2001 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Flat conduction-band alignment at the CdS/CuInSe2 thin-film solar-cell heterojunction

M. Morkel, L. Weinhardt, B. Lohmüller, C. Heske, E. Umbach, W. Riedl, S. Zweigart, and F. Karg

Appl. Phys. Lett. 79, 4482 (2001); http://dx.doi.org/10.1063/1.1428408 (3 pages) | Cited 60 times

Online Publication Date: 13 March 2002

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By combining ultraviolet and x-ray photoelectron spectroscopy with inverse photoemission spectroscopy, we find that the conduction-band alignment at the CdS/CuInSe2 thin-film solar-cell heterojunction is flat (0.0±0.2 eV). Furthermore, we observe a valence-band offset of 0.8±0.2 eV. The electronic level alignment is dominated by (1) an unusually large surface band gap of the CuInSe2 thin film (1.4 eV), (2) by a reduced surface band gap of the CdS overlayer (2.2 eV) due to intermixing effects, and (3) by a general influence of the intermixing on the chemical state near the interface. © 2001 American Institute of Physics.
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84.60.Jt Photoelectric conversion
73.20.At Surface states, band structure, electron density of states
73.61.Ga II-VI semiconductors
73.61.Le Other inorganic semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.60.Jv Interfaces; heterostructures; nanostructures

Time resolved synthetic aperture terahertz impulse imaging

K. McClatchey, M. T. Reiten, and R. A. Cheville

Appl. Phys. Lett. 79, 4485 (2001); http://dx.doi.org/10.1063/1.1427745 (3 pages) | Cited 25 times

Online Publication Date: 13 March 2002

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Using a well characterized terahertz (THz) impulse ranging system we demonstrate broad bandwidth imaging at THz frequencies using an inverse synthetic aperture deconvolution technique. The system demonstrates millimeter and submillimeter resolutions along the cross range and range axes, respectively. The range resolution, determined by the THz pulse bandwidth is 0.12 mm, while the cross range resolution is 1.2 mm; both resolutions agree well with theoretical predictions. Through imaging of cylindrical targets we demonstrate quantitative measurement of target position in the image plane within the experimental error of 0.2 mm. Imaging of geometrically scaled complex targets is demonstrated for a 1:2400 scale model ship (1 mm=24 m) corresponding to a full scale frequency bandwidth of 83–625 MHz at a distance of 840 m. © 2001 American Institute of Physics.
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84.40.Xb Telemetry: remote control, remote sensing; radar
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.05.Pj Image processing

Optical amplification in nematics doped with carbon nanotubes

Wei Lee and Sheng-Long Yeh

Appl. Phys. Lett. 79, 4488 (2001); http://dx.doi.org/10.1063/1.1430860 (3 pages) | Cited 25 times

Online Publication Date: 13 March 2002

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We present results on the orientational photorefractive effect in a mesogenic nematic doped with multiwalled carbon nanotubes. Efficient coherent-beam amplification of a signal beam by energy exchange with a pump beam was observed in homogeneous cells of the doped liquid crystal E7 at electric fields of ∼ 0.5 V/μm. Photorefractive gains as high as 103 cm−1 are achieved in the Raman–Nath regime. It is found that the gain coefficient depends strongly on the externally applied dc voltage, the pump/probe intensity ratio and the total input intensity. © 2001 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Df Liquid crystals
78.67.Ch Nanotubes

Emission zone in organic light-emitting devices having a single layer of polyphenylenevinylene derivatives

Michio Matsumura and Kaoru Manabe

Appl. Phys. Lett. 79, 4491 (2001); http://dx.doi.org/10.1063/1.1428407 (3 pages) | Cited 12 times

Online Publication Date: 13 March 2002

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Light-emitting properties of devices fabricated from a copolymer of p-phenylenevinylene derivatives, 98% 3-[4′-(3,7-dimethyloctyloxy)phenylene]-p-phenylenevinylene and 2% 2-methoxy-5-(2-ethylhexyloxy)-p-phenylenevinylene (MEH–PV), were investigated. The emission efficiency of the devices showed strong oscillatory dependence on the film thickness, and the frequency agreed with that expected from a localized emission near the indium–tin–oxide (ITO) electrode. Although holes are injected from the ITO electrode into the copolymer layer, they are probably trapped by the MEH–PV unit of the copolymer. On the other hand, electrons are easily transported through the copolymer layer. These are probably the reasons for the confinement of the light-emitting zone near the ITO/copolymer interface. The confined light-emitting zone leads to high emission. For comparison, the properties of devices based on a homopolymer were examined. In this case, the emission zone was distributed over a wide region, and the light-emission efficiency was low. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.70.Jk Polymers and organics

Focused ion beam modification of atomic force microscopy tips for near-field scanning optical microscopy

Jeffrey R. Krogmeier and Robert C. Dunn

Appl. Phys. Lett. 79, 4494 (2001); http://dx.doi.org/10.1063/1.1430028 (3 pages) | Cited 5 times

Online Publication Date: 13 March 2002

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A probe for near-field scanning optical microscopy is demonstrated based on a high index glass sphere attached to the end of a conventional atomic force microscopy tip. The sphere is machined into a pyramid geometry using a focused ion beam (FIB) instrument, coated with aluminum to confine the excitation light, and milled further with the FIB to open an aperture at the end of the tip. Near-field fluorescence images of 50 nm fluorescent latex spheres reveal subdiffraction limit spatial resolution, illustrating the utility of these probes for near-field scanning optical microscopy. © 2001 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.79.Lh Atomic force microscopes

Photoluminescence and photoelectron spectroscopic analysis of InGaAsN grown by metalorganic chemical vapor deposition

W. Chang, J. Lin, W. Zhou, S. J. Chua, and Z. C. Feng

Appl. Phys. Lett. 79, 4497 (2001); http://dx.doi.org/10.1063/1.1430857 (3 pages) | Cited 6 times

Online Publication Date: 13 March 2002

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InGaAsN films and InGaAsN/GaAs quantum wells were grown by metalorganic chemical vapor deposition using 1,1-dimethylhydrazine and tetrirybutylarsice as N and As sources, respectively. A photoluminescence peak at 1.22 μm wavelength at low temperature was observed for the In0.26Ga0.74As1−yNy/GaAs quantum wells. X-ray photoelectron spectroscopy investigation on the InGaAsN films demonstrated the success of nitrogen incorporation and provided evidence of the existence of two principle N configurations, indicating the formation of N–In and N–O,H bonds. The addition of N atoms increases the In concentration in InGaAsN wafers, whereas postgrowth annealing results in In diffusion in surface region.© 2001 American Institute of Physics.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
79.60.Dp Adsorbed layers and thin films
79.60.Jv Interfaces; heterostructures; nanostructures

Coupled strained-layer InGaAs quantum-well improvement of an InAs quantum dot AlGaAs–GaAs–InGaAs–InAs heterostructure laser

T. Chung, G. Walter, and N. Holonyak

Appl. Phys. Lett. 79, 4500 (2001); http://dx.doi.org/10.1063/1.1430025 (3 pages) | Cited 25 times

Online Publication Date: 13 March 2002

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Data are presented showing that, besides the improvement in carrier collection, it is advantageous to locate strain-matching auxiliary InGaAs layers [quantum wells (QWs)] within tunneling distance of a single-quantum-dot (QD) layer of an AlGaAs–GaAs–InGaAs–InAs QD heterostructure laser to realize also smaller size QDs of greater density and uniformity. The QD density is changed from 2×1010/cm2 for a 50 Å GaAs coupling barrier (QW to QD) to 3×1010/cm2 for a 5 Å barrier. The improved QD density and uniformity, as well as improved carrier collection, make possible room-temperature continuous-wave (cw) QD+QW laser operation (a single InAs QD layer) at reasonable diode length (∼1 mm), current density 586 A/cm2, and wavelength 1057 nm. The cw 300 K coupled InAs QD and InGaAs QW AlGaAs–GaAs–InGaA–InAs heterostructure lasers are grown by metalorganic chemical vapor deposition. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
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Repetitive plasma discharges in saline solutions

K. R. Stalder, J. Woloszko, I. G. Brown, and C. D. Smith

Appl. Phys. Lett. 79, 4503 (2001); http://dx.doi.org/10.1063/1.1429752 (3 pages) | Cited 42 times

Online Publication Date: 13 March 2002

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We describe some observations of plasma formation in aqueous electrolyte solutions (containing either sodium chloride or barium chloride), using a small planar electrode configuration driven by a repetitive bipolar voltage source. Plasma pulses of a few microseconds duration were established by a 100 kHz square wave of a few hundred volts peak to peak, drawing a current during the plasma period of several hundred milliamperes. Spectral measurements show the presence of strong ion lines, confirming that plasma is formed in the liquid. The process produces chemical radicals such as OH and, when placed in proximity to biological tissue, causes biological material volumetric removal, opening possibilities for new kinds of plasma-driven electrosurgery such as tissue debulking or cutting. © 2001 American Institute of Physics.
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52.80.Wq Discharge in liquids and solids
87.80.-y Biophysical techniques (research methods)
52.50.-b Plasma production and heating

Cross-correlation measurement of ultrashort soft x-ray pulse emitted from femtosecond laser-produced plasma using optical field-induced ionization

Katsuya Oguri, Hidetoshi Nakano, Tadashi Nishikawa, and Naoshi Uesugi

Appl. Phys. Lett. 79, 4506 (2001); http://dx.doi.org/10.1063/1.1430506 (3 pages) | Cited 4 times

Online Publication Date: 13 March 2002

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We propose a cross-correlation technique for measuring ultrashort soft x-ray pulse shapes using the rapid increase in Kr+ ion density caused by optical field-induced ionization, which operates as an ultrafast x-ray absorption switch. Using this technique, we measured the shape of a soft x-ray pulse near 15.6 nm emitted from W plasma produced by a 100 fs laser pulse, and found the duration to be about 4 ps assuming a Gaussian pulse. This result was in good agreement with the duration measured with an x-ray streak camera thus confirming the feasibility of our technique. The temporal resolution of this technique has the potential to overcome the limitation of the ionizing pulse duration. © 2001 American Institute of Physics.
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52.70.La X-ray and γ-ray measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
06.60.Jn High-speed techniques (microsecond to femtosecond)
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
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Carrier relaxation dynamics in an ultrafast all-optical modulator using an intersubband transition

T. Asano, S. Yoshizawa, and S. Noda

Appl. Phys. Lett. 79, 4509 (2001); http://dx.doi.org/10.1063/1.1427154 (3 pages) | Cited 12 times

Online Publication Date: 13 March 2002

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An improvement of an all-optical modulation scheme that utilizes an intersubband transition is proposed and investigated in connection with intersubband carrier relaxation dynamics. N-doped GaAs/AlGaAs quantum wells are pumped by an ultrashort (∼120 fs) intersubband-resonant pulse and probed by an interband-resonant white-light continuum. Ultrafast modulation speed of ∼0.4 ps is demonstrated, which is faster than that of the previous scheme by as much as a factor of 10. It is found that a large part of the carriers, which are excited from the first conduction subband to the second conduction subband, transfer to unknown trapping states at a relaxation time that is comparable to that of the pump–pulse duration. The existence of the carrier relaxation path via L valley subbands is strongly suggested as the cause. © 2001 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
78.67.De Quantum wells

Fast switchable nematic emulsions with twisted director

G. Di Profio, J. Lanzo, F. P. Nicoletta, G. De Filpo, and G. Chidichimo

Appl. Phys. Lett. 79, 4512 (2001); http://dx.doi.org/10.1063/1.1428630 (3 pages) | Cited 9 times

Online Publication Date: 13 March 2002

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Switchable nematic emulsions, obtained by a fast cooling of isotropic mixtures of nematic liquid crystal and monomers, show very low saturation fields but rather long relaxation times because of the bipolar configuration adopted by nematic directors. Such inconvenience has prevented up to now use of switchable nematic emulsions as electro-optical devices. In order to obtain a good compromise between low saturation fields and fast relaxation times, we have experimentally studied the effect of the addition of a chiral dopant on the electro-optical properties of switchable nematic emulsions. The addition of chiral molecules results in a significant decrease of decay times, while the saturation fields are slightly affected. Results are in a rather good agreement with a phenomenological model, which takes into account the increase of elastic energy due to the induced twist deformation. © 2001 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
82.70.Kj Emulsions and suspensions
78.20.Jq Electro-optical effects

Creep deformation and stress-induced structural disorder near Tg in a Zr55Al10Ni5Cu30 glassy alloy

H. Kato, A. Inoue, and H. S. Chen

Appl. Phys. Lett. 79, 4515 (2001); http://dx.doi.org/10.1063/1.1430269 (3 pages) | Cited 15 times

Online Publication Date: 13 March 2002

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Creep deformation under a constant applied load in a Zr55Al10Ni5Cu30 glassy alloy at the glass transition region is investigated. At an initial stress, σ0, less than a critical stress, σc = 80 MPa, the glass shows a Newtonian flow. When σ0 ≥ σc, the flow viscosity, η, initially decreases and attains a minimum. It then increases as the true stress, σ, decreases with further deformation. The initial decrease in η and the attendance of viscosity minimum are due to the stress-induced structural disorder and the structural equilibration with the applied stress, respectively. For stress, σ, less than the viscosity minimum stress, the stress dependence of viscosity, η(σ), curves all tend to merge together, and is fitted well with a master curve, η(σ), established previously for the steady-state flow under constant strain-rate experiments. These results render further support to the hypothesis of stress-induced structural disorder and the concept of fictive stress. © 2001 American Institute of Physics.
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81.40.Lm Deformation, plasticity, and creep
61.43.Fs Glasses
62.20.Hg Creep
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
81.05.Kf Glasses (including metallic glasses)
83.60.Df Nonlinear viscoelasticity

Evolution of self-assembled Ge/Si(211) islands

Margaret Floyd, Yangting Zhang, Jeff Drucker, David J. Smith, S. Tari, and S. Sivananthan

Appl. Phys. Lett. 79, 4518 (2001); http://dx.doi.org/10.1063/1.1428772 (3 pages) | Cited 2 times

Online Publication Date: 13 March 2002

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Atomic force microscopy (AFM) and transmission electron microscopy have been used to investigate Ge islands, grown by molecular-beam epitaxy on Si(211) substrates with a nominal 15 Å Ge coverage at temperatures between 600 and 700 °C. The majority of islands grown at all three temperatures had irregular hexagonal footprints. Intermediate-sized islands grown at 650 and 700 °C became elongated laterally in the 〈111〉 direction parallel to the direction of substrate surface step edges. AFM cross-sectional analysis indicated that small coherent clusters were bound by {111} and {113} facets, whereas the largest dislocated clusters were primarily bound by {111} and {001} facets. The upper size bound for coherent clusters increased with increasing growth temperature. © 2001 American Institute of Physics.
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68.55.A- Nucleation and growth
81.05.Cy Elemental semiconductors
81.16.Dn Self-assembly
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Lp Transmission electron microscopy (TEM)
68.37.Ps Atomic force microscopy (AFM)
68.55.-a Thin film structure and morphology

Determination of coverage in passivated porous silicon by Brillouin spectroscopy

H. J. Fan, M. H. Kuok, S. C. Ng, R. Boukherroub, and D. J. Lockwood

Appl. Phys. Lett. 79, 4521 (2001); http://dx.doi.org/10.1063/1.1428628 (3 pages) | Cited 3 times

Online Publication Date: 13 March 2002

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Brillouin scattering has been performed to probe surface acoustic waves in porous silicon films that have been chemically modified with various surface passivators. The surface Rayleigh mode and two film acoustic modes are observed. Unlike the Rayleigh mode, the two film modes are found to exhibit velocity dispersion. The effect of passivation is manifested as a shift of Brillouin peaks to lower frequencies relative to those of the freshly prepared porous silicon samples. The coverage of the surface area of the pores of the entire porous layers by the respective chemical passivators has been estimated from the phase velocity of one of the film modes. © 2001 American Institute of Physics.
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78.66.Db Elemental semiconductors and insulators
78.35.+c Brillouin and Rayleigh scattering; other light scattering
81.65.Rv Passivation
81.05.Rm Porous materials; granular materials
68.35.Iv Acoustical properties
81.05.Cy Elemental semiconductors

Incorporation-related structural issues for beryllium doping during growth of GaN by rf-plasma molecular-beam epitaxy

A. J. Ptak, Lijun Wang, N. C. Giles, T. H. Myers, L. T. Romano, C. Tian, R. A. Hockett, S. Mitha, and P. Van Lierde

Appl. Phys. Lett. 79, 4524 (2001); http://dx.doi.org/10.1063/1.1429290 (3 pages) | Cited 11 times

Online Publication Date: 13 March 2002

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Beryllium incorporation was studied for both Ga-polarity and N-polarity GaN using a series of Be step-doped epitaxial layers. Dopant concentration profiles indicated that surface polarity-related incorporation differences are not pronounced for Be. Significant surface accumulation of Be occurs during growth with surface accumulations approaching a monolayer for heavier doping levels. Transmission electron microscopy studies indicate the surface layer of Be has a significant effect on the microstructure, particularly for near monolayer coverage. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Ea III-V semiconductors
61.72.uj III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Stability of carbon nanotubes under electric field studied by scanning electron microscopy

Yi Wei, Chenggang Xie, Kenneth A. Dean, and Bernard F. Coll

Appl. Phys. Lett. 79, 4527 (2001); http://dx.doi.org/10.1063/1.1429300 (3 pages) | Cited 53 times

Online Publication Date: 13 March 2002

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The influence of an applied electric field on carbon nanotubes protruding from a surface was investigated in situ using a high-resolution scanning electron microscopy. Under the applied electric field, the nanotubes flexed to orient themselves parallel to the electric field lines. For moderate field strengths below the electron field emission threshold, the flexed nanotubes relaxed back to their original shapes after the electric field was removed. However, when high electron field emission currents were extracted from the nanotubes, they were permanently deformed, leaving them aligned to the electric field direction after the electric field was removed. For high currents, the length of the carbon nanotubes were found to be shortened after field emission lasted for a period of time. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
79.70.+q Field emission, ionization, evaporation, and desorption

High-quality, faceted cubic boron nitride films grown by chemical vapor deposition

W. J. Zhang, X. Jiang, and S. Matsumoto

Appl. Phys. Lett. 79, 4530 (2001); http://dx.doi.org/10.1063/1.1428762 (3 pages) | Cited 19 times

Online Publication Date: 13 March 2002

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Thick cubic boron nitride (cBN) films showing clear crystal facets were achieved by chemical vapor deposition. The films show the highest crystallinity of cBN films ever achieved from gas phase. Clear evidence for the growth via a chemical route is obtained. A growth mechanism is suggested, in which fluorine preferentially etches hBN and stabilizes the cBN surface. Ion bombardment of proper energy activates the cBN surface bonded with fluorine so as to enhance the bonding probability of nitrogen-containing species on the F-stabilized B (111) surface. © 2001 American Institute of Physics.
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68.55.A- Nucleation and growth
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
68.37.Ps Atomic force microscopy (AFM)
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
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Field emission characteristics of BN/GaN structure

Chiharu Kimura, Tomohide Yamamoto, Takamitsu Hori, and Takashi Sugino

Appl. Phys. Lett. 79, 4533 (2001); http://dx.doi.org/10.1063/1.1427755 (3 pages) | Cited 14 times

Online Publication Date: 13 March 2002

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n-type gallium nitride (GaN) layers grown on sapphire substrates by metalorganic chemical vapor deposition are used to examine field emission characteristics. The electron concentration of the GaN is 2×1017 cm−3. In order to enhance the electric field, the GaN surface is roughened by hydrogen (H2) plasma treatment. Boron nitride (BN) films are grown on the roughened surface of the GaN by plasma-assisted chemical vapor deposition. The turn-on electric field between the anode and sample surface is estimated to be 12.4 and 8.8 V/μm from the field emission characteristics of the roughened GaN and the BN/GaN samples, respectively. It is demonstrated that BN coating is effective in improving the field emission characteristics.© 2001 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption

Study of Schottky barrier of Ni on p-GaN

L. S. Yu, D. Qiao, L. Jia, S. S. Lau, Y. Qi, and K. M. Lau

Appl. Phys. Lett. 79, 4536 (2001); http://dx.doi.org/10.1063/1.1428773 (3 pages) | Cited 19 times

Online Publication Date: 13 March 2002

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The Schottky barrier characteristics of Ni on p-GaN have been investigated using current–voltage–temperature (I–V–T) and capacitance–voltage characteristics (C–V) measurements. Barrier height values ranging from 2.68 to 2.87 eV were obtained from C–V measurements. The temperature dependence of I–V characteristics clearly indicated the dominance of tunneling current in the transport mechanism of the diodes, therefore, barrier height determination using I–V measurements can lead to erroneous results, as indicated by the wide range of barrier heights reported in the literature. Acceptor concentration, deduced from C–V measurements, was found to be of 1019/cm3 within 200 Å of the sample surface, and tapered off to be ∼ 1018/cm3. These values are 10–100 times higher than the hole concentration of ∼ 1017/cm3 obtained from Hall measurements. © 2001 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Traps at the bonded interface in silicon-on-insulator structures

I. V. Antonova, O. V. Naumova, D. V. Nikolaev, V. P. Popov, J. Stano, and V. A. Skuratov

Appl. Phys. Lett. 79, 4539 (2001); http://dx.doi.org/10.1063/1.1428412 (2 pages) | Cited 7 times

Online Publication Date: 13 March 2002

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In this study, we compared the trap density distributions, Dit, in the band gap of silicon at the Si/thermal SiO2 interface and at the bonded interface of the silicon–on–insulator structure, deduced from deep level transient spectroscopy measurements. The trap energies for the bonded Si/SiO2 interface are localized in the range from Ec–0.17 to Ec–0.37 eV. The lack of the transient SiOx layer at the bonded interface is suggested to lead to a relatively narrow interval of trap energies. © 2001 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Hydrogen-induced transport properties of holes in diamond surface layers

C. E. Nebel, C. Sauerer, F. Ertl, M. Stutzmann, C. F. O. Graeff, P. Bergonzo, O. A. Williams, and R. Jackman

Appl. Phys. Lett. 79, 4541 (2001); http://dx.doi.org/10.1063/1.1429756 (3 pages) | Cited 31 times

Online Publication Date: 13 March 2002

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Three hydrogen-terminated diamonds with different surface roughness and morphologies have been investigated by conductivity and Hall experiments in the temperature regime 0.34–350 K. The sheet hole densities are weakly temperature dependent above a critical temperature Tc (20 K ⩽ Tc ⩽ 70 K), below Tc carriers freeze out. The mobilities of holes show a minimum at Tc increasing towards higher and even stronger towards lower temperatures significantly up to 400 cm2/V s. A transport model is introduced where holes propagate in the valence band where a disorder-induced tail of localized states is present. © 2001 American Institute of Physics.
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73.25.+i Surface conductivity and carrier phenomena
72.80.Sk Insulators
72.20.My Galvanomagnetic and other magnetotransport effects
68.35.B- Structure of clean surfaces (and surface reconstruction)
72.20.Fr Low-field transport and mobility; piezoresistance
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Response of superconducting Y–Ba–Cu–O films to millimeter wave radiation

K. Repšas, A. Laurinavičius, A. R. Vaškevičius, and F. Anisimovas

Appl. Phys. Lett. 79, 4544 (2001); http://dx.doi.org/10.1063/1.1428112 (3 pages) | Cited 6 times

Online Publication Date: 13 March 2002

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The origin of temperature and radiation power response dependencies to millimeter wave radiation is analyzed for Y–Ba–Cu–O thin films. These dependencies were both experimentally measured and described by an empirical formula. The results which were obtained indicate that the peak shape of temperature dependence for the nonbolometric response is determined by the temperature of the thermostat and is less inertial than for τ = 1/f (f = 35 GHz). © 2001 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.25.N- Response to electromagnetic fields
74.72.-h Cuprate superconductors

Sputtered nanodots: A costless method for inducing effective pinning centers in superconducting thin films

A. Crisan, S. Fujiwara, J. C. Nie, A. Sundaresan, and H. Ihara

Appl. Phys. Lett. 79, 4547 (2001); http://dx.doi.org/10.1063/1.1428632 (3 pages) | Cited 61 times

Online Publication Date: 13 March 2002

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A straightforward and cheap method for creating extended defects, strong pinning centers, in superconducting thin films is proposed. Clearly, by very short time (3–5 s) rf sputtering at suitable substrate temperatures, we deposited Ag nanodots on SrTiO3 substrates prior to the growth of superconducting thin films. The nanodots were studied by atomic force microscopy. Due to the lattice mismatch and/or chemical poisoning, on top of the nanodots the superconducting phase does not form, creating in this way extended and effective pinning centers which increase the critical current density of the film. The method was applied to (Cu, Tl)BaSrCa2Cu3Oy films grown by amorphous phase epitaxy. Thin films grown in similar conditions, with and without nanodots, were characterized by x-ray diffraction and ac susceptibility. The results show that the nanodots increased the critical current density more than one order of magnitude. © 2001 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.72.-h Cuprate superconductors
68.65.Hb Quantum dots (patterned in quantum wells)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Sv Critical currents
81.07.Ta Quantum dots
81.15.Cd Deposition by sputtering

Ballistic magnetoresistance in a magnetic nanometer sized contact: An effective gate for spintronics

N. García, M. Muñoz, G. G. Qian, H. Rohrer, I. G. Saveliev, and Y.-W. Zhao

Appl. Phys. Lett. 79, 4550 (2001); http://dx.doi.org/10.1063/1.1427152 (3 pages) | Cited 53 times

Online Publication Date: 13 March 2002

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We present experimental results of unprecedented large magnetoresistance obtained in stable electrodeposited Ni–Ni nanocontacts 10–30 nm in diameter. The contacts exhibit magnetoresistance of up to 700% at room temperature and low applied fields and, therefore, act as very effective spin filters. These large values of the magnetoresistance are attributed to spin ballistic transport through a magnetic “dead layer” at the contact of width of about 1 nm or smaller. Nanometer sized, high sensitive magnetoresistive sensors could become key elements for magnetic storage in the terabit/in.2 range and in high density magnetic random access memories. © 2001 American Institute of Physics.
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75.75.-c Magnetic properties of nanostructures
85.75.Bb Magnetic memory using giant magnetoresistance
75.47.De Giant magnetoresistance
81.07.Lk Nanocontacts
73.63.Rt Nanoscale contacts
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.15.Pq Electrodeposition, electroplating
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