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22 Mar 2004

Volume 84, Issue 12, pp. 2013-2211

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 2100 (2004); http://dx.doi.org/10.1063/1.1688997 (3 pages)

P. Sutter, E. Sutter, and T. R. Ohno
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Effect of gate oxidation method on electrical properties of metal-oxide-semiconductor field-effect transistors fabricated on 4H-SiC C(000math) face

Kenji Fukuda, Makoto Kato, Kazutoshi Kojima, and Junji Senzaki

Appl. Phys. Lett. 84, 2088 (2004); http://dx.doi.org/10.1063/1.1682680 (3 pages) | Cited 28 times

Online Publication Date: 16 March 2004

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The effect of gate oxidation method on the electrical properties of metal-oxide-semiconductor field-effect transistors (MOSFETs) fabricated on 4H-SiC C(000math) face has been investigated. In the case of SiC MOSFETs fabricated by dry gate oxidation, the peak value of field-effect mobility (μFE) is 16.3 cm2/V s. On the other hand, pyrogenic gate oxidation and pyrogenic gate oxidation followed by H2 postoxidation annealing (POA) considerably decreased the interface trap density (Dit) and the threshold voltage, and markedly improved the μFE. The depth profiles of hydrogen density were measured using secondary ion mass spectroscopy. These verified that pyrogenic gate oxidation increases hydrogen density at the SiO2/SiC interface compared to dry gate oxidation, and that the pyrogenic gate oxidation followed by H2 POA increases considerably it. It is thought that the Dit reduction might be caused by the passivation of interface states by –H or –OH. The peak value of μFE for SiC MOSFETs fabricated by pyrogenic gate oxidation followed by H2 POA is 111 cm2/V s, which is much higher than that of SiC MOSFETs fabricated on a Si(0001) face. Therefore, the 4H-SiC C(000math) face is suitable for the fabrication of SiC power MOSFETs. © 2004 American Institute of Physics.
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85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Mq Oxidation
81.65.Rv Passivation
81.40.Gh Other heat and thermomechanical treatments
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Picosecond response of gallium-nitride metal–semiconductor–metal photodetectors

Jianliang Li, Ying Xu, T. Y. Hsiang, and W. R. Donaldson

Appl. Phys. Lett. 84, 2091 (2004); http://dx.doi.org/10.1063/1.1688454 (3 pages) | Cited 13 times

Online Publication Date: 16 March 2004

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Metal–semiconductor–metal ultraviolet photodiodes fabricated on GaN were tested in the picosecond regime with an electro-optic sampling system. A device with a feature size of 1 μm showed a response with 1.4 ps rise time and 3.5 ps full width at half maximum. The derived electron velocity, 1.43×107 cm/s, is in good agreement with independent photoexcitation measurements. A slower impulse response was observed in a device with smaller feature size of 0.5 μm. © 2004 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
73.40.Sx Metal-semiconductor-metal structures

Memory effect of oxide/SiC:O/oxide sandwiched structures

T. C. Chang, S. T. Yan, F. M. Yang, P. T. Liu, and S. M. Sze

Appl. Phys. Lett. 84, 2094 (2004); http://dx.doi.org/10.1063/1.1675924 (3 pages) | Cited 5 times

Online Publication Date: 16 March 2004

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The memory effects of the oxide/oxygen-incorporated silicon carbide (SiC:O)/oxide sandwiched structure were investigated. The memory window is decreased with the increase of the oxygen content in the SiC:O film due to the reduction of dangling bonds. A concise model is proposed to explain the reduction of dangling bonds with increasing oxygen content. Also, a higher breakdown voltage is observed with less oxygen content in the SiC:O film, which is attributed to the high barrier height induced by electron trapping in the SiC:O film. © 2004 American Institute of Physics.
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71.55.Ht Other nonmetals
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Le Other inorganic semiconductors

High-mobility, sputtered films of indium oxide doped with molybdenum

Yuki Yoshida, David M. Wood, Timothy A. Gessert, and Timothy J. Coutts

Appl. Phys. Lett. 84, 2097 (2004); http://dx.doi.org/10.1063/1.1687984 (3 pages) | Cited 34 times

Online Publication Date: 16 March 2004

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Thin films of molybdenum-doped indium oxide, an n-type transparent conducting oxide, were deposited on glass substrates by a large-area deposition technique, radio-frequency magnetron sputtering, and their electrical properties were examined. Molybdenum content was varied from 1 to 4 wt%, and the highest mobility achieved was 83 cm2 V−1 s−1 at a carrier concentration of 3.0×1020 cm−3 without any postdeposition treatment for one of the films made from the target with 2 wt% Mo. Temperature-dependent Hall analysis indicated that this high mobility is limited by phonon scattering, whereas the method of four coefficients analysis showed that the conduction band is parabolic. © 2004 American Institute of Physics.
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68.55.A- Nucleation and growth
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Le Other inorganic semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.15.Cd Deposition by sputtering
81.05.Hd Other semiconductors

High-resolution mapping of nonuniform carrier transport at contacts to polycrystalline CdTe/CdS solar cells

P. Sutter, E. Sutter, and T. R. Ohno

Appl. Phys. Lett. 84, 2100 (2004); http://dx.doi.org/10.1063/1.1688997 (3 pages) | Cited 12 times

Online Publication Date: 16 March 2004

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We demonstrate a spectroscopic technique based on scanning tunneling microscopy that provides high-resolution maps of local carrier transport across contacts to polycrystalline thin-film solar cells. Using this technique, preferential transport channels across a p+-ZnTe/p-CdTe back contact of a p-CdTe/n-CdS solar cell are imaged with 20 nm spatial resolution. Transport across this contact is highly nonuniform. Large areas of high resistance coexist with nanoscale low-resistance regions that are strongly correlated with grain boundaries in the CdTe absorber. These results suggest an important role of grain boundaries as near-contact conducting channels. © 2004 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
84.60.Jt Photoelectric conversion
61.72.Mm Grain and twin boundaries
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
73.61.Ga II-VI semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
61.46.-w Structure of nanoscale materials

Mapping In concentration, strain, and internal electric field in InGaN/GaN quantum well structure

M. Takeguchi, M. R. McCartney, and David J. Smith

Appl. Phys. Lett. 84, 2103 (2004); http://dx.doi.org/10.1063/1.1689400 (3 pages) | Cited 20 times

Online Publication Date: 16 March 2004

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Quantitative comparisons have been made of the In concentration, strain, and internal electric field present in a pseudomorphic InGaN/GaN quantum well. Z-contrast scanning transmission electron microscopy was used for mapping In concentration with atomic resolution, variations of the c-lattice parameter of the InGaN layer were measured from (0001) lattice fringes in high-resolution transmission electron micrographs, and the internal electric fields were determined by differentiating phase images obtained by electron holography. Based on these measurements, it was concluded that local fluctuations of In concentration caused inhomogeneities in the internal electric field across the quantum well. The band structure of the quantum well would thus be altered not only by quantum dot effects but also by the additional modulation of the internal electric field, leading to further broadening of the light emission. © 2004 American Institute of Physics.
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68.65.Fg Quantum wells
73.21.Fg Quantum wells
68.37.Lp Transmission electron microscopy (TEM)

Room-temperature silicon light-emitting diodes based on dislocation luminescence

V. Kveder, M. Badylevich, E. Steinman, A. Izotov, M. Seibt, and W. Schröter

Appl. Phys. Lett. 84, 2106 (2004); http://dx.doi.org/10.1063/1.1689402 (3 pages) | Cited 61 times

Online Publication Date: 16 March 2004

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We demonstrate electroluminescence (EL) with an external efficiency of more than 0.1% at room temperature from glide dislocations in silicon. The key to this achievement is a considerable reduction of nonradiative carrier recombination at dislocations due to impurities and core defects by impurity gettering and hydrogen passivation, respectively, which is shown by means of deep-level transient spectroscopy. Time-resolved EL measurements reveal a response time below 1.8 μs, which is much faster, compared to the band-to-band luminescence of bulk silicon. © 2004 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
81.65.Rv Passivation
78.55.Ap Elemental semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Mapping the potential within a nanoscale undoped GaAs region using a scanning electron microscope

B. Kaestner, C. Schönjahn, and C. J. Humphreys

Appl. Phys. Lett. 84, 2109 (2004); http://dx.doi.org/10.1063/1.1689755 (3 pages) | Cited 8 times

Online Publication Date: 16 March 2004

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Semiconductor dopant profiling using secondary electron imaging in a scanning electron microscope has been developed in recent years. In this letter, we show that the mechanism behind it also allows mapping of the electric potential of undoped regions. By using an unbiased GaAs/AlGaAs heterostructure, this letter demonstrates the direct observation of the electrostatic potential variation inside a 90-nm-wide undoped GaAs channel surrounded by ionized dopants. The secondary electron emission intensities are compared with two-dimensional numerical solutions of the electric potential. © 2004 American Institute of Physics.
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79.20.Hx Electron impact: secondary emission
61.46.-w Structure of nanoscale materials
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Effects of hydrostatic and uniaxial stress on the Schottky barrier heights of Ga-polarity and N-polarity n-GaN

Y. Liu, M. Z. Kauser, M. I. Nathan, P. P. Ruden, S. Dogan, H. Morkoç, S. S. Park, and K. Y. Lee

Appl. Phys. Lett. 84, 2112 (2004); http://dx.doi.org/10.1063/1.1689392 (3 pages) | Cited 14 times

Online Publication Date: 16 March 2004

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We report measurements of the Schottky barrier heights of Ni/Au contacts on Ga-polarity and N-polarity n-GaN under hydrostatic pressure and applied in-plane uniaxial stress. Under hydrostatic pressure the two different polarities of GaN yield significantly different rates of Schottky barrier height increase with increasing pressure. Uniaxial stress parallel to the surface affects the Schottky barrier height only minimally. The observed changes in barrier height under stress are attributed to a combination of band structure and piezoelectric effects. © 2004 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.Kk Junction diodes
71.20.Nr Semiconductor compounds
73.20.At Surface states, band structure, electron density of states
77.65.Bn Piezoelectric and electrostrictive constants
73.40.Ns Metal-nonmetal contacts

Field emission properties of heavily Si-doped AlN in triode-type display structure

Yoshitaka Taniyasu, Makoto Kasu, and Toshiki Makimoto

Appl. Phys. Lett. 84, 2115 (2004); http://dx.doi.org/10.1063/1.1689398 (3 pages) | Cited 40 times

Online Publication Date: 16 March 2004

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Using heavily Si-doped AlN, a triode-type field emission display is demonstrated. The device consists of the heavily Si-doped AlN field emitter, mesh grid, and phosphor-coated anode screen. The device exhibits a low turn-on electric field of 11 V/μm, and the field emission current exponentially increases as the grid voltage increases. The field emission current reaches 9.5 μA at an electric field strength of 23 V/μm. Luminescence from the phosphor excited by the field-emitted electrons is uniform over the anode screen and is intense enough for the display application. The field emission current is stable over time. © 2004 American Institute of Physics.
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85.45.Fd Field emission displays (FEDs)
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A class of spin injection-precession ultrafast nanodevices

V. V. Osipov and A. M. Bratkovsky

Appl. Phys. Lett. 84, 2118 (2004); http://dx.doi.org/10.1063/1.1667002 (3 pages) | Cited 22 times

Online Publication Date: 16 March 2004

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Spin valve ultrafast spin injection devices with small dissipated power are described: an amplifier, a frequency multiplier, and a square-law detector. Their operation is based on injection of spin polarized electrons from one ferromagnet to another through a semiconductor layer and spin precession of the electrons in the semiconductor layer in a magnetic field induced by a (base) current in an adjacent nanowire. The base current can control the emitter current between the magnetic layers with frequencies up to several 100 GHz. © 2004 American Institute of Physics.
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72.25.Hg Electrical injection of spin polarized carriers
72.25.Mk Spin transport through interfaces
85.35.Ds Quantum interference devices
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
85.35.Kt Nanotube devices
75.50.Dd Nonmetallic ferromagnetic materials
75.47.-m Magnetotransport phenomena; materials for magnetotransport
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Angular-dependent vortex pinning mechanisms in YBa2Cu3O7 coated conductors and thin films

L. Civale, B. Maiorov, A. Serquis, J. O. Willis, J. Y. Coulter, H. Wang, Q. X. Jia, P. N. Arendt, J. L. MacManus-Driscoll, M. P. Maley, and S. R. Foltyn

Appl. Phys. Lett. 84, 2121 (2004); http://dx.doi.org/10.1063/1.1655707 (3 pages) | Cited 114 times

Online Publication Date: 16 March 2004

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We compare the angular-dependent critical current density (Jc) in YBa2Cu3O7 films deposited on MgO templates grown by ion-beam-assisted deposition (IBAD), and on single-crystal substrates. We identify three angular regimes in which pinning is dominated by different types of correlated and uncorrelated defects. Those regimes are present in all cases, but their extension and characteristics are sample dependent, reflecting differences in texture and defect density. The more defective nature of the films on IBAD turns into an advantage as it results in higher Jc, demonstrating that the performance of the films on single crystals is not an upper limit for the IBAD coated conductors. © 2004 American Institute of Physics.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
81.15.Jj Ion and electron beam-assisted deposition; ion plating
74.81.Bd Granular, melt-textured, amorphous, and composite superconductors

Giant magnetostriction on Fe85Ga15 stacked ribbon samples

G. D. Liu, L. B. Liu, Z. H. Liu, M. Zhang, J. L. Chen, J. Q. Li, G. H. Wu, Y. X. Li, J. P. Qu, and T. S. Chin

Appl. Phys. Lett. 84, 2124 (2004); http://dx.doi.org/10.1063/1.1688452 (3 pages) | Cited 16 times

Online Publication Date: 16 March 2004

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Large magnetostrictions of −1300 and +1100 ppm related in the different directions have been obtained in our stacked Fe85Ga15 ribbon samples. In the case of non-180° domain magnetization in the high anisotropic samples, the magnetostrictions are mainly attributed to the existence of Ga clusters which preferentially orient with the ribbon normal due to the ribbon grain texturing. Forming the modified DO3 structure, the Ga–Ga atom pairs distribute in the matrix and cause the x-ray diffraction peak split in melt-spun ribbons. As a special micromorphology, Ga clusters highly condensed in some nanoscale dots have also been experimentally observed. © 2004 American Institute of Physics.
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75.80.+q Magnetomechanical effects, magnetostriction
75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

Y. Yuan, J. Jiang, X. Y. Cai, D. C. Larbalestier, E. E. Hellstrom, Y. Huang, and R. Parrella

Appl. Phys. Lett. 84, 2127 (2004); http://dx.doi.org/10.1063/1.1682675 (3 pages) | Cited 17 times

Online Publication Date: 16 March 2004

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Overpressure (OP) processing otherwise fully treated, commercial Ag-sheathed multifilament (Bi,Pb)2Sr2Ca2Cu3Ox (2223) composite conductors increased the critical current density Jc (0.1 T, 77 K) by 37% to 30.8 kA/cm2 and the self-field Jc (SF, 77 K) to 69.6 kA/cm2. These improvements were obtained on full-size high current conductors such that critical current Ic (0.1 T, 77 K) reached 80.6 A and Ic (SF, 77 K) 181.7 A, even though there was a very strong self-field suppression of Ic. Estimated values for the non-self-field-limited Ic and Jc (0 T, 77 K) reached 235 A and 90 kA/cm2. Scanning electron microscopy and superconducting quantum inference device measurement revealed that OP processing effectively suppressed cracks, porosity, and the volume fraction of the Bi2Sr2Ca1Cu2Oy (2212) phase, which are all major current-limiting mechanisms in present 2223 conductors. © 2004 American Institute of Physics.
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74.72.-h Cuprate superconductors
84.71.Mn Superconducting wires, fibers, and tapes
81.40.Vw Pressure treatment
74.25.Sv Critical currents
62.50.-p High-pressure effects in solids and liquids
81.05.Mh Cermets, ceramic and refractory composites
74.25.Ld Mechanical and acoustical properties, elasticity, and ultrasonic attenuation

Unidirectional magnetostrictive Terfenol/epoxy composite

Jong Chul Kim, Oh Yeoul Kwon, and Zin Hyoung Lee

Appl. Phys. Lett. 84, 2130 (2004); http://dx.doi.org/10.1063/1.1688449 (3 pages) | Cited 3 times

Online Publication Date: 16 March 2004

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We have developed a unidirectional composite for improving magnetostrictive properties and mechanical properties of giant magnetostrictive composite. The composite consists of bulk RFe2 dendrites with a preferred orientation of 〈112〉 and an electrically insulated binder between the dendrites, which is analogous to a lamination pattern. We investigated the magnetostrictive properties of composites by varying the volume fraction of RFe2 phase in the range of 60%–80%. The results demonstrated that the unidirectional composites had much higher strain and d33 than a monolithic Terfenol-D at the same volume fraction of RFe2 phase and these results were compared with the model for uniform strain. © 2004 American Institute of Physics.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Bb Fe and its alloys
75.47.De Giant magnetoresistance

Timing jitter measurement of single-flux-quantum pulse in Josephson transmission line

Hirotaka Terai, Zhen Wang, Yoshihito Hishimoto, Shinichi Yorozu, Akira Fujimaki, and Nobuyuki Yoshikawa

Appl. Phys. Lett. 84, 2133 (2004); http://dx.doi.org/10.1063/1.1650912 (3 pages) | Cited 18 times

Online Publication Date: 16 March 2004

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Timing jitter is an important factor in determining the limit of speed and scale of single-flux-quantum circuits. We estimated the timing jitter by a simple method using 2-bit shift registers. It was estimated by observing the transition between 1- and 2-mode operations while changing the bias current to the clock line. A sharp transition was observed in the shift register with a smaller number of Josephson junctions in the clock and data lines, suggesting the existence of a finite timing jitter. The timing jitter per Josephson junction was estimated to be 0.09 ps at a designed bias current. The temperature dependence supported that the timing jitter comes from thermal fluctuation. © 2004 American Institute of Physics.
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84.30.Sk Pulse and digital circuits
85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits

Electron-doped infinite-layer thin films with TC over 40 K grown on DyScO3 substrates

Shin-ichi Karimoto and Michio Naito

Appl. Phys. Lett. 84, 2136 (2004); http://dx.doi.org/10.1063/1.1688979 (3 pages) | Cited 8 times

Online Publication Date: 16 March 2004

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We report high-quality electron-doped infinite-layer superconducting thin films with a TC of over 40 K grown on lattice-matched DyScO3 substrates by molecular-beam epitaxy. The optimally doped film seems to be free from strain, thus leading to a low resistivity of 75 μΩ cm at room temperature and 15 μΩ cm just above TC. © 2004 American Institute of Physics.
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74.62.Dh Effects of crystal defects, doping and substitution
74.25.F- Transport properties
68.55.A- Nucleation and growth
74.78.-w Superconducting films and low-dimensional structures
74.10.+v Occurrence, potential candidates
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Capping-layer-induced magnetic coupling in a two-dimensional nanostructured system

E. Navarro, Y. Huttel, C. Clavero, G. Armelles, and A. Cebollada

Appl. Phys. Lett. 84, 2139 (2004); http://dx.doi.org/10.1063/1.1689739 (3 pages) | Cited 11 times

Online Publication Date: 16 March 2004

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The magnetic polarization of a Pt capping layer leads to an increase of the interisland magnetic coupling in a two-dimensional array of Fe islands. For small superparamagnetic islands, Pt deposition leads to a superparamagnetic–ferromagnetic transition. For larger ferromagnetic but weakly coupled islands, Pt deposition produces a stronger interisland coupling. Polar Kerr spectroscopy measurements and simulations evidence the magnetic polarization of Pt in contact with Fe. The described effects and their interpretation are supported by the use of a nonpolarizable Al capping, where both the superparamagnetic-to-ferromagnetic transition and the increase of the interisland coupling are absent. © 2004 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.20.En Metals and alloys
78.20.Ls Magneto-optical effects
61.46.-w Structure of nanoscale materials
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Domain structure of epitaxial CaHfO3 gate insulator films on SrTiO3

Keisuke Shibuya, Tsuyoshi Ohnishi, Mikk Lippmaa, Masashi Kawasaki, and Hideomi Koinuma

Appl. Phys. Lett. 84, 2142 (2004); http://dx.doi.org/10.1063/1.1689394 (3 pages) | Cited 13 times

Online Publication Date: 16 March 2004

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Thin CaHfO3 films were grown on (100) and (110)-oriented SrTiO3 surfaces with the aim of obtaining an insulator film for epitaxial oxide device design. We show that films grown on the (100) surface of SrTiO3 have a multidomain structure, which increases film roughness and decreases the maximum breakdown field of the insulator. Single-domain films were obtained on the SrTiO3 (110) surface. These films had a breakdown field of 5 MV/cm and a dielectric constant of εr = 16 to 17 at room temperature. © 2004 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.55.-g Dielectric thin films
77.22.Jp Dielectric breakdown and space-charge effects
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.35.B- Structure of clean surfaces (and surface reconstruction)

Dielectric behavior of electroactive fluorinate-based terpolymers

Chen Ang and Zhi Yu

Appl. Phys. Lett. 84, 2145 (2004); http://dx.doi.org/10.1063/1.1688455 (3 pages) | Cited 3 times

Online Publication Date: 16 March 2004

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The dielectric and ferroelectric properties of the poly(vinylidene fluoride–trifluoroethylene–chlorotrifluoroethylene) terpolymers are studied in the temperature range 160–380 K. More attention was given to the dielectric loss in the dielectric spectra and the following results were obtained: (1) there are two dielectric polarization mechanisms, modes A and B, contributing to the majority of the dielectric permittivity; (2) by using the Cole–Cole plot method, precise relaxation rates of mode B can be obtained, which follow the Vogel–Fulcher relation with reasonable parameters, TVF = ∼ 160±2 K, UVF = ∼ 0.16±0.01 eV, ν0 = 1×1012 Hz. The temperature where mode A occurs does not shift with the variation of frequency and a well-developed hysteresis loop is observed, indicating the existence of a normal “paraelectric–ferroelectric” transition in the terpolymer. © 2004 American Institute of Physics.
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77.84.Jd Polymers; organic compounds
77.22.Gm Dielectric loss and relaxation
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization

Effects of dielectric structure of HfO2 on carrier generation rate in Si substrate and channel mobility

Chang Yong Kang, Hag-Ju Cho, Rino Choi, Chang Seok Kang, Young Hee Kim, Se Jong Rhee, Chang Hwan Choi, Shahriar M. Akbar, and Jack C. Lee

Appl. Phys. Lett. 84, 2148 (2004); http://dx.doi.org/10.1063/1.1689744 (3 pages) | Cited 9 times

Online Publication Date: 16 March 2004

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This letter presents the effects of surface preparation for hafnium-based dielectrics on the bulk carrier generation rates and the carrier mobility. Different surface preparations result in different interfacial layers. Nitrogen-incorporated layers effectively block impurity penetration from hafnium oxide, and lead to the increase of bulk carrier generation lifetime. However, nitrogen-incorporated interface layers increase interface state density and degrade channel mobility, even though bulk carrier generation lifetime is increased. Thus, mobility degradation is preliminarily caused by fixed charge and interface states of the high-k dielectrics. © 2004 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Fr Low-field transport and mobility; piezoresistance
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
61.72.up Other materials
73.20.Hb Impurity and defect levels; energy states of adsorbed species
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Nanostructuring the Er–Yb distribution to improve the photoluminescence response of thin films

A. Suarez-Garcia, R. Serna, M. Jiménez de Castro, C. N. Afonso, and I. Vickridge

Appl. Phys. Lett. 84, 2151 (2004); http://dx.doi.org/10.1063/1.1664034 (3 pages) | Cited 20 times

Online Publication Date: 16 March 2004

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Thin films of amorphous aluminum oxide (a-Al2O3) codoped with Er3+ and Yb3+ ions have been in-depth nanostructured by distributing the rate earth (RE) ions in layers separated in the 0–3 nm range. The Yb to Er concentration ratio is varied from 0 to 3.6. The photoluminescence (PL) response at 1.53 μm exhibits an increase of up to two orders of magnitude with respect to that of films doped only with Er. The PL intensity is improved when Yb3+ and Er3+ ions are in separate layers and the results show that efficient Yb3+ to Er3+ energy transfer can be achieved for separations up to 3 nm. Furthermore, it is shown that designing an adequate RE distribution, for the same total RE content and Yb to Er concentration ratio, can enhance the PL intensity by a further factor of two. It is shown that the Er3+ PL response is improved because of a reduction of the RE clustering and an improvement of the energy transfer from Yb3+ to Er3+ ions. © 2004 American Institute of Physics.
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78.66.Nk Insulators
81.16.Mk Laser-assisted deposition
61.46.-w Structure of nanoscale materials
78.55.Hx Other solid inorganic materials

Azafullerene (C59N)2 thin-film field-effect transistors

Ryotaro Kumashiro, Katsumi Tanigaki, Hirotaka Ohashi, Nikos Tagmatarchis, Haruhito Kato, Hisanori Shinohara, Takeshi Akasaka, Kenichi Kato, Shinobu Aoyagi, Shigeru Kimura, and Masaki Takata

Appl. Phys. Lett. 84, 2154 (2004); http://dx.doi.org/10.1063/1.1667013 (3 pages) | Cited 7 times

Online Publication Date: 16 March 2004

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Thin-film field-effect transistors (FETs) of azafullerene (C59N)2 are fabricated, and their properties are investigated. The (C59N)2 FET exhibits n-channel characteristics with the field-effect electron mobility of 3.8×10−4 cm2 V−1 s−1 and the on–off current ratio of 103 at room temperature. The observed differences are ascribed to the much smaller grain size and the worse crystallinity of (C59N)2 thin films, on a basis of low angle x-ray diffraction structural data. The anticipated dimer to monomer conversion with electron carrier injection is not observed. The FET characteristics are discussed from the temperature evolution of the mobilities between (C59N)2 and C60 FETs. © 2004 American Institute of Physics.
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85.30.Tv Field effect devices

Synthesis and photoluminescence properties of ZnMnS nanobelts

B. Y. Geng, L. D. Zhang, G. Z. Wang, T. Xie, Y. G. Zhang, and G. W. Meng

Appl. Phys. Lett. 84, 2157 (2004); http://dx.doi.org/10.1063/1.1687985 (3 pages) | Cited 33 times

Online Publication Date: 16 March 2004

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Mn-doped ZnS nanobelts have been prepared through a thermal evaporation method starting with a mixture of acetylacetonates and H2S at 900 °C. The nanobelts had a uniform single-crystal hexagonal wurtzite structure and grew along [001] direction. Undoped ZnS nanobelts and ZnMnS nanobelts with 1%, 3%, and 5% Mn so obtained have been characterized by x-ray diffraction, energy dispersive x-ray analysis, and photoluminescence (PL) spectra. PL measurements showed that the fluorescence efficiencies increased and the glow peaks shifted to longer wavelengths as the Mn-doped ratios increased, and the doping was found responsible for the changes in the defect-related emission of the ZnS nanobelts. © 2004 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.46.-w Structure of nanoscale materials
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Optical measurement of rolling and spinning of half-coated nanoparticles

Jaehyuck Choi and Y.-H. Lo

Appl. Phys. Lett. 84, 2160 (2004); http://dx.doi.org/10.1063/1.1689399 (3 pages)

Online Publication Date: 16 March 2004

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A technique of detecting the rolling and spinning of half-coated nanoparticles using interference ring patterns of the fluorescence has been demonstrated. Using the unique ability to measure nanoparticle rotations in multiple degrees of freedom, we are able to determine the orientation of a moving nanoparticle in real time. Ultimately, the detailed knowledge of the rotational behavior of half-coated nanoparticles is expected to produce physical insight of nano biomechanical systems. © 2004 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
87.15.M- Spectra of biomolecules
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