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4 Aug 2003

Volume 83, Issue 5, pp. 817-1056

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 611 (2003); http://dx.doi.org/10.1063/1.1595724 (3 pages)

Chung-Chih Wu, Chieh-Wei Chen, and Ting-Yi Cho
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YBa2Cu3O7−δ step-edge Josephson junctions fabricated on sapphire substrates

Bin Ming and T. Venkatesan

Appl. Phys. Lett. 83, 963 (2003); http://dx.doi.org/10.1063/1.1596373 (3 pages)

Online Publication Date: 30 July 2003

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Sapphire is an ideal substrate for cryogenic device technologies. We report here the fabrication of YBa2Cu3O7−δ step-edge junctions on the R-plane (1math02) sapphire substrates. With an “overhang” shadow mask produced by a photolithography technique, a steep step edge was created on the CeO2 buffer layer by Ar+ ion milling with optimized parameters for minimum ion-beam divergence. The step angle was determined to be in excess of 80° by atomic force microscopy. Josephson junctions fabricated from those step edges exhibited resistively shunted junction like current–voltage characteristics. IcRn values in the 200–500 μV range were measured at 77 K. Shapiro steps were observed under microwave irradiation. The magnetic field dependence of the junction Ic indicates uniform current distribution. © 2003 American Institute of Physics.
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74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures
61.80.Jh Ion radiation effects

Magnetically induced phase separation and magnetic properties of Co–Mo hexagonal-close-packed structure thin films

K. Oikawa, G. W. Qin, M. Sato, O. Kitakami, Y. Shimada, J. Sato, K. Fukamichi, and K. Ishida

Appl. Phys. Lett. 83, 966 (2003); http://dx.doi.org/10.1063/1.1597746 (3 pages) | Cited 7 times

Online Publication Date: 30 July 2003

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Magnetically induced phase separation along the Curie temperature in the hexagonal-close-packed phase of a Co–Mo binary system has been predicted by thermodynamic calculations. Furthermore, the phase separation and magnetic properties of Co–Mo sputtered thin films have been investigated. Nanoscale compositional fluctuation caused by the magnetically induced phase separation has been confirmed in the films deposited on a heated substrate in the same manner as Co–Cr-based alloys. The magnetic anisotropy constant of the Co–Mo films is larger than that of Co–Cr films. From these results, it is concluded that the Co–Mo system is promising for use as a base alloy system for high density recording media. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
64.75.-g Phase equilibria
68.55.Nq Composition and phase identification
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Gw Magnetic anisotropy
75.50.Ss Magnetic recording materials
81.15.Cd Deposition by sputtering

Effects of magnetic field on two-dimensional superconducting quantum interference filters

J. Oppenländer, P. Caputo, Ch. Häussler, T. Träuble, J. Tomes, A. Friesch, and N. Schopohl

Appl. Phys. Lett. 83, 969 (2003); http://dx.doi.org/10.1063/1.1597753 (3 pages) | Cited 9 times

Online Publication Date: 30 July 2003

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We present an experimental study of two-dimensional (2D) superconducting quantum interference filters (SQIFs) in the presence of a magnetic field B. Although the nonlinear dynamics of the 2D SQIF are much more complex than those of previously studied one-dimensional SQIFs, we found for the 2D SQIF a similar dependence of the voltage V on the magnetic field applied, which is characterized by a unique delta-like dip at B = 0. The voltage span of the dip depends on the distribution of areas of the individual loops, and on the bias current, and it scales proportionally to the number of rows simultaneously operating at the same working point. In addition, the voltage response of individual rows of the 2D SQIF is sensitive to the field gradient generated by a control line superimposed on the homogeneous field of a coil. This feature suggests the use of these devices as highly sensitive absolute detectors of spatial gradients of the magnetic field. © 2003 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.30.Vn Filters

Propagating spin wave spectroscopy in a permalloy film: A quantitative analysis

Matthieu Bailleul, Dominik Olligs, and Claude Fermon

Appl. Phys. Lett. 83, 972 (2003); http://dx.doi.org/10.1063/1.1597745 (3 pages) | Cited 10 times

Online Publication Date: 30 July 2003

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We report on the microwave response of micrometer-wide antennas inductively coupled to a 30 nm thick permalloy film. We show that the self-inductance of a single antenna measures the coupling between the exciting current and the spin wave modes of the film. On the other hand, the signal transmitted to a second, distant antenna is used to observe the free relaxation law of a magnetostatic wave packet. All measurements, performed over a frequency range of 1–20 GHz, are quantitatively consistent with magnetostatic wave theory combined with Gilbert formulation of the damping. © 2003 American Institute of Physics.
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75.30.Ds Spin waves
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films

Epitaxial growth and magnetic properties of EuO on (001) Si by molecular-beam epitaxy

J. Lettieri, V. Vaithyanathan, S. K. Eah, J. Stephens, V. Sih, D. D. Awschalom, J. Levy, and D. G. Schlom

Appl. Phys. Lett. 83, 975 (2003); http://dx.doi.org/10.1063/1.1593832 (3 pages) | Cited 26 times

Online Publication Date: 30 July 2003

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Epitaxial (001) EuO thin films have been grown on (001) Si utilizing an intermediate, epitaxial SrO buffer layer by molecular-beam epitaxy. Four-circle x-ray diffraction reveals nearly phase-pure samples. Magnetic measurements indicate that the EuO layer is ferromagnetic, with a transition temperature (68 K) close to the bulk value and a saturation magnetic moment of 4.7 Bohr magnetons per Eu atom. The magneto-optic Kerr effect observed is also comparable to bulk EuO. Such heterostructures have potential as a means to inject spin-polarized electrons into silicon for use in spintronics applications. © 2003 American Institute of Physics.
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75.50.Pp Magnetic semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.25.Dc Spin polarized transport in semiconductors
72.25.Hg Electrical injection of spin polarized carriers
68.55.Nq Composition and phase identification
75.50.Dd Nonmetallic ferromagnetic materials
78.20.Ls Magneto-optical effects
81.05.Hd Other semiconductors
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Electric fatigue in Pb(Nb,Zr,Sn,Ti)O3 thin films grown by a sol–gel process

Jiwei Zhai and Haydn Chen

Appl. Phys. Lett. 83, 978 (2003); http://dx.doi.org/10.1063/1.1594843 (3 pages) | Cited 10 times

Online Publication Date: 30 July 2003

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Antiferroelectric Pb(Nb,Zr,Sn,Ti)O3 (PNZST) thin films were deposited via a sol–gel process on LaNiO3-buffered Pt/Ti/SiO2/Si substrates. The highly (100)-oriented LaNiO3 buffer layer facilitated the formation of high-quality PNZST films with a strong (100) preferred orientation. These films showed improved electric fatigue properties than those grown on Pt/Ti/SiO2/Si substrates. With increasing cycling field, the remanent polarization increases but the saturated polarization decreases. Fatigue properties of PNZST antiferroelectric thin films might be closely related to the nonuniform strain buildup due to switching that tends to stabilize the ferroelectric phase. © 2003 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.80.Fm Switching phenomena
68.55.-a Thin film structure and morphology
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Improvement in retention time of metal–ferroelectric–metal– insulator–semiconductor structures using MgO doped Ba0.7Sr0.3TiO3 insulator layer

T. Y. Tseng and S. Y. Lee

Appl. Phys. Lett. 83, 981 (2003); http://dx.doi.org/10.1063/1.1597412 (3 pages) | Cited 5 times

Online Publication Date: 30 July 2003

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We report the results of the fabrication and characterization of Pt/Bi3.35La0.85Ti3O12 (BLT)/LaNiO3 (LNO)/Ba0.7Sr0.3TiO3 (BST)/Si metal–ferroelectric–metal–insulator–semiconductor (MFMIS) structures for ferroelectric memory field effect transistor applications. The BLT films were deposited on LNO/BST/Si using the metalorganic decomposition method and annealed by rapid thermal annealing (RTA) process at 600 °C for 3 min. The ratio of remanent polarization to saturation polarization (Pr/Ps) increases with reducing area ratio, AF/AI. A large memory window of 3.1 V can be obtained for a small AF/AI ratio. By the utilization of 5 mol % MgO doped BST insulator layer, LNO bottom electrode layer for BLT, and small area ratio, AF/AI = 1/12 in the MFMIS structure, large Pr/Ps ratio in BLT film and low leakage current and good capacitance matching of the ferroelectric and the insulator in the MFMIS structures have been achieved and, hence, long data retention time >106 s has been obtained in this study. Experimental results demonstrate the significant progress in increase of the retention time of these structures, which make them attractive for practical ferroelectric memory field effect transistor applications. © 2003 American Institute of Physics.
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85.50.Gk Non-volatile ferroelectric memories
85.30.Tv Field effect devices
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
61.72.Cc Kinetics of defect formation and annealing
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Size-dependent radiative decay time of excitons in GaN/AlN self-assembled quantum dots

S. Kako, M. Miyamura, K. Tachibana, K. Hoshino, and Y. Arakawa

Appl. Phys. Lett. 83, 984 (2003); http://dx.doi.org/10.1063/1.1596382 (3 pages) | Cited 24 times

Online Publication Date: 30 July 2003

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Size-dependent radiative decay time of excitons in GaN/AlN self-assembled quantum dots is reported. Two samples having different average size of quantum dots (QDs) have been investigated at the temperature of 3.5 K. The measurement has revealed that larger-QD sample shows longer photoluminescence (PL) decay time and smaller emission energy than smaller one. The dependence of radiative decay time of the samples on emission energy smoothly connects with each other reflecting the size distribution. The radiative decay time strongly increases by almost three orders magnitude, reaching microseconds, upon increasing the size of QDs. The increase of PL decay time with increasing the size of QDs is attributed to the reduction of oscillator-strength due to the strong built-in electric field in the GaN/AlN heterostructures. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
71.35.-y Excitons and related phenomena

InGaAs/GaAs three-dimensionally-ordered array of quantum dots

Yu. I. Mazur, W. Q. Ma, X. Wang, Z. M. Wang, G. J. Salamo, M. Xiao, T. D. Mishima, and M. B. Johnson

Appl. Phys. Lett. 83, 987 (2003); http://dx.doi.org/10.1063/1.1596712 (3 pages) | Cited 48 times

Online Publication Date: 30 July 2003

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We report on the first fabrication of (In,Ga)As/GaAs quantum dots with both vertical and lateral ordering forming a three-dimensional array. An investigation of the photoluminescence spectra from the ordered array of quantum dots, as a function of both temperature and optical excitation intensity, reveals both a lateral and vertical transfer of excitation. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
78.55.Cr III-V semiconductors

Fabrication and mechanical characterization of ultrashort nanocantilevers

S. G. Nilsson, E.-L. Sarwe, and L. Montelius

Appl. Phys. Lett. 83, 990 (2003); http://dx.doi.org/10.1063/1.1592303 (3 pages) | Cited 10 times

Online Publication Date: 30 July 2003

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Three aspects on nanocantilevers are presented in this letter. First, we present the fabrication process of 2 μm long freestanding chromium cantilevers with width 150 nm, and thickness 50 nm. Second, a measurement scheme using an atomic force microscope operating in contact mode was employed to study the mechanical properties along the length of the cantilevers. Third, we have investigated extremely large deflections on these nanoscale cantilevers demonstrating their high ductility. The spring constants calculated from the experimental data are smaller than expected from classical mechanics calculations, but show good agreement with previously reported calculations for largely deflected beams. © 2003 American Institute of Physics.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.07.-b Nanoscale materials and structures: fabrication and characterization
62.25.-g Mechanical properties of nanoscale systems
68.37.Ps Atomic force microscopy (AFM)
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep

Nanoscale mechanical behavior of individual semiconducting nanobelts

Scott X. Mao, Minhua Zhao, and Zhong Lin Wang

Appl. Phys. Lett. 83, 993 (2003); http://dx.doi.org/10.1063/1.1597754 (3 pages) | Cited 43 times

Online Publication Date: 30 July 2003

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Nanobelts are a group of materials that have a rectangle-like cross section with typical widths of several hundred nanometers, width-to-thickness ratios of 5–10, and lengths of hundreds of micrometers. In this letter, nanoindentations were made in individual ZnO and SnO2 nanobelts by a cube corner diamond indenter. It is shown that the effect of indentation size is still obvious for indentation depths less than 50 nm. It is also demonstrated that nanomachining of nanobelts is possible using an atomic force microscope tip. © 2003 American Institute of Physics.
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62.25.-g Mechanical properties of nanoscale systems
68.35.Gy Mechanical properties; surface strains
61.46.-w Structure of nanoscale materials

Polarization-dependent reflectivity from dielectric nanowires

Y. Du, Song Han, Wu Jin, C. Zhou, and A. F. J. Levi

Appl. Phys. Lett. 83, 996 (2003); http://dx.doi.org/10.1063/1.1598283 (3 pages) | Cited 8 times

Online Publication Date: 30 July 2003

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The presence of GaN nanowires grown primarily normal to the surface of a sapphire substrate has a dramatic influence on the polarization dependence of laser light reflectivity at λ = 1550-nm wavelength. Even at 12% substrate surface coverage, there is a factor of 2 enhancement in polarization dependence of reflectivity relative to bulk sapphire at values of incident angle greater than ϕ = 72°. © 2003 American Institute of Physics.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
61.46.-w Structure of nanoscale materials
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Ga-filled single-crystalline MgO nanotube: Wide-temperature range nanothermometer

Y. B. Li, Y. Bando, D. Golberg, and Z. W. Liu

Appl. Phys. Lett. 83, 999 (2003); http://dx.doi.org/10.1063/1.1597422 (3 pages) | Cited 39 times

Online Publication Date: 30 July 2003

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A highly effective one-step approach was developed to synthesize single-crystalline MgO nanotubes and in situ fill nanotubes with Ga. The axes of nanotubes are in the [100] direction of cubic MgO. The prepared nanotube exhibits a square-like cross section both for its interior and exterior. The liquid metal-assisted route is suggested to be a general way to prepare oxide nanotubes. Linear thermal expansion behavior recorded for liquid gallium column confined in the MgO nanotube makes possible creation of a wide-temperature range nanothermometer with superior mechanical properties and environmental structural stability. © 2003 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
07.20.Dt Thermometers
85.35.Kt Nanotube devices
81.07.De Nanotubes
65.40.De Thermal expansion; thermomechanical effects
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems

Nanoscale radio-frequency thermometry

D. R. Schmidt, C. S. Yung, and A. N. Cleland

Appl. Phys. Lett. 83, 1002 (2003); http://dx.doi.org/10.1063/1.1597983 (3 pages) | Cited 21 times

Online Publication Date: 30 July 2003

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We experimentally demonstrate the high bandwidth readout of a thermometer based on a superconductor–insulator–normal metal (SIN) tunnel junction, embedded in a rf resonant circuit. Our implementation enables basic studies of the thermodynamics of mesoscopic nanostructures. It can also be applied to the development of fast calorimeters, as well as ultrasensitive bolometers for the detection of far-infrared radiation. We discuss the operational details of this device, and estimate the ultimate temperature sensitivity and measurement bandwidth. © 2003 American Institute of Physics.
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07.20.Dt Thermometers
07.20.Fw Calorimeters
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.35.-p Nanoelectronic devices
85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors

High resolution-high energy x-ray photoelectron spectroscopy using third-generation synchrotron radiation source, and its application to Si-high k insulator systems

K. Kobayashi, M. Yabashi, Y. Takata, T. Tokushima, S. Shin, K. Tamasaku, D. Miwa, T. Ishikawa, H. Nohira, T. Hattori, Y. Sugita, O. Nakatsuka, A. Sakai, and S. Zaima

Appl. Phys. Lett. 83, 1005 (2003); http://dx.doi.org/10.1063/1.1595714 (3 pages) | Cited 138 times

Online Publication Date: 30 July 2003

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High-resolution x-ray photoelectron spectroscopy (XPS) at 6 keV photon energy has been realized utilizing high-flux-density x rays from the third generation high-energy synchrotron radiation facility, SPring-8. The method has been applied to analysis of high-k HfO2/interlayer/Si complementary metal–oxide–semiconductor gate-dielectric structures. With the high energy resolution and high throughput of our system, chemical-state differences were observed in the Si 1s, Hf 3d, and O 1s peaks for as-deposited and annealed samples. The results revealed that a SiOxNy interlayer is more effective in controlling the interface structure than SiO2. Our results show the wide applicability of high resolution XPS with hard x rays from a synchrotron source. © 2003 American Institute of Physics.
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79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Cc Kinetics of defect formation and annealing
68.35.Ct Interface structure and roughness

Temperature-mediated switching of magnetoresistance in Co-contacted multiwall carbon nanotubes

S. Chakraborty, K. M. Walsh, B. W. Alphenaar, Lei Liu, and K. Tsukagoshi

Appl. Phys. Lett. 83, 1008 (2003); http://dx.doi.org/10.1063/1.1597965 (3 pages) | Cited 11 times

Online Publication Date: 30 July 2003

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We present temperature-dependent measurements of the magnetoresistance in ferromagnetically contacted multiwall nanotubes. At low temperature, the resistance increases sharply near zero-field due to misalignment of the contact magnetizations. As temperature increases, the resistance peak transforms into a resistance dip, with a peak-to-valley ratio of similar magnitude, but opposite sign. The resistance switch has a distinct temperature dependence compared with the background magnetoresistance, suggesting that the two have different origins. We propose that a ferromagnetic transition near the contact interfaces reverses the polarity of the injected spin, and changes the sign of the resistance switch. © 2003 American Institute of Physics.
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73.63.Fg Nanotubes
72.25.Mk Spin transport through interfaces
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Direct observation of confined states in metallic single-walled carbon nanotubes

Theophilos Maltezopoulos, André Kubetzka, Markus Morgenstern, Roland Wiesendanger, Serge G. Lemay, and Cees Dekker

Appl. Phys. Lett. 83, 1011 (2003); http://dx.doi.org/10.1063/1.1598282 (3 pages) | Cited 19 times

Online Publication Date: 30 July 2003

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We investigated the local density of states (LDOS) of extended individual metallic single-walled carbon nanotubes using low-temperature scanning tunneling spectroscopy. We observed that the LDOS oscillates with energy close to the Fermi level. The oscillation period of about 50 meV varies with position on the nanotube. Maps of the LDOS reveal that the peaks in the oscillation are related to confined states. The widths of the peaks increase with increasing distance from the Fermi level. © 2003 American Institute of Physics.
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73.22.Dj Single particle states

Size-dependent charge storage in amorphous silicon quantum dots embedded in silicon nitride

Nae-Man Park, Sang-Hun Jeon, Hyun-Deok Yang, Hyunsang Hwang, Seong-Ju Park, and Suk-Ho Choi

Appl. Phys. Lett. 83, 1014 (2003); http://dx.doi.org/10.1063/1.1596371 (3 pages) | Cited 23 times

Online Publication Date: 30 July 2003

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Size-dependent charge storage was observed in metal–insulator–semiconductor structures containing amorphous Si quantum dots (a-Si QDs) grown by plasma-enhanced chemical vapor deposition. For a-Si QDs as large as 2 nm in diameter, one electron or one hole was stored in each a-Si QD. For small-sized a-Si QDs of 1.4 nm in diameter, however, the width of capacitance–voltage hysteresis was decreased, indicating that the charge density in the a-Si QDs was reduced. This can be attributed to the lowered tunneling barrier in the small-sized a-Si QDs resulting from a large quantum confinement effect. Long-term charge storage was observed in the fully charged a-Si QDs; this is attributed to a suppression of the discharge process by electrostatic repulsion among the charged dots. © 2003 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.65.Hb Quantum dots (patterned in quantum wells)

Quantum-well microtube constructed from a freestanding thin quantum-well layer

M. Hosoda, Y. Kishimoto, M. Sato, S. Nashima, K. Kubota, S. Saravanan, P. O. Vaccaro, T. Aida, and N. Ohtani

Appl. Phys. Lett. 83, 1017 (2003); http://dx.doi.org/10.1063/1.1599621 (3 pages) | Cited 16 times

Online Publication Date: 30 July 2003

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We fabricated and experimentally investigated a nanostructure known as a quantum-well (QW) microtube, which is a fine tube with a micron- or nanometer-order diameter fabricated by rolling a semiconductor GaAs QW. Although the wall thickness is only 40 nm, the system retains the quantum properties of a QW, and photoluminescence from the QW subband can be clearly observed. Even though the QW width is sufficiently small to make the QW subband type-II band-aligned, a type-II to type-I transition caused by uniaxial strain in the microtube allows for optical emission. © 2003 American Institute of Physics.
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81.07.St Quantum wells
68.65.Fg Quantum wells
78.67.De Quantum wells
78.55.Cr III-V semiconductors
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A monolayer organic light-emitting diode using an organic dye salt

Hongguang Xu, Ruiping Meng, Chunxiang Xu, Junxiang Zhang, Guohua He, and Yiping Cui

Appl. Phys. Lett. 83, 1020 (2003); http://dx.doi.org/10.1063/1.1591068 (3 pages) | Cited 8 times

Online Publication Date: 30 July 2003

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Monolayer organic light-emitting diodes (OLEDs) are fabricated with an organic dye salt as an emitting layer. The emission intensity is one order of magnitude stronger and the luminescent efficiency is four times higher than those of the corresponding monolayer tris(8-hydroxyquinolino) aluminum devices. The optical and electrical characteristics demonstrate the organic salt efficiently balances the charge injection from electrodes, which may be interpreted by considering the polarity of the organic ionic salt. These results suggest a class of novel materials for OLEDs. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices

Generation of coherent gigahertz acoustic phonons in AlGaN/GaN microwave field-effect transistors

Jung-Hoon Song, Qiang Zhang, W. Patterson, A. V. Nurmikko, M. J. Uren, K. P. Hilton, R. S. Balmer, and T. Martin

Appl. Phys. Lett. 83, 1023 (2003); http://dx.doi.org/10.1063/1.1597982 (3 pages) | Cited 3 times

Online Publication Date: 30 July 2003

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We apply an optical probing technique on AlGaN/GaN field-effect transistors to demonstrate that coherent gigahertz phonons are generated copiously under large signal operation. The phonon generation originates from time varying electron screening of the piezoelectric polarization fields in the active region, and may provide a nondiffusive means of energy dissipation for high power devices. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
63.20.-e Phonons in crystal lattices

Improving images from a near-field scanning microwave microscope using a hybrid probe

Jooyoung Kim, Myungsick Kim, Hyun Kim, Doohee Song, Kiejin Lee, and Barry Friedman

Appl. Phys. Lett. 83, 1026 (2003); http://dx.doi.org/10.1063/1.1595134 (3 pages) | Cited 12 times

Online Publication Date: 30 July 2003

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We fabricated a near-field scanning microwave microscope (NSMM) using a hybrid tip combining a reduced length of the tapered part with a small apex. In order to understand the function of the probe, we fabricated three different tips using a conventional chemical etching technique and observed three different NSMM images for patterned Cr films on glass substrates. These probe tips were coupled to a high-quality dielectric resonator at an operating frequency f = 4.46 GHz. By using the hybrid tip, we demonstrated an improved, high-contrast NSMM image of lambda phage DNA on a glass substrate. © 2003 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
68.37.-d Microscopy of surfaces, interfaces, and thin films
87.64.Dz Scanning tunneling and atomic force microscopy
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
81.65.Cf Surface cleaning, etching, patterning
68.55.-a Thin film structure and morphology
87.14.G- Nucleic acids
87.15.B- Structure of biomolecules
87.80.-y Biophysical techniques (research methods)

Fabrication and photoresponse of a pn-heterojunction diode composed of transparent oxide semiconductors, p-NiO and n-ZnO

Hiromichi Ohta, Masahiro Hirano, Ken Nakahara, Hideaki Maruta, Tetsuhiro Tanabe, Masao Kamiya, Toshio Kamiya, and Hideo Hosono

Appl. Phys. Lett. 83, 1029 (2003); http://dx.doi.org/10.1063/1.1598624 (3 pages) | Cited 81 times

Online Publication Date: 30 July 2003

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Transparent trilayered oxide films of ZnO/NiO/indium tin oxide were heteroepitaxially grown on a YSZ (111) substrate by pulsed-laser deposition combined with a solid-phase-epitaxy technique, and were processed to fabricate a p-NiO/n-ZnO diode. The diode exhibited a clear rectifying I–V characteristic with an ideality factor of ∼2 and a forward threshold voltage of ∼1 V. Although the photoresponsivity was fairly weak at the zero-bias voltage, it was enhanced up to ∼0.3 A W−1 through the application of a reverse bias of −6 V under the irradiation of 360 nm light, a value comparable to that of commercial devices. © 2003 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Kk Junction diodes
81.15.Fg Pulsed laser ablation deposition
81.15.Np Solid phase epitaxy; growth from solid phases
85.30.De Semiconductor-device characterization, design, and modeling
85.60.Dw Photodiodes; phototransistors; photoresistors

Near-field scanning microwave microscope using a dielectric resonator

Jooyoung Kim, Kiejin Lee, Barry Friedman, and Deokjoon Cha

Appl. Phys. Lett. 83, 1032 (2003); http://dx.doi.org/10.1063/1.1597984 (3 pages) | Cited 13 times

Online Publication Date: 30 July 2003

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We describe a near-field scanning microwave microscope which uses a high-quality dielectric resonator with a tunable screw. The operating frequency is f = 4.5 GHz. The probe tip is mounted in a cylindrical resonant cavity coupled to a dielectric resonator for the TE011 mode. We tuned the resonance cavity to match the impedance of 50 Ω by using a tunable screw and could improve sensitivity and spatial resolution to better than 1 μm. To demonstrate the ability of local microwave characterization, the surface resistance dependence of the metallic thin films on film thickness has been mapped. © 2003 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
68.37.Uv Near-field scanning microscopy and spectroscopy

High current gain (>2000) of GaN/InGaN double heterojunction bipolar transistors using base regrowth of p-InGaN

Toshiki Makimoto, Kazuhide Kumakura, and Naoki Kobayashi

Appl. Phys. Lett. 83, 1035 (2003); http://dx.doi.org/10.1063/1.1597989 (3 pages) | Cited 21 times

Online Publication Date: 30 July 2003

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GaN/InGaN double heterojunction bipolar transistors with a regrown p-InGaN extrinsic base have been fabricated on SiC substrates. The maximum common-emitter current gain exceeds 2000 at the collector current of 15 mA for a 50 μm×30 μm device. In addition, the offset voltage in the common-emitter current–voltage characteristics was reduced from 5 to 1 V. This indicates that the large offset voltage reported previously was mainly due to the degraded base ohmic characteristics. The regrowth of p-InGaN is effective for improving the characteristics of nitride heterojunction bipolar transistors. © 2003 American Institute of Physics.
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85.30.Pq Bipolar transistors
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