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2 Aug 1999

Volume 75, Issue 5, pp. 597-739

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Multiple gated InAs dot ensembles

D. G. Austing, S. Tarucha, P. C. Main, M. Henini, S. T. Stoddart, and L. Eaves

Appl. Phys. Lett. 75, 671 (1999); http://dx.doi.org/10.1063/1.124477 (3 pages) | Cited 18 times

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We adapt a multiple gating technology to characterize electrically an ensemble of “self-assembled” InAs dots embedded in a plane within an Al0.20Ga0.80As tunneling barrier. Although the μm-sized mesa incorporates several hundred dots, we find that only a few of them contribute to the current close to threshold. Gating allows us to probe the origin of the sharp current peaks, and we can classify these peaks into families in a simple way according to their gate voltage dependence. © 1999 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
73.40.Gk Tunneling

Analysis of the polar direction of GaN film growth by coaxial impact collision ion scattering spectroscopy

M. Sumiya, M. Tanaka, K. Ohtsuka, S. Fuke, T. Ohnishi, I. Ohkubo, M. Yoshimoto, H. Koinuma, and M. Kawasaki

Appl. Phys. Lett. 75, 674 (1999); http://dx.doi.org/10.1063/1.124478 (3 pages) | Cited 52 times

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Nondestructive determination of the polarity of GaN has been achieved by the use of coaxial impact-collision ion scattering spectroscopy analysis. The polarity of a GaN film with a smooth surface on non-nitrided c-plane sapphire was identified (0001) (Ga face; +c). GaN films with a 20 nm buffer layer on nitrided sapphire had (000math) (N face; −c) polarity and a hexagonal faceted surface. The influence of both the buffer layer and of substrate nitridation on the polarity of wurtzite {0001} GaN films deposited by two-step metal organic chemical vapor deposition (MOCVD) has been investigated. The polarity of the buffer layer on a nitrided sapphire substrate was altered by varying its thickness or the annealing time. It was found that the polarity of the GaN film is determined by the polarity of the annealed buffer layer; MOCVD-GaN films on buffer layers with +c and −c polarity have either +c (smooth surface) or −c (hexagonal facet) polarity, respectively. © 1999 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.40.Gh Other heat and thermomechanical treatments

Hydrogen cleaning and smoothing of semiconductor surfaces: The case of II–VI compounds

E. Picard, P. Gentile, D. Martrou, and N. Magnea

Appl. Phys. Lett. 75, 677 (1999); http://dx.doi.org/10.1063/1.124479 (3 pages) | Cited 2 times

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Hydrogen radicals produced by a dc plasma cell have been used for cleaning II–VI semiconductor substrates for molecular beam epitaxy. Surface and chemical analysis experiments, including scanning tunneling microscopy, show a clear improvement of the chemical purity and morphology of the surface prior and after epitaxial growth. © 1999 American Institute of Physics.
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81.05.Dz II-VI semiconductors
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
68.35.Dv Composition, segregation; defects and impurities
82.80.-d Chemical analysis and related physical methods of analysis
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Incorporation of N into Si/SiO2 interfaces: Molecular orbital calculations to evaluate interface strain and heat of reaction

Jiro Ushio, Takuya Maruizumi, and Masanobu Miyao

Appl. Phys. Lett. 75, 680 (1999); http://dx.doi.org/10.1063/1.124480 (3 pages) | Cited 5 times

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The determining factor for the accumulation of N at a Si/SiO2 interface during oxynitridation of the interface was investigated using a quantum-chemical method. Both mechanical and chemical factors (the interface strains and the heats of reaction of the oxynitridation) were considered. Though a slight relaxation of interface strain occurs when the interface has a certain type of oxygen-vacancy defect, we found the N incorporation does not relax the interface strain in most cases. The exothermicity and endothermicity of the oxynitridation reaction in the Si and SiO2 films, respectively, are the primary cause of the accumulation of N at the interface. © 1999 American Institute of Physics.  
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81.65.Mq Oxidation
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
68.35.Ct Interface structure and roughness
82.60.Cx Enthalpies of combustion, reaction, and formation
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
61.72.J- Point defects and defect clusters
68.35.Gy Mechanical properties; surface strains

A phosphorous-rich structure of InP (001) produced by metalorganic vapor-phase epitaxy

L. Li, B.-K. Han, D. Law, C. H. Li, Q. Fu, and R. F. Hicks

Appl. Phys. Lett. 75, 683 (1999); http://dx.doi.org/10.1063/1.124481 (3 pages) | Cited 17 times

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A phosphorous-rich structure is generated on the InP (001) surface during metalorganic vapor-phase epitaxy. It consists of phosphorous dimers, alkyl groups, and hydrogen atoms adsorbed onto a layer of phosphorous atoms. The adsorbed dimers produce c(2×2) and p(2×2) domains, with total phosphorous coverages of 2.0 and 1.5 ML. The alkyl groups and hydrogen atoms adsorb onto half of the exposed phosphorous atoms in the first layer. These atoms dimerize producing a (2×1) structure. It is proposed that the first layer of phosphorous atoms is the active site for the deposition reaction, and that the organometallic precursors compete with phosphorous dimers, alkyl radicals, and hydrogen for these sites during growth. © 1999 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Nucleation layer microstructure, grain size, and electrical properties in GaN grown on a-plane sapphire

M. E. Twigg, R. L. Henry, A. E. Wickenden, D. D. Koleske, and J. C. Culbertson

Appl. Phys. Lett. 75, 686 (1999); http://dx.doi.org/10.1063/1.124482 (3 pages) | Cited 11 times

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We have investigated the microstructural origins of center-to-edge differences in the electrical properties of GaN films grown on a-plane sapphire via metal–organic vapor-phase epitaxy. Using cross-sectional transmission electron microscopy, we have observed that the grain size at the wafer edge is approximately 1 μm, whereas the grain size in the wafer center ranges from 0.1 to 0.5 μm. The smaller grain size at the wafer center is traced to a higher density of extended defects in the AlN nucleation layer: defects which, in turn, act as nucleation sites for GaN grain growth. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
61.72.Nn Stacking faults and other planar or extended defects
73.61.Ey III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Evaluation of strain and In content in (InGaN/GaN) multiquantum wells by x-ray analysis

A. Krost, J. Bläsing, M. Lünenbürger, H. Protzmann, and M. Heuken

Appl. Phys. Lett. 75, 689 (1999); http://dx.doi.org/10.1063/1.124483 (3 pages) | Cited 9 times

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A comprehensive x-ray analysis including Θ–2Θ scans, reciprocal space mapping, and x-ray reflectivity of 10×(InGaN/GaN) multiple quantum wells (MQWs) is presented. The layers were grown by low-pressure metal–organic chemical-vapor deposition. The strain state and the In concentration in (InGaN/GaN) MQW systems are evaluated with the help of reciprocal space maps around the symmetric (0002) and asymmetric (10math5) Bragg reflections. Depending on the In incorporation, the MQW system is fully strained, partially relaxed, or exhibits phase decomposition effects. The room-temperature photoluminescence emission energy of a fully strained 10×(In0.125Ga0.875N/GaN) MQW sample is 2.792 eV, which is 133 meV less than the calculated energy gap of 2.925 eV. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
61.05.cm X-ray reflectometry (surfaces, interfaces, films)

Spatially distributed p-n heterojunction based on nanoporous TiO2 and CuSCN

C. Rost, I. Sieber, S. Siebentritt, M. C. Lux-Steiner, and R. Könenkamp

Appl. Phys. Lett. 75, 692 (1999); http://dx.doi.org/10.1063/1.124484 (3 pages) | Cited 15 times

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Directed semiconductor growth in nanoporous ceramic films is reported. A p-n heterojunction with an interface that is spatially distributed across the complete thickness of the ceramic film is established. The interface area is estimated to be several 100 times larger than its geometric projection. The p-n junction shows excellent rectification and may serve as the basic building block for photovoltaic devices. © 1999 American Institute of Physics.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.40.Xx Hybrid microelectronics; thick films
81.05.Rm Porous materials; granular materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
73.40.Ei Rectification
73.50.Pz Photoconduction and photovoltaic effects
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Spin-interference device

Junsaku Nitta, Frank E. Meijer, and Hideaki Takayanagi

Appl. Phys. Lett. 75, 695 (1999); http://dx.doi.org/10.1063/1.124485 (3 pages) | Cited 27 times

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We propose a spin-interference device which works even without any ferromagnetic electrodes and any external magnetic field. The interference can be expected in the Aharonov–Bohm (AB) ring with a uniform spin-orbit interaction, which causes the phase difference between the spin wave functions traveling in the clockwise and anticlockwise direction. The gate electrode, which covers the whole area of the AB ring, can control the spin-orbit interaction, and therefore, the interference. A large conductance modulation effect can be expected due to the spin interference. © 1999 American Institute of Physics.
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85.35.Ds Quantum interference devices
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.23.-b Electronic transport in mesoscopic systems
85.30.De Semiconductor-device characterization, design, and modeling

Radio-frequency amplifier with tenth-kelvin noise temperature based on a microstrip direct current superconducting quantum interference device

Marc-Olivier André, Michael Mück, John Clarke, Jost Gail, and Christoph Heiden

Appl. Phys. Lett. 75, 698 (1999); http://dx.doi.org/10.1063/1.124486 (3 pages) | Cited 22 times

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A dc superconducting quantum interference device (SQUID) with a resonant microstrip input and a cooled heterostructure field-effect transistor as a postamplifier is used as a radio-frequency amplifier in the frequency range 90–500 MHz. At liquid 3He temperatures, gains of 24 and 20 dB and intrinsic noise temperatures of 0.06±0.02 and 0.12±0.10 K were achieved at 89.6 and 438 MHz, respectively. The system noise temperature at 438 MHz was also estimated from the Nyquist noise produced by a resonant circuit coupled to the input of the microstrip SQUID. © 1999 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.40.Az Waveguides, transmission lines, striplines
84.30.Le Amplifiers
84.40.Dc Microwave circuits
85.30.Tv Field effect devices

Interface and tunneling barrier heights of NbN/AlN/NbN tunnel junctions

Zhen Wang, Hirotaka Terai, Akira Kawakami, and Yoshinori Uzawa

Appl. Phys. Lett. 75, 701 (1999); http://dx.doi.org/10.1063/1.124487 (3 pages) | Cited 37 times

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The tunneling barrier height of NbN/AlN/NbN tunnel junctions was measured by investigating the barrier thickness dependence of the current density, and the junction interface was studied by cross-sectional transmission electron microscopy (TEM). We found that the current density of the junctions has two distinct types of dependency on the AlN barrier thickness, corresponding to two average barrier heights in different regions for the current density. The TEM observations showed that the junctions had a very smooth and clear electrode–barrier interface, and the crystal structures of the counterelectrode NbN films were strongly dependent on the thickness of AlN barriers. The average barrier height was estimated to be 2.35 eV in the low-Jc region, Jc<5 kA/cm2, and to be 0.88 eV in the high-Jc region, Jc>5 kA/cm2. © 1999 American Institute of Physics.
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74.50.+r Tunneling phenomena; Josephson effects
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)

Nonlinear electron transport in magnetic multilayers

F. G. Aliev, R. Schad, P. Lobotka, I. Vavra, E. Seynaeve, V. V. Moshchalkov, and Y. Bruynseraede

Appl. Phys. Lett. 75, 704 (1999); http://dx.doi.org/10.1063/1.124488 (3 pages) | Cited 1 time

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We report on measurements of the second harmonics in the magnetovoltage generated in [Fe(12 Å)/Cr(12 Å)]10 epitaxial multilayers. It is shown that the variation of the amplitude of the second-harmonic signal with magnetic field is up to three times larger compared to the first harmonic. The enhanced “magnetovoltage” second-harmonic effect may be of practical use in systems based on spin electronic phenomena. © 1999 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.61.At Metal and metallic alloys
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Enhanced coercivity of exchange-bias Fe/MnPd bilayers

Y. J. Tang, B. Roos, T. Mewes, S. O. Demokritov, B. Hillebrands, and Y. J. Wang

Appl. Phys. Lett. 75, 707 (1999); http://dx.doi.org/10.1063/1.124489 (3 pages) | Cited 32 times

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We present detailed studies of the enhanced coercivity of exchange-bias bilayer Fe/MnPd, both experimentally and theoretically. We have demonstrated that the existence of large higher-order anisotropies due to exchange coupling between different Fe and MnPd layers can account for the large increase of coercivity in the Fe/MnPd system. The linear dependence of coercivity on inverse Fe thickness is well explained by a phenomenological model by introducing higher-order anisotropy terms into the total free energy of the system. © 1999 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
65.20.-w Thermal properties of liquids
65.40.gd Entropy
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy

Blocking temperature, energy barrier, and reversal field variation of fine magnetic particles

Huei Li Huang and Jing Ju Lu

Appl. Phys. Lett. 75, 710 (1999); http://dx.doi.org/10.1063/1.124490 (3 pages) | Cited 9 times

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Blocking temperature, energy barrier, and reversal field variation of interacting fine magnetic particles display similar characteristics as a function of the bonding angle and interparticle distance in the context of the dipole interaction. The energy barrier and reversal field exhibit local maxima at the bonding angles β = 0° and π/2 and a global minimum at β ≃ 60°. Thus, the sample average of these quantities is found to reduce with decreasing interparticle distance, in agreement with the latest experimental data. For a system with easy-axis misorientation, magnetization reversal will traverse along the direction in which the misorientation angle and bonding angle have the same sign. © 1999 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Influence of strain on the magnetic properties of epitaxial (100) chromium dioxide (CrO2) films

X. W. Li, A. Gupta, and Giang Xiao

Appl. Phys. Lett. 75, 713 (1999); http://dx.doi.org/10.1063/1.124491 (3 pages) | Cited 63 times

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Chromium dioxide (CrO2) films have been grown epitaxially on (100) TiO2 substrates using chemical vapor deposition and their magnetic properties were studied as a function of film thickness (500 Å–1.2 μm). Because of the lattice mismatch with the substrate, the films are strained as evidenced by x-ray diffraction measurements. The amount of strain depends on the thickness and also on the substrate cleaning conditions used prior to growth. Independent of their thickness, the films exhibit a sharp ferromagnetic transition with a Curie temperature in the range of 390–395 K. In-plane magnetic anisotropy is observed for the films, with [001] and [010] being the easy axis and hard axis directions, respectively, for the thicker films. The anisotropy field decreases with decreasing thickness, with the easy and hard axes switching directions for the thinnest films. The results are explained in terms of the competition between magnetocrystalline and strain anisotropies that favor the [001] and [010] magnetization directions, respectively. © 1999 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Gw Magnetic anisotropy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
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Can lead nonstoichiometry influence ferroelectric properties of Pb(Zr,Ti)O3 thin films?

S. Aggarwal, S. Madhukar, B. Nagaraj, I. G. Jenkins, R. Ramesh, L. Boyer, and J. T. Evans

Appl. Phys. Lett. 75, 716 (1999); http://dx.doi.org/10.1063/1.124492 (3 pages) | Cited 25 times

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In this letter, we report on the influence of lead content on thin-film ferroelectric properties of lead niobium zirconate titanate. These films were prepared by the sol-gel technique and deposited on (La,Sr)CoO3 electrodes. It was determined that 7% excess lead in the sol was required to obtain nominally stoichiometric films. Lead deficiency in the film results in lead vacancies and excess lead is accommodated by forming octahedral site vacancies. Further amounts of lead in the sol leads to second phase PbO, which then coexists with the perovskite phase. The charged vacancies are compensated by mobile holes, which can interact with domains during switching. Under applied field and short pulse widths, the films with larger number of holes exhibited poor switching. Significant polarization relaxation was measured for films with excess lead, which is attributed to interaction of ionic defects with domains. Our results indicate that lead excess leads to poor reliability properties,whereas lead deficiency suppresses the polarization of the capacitors. © 1999 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
61.66.Bi Elemental solids
61.66.Dk Alloys
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis
61.72.J- Point defects and defect clusters
77.22.Ej Polarization and depolarization

Ferroelectricity of YMnO3 thin films prepared via solution

Hiroya Kitahata, Kiyoharu Tadanaga, Tsutomu Minami, Norifumi Fujimura, and Taichiro Ito

Appl. Phys. Lett. 75, 719 (1999); http://dx.doi.org/10.1063/1.124493 (3 pages) | Cited 33 times

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We have observed the ferroelectricity at room temperature in YMnO3 thin films prepared via solution. Precursor films of YMnO3 on Pt/sapphire or Y2O3/Si substrates were heat treated in vacuum or in air for controlling the crystallinity. X-ray diffraction measurements indicated that each film was a single phase of hexagonal YMnO3. While the film heat treated in air indicated an insufficient crystallinity, the film heat treated in vacuum showed a high crystallinity with a c-axis preferred orientation. The leakage current of the film heat treated in vacuum was at least three orders of magnitude lower than that heat treated in air. The ferroelectricity of the film heat treated in vacuum was confirmed in the capacitance–voltage measurement at room temperature due to its high crystallinity with the c-axis preferred orientation and the small leakage current. © 1999 American Institute of Physics.
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77.80.-e Ferroelectricity and antiferroelectricity
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Metal/ferroelectric/insulator/semiconductor structure of Pt/SrBi2Ta2O9/YMnO3/Si using YMnO3 as the buffer layer

Kyu-Jeong Choi, Woong-Chul Shin, Jung-Hwan Yang, and Soon-Gil Yoon

Appl. Phys. Lett. 75, 722 (1999); http://dx.doi.org/10.1063/1.124255 (3 pages) | Cited 25 times

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The ferroelectric SrBi2Ta2O9 (SBT) and YMnO3 buffer layers for the metal/ferroelectric/ insulator/semiconductor (MFIS) structure were deposited using pulsed-laser ablation and metalorganic chemical vapor deposition, respectively. Memory windows of the MFIS structure were in the range of 0.3–1.5 V when the gate voltage varied from 2 to 6 V. There were no reactions between ferroelectric SBT and Si in the MFIS structure annealed at 900 °C. The YMnO3 buffer layer plays an important role in alleviating the interdiffusion between elements of SBT and Si. The proposed MFIS structure of Pt/200 nm–SBT/25 nm–YMnO3/Si is attractive for nondestructive read-out ferroelectric random access memory applications. © 1999 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Fg Pulsed laser ablation deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Cc Kinetics of defect formation and annealing
85.30.Tv Field effect devices

Low-temperature anodic oxidation of silicon using a wave resonance plasma source

S. Uchikoga, D. F. Lai, J. Robertson, W. I. Milne, N. Hatzopoulos, R. A. Yankov, and M. Weiler

Appl. Phys. Lett. 75, 725 (1999); http://dx.doi.org/10.1063/1.124494 (3 pages) | Cited 3 times

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A rf wave resonance plasma (WARP) source has been used to plasma oxidize Si at temperatures below 100 °C. Oxidation under positive substrate bias in constant current mode gives an oxidation rate of 1–8 nm/min for current densities of 0.4–5.5 mA/cm2. This corresponds to an ionic (O−) current of about 10% of the total current, which is 2–5 times higher than previously reported, due to the high plasma density of 1012–1013 cm−3 achieved by the WARP source. The breakdown field of ∼10 MV/cm and the etch rate of 60 nm/min of the oxide are independent of the oxidation rate and similar to those of the thermal oxide. Results from capacitance–voltage measurements, Fourier transform infrared absorbance spectroscopy, null ellipsometry, and Rutherford backscattering spectroscopy suggest that the oxide grown at low rates (<2 nm/min) is very close to stoichiometric SiO2 while the oxide grown at high rates (>3 nm/min) is Si rich (35%–40% atomic Si). © 1999 American Institute of Physics.
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81.65.Mq Oxidation
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
82.45.-h Electrochemistry and electrophoresis
61.66.Bi Elemental solids
61.66.Dk Alloys
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Single-electron transistor made of multiwalled carbon nanotube using scanning probe manipulation

Leif Roschier, Jari Penttilä, Michel Martin, Pertti Hakonen, Mikko Paalanen, Unto Tapper, Esko I. Kauppinen, Catherine Journet, and Patrick Bernier

Appl. Phys. Lett. 75, 728 (1999); http://dx.doi.org/10.1063/1.124495 (3 pages) | Cited 44 times

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We positioned semiconducting multiwalled carbon nanotube, using an atomic force microscope, between two gold electrodes at SiO2 surface. Transport measurements exhibit single-electron effects with a charging energy of 24 K. Using the Coulomb staircase model, the capacitances and resistances between the tube and the electrodes can be characterized in detail. © 1999 American Institute of Physics.
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85.35.Gv Single electron devices
81.05.ub Fullerenes and related materials
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
73.23.Hk Coulomb blockade; single-electron tunneling
85.35.Ds Quantum interference devices

A monolithic field-effect-transistor-amplified magnetic field sensor

D. M. Schaadt, E. T. Yu, S. Sankar, and A. E. Berkowitz

Appl. Phys. Lett. 75, 731 (1999); http://dx.doi.org/10.1063/1.124496 (3 pages) | Cited 2 times

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We propose and demonstrate the operation of a monolithic field-effect-transistor-amplified magnetic field sensor device, in which a tunnel-magnetoresistive (TMR) material is incorporated within the gate of a Si metal–oxide–semiconductor–field-effect transistor. A fixed voltage is applied across the TMR layer, which leads charge to build up within the gate. Applying or changing an external magnetic field causes a change in the charge within the TMR layer and, consequently, a shift in the transistor threshold voltage, which leads to an exponential change in subthreshold current IDS sub and a quadratic change in saturation current IDS sat. The application of a 6 kOe magnetic field at room temperature leads in our device to an absolute change in IDS sub three times as large and in IDS sat 500 times as large as the corresponding change in current through the TMR layer alone. The relative change in IDS sub is a factor of four larger than that in the current through the TMR layer. © 1999 American Institute of Physics.
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07.55.Ge Magnetometers for magnetic field measurements
85.30.Tv Field effect devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Transient effects of positive oxide charge on stress-induced leakage current in tunnel oxides

Nian-Kai Zous, Tahui Wang, Chih-Chich Yeh, C. W. Tsai, and Chimoon Huang

Appl. Phys. Lett. 75, 734 (1999); http://dx.doi.org/10.1063/1.124497 (3 pages) | Cited 2 times

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The role of positive oxide charge in excess low-level leakage current in tunnel oxides induced by Fowler/Nordheim stress is investigated. A correlation between stress-induced gate current and substrate current in an n-channel metal-oxide-semiconductor field-effect transistor is observed. Both the gate current and the substrate current exhibit a significant transient effect. The mechanisms of the stress-induced currents and their field dependence are explored. Positive oxide charge tunnel detrapping is found to be the cause of the observed transient behavior in the two currents. The stress-created positive oxide charge can be significantly annealed by substrate hot electron injection. © 1999 American Institute of Physics.
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85.30.Tv Field effect devices
73.40.Gk Tunneling
73.50.Fq High-field and nonlinear effects
85.30.De Semiconductor-device characterization, design, and modeling
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Optically-induced growth of fiber patterns into a photopolymerizable resin

Satoru Shoji and Satoshi Kawata

Appl. Phys. Lett. 75, 737 (1999); http://dx.doi.org/10.1063/1.124498 (3 pages) | Cited 27 times

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We present evidence of optically-induced growth of fiber patterns into a photopolymerizable resin. Optical growth of a single or multiple fibers is achieved by focusing an ultraviolet (UV)-laser light into the photopolymerizable resin used. The fiber growth is due to an effect in which photopolymerization of the resin upon light irradiation produces an increase of the resin refractive index, the change of which, in turn, confines the light propagation into waveguide-type fiber structures. We have also observed that two optically grown independent fibers can merge to form a single fiber under specific conditions. We have studied the dependence of this optical growth of fiber structures phenomena on all the experimental parameters, including the numerical aperture (NA) of the lens used to focus the light, the light power, and the exposure time. © 1999 American Institute of Physics.
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42.70.Jk Polymers and organics
42.81.Bm Fabrication, cladding, and splicing
42.81.Dp Propagation, scattering, and losses; solitons
82.35.-x Polymers: properties; reactions; polymerization
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