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3 Jun 2002

Volume 80, Issue 22, pp. 4085-4270

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Strained-Si/SiGe-on-insulator inversion layers: The role of strained-Si layer thickness on electron mobility

F. Gámiz, J. B. Roldán, and A. Godoy

Appl. Phys. Lett. 80, 4160 (2002); http://dx.doi.org/10.1063/1.1483907 (3 pages) | Cited 1 time

Online Publication Date: 23 May 2002

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We show by Monte Carlo simulation that electron mobility is greater when strained-silicon inversion layers are grown on SiGe-on-insulator substrates than when unstrained-silicon-on-insulator devices are employed (as experimentally observed). However, the electron mobility in strained-Si/SiGe-on-insulator inversion layers is strongly dependent on the strained-silicon layer thickness, TSi, due to an increase of the phonon scattering, which partially counteracts the increase in the mobility achieved by the strain. This effect is less important as the germanium mole fraction, x, is reduced, and as the value of TSi increases. © 2002 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Effects of amorphizing species’ ion mass on the end-of-range damage formation in silicon

Mark H. Clark, Kevin S. Jones, Tony E. Haynes, Charles J. Barbour, Kenneth G. Minor, and Ebrahim Andideh

Appl. Phys. Lett. 80, 4163 (2002); http://dx.doi.org/10.1063/1.1483383 (3 pages) | Cited 8 times

Online Publication Date: 23 May 2002

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The effects of preamorphizing ion mass on the end-of-range (EOR) damage and subsequent enhanced diffusivity have been investigated. Amorphizing silicon with implants of 22 keV 28Si+, 32 keV 73Ge+, 40 keV 119Sn+, and 45 keV 207Pb+ provided the mass comparisons. Cross-sectional transmission electron microscopy analysis showed that the amorphous layer depths were approximately 400 Å. After postimplantation annealing at 750 °C for 30 min, plan-view transmission electron microscopy (PTEM) revealed that increasing the ion mass decreased the defect size and density. Quantitative analysis of PTEM results also showed that increasing ion mass decreased the population of interstitials trapped in the EOR. Secondary ion mass spectrometry depth profiles of grown-in boron marker layers showed that increasing the ion mass decreased the time average diffusivity enhancements of boron (〈DB〉/DB∗). © 2002 American Institute of Physics.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
66.30.J- Diffusion of impurities
61.72.S- Impurities in crystals
61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing

Piezoresponse force microscopy for polarity imaging of GaN

B. J. Rodriguez, A. Gruverman, A. I. Kingon, R. J. Nemanich, and O. Ambacher

Appl. Phys. Lett. 80, 4166 (2002); http://dx.doi.org/10.1063/1.1483117 (3 pages) | Cited 44 times

Online Publication Date: 23 May 2002

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The polarity distribution of GaN based lateral polarity heterostructures is investigated by piezoresponse force microscopy (PFM). Simultaneous imaging of surface morphology, as well as the phase and magnitude of the piezoelectric response, is performed by PFM on a GaN film with patterned polarities on a c-Al2O3 substrate. We demonstrate that the polarity distribution of GaN based lateral polarity heterostructures can be deduced from the phase image of the piezoresponse with nanometer scale spatial resolution. © 2002 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.65.Bn Piezoelectric and electrostrictive constants
77.22.Ej Polarization and depolarization
68.37.Ps Atomic force microscopy (AFM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
77.55.-g Dielectric thin films

Electron conduction through quasi-one-dimensional indium wires on silicon

Takashi Uchihashi and Urs Ramsperger

Appl. Phys. Lett. 80, 4169 (2002); http://dx.doi.org/10.1063/1.1483929 (3 pages) | Cited 40 times

Online Publication Date: 23 May 2002

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Electron conduction through quasi-one-dimensional (1D) indium atomic wires on silicon (the Si(111)-4×1-In reconstruction) is clarified with the help of local structural analysis using scanning tunneling microscopy. The reconstruction has a conductance per square as high as 100 μS, with global conduction despite numerous surface steps. A complete growth of indium wires up to both the surface steps and the lithographically printed electrodes is essential for the macroscopic transport. The system exhibits a metal–insulator transition at 130 K, consistent with a recent ultraviolet photoemission study [H. W. Yeom, S. Takeda, E. Rotenberg, I. Matsuda, K. Horikoshi, J. Schaefer, C. M. Lee, S. D. Kevan, T. Ohta, T. Nagao, and S. Hasegawa, Phys. Rev. Lett. 82, 4898 (1999)]. © 2002 American Institute of Physics.
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73.63.Nm Quantum wires
81.07.Vb Quantum wires
73.40.Ns Metal-nonmetal contacts
71.30.+h Metal-insulator transitions and other electronic transitions
68.65.La Quantum wires (patterned in quantum wells)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.25.+i Surface conductivity and carrier phenomena
72.60.+g Mixed conductivity and conductivity transitions

Fast time response from Si–SiGe undulating layer superlattices

D. Buca, S. Winnerl, S. Lenk, Ch. Buchal, and D.-X. Xu

Appl. Phys. Lett. 80, 4172 (2002); http://dx.doi.org/10.1063/1.1483121 (3 pages) | Cited 9 times

Online Publication Date: 23 May 2002

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We have grown Si–Si1−xGex undulating layer superlattices with x = 0.39 and 0.45 by molecular-beam epitaxy on top of epitaxial implanted CoSi2 layers and fabricated vertical metal–semiconductor–metal detectors. The detectors show a quantum efficiency of 5% for the wavelength of 1320 nm and 0.9% for 1550 nm. We performed temporal response measurements, using a Ti:sapphire laser and an optical parametric oscillator which generates ultrafast pulses at infrared wavelengths. An electrical response time of 16 ps full width at half maximum was obtained at a wavelength of 1300 nm. © 2002 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
73.40.Sx Metal-semiconductor-metal structures
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.30.De Semiconductor-device characterization, design, and modeling

Effects of postmetallization annealing on ultrathin SiO2 layer properties

Asuha, Toshiro Yuasa, Osamu Maida, and Hikaru Kobayashi

Appl. Phys. Lett. 80, 4175 (2002); http://dx.doi.org/10.1063/1.1482147 (3 pages) | Cited 14 times

Online Publication Date: 23 May 2002

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Observation of both longitudinal optical and transverse optical phonons of ∼1.3 nm ultrathin silicon dioxide (SiO2) layers formed by immersion in nitric acid shows that the SiO2 density increases by 16% after postoxidation annealing (POA) at 900 °C. For the SiO2 layers without POA, postmetalization annealing (PMA) greatly decreases the SiO2 thickness from 1.3 to 0.2 nm, the effect of which is attributable to the reaction of aluminum with SiO2 to form a metallic mixture of aluminum oxide and Si. For SiO2 layers with POA, PMA decreases the SiO2 thickness to a lesser extent (from 1.4 to 0.9 nm), because of the suppression of aluminum diffusion into SiO2 due to its dense structure. PMA is found to decrease the interface state density but increase the leakage current density. © 2002 American Institute of Physics.
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61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
85.40.Ls Metallization, contacts, interconnects; device isolation
63.20.-e Phonons in crystal lattices
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.40.Ns Metal-nonmetal contacts
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Local control of dynamic nuclear polarization in quantum Hall devices

Tomoki Machida, Tomoyuki Yamazaki, and Susumu Komiyama

Appl. Phys. Lett. 80, 4178 (2002); http://dx.doi.org/10.1063/1.1483910 (3 pages) | Cited 18 times

Online Publication Date: 23 May 2002

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We manipulate and detect local nuclear spin polarization in integer quantum Hall (IQH) systems using micrometal strips fabricated on top of Al0.3Ga0.7As/GaAs Hall bar devices. The radio-frequency (rf) magnetic fields generated by transmitting rf electrical currents through the micrometal strips causes nuclear magnetic resonance in a limited region along IQH edge channels, and resulting changes in the nuclear spin polarization are detected via Hall resistance of the devices. © 2002 American Institute of Physics.
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73.43.-f Quantum Hall effects
76.70.Fz Double nuclear magnetic resonance (DNMR), dynamical nuclear polarization
85.30.Fg Bulk semiconductor and conductivity oscillation devices (including Hall effect devices, space-charge-limited devices, and Gunn effect devices)

Room-temperature observation of high-spin polarization of epitaxial CrO2(100) island films at the Fermi energy

Yu. S. Dedkov, M. Fonine, C. König, U. Rüdiger, G. Güntherodt, S. Senz, and D. Hesse

Appl. Phys. Lett. 80, 4181 (2002); http://dx.doi.org/10.1063/1.1482142 (3 pages) | Cited 41 times

Online Publication Date: 23 May 2002

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Epitaxial CrO2(100) island films have been grown on TiO2(100) substrates by a chemical-vapor deposition technique. Well-controlled surface and interface properties of the CrO2(100) films were confirmed by scanning tunneling microscopy and transmission electron microscopy, respectively. Spin- and angle-resolved photoemission spectroscopy at room temperature revealed an energy gap of about 2 eV below Fermi level EF for spin-down electrons and a spin polarization of about +95% at EF. After extended sputtering, the spin polarization can be recovered from about +10% up to +85% upon annealing. © 2002 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
68.55.-a Thin film structure and morphology
72.25.-b Spin polarized transport
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
75.70.Ak Magnetic properties of monolayers and thin films
79.60.Dp Adsorbed layers and thin films
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.20.Ps Other inorganic compounds

Characterization of superconducting structures designed for qubit realizations

E. Il’ichev, Th. Wagner, L. Fritzsch, J. Kunert, V. Schultze, T. May, H. E. Hoenig, H. G. Meyer, M. Grajcar, D. Born, W. Krech, M. V. Fistul, and A. M. Zagoskin

Appl. Phys. Lett. 80, 4184 (2002); http://dx.doi.org/10.1063/1.1481988 (3 pages) | Cited 21 times

Online Publication Date: 23 May 2002

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We implement the impedance measurement technique in order to characterize superconducting structures designed for applications in quantum computing. We report an experimental study of the circuit consisting of three small Josephson junctions incorporated in a low-inductance superconducting loop. Measurements of the circuit response to an applied weak ac bias as a function of the external magnetic flux ϕe yield complete information on the properties of the circuit. We found that the system displays two metastable states. From experimental data, we have determined the magnetic field dependent Josephson energy U(ϕe) of these states, the potential barrier ΔU between these states, as well as the difference of the critical currents of the junction in the loop. © 2002 American Institute of Physics.
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85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits
85.25.Cp Josephson devices
03.67.Lx Quantum computation architectures and implementations
74.50.+r Tunneling phenomena; Josephson effects
74.25.Sv Critical currents
84.30.Sk Pulse and digital circuits

Room-temperature ferromagnetism in Cr-doped GaN single crystals

Sang Eon Park, Hyeon-Jun Lee, Yong Chan Cho, Se-Young Jeong, Chae Ryong Cho, and Sunglae Cho

Appl. Phys. Lett. 80, 4187 (2002); http://dx.doi.org/10.1063/1.1483115 (3 pages) | Cited 111 times

Online Publication Date: 23 May 2002

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We report on the discovery of a room-temperature ferromagnetism in Cr-doped GaN single crystals with a Tc = 280 K. The addition of Cr into GaN single crystals grown by the flux method induces the lattice constant increase due to the larger Cr atomic radius. In x-ray photoelectron spectroscopy measurement, Cr 2p3/2 core-level exhibited spectra near 575.7 eV. This binding energy is similar to the reported value of CrN. The coercive field by magnetization–magnetic field (M–H) hysteresis curve at 250 K was 54 Oe. We verified the presence of ferromagnetic transition in the temperature dependence of the electrical resistance measurements. We discuss the ferromagnetic ordering in Cr-doped GaN bulk single crystals excluding the contribution of the substrate crystal structure. © 2002 American Institute of Physics.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
81.05.Ea III-V semiconductors
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.20.At Surface states, band structure, electron density of states
79.60.Bm Clean metal, semiconductor, and insulator surfaces
61.66.Fn Inorganic compounds

Magnetic force microscopy observation of antivortex core with perpendicular magnetization in patterned thin film of permalloy

K. Shigeto, T. Okuno, K. Mibu, T. Shinjo, and T. Ono

Appl. Phys. Lett. 80, 4190 (2002); http://dx.doi.org/10.1063/1.1483386 (3 pages) | Cited 35 times

Online Publication Date: 23 May 2002

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The cross-tie wall is a kind of magnetic domain wall composed of a main straight wall and crossing subwalls and observed in magnetic thin films. This wall contains two kinds of magnetic vortex structures: “circular vortex” and “antivortex.” At the cores of both vortices, the existence of a spot with perpendicular magnetization has been theoretically predicted. We have detected the perpendicular magnetization spots at each vortex core and identified the direction of it by applying magnetic force microscopy imaging to cross-tie walls in patterned rectangular thin permalloy (Ni80Fe20) films. We also fabricated magnetic structures that contain only antivortex by engineering the shape of thin films. © 2002 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.37.Rt Magnetic force microscopy (MFM)

Magnetic moment and anisotropy in FenCom clusters

J. Kortus, T. Baruah, M. R. Pederson, C. Ashman, and S. N. Khanna

Appl. Phys. Lett. 80, 4193 (2002); http://dx.doi.org/10.1063/1.1482793 (3 pages) | Cited 12 times

Online Publication Date: 23 May 2002

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Electronic structure calculations of FenCom (n+m = 5 and 13) are used to examine the effects of alloying on the magnetic moment and magnetic anisotropies. Our density-functional studies show that many mixed clusters have moments comparable to or higher than the pure clusters. The mixed clusters, however, have very low anisotropies and could be ideal as soft magnetic materials. It is shown that shape, composition, and compositional ordering must be considered for optimization of anisotropy energies. © 2002 American Institute of Physics.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Bb Fe and its alloys
75.30.Gw Magnetic anisotropy
75.10.Lp Band and itinerant models
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
75.40.Mg Numerical simulation studies

Superconductivity in thin-film YBa2Cu3O7−δ/La0.7Ca0.3MnO3 bilayers

M. D. Allsworth, R. A. Chakalov, M. S. Colclough, P. Mikheenko, and C. M. Muirhead

Appl. Phys. Lett. 80, 4196 (2002); http://dx.doi.org/10.1063/1.1480888 (3 pages) | Cited 10 times

Online Publication Date: 23 May 2002

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We report the influence of the magnetic state of thin films of La0.7Ca0.3MnO3 (LCMO) on the superconducting order parameter in LCMO/YBa2Cu3O7−δ (YBCO) thin-film bilayers. We find that the number density of Cooper pairs is enhanced at the coercive field of the LCMO layer relative to that where the magnetic moment is saturated. This effect is at most ∼ 10% and is only observable within a few degrees of the superconducting transition temperature. Experiments with thin SrTiO3 layers between the LCMO and YBCO layers provide strong evidence that the effect is a consequence of the spin-polarized nature of the electrons at the interface, rather than a direct magnetic effect. © 2002 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.78.Fk Multilayers, superlattices, heterostructures
74.20.Fg BCS theory and its development
74.50.+r Tunneling phenomena; Josephson effects
72.25.Mk Spin transport through interfaces
74.10.+v Occurrence, potential candidates
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.De Giant magnetoresistance

Detection of a single magnetic microbead using a miniaturized silicon Hall sensor

Pierre-A. Besse, Giovanni Boero, Michel Demierre, Vincent Pott, and Radivoje Popovic

Appl. Phys. Lett. 80, 4199 (2002); http://dx.doi.org/10.1063/1.1483909 (3 pages) | Cited 89 times

Online Publication Date: 23 May 2002

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Using a highly sensitive silicon Hall sensor fabricated in a standard complementary metal–oxide–semiconductor (CMOS) technology, we detect a single magnetic microbead of 2.8 μm in diameter. The miniaturized sensor has an active area of 2.4×2.4 μm2, a sensitivity of 175 V/AT and a resistance of 8.5 kΩ. Two detection methods, both exploiting the superparamagnetic behavior of the bead, are experimentally tested and their performances are compared. This work opens the way to the fabrication of low cost microsystems for biochemical applications based on the use of dense arrays of silicon Hall sensors and CMOS electronics. © 2002 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
75.50.Tt Fine-particle systems; nanocrystalline materials
87.80.-y Biophysical techniques (research methods)
72.20.My Galvanomagnetic and other magnetotransport effects

Transport properties of CrO2 (110) films grown on TiO2 buffered Si substrates by chemical vapor deposition

S. J. Liu, J. Y. Juang, K. H. Wu, T. M. Uen, Y. S. Gou, and J.-Y. Lin

Appl. Phys. Lett. 80, 4202 (2002); http://dx.doi.org/10.1063/1.1481534 (3 pages) | Cited 8 times

Online Publication Date: 23 May 2002

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Epitaxial CrO2 (110)-oriented films were fabricated on Si (100) substrates buffered by rutile TiO2 derived from oxidation of a pulsed-laser-deposited TiN layer. The epitaxial films of CrO2 were prepared by chemical vapor deposition in a two-zone furnace with oxygen flow from a CrO3 precursor. The transport measurements show that the CrO2 films are metallic with a Curie temperature of about 380 K. The temperature dependence of resistivity was best described by a phenomenological expression ρ(T) = ρ0+AT2e(−Δ/T) over the range of 5–350 K with Δ = 94 K. The magnetic measurements show the in-plane coercive fields are about 30 and 60 Oe at 300 and 5 K, respectively. The temperature dependent spontaneous magnetization follows Bloch’s T3/2 law and the slope suggests a critical wavelength of λΔ ∼ 30.6 Å beyond which spin-flip scattering becomes important. © 2002 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.-s Critical-point effects, specific heats, short-range order
75.50.Dd Nonmetallic ferromagnetic materials
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Dielectric and piezoelectric enhancement due to 90° domain rotation in the tetragonal phase of Pb(Mg1/3Nb2/3)O3-PbTiO3

T. Y. Koo and S-W. Cheong

Appl. Phys. Lett. 80, 4205 (2002); http://dx.doi.org/10.1063/1.1483120 (3 pages) | Cited 26 times

Online Publication Date: 23 May 2002

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The anomalous enhancement in dielectric (ϵ>6000) and piezoelectric constant (d33>600 pC/N) in the tetragonal side (x = 35%) of morphotropic phase boundary (MPB) has been observed in polycrystalline (1−x)Pg(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT). On the other hand, x-ray peak position shifts under electric field (E) demonstrate that the intrinsic piezoelectric response becomes maximum at MPB (x = 33%–34%), which may be associated with the recently discovered monoclinic phase. Intensity change of Bragg peaks under E indicates that 90° domain rotation is the main contribution to additional strain in the tetragonal side of MPB, which dominates the intrinsic contribution of monoclinic phase in polycrystalline PMN-PT. © 2002 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.-j Piezoelectricity and electromechanical effects
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
77.80.B- Phase transitions and Curie point

Anomalous isothermal charging and discharging currents in polytetrafluoroethylene

Eugen R. Neagu and Jose N. Marat-Mendes

Appl. Phys. Lett. 80, 4208 (2002); http://dx.doi.org/10.1063/1.1483928 (3 pages) | Cited 3 times

Online Publication Date: 23 May 2002

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Transient charging and discharging currents in polytetrafluoroethylene have been investigated at various temperatures and field strengths in a vacuum. Anomalous charging and discharging currents have been identified. At low electric fields, the anomalous discharging current is almost the mirror image of the anomalous charging current. Three characteristic zones have been identified that can provide information about dielectric polarization, bulk conduction, electrode effects, and diffusion. The mobility at 140 °C and 16 MV m−1 was determined to be 5.4×10−16 m2 V−1 s−1. © 2002 American Institute of Physics.
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77.22.Ej Polarization and depolarization
77.84.Jd Polymers; organic compounds
72.80.Le Polymers; organic compounds (including organic semiconductors)

Nonlinear macroscopic polarization in GaN/AlxGa1−xN quantum wells

G. Vaschenko, D. Patel, C. S. Menoni, H. M. Ng, and A. Y. Cho

Appl. Phys. Lett. 80, 4211 (2002); http://dx.doi.org/10.1063/1.1483906 (3 pages) | Cited 12 times

Online Publication Date: 23 May 2002

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We present experimental evidence of the nonlinear behavior of the macroscopic polarization in GaN/AlxGa1−xN quantum wells. This behavior is revealed by determining the barrier-well polarization difference as a function of applied hydrostatic pressure. The polarization difference and corresponding built-in electric field in the wells increase with applied pressure at a much higher rate than expected from the linear model of polarization. This result, universally observed in the quantum well structures with different AlN mole fraction in the barriers, is explained by the nonlinear dependence of the piezoelectric polarization in GaN and AlN on the strain generated by pressure. © 2002 American Institute of Physics.
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77.22.Ej Polarization and depolarization
77.65.Ly Strain-induced piezoelectric fields
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.07.St Quantum wells
62.50.-p High-pressure effects in solids and liquids
73.61.Ey III-V semiconductors

Effect of annealing on dielectric constant of boron carbon nitride films synthesized by plasma-assisted chemical vapor deposition

Tomohiko Sugiyama, Tomoyoshi Tai, and Takashi Sugino

Appl. Phys. Lett. 80, 4214 (2002); http://dx.doi.org/10.1063/1.1482788 (3 pages) | Cited 12 times

Online Publication Date: 23 May 2002

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Polycrystalline boron carbon nitride (BCN) films are synthesized by plasma-assisted chemical vapor deposition. The dielectric constant is estimated from the accumulation region of capacitance–voltage characteristics of Cu/BCN/p-Si samples. It is found that the dielectric constant of the BCN film is reduced by annealing at 400 °C. The BCN film before and after annealing is characterized by Fourier transform infrared absorption measurements. The infrared absorption intensities due to the C�H and C�C bonds decrease after annealing. It is suggested that the C�H and C�C bonds are undesirable to obtain a low dielectric constant. A dielectric constant as low as 2.1 is achieved for the BCN film which is treated by annealing process. © 2002 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
78.66.Nk Insulators
78.30.Hv Other nonmetallic inorganics

Importance of structural irregularity on dielectric loss in (1−x)Pb(Mg1/3Nb2/3)O3−(x)PbTiO3 crystals

Shashank Priya, D. Viehland, and K. Uchino

Appl. Phys. Lett. 80, 4217 (2002); http://dx.doi.org/10.1063/1.1482791 (3 pages) | Cited 19 times

Online Publication Date: 23 May 2002

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The dielectric properties of (1−x)Pb(Mg1/3Nb2/3)O3−(x)PbTiO3 (PMN–PT) crystals have been investigated over a temperature range of 4 to 450 K at various frequencies. At low temperatures, an unusual frequency dependent plateau region in the absorption was observed between 75 and 175 K. At both higher and lower temperatures, the absorption was frequency independent. Analysis of the relaxation time constant revealed power-law divergence, typical of fractal behavior in disordered magnetic systems. The results demonstrate the importance of structural irregularities on the dielectric loss mechanism in poled oriented PMN–PT crystals. © 2002 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Gm Dielectric loss and relaxation
61.66.Fn Inorganic compounds
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Molecular patterning through high-resolution polymethylmethacrylate masks

Qingling Hang, Yuliang Wang, Marya Lieberman, and Gary H. Bernstein

Appl. Phys. Lett. 80, 4220 (2002); http://dx.doi.org/10.1063/1.1481784 (3 pages) | Cited 11 times

Online Publication Date: 23 May 2002

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Electron beam lithography was used to make nanometer trenches in thin polymethylmethacrylate (PMMA). After development, the wafers were dipped in an aqueous solution of the Creutz–Taube ion [(NH3)5Ru(pyrazine)Ru(NH3)5](o-toluenesulphonate)5 (CT5), and the PMMA was removed with acetone or dichloromethane. Atomic force microscopy and x-ray photoelectron spectroscopy were used to investigate the surface characteristics of wafers after dissolution of the PMMA and to confirm the binding of a monolayer of CT5 molecules on the wafer within the areas delimited by the PMMA trenches. This masking technique has so far been demonstrated to pattern 35 nm lines of a monolayer of CT5 molecules on silicon dioxide. © 2002 American Institute of Physics.
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85.65.+h Molecular electronic devices
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Size-dependent oxidation of hydrogenated silicon clusters

R. Q. Zhang, W. C. Lu, and S. T. Lee

Appl. Phys. Lett. 80, 4223 (2002); http://dx.doi.org/10.1063/1.1473876 (3 pages) | Cited 2 times

Online Publication Date: 23 May 2002

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We show explicitly the size-dependent chemical reactivity of hydrogenated silicon clusters reacting with water. A unique trend of decreasing reactivity with decreasing cluster size has been deduced from reaction energetics, frontier orbital analysis, and chemical reaction rates determined by the transition state theory in conjunction with ab initio calculations at Hartree–Fock and Møller–Plesset perturbation levels of theory, for water reaction with both dihydride and trihydride silicon configurations. This study indicates the possibility of fabricating stable hydrogenated silicon structures by reducing their size to nanometers. © 2002 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.65.Mq Oxidation
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials

Template-catalyst-free growth of highly ordered boron nanowire arrays

L. M. Cao, K. Hahn, C. Scheu, M. Rühle, Y. Q. Wang, Z. Zhang, C. X. Gao, Y. C. Li, X. Y. Zhang, M. He, L. L. Sun, and W. K. Wang

Appl. Phys. Lett. 80, 4226 (2002); http://dx.doi.org/10.1063/1.1483131 (3 pages) | Cited 16 times

Online Publication Date: 23 May 2002

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Well-aligned boron nanowire arrays were grown vertically on silicon substrates over areas up to several tens of square centimeters using radio-frequency magnetron sputtering of highly pure boron. During growth and self-assembly of boron nanowire arrays, no template or catalyst was needed. The morphology, structure, and composition of the self-organized boron nanowires were characterized in detail using scanning electron microscopy, transmission electron microscopy, and electron energy-loss spectroscopy. Our results might provide insight into the controllable formation of a wide variety of ordered nanostructures with advanced properties. © 2002 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.15.Cd Deposition by sputtering
68.65.La Quantum wires (patterned in quantum wells)
81.16.Dn Self-assembly
73.63.Fg Nanotubes
81.07.De Nanotubes
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
79.20.Uv Electron energy loss spectroscopy

Spin splitting of the electron ground states of InAs quantum dots

G. Medeiros-Ribeiro, M. V. B. Pinheiro, V. L. Pimentel, and E. Marega

Appl. Phys. Lett. 80, 4229 (2002); http://dx.doi.org/10.1063/1.1483112 (3 pages) | Cited 26 times

Online Publication Date: 23 May 2002

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Here, we present results on the spin splitting of electrons in the ground state of InAs self-assembled quantum dots (QDs). The spin splitting is assessed by capacitance spectroscopy, which allows direct measurement of the electronic g-factor modulus. By applying the magnetic field parallel to the [001], [110], and [1math0] crystallographic directions, we found that for magnetic fields below 5 T the g factor depends on the orientation, reflecting the QD anisotropy. For higher fields, the g factor does not exhibit the same degree of anisotropy, indicating a compression of the wave function inside the QD along the [001] direction, and consequently, a dependence on the magnitude of the applied field. © 2002 American Institute of Physics.
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73.21.La Quantum dots
71.70.-d Level splitting and interactions

Metalorganic vapor-phase epitaxial growth of vertically well-aligned ZnO nanorods

W. I. Park, D. H. Kim, S.-W. Jung, and Gyu-Chul Yi

Appl. Phys. Lett. 80, 4232 (2002); http://dx.doi.org/10.1063/1.1482800 (3 pages) | Cited 454 times

Online Publication Date: 23 May 2002

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We report metalorganic vapor-phase epitaxial growth and structural and photoluminescent characteristics of ZnO nanorods. The nanorods were grown on Al2O3(00⋅1) substrates at 400 °C without employing any metal catalysts usually needed in other methods. Electron microscopy revealed that nanorods with uniform distributions in their diameters, lengths, and densities were grown vertically from the substrates. The mean diameter of the nanorods is as narrow as 25 nm. In addition, x-ray diffraction measurements clearly show that ZnO nanorods were grown epitaxially with homogeneous in-plane alignment as well as a c-axis orientation. More importantly, from photoluminescence spectra of the nanorods strong and narrow excitonic emission and extremely weak deep level emission were observed, indicating that the nanorods are of high optical quality. © 2002 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
81.05.Dz II-VI semiconductors
61.46.-w Structure of nanoscale materials
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
68.35.Ct Interface structure and roughness
71.35.-y Excitons and related phenomena
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