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27 Dec 2004

Volume 85, Issue 26, pp. 6323-6432

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 6409 (2004); http://dx.doi.org/10.1063/1.1839274 (3 pages)

Peter D. D. Schwindt, Svenja Knappe, Vishal Shah, Leo Hollberg, John Kitching, Li-Anne Liew, and John Moreland
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Single-mode subwavelength waveguide with channel plasmon-polaritons in triangular grooves on a metal surface

D. K. Gramotnev and D. F. P. Pile

Appl. Phys. Lett. 85, 6323 (2004); http://dx.doi.org/10.1063/1.1839283 (3 pages) | Cited 97 times

Online Publication Date: 17 December 2004

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We demonstrate that single-mode operation of a subwavelength plasmonic waveguide in the form of a V-groove on a metal surface can be achieved by adjusting the depth of the groove. Strongly localized channel plasmon-polaritons (CPPs) are shown to propagate in such waveguides. If the groove depth is close to the penetration depth of the fundamental CPP mode, then all higher modes are not supported by the structure, leaving only the fundamental mode propagating in the groove. In this case, propagation distances of fundamental mode ∼10 μm can easily be achieved together with strong subwavelength localization.
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42.82.Et Waveguides, couplers, and arrays
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Optical limiting of semiconductor nanoparticles for nanosecond laser pulses

Wenling Jia, Elliot P. Douglas, Fenggi Guo, and Wenfang Sun

Appl. Phys. Lett. 85, 6326 (2004); http://dx.doi.org/10.1063/1.1836871 (3 pages) | Cited 42 times

Online Publication Date: 17 December 2004

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Optical limiting of nanosecond laser pulses at 532 nm has been observed in CdxAg1−xS semiconductor nanoparticles within organic solution of polymeric ionic aggregates. Both free-carrier absorption (FCA) and nonlinear scattering contribute to the optical limiting performance. The optical limiting response of CdS nanoparticles, in the diameter range of 2–9 nm, increases with the increase of particle size. It can be further increased by surface coating of the CdS particle with a thin layer of Ag2S or forming ternary CdxAg1−xS particle. The FCA cross sections of CdxAg1−xS solutions were estimated to be between 10−19 and 10−18 cm2, which are comparable with those of bulk semiconductors.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

Measuring multimodal size distributions of aquatic colloids at trace concentrations

C. Walther, H. R. Cho, and Th. Fanghänel

Appl. Phys. Lett. 85, 6329 (2004); http://dx.doi.org/10.1063/1.1842359 (3 pages) | Cited 11 times

Online Publication Date: 17 December 2004

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Many applications in research as well as industry require a highly sensitive detection of particulate matter in water or process liquids. We present a technique to measure the distribution of colloid sizes between 20 and 100 nm in situ at ultratrace concentrations. The method is based on laser-induced breakdown detection, which has been applied for trace detection of colloids and determination of the weighted mean size. Using a refined method of data evaluation, we are now able to measure the number density of inorganic colloids in six size classes between 20 and 100 nm simultaneously below ppb concentration.
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82.70.Dd Colloids
82.70.Kj Emulsions and suspensions
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
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Cathode priming of a relativistic magnetron

M. C. Jones, V. B. Neculaes, Y. Y. Lau, R. M. Gilgenbach, and W. M. White

Appl. Phys. Lett. 85, 6332 (2004); http://dx.doi.org/10.1063/1.1841454 (3 pages) | Cited 21 times

Online Publication Date: 17 December 2004

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A cathode priming technique of a relativistic magnetron is analyzed via a three-dimensional particle-in-cell simulation. By imposing a threefold azimuthal variation on the emitting cathode of a six-cavity relativistic magnetron, the electrons are prebunched at birth. This leads to fast startup of the pi mode with three electron spokes. Suppression of unwanted modes during startup is observed in the simulation.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
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Effects of rapid thermal annealing on quality of In0.52Al0.48As∕In0.53Ga0.47As multiquantum wells grown on a compositionally graded InAlAs∕InAlGaAs metamorphic buffer layer

Soo-Ghang Ihn, Seong-June Jo, and Jong-In Song

Appl. Phys. Lett. 85, 6335 (2004); http://dx.doi.org/10.1063/1.1833566 (3 pages) | Cited 2 times

Online Publication Date: 17 December 2004

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We report improvement in crystalline quality of In0.52Al0.48As∕In0.53Ga0.47As multiquantum wells (MQWs) and compositionally graded InAlAs∕InAlGaAs metamorphic buffer grown on GaAs by using postgrowth rapid thermal annealing (RTA). Dependence of optical and structural properties of the MQWs on RTA was investigated by using photoluminescence (PL) and triple-axis x-ray diffraction measurements. After the RTA, the PL intensity of the MQWs increased, while the linewidth decreased. Also, the triple-axis contour maps of the MQWs showed increase in peak intensity of epilayers as well as crystalline reformation indicated by narrower mosaic spread and restoration of epilayer tilt to the substrate orientation.
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81.05.Ea III-V semiconductors
81.07.St Quantum wells
78.67.De Quantum wells
68.65.Fg Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
81.40.Tv Optical and dielectric properties related to treatment conditions

Epitaxial growth and surface modeling of ZnO on c-plane Al2O3

T. E. Murphy, S. Walavalkar, and J. D. Phillips

Appl. Phys. Lett. 85, 6338 (2004); http://dx.doi.org/10.1063/1.1842357 (3 pages) | Cited 3 times

Online Publication Date: 17 December 2004

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The growth of ZnO on c-plane sapphire by molecular beam epitaxy is presented for varying ratios of zinc and oxygen flux. Reflection high energy electron diffraction patterns during epitaxial growth suggest clear differences in the evolution of surface morphology for differing Zn flux. Atomic force microscope images indicate sizable hexagonal features in the surface morphology for Zn-rich material. A stochastic growth model is presented to represent the experimental ZnO surface, where differences in adatom lateral diffusion length are suspected to be the cause of the differing surface morphology.
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81.05.Dz II-VI semiconductors
81.15.Aa Theory and models of film growth
66.30.Dn Theory of diffusion and ionic conduction in solids
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Ps Atomic force microscopy (AFM)

Near-field second-harmonic imaging of thin ferromagnetic films

W. Dickson, S. Takahashi, R. Pollard, and A. V. Zayats

Appl. Phys. Lett. 85, 6341 (2004); http://dx.doi.org/10.1063/1.1842369 (3 pages) | Cited 3 times

Online Publication Date: 17 December 2004

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The principles of magnetic domain image formation in second-harmonic near-field microscopy have been investigated in the case of in-plane magnetic anisotropy. Due to the electromagnetic interaction between a probe and a surface, magnetic contrast can be achieved by observing near-field intensity variations of the SH light for both polarizations of the fundamental light in the longitudinal and transverse illumination configurations without polarization analysis. Domains in thin ferromagnetic films of Ni and Co exhibiting in-plane magnetization have been imaged using the developed approach.
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75.50.Cc Other ferromagnetic metals and alloys
68.55.-a Thin film structure and morphology
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.37.Uv Near-field scanning microscopy and spectroscopy
75.30.Gw Magnetic anisotropy
78.20.Ls Magneto-optical effects

Charge controlled, fixed optic axis analog (“v-shaped”) switching of a bent-core ferroelectric liquid crystal

Michael J. O’Callaghan, Michael D. Wand, Christopher M. Walker, and Michi Nakata

Appl. Phys. Lett. 85, 6344 (2004); http://dx.doi.org/10.1063/1.1842372 (3 pages) | Cited 11 times

Online Publication Date: 17 December 2004

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Recently discovered anticlinic ferroelectric liquid crystals (FLCs) offer a mode of fast fixed-optic-axis electro-optic modulation useful for a variety of applications. In addition, the high spontaneous polarization of a member of this class of FLCs (∼500–600 nC∕cm2) suggests that it is a good candidate for electrostatically controlled thresholdless analog switching, whereas conventional SmC* FLCs have a binary response. Using a simple charge control drive circuit, we have found that this FLC is in fact capable of hysteresis-free analog switching. An optical model suggests that this class of FLCs might be engineered to have a much larger electro-optic effect than seen in this example.
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77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.80.Fm Switching phenomena
77.22.Ej Polarization and depolarization
78.20.Jq Electro-optical effects
77.80.Dj Domain structure; hysteresis
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Evaluation of optical quality and defect properties of GaNxP1−x alloys lattice matched to Si

M. Izadifard, J. P. Bergman, I. Vorona, W. M. Chen, I. A. Buyanova, A. Utsumi, Y. Furukawa, S. Moon, A. Wakahara, and H. Yonezu

Appl. Phys. Lett. 85, 6347 (2004); http://dx.doi.org/10.1063/1.1839286 (3 pages) | Cited 4 times

Online Publication Date: 17 December 2004

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By using a variety of optical characterization techniques, including cathodoluminescence, temperature-dependent cw- and time-resolved photoluminescence (PL), and PL excitation spectroscopies, high optical quality of the GaN0.018P0.982 epilayers lattice matched to Si substrates is demonstrated and is shown to be comparable to that of the “state-of-the-art” GaNP alloys grown on GaP substrates. The growth of GaNP on Si is, however, found to facilitate the formation of several point defects, including complexes involving Ga interstitial atoms (Gai).
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78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.J- Point defects and defect clusters
78.60.Hk Cathodoluminescence, ionoluminescence
78.55.Cr III-V semiconductors
68.55.-a Thin film structure and morphology

Time-resolved photoluminescence in Mobil Composition of Matter-48

Y. L. Liu, W. Z. Lee, J. L. Shen, Y. C. Lee, P. W. Cheng, and C. F. Cheng

Appl. Phys. Lett. 85, 6350 (2004); http://dx.doi.org/10.1063/1.1842351 (3 pages) | Cited 4 times

Online Publication Date: 17 December 2004

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Dynamical properties of Mobil Composition of Matter (MCM)-48 were studied by time-resolved photoluminescence (PL). The PL intensity exhibits a clear nonexponential profile, which can be fitted by a stretched exponential function. In the temperature range from 50 to 300 K, the PL decay lifetime becomes thermally activated by a characteristic energy of 25 meV, which is suggested to be an indication of the phonon-assisted nonradiative process. A model is proposed to explain the relaxation behavior of the PL in MCM-48.
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78.55.Mb Porous materials
78.55.Hx Other solid inorganic materials
78.47.-p Spectroscopy of solid state dynamics

In situ formation of two amorphous phases by liquid phase separation in Y–Ti–Al–Co alloy

B. J. Park, H. J. Chang, D. H. Kim, and W. T. Kim

Appl. Phys. Lett. 85, 6353 (2004); http://dx.doi.org/10.1063/1.1842360 (3 pages) | Cited 66 times

Online Publication Date: 17 December 2004

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The Y28Ti28Al24Co20 alloy undergoes metastable liquid phase separation in the under-cooled liquid state and subsequently solidifies into two different Y-rich and Ti-rich amorphous phases. Secondary phase separation occurs due to the supersaturation of the primary separated liquids as the temperature decreases. Depending on the degree of local undercooling, a wide range of length scale of the microstructure is observed. The characteristic length scale of the two amorphous phases is ∼250 nm near the air side of the ribbon, and ∼25 nm near the wheel side of the ribbon.
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81.05.Kf Glasses (including metallic glasses)
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
61.43.Fs Glasses
64.60.My Metastable phases
64.75.-g Phase equilibria
81.30.Fb Solidification
64.70.D- Solid-liquid transitions

Ce3+-doped fibers for remote radiation dosimetry

A. Vedda, N. Chiodini, D. Di Martino, M. Fasoli, S. Keffer, A. Lauria, M. Martini, F. Moretti, G. Spinolo, M. Nikl, N. Solovieva, and G. Brambilla

Appl. Phys. Lett. 85, 6356 (2004); http://dx.doi.org/10.1063/1.1840127 (3 pages) | Cited 17 times

Online Publication Date: 17 December 2004

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A radioluminescent (RL) dosimetric system, based on a SiO2 optical fiber with the core doped by Ce3+ ions as luminescent activators has been investigated. Structural and optical properties of the luminescent fiber have been studied by Raman, refractive index, RL and scintillation time decay measurements, and compared to those obtained on bulk material. The RL response of a composite fiber made of a short portion of active Ce-doped fiber coupled to a long commercial one has been investigated by x-ray irradiation. A linear RL intensity response has been found in the dose rate interval 6×10−3–40 mGy∕s together with a good radiation hardness, suggesting possible application in low-dose monitoring.
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42.70.Ce Glasses, quartz
42.81.Cn Fiber testing and measurement of fiber parameters
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Qr Amorphous materials; glasses and other disordered solids
78.35.+c Brillouin and Rayleigh scattering; other light scattering
61.80.Cb X-ray effects
61.82.Ms Insulators

Composition measurement in strained AlGaN epitaxial layers using x-ray diffraction

D. J. Wallis, A. M. Keir, R. S. Balmer, D. E. J. Soley, and T. Martin

Appl. Phys. Lett. 85, 6359 (2004); http://dx.doi.org/10.1063/1.1835999 (3 pages) | Cited 3 times

Online Publication Date: 17 December 2004

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An x-ray diffraction technique is described which, by careful choice of the x-ray reflection used, minimizes errors in composition measurements resulting from strain and uncertainties in the elastic constants of a material. The method is applied to the AlGaN system, which shows a wide range of values for Poisson’s ratio in the literature and significant variation in strain state due to the high dislocation content and large thermal expansion mismatch with the substrate. It is demonstrated that accurate composition measurements of partially relaxed AlxGa1−xN layers (x<0.3) with thickness >20 nm can be made from a single measurement.
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81.05.Ea III-V semiconductors
68.55.Nq Composition and phase identification
68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
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Weak localization thickness measurements of Si:P delta-layers

D. F. Sullivan, B. E. Kane, and P. E. Thompson

Appl. Phys. Lett. 85, 6362 (2004); http://dx.doi.org/10.1063/1.1842366 (3 pages) | Cited 5 times

Online Publication Date: 17 December 2004

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We report on our results for the characterization of Si:P delta-layers grown by low temperature molecular beam epitaxy. Our data show that the effective thickness of a delta-layer can be obtained through a weak localization analysis of electrical transport measurements performed in perpendicular and parallel magnetic fields. An estimate of the diffusivity of phosphorus in silicon is obtained by applying this method to several samples annealed at 850 °C for intervals of 0–15 min. With further refinements, this may prove to be the most precise method of measuring delta-layer widths developed to date, including that of secondary ion mass spectrometry analysis.
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81.05.Cy Elemental semiconductors
73.20.Fz Weak or Anderson localization
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Cc Kinetics of defect formation and annealing
61.72.S- Impurities in crystals
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Lightly phosphorus-doped homoepitaxial diamond films grown by chemical vapor deposition

Masayuki Katagiri, Junichi Isoya, Satoshi Koizumi, and Hisao Kanda

Appl. Phys. Lett. 85, 6365 (2004); http://dx.doi.org/10.1063/1.1840119 (3 pages) | Cited 48 times

Online Publication Date: 17 December 2004

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Lightly phosphorus-doped {111} homoepitaxial diamond films have been grown by microwave plasma-assisted chemical vapor deposition under optimized growth conditions. The Phosphorus concentration in the film can be controlled at a low doping level of the order of 1016 cm−3. N-type conductivity of the films with phosphorus concentrations above 1×1016 cm−3 is reproducibly confirmed by Hall-effect measurements in the temperature range from 300 to 873 K. The highest value of the Hall mobility at room temperature is 660 cm2∕V s obtained for a film with a phosphorus concentration of 7×1016 cm−3.
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73.61.Cw Elemental semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

An organic thin-film transistor of high mobility by dielectric surface modification with organic molecule

Jong-Moo Kim, Joo-Won Lee, Jai-Kyeong Kim, Byeong-Kwon Ju, Jong-Seung Kim, Yun-Hi Lee, and Myung-Hwan Oh

Appl. Phys. Lett. 85, 6368 (2004); http://dx.doi.org/10.1063/1.1841470 (3 pages) | Cited 26 times

Online Publication Date: 17 December 2004

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Organic thin-film transistors (OTFTs) based on pentacene semiconductor are elaborated on the plastic substrates through a four-level mask process without photolithographic patterning to yield a simple fabrication process. Octadecyltrimethoxysilane (OTMS) as an organic molecule for self-assembled monolayers is deposited on the surface of zirconium oxide dielectric layer. The effect of OTMS interlayer with gate dielectric surface modification on the field effect mobility of OTFTs has been examined and these prototype organic transistors showed excellent electrical characteristics with field effect mobility >0.66 cm2∕V s and Ion∕Ioff>10.5
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81.16.Dn Self-assembly
72.80.Le Polymers; organic compounds (including organic semiconductors)
81.65.-b Surface treatments
85.30.Tv Field effect devices

Metal/semiconductor phase transition in chromium nitride(001) grown by rf-plasma-assisted molecular-beam epitaxy

Costel Constantin, Muhammad B. Haider, David Ingram, and Arthur R. Smith

Appl. Phys. Lett. 85, 6371 (2004); http://dx.doi.org/10.1063/1.1836878 (3 pages) | Cited 19 times

Online Publication Date: 17 December 2004

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Structural and electronic properties of stoichiometric single-phase CrN(001) thin films grown on MgO(001) substrates by radio-frequency N plasma-assisted molecular-beam epitaxy, are investigated. In situ room-temperature scanning tunneling microscopy clearly shows the 1×1 atomic periodicity of the crystal structure as well as long-range topographic distortions which are characteristic of a semiconductor surface. This semiconductor behavior is consistent with ex situ resistivity measurements over the range 285 K and higher, whereas below 260 K, metallic behavior is observed. The resistivity-derived band gap for the high-temperature region, 71 meV, is consistent with the tunneling spectroscopy results. The observed electronic (semiconductor/metal) transition temperature coincides with the temperature of the known coincident magnetic (para-antiferro) and structural (cubic-orthorhombic) phase transitions.
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71.30.+h Metal-insulator transitions and other electronic transitions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Highly transparent Ag∕SnO2 ohmic contact to p-type GaN for ultraviolet light-emitting diodes

June-O Song and Tae-Yeon Seong

Appl. Phys. Lett. 85, 6374 (2004); http://dx.doi.org/10.1063/1.1834990 (3 pages) | Cited 20 times

Online Publication Date: 17 December 2004

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We report on the formation of highly transparent and low-resistance Ag(3 nm)∕Sb-doped SnO2 (ATO) (200 nm) ohmic contacts to p-GaN (5×1017 cm−3). It is shown that the samples become ohmic with a specific contact resistance of 8.7×10−5 Ω cm2 upon annealing at 530 °C for 1 min in air. The oxidized contacts produce an extremely high light transmittance of 99% at a wavelength of 400 nm. The light-emitting diodes (LEDs) fabricated with the annealed Ag/ATO p-type contact layers give a forward-bias voltage of 3.42 V at injection current of 20 mA, which is better than that of LEDs with the most common oxidized Ni(5 nm)∕Au(5 nm) contact layers. Based on scanning electron microscopy and x-ray photoemission spectroscopy results, the ohmic formation mechanisms are discussed.
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85.60.Jb Light-emitting devices
61.72.Cc Kinetics of defect formation and annealing
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
79.60.Jv Interfaces; heterostructures; nanostructures
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
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Magnetism in thin films of CaB6 and SrB6

L. S. Dorneles, M. Venkatesan, M. Moliner, J. G. Lunney, and J. M. D. Coey

Appl. Phys. Lett. 85, 6377 (2004); http://dx.doi.org/10.1063/1.1840113 (3 pages) | Cited 25 times

Online Publication Date: 17 December 2004

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Thin films of disordered hexaborides CaB6 and SrB6 deposited by pulsed-laser deposition on MgO (100) or Al2O3 (001) substrates are ferromagnetic. A typical room-temperature moment per unit area of substrate is 350 μB nm−2, with the largest values being found for CaB6 on Al2O3. Lattice defects are the likely origin of the exotic, high-temperature magnetism. The moment, which is present in films as thin as 12 nm, appears to reside in an interface layer whose polarization is approximately 0.4 Tesla.
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75.70.Ak Magnetic properties of monolayers and thin films
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
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Transformed material coefficients for single-domain 0.67Pb(Mg1∕3Nb2∕3)O3–0.33PbTiO3 single crystals under differently defined coordinate systems

Rui Zhang and Wenwu Cao

Appl. Phys. Lett. 85, 6380 (2004); http://dx.doi.org/10.1063/1.1842365 (3 pages) | Cited 12 times

Online Publication Date: 17 December 2004

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Due to the confusion in choosing coordinate systems, there occurred some misrepresentations/calculations of effective material properties of 0.67Pb(Mg1∕3Nb2∕3)O3–0.33PbTiO3 single crystals based on its single-domain data. This letter is to clarify these confusions by providing proper data set for each of the currently used coordinate systems.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Bn Piezoelectric and electrostrictive constants
61.66.Fn Inorganic compounds
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Shapes of InAs quantum dots on InGaAs∕InP

Heedon Hwang, Sukho Yoon, Hyeok Kwon, Euijoon Yoon, Hong-Seung Kim, Jeong Yong Lee, and Benjamin Cho

Appl. Phys. Lett. 85, 6383 (2004); http://dx.doi.org/10.1063/1.1840123 (3 pages) | Cited 15 times

Online Publication Date: 17 December 2004

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InAs self-assembled quantum dots were grown on InGaAs lattice-matched on InP by metalorganic chemical vapor deposition. The facet formation on the dot was investigated by atomic force microscopy and transmission electron microscopy. The {136}-faceted InAs dots were elongated along either [1math0] or [math10] to form parallelogram-shaped islands analogous to hut cluster formation in SiGe∕Si quantum dots. Some parallelogram dots also exhibited {110} faceting, presumably on undergoing a shape transition toward dots with facets of higher symmetry.
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81.05.Ea III-V semiconductors
81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.47.Fg Semiconductor surfaces
68.37.Lp Transmission electron microscopy (TEM)
68.37.Ps Atomic force microscopy (AFM)

Nanoscale chemical sensor based on organic thin-film transistors

Liang Wang, Daniel Fine, and Ananth Dodabalapur

Appl. Phys. Lett. 85, 6386 (2004); http://dx.doi.org/10.1063/1.1842364 (3 pages) | Cited 45 times

Online Publication Date: 17 December 2004

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Nanoscale organic thin-film transistors were fabricated to investigate their chemical sensing properties. The use of a four-terminal geometry ensures that the sensor active area is truly nanoscale, and eliminates undesirable spreading currents. The sensor response was markedly different in nanoscale sensors compared to large-area sensors for the same analyte–semiconductor combination. The chemical sensing mechanisms in both microscale and nanoscale transistors are briefly discussed.
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85.30.Tv Field effect devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Oxygen sensing characteristics of individual ZnO nanowire transistors

Q. H. Li, Y. X. Liang, Q. Wan, and T. H. Wang

Appl. Phys. Lett. 85, 6389 (2004); http://dx.doi.org/10.1063/1.1840116 (3 pages) | Cited 125 times

Online Publication Date: 17 December 2004

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Individual ZnO nanowire transistors are fabricated, and their sensing properties are investigated. The transistors show a carrier density of 2300 μm−1 and mobility up to 6.4 cm2∕V s, which are obtained from the ISD−VG curves. The threshold voltage shifts in the positive direction and the source-drain current decreases as ambient oxygen concentration increases. However, the opposite occurs when the transistors are under illumination. Surface adsorbates on the ZnO nanowires affect both the mobility and the carrier density. Our data are helpful in understanding the sensing mechanism of the gas sensors.
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85.30.Tv Field effect devices
81.16.Nd Micro- and nanolithography
72.20.Fr Low-field transport and mobility; piezoresistance
68.43.Mn Adsorption kinetics
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.82.Fk Semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Rx Nanocrystalline materials

Electrical probe storage using Joule heating in phase change media

S. Gidon, O. Lemonnier, B. Rolland, O. Bichet, C. Dressler, and Y. Samson

Appl. Phys. Lett. 85, 6392 (2004); http://dx.doi.org/10.1063/1.1834718 (3 pages) | Cited 48 times

Online Publication Date: 17 December 2004

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We demonstrate the feasibility of ultrahigh-density probe recording in chalcogenide-based phase change media. The multilayer medium has been optimized with respect to electrical, thermal, and tribological requirements. Design of the multilayer takes into account the nonlinear dependence of the electrical properties of the phase change layer with respect to both electrical field and temperature. Memory dots as small as 15 nm have been written and read repeatably. Data storage density of greater than Tbit∕in.2 density has been successfully achieved.
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42.79.Vb Optical storage systems, optical disks
64.70.K- Solid-solid transitions
72.80.Ng Disordered solids
81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness

CdSe self-assembled quantum dots with ZnCdMgSe barriers emitting throughout the visible spectrum

M. Noemi Perez-Paz, Xuecong Zhou, Martin Muñoz, Hong Lu, Mohammad Sohel, Maria C. Tamargo, Fleumingue Jean-Mary, and Daniel L. Akins

Appl. Phys. Lett. 85, 6395 (2004); http://dx.doi.org/10.1063/1.1834993 (3 pages) | Cited 14 times

Online Publication Date: 17 December 2004

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Self-assembled quantum dots of CdSe with ZnCdMgSe barriers have been grown by molecular beam epitaxy on InP substrates. The optical and microstructural properties were investigated using photoluminescence (PL) and atomic force microscopy (AFM) measurements. Control and reproducibility of the quantum dot (QD) size leading to light emission throughout the entire visible spectrum range has been obtained by varying the CdSe deposition time. Longer CdSe deposition times result in a redshift of the PL peaks as a consequence of an increase of QD size. AFM studies demonstrate the presence of QDs in uncapped structures. A comparison of this QD system with CdSe∕ZnSe shows that not only the strain but also the chemical properties of the system play an important role in QD formation.
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81.07.Ta Quantum dots
81.05.Dz II-VI semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
78.67.Hc Quantum dots
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Et II-VI semiconductors
68.37.Ps Atomic force microscopy (AFM)
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