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3 Feb 2003

Volume 82, Issue 5, pp. 665-834

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 775 (2003); http://dx.doi.org/10.1063/1.1541091 (3 pages)

Sebastiaan van Dijken, Xin Jiang, and Stuart S. P. Parkin
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Mode splitting in photoluminescence spectra of a quantum-dot-embedded microcavity

C. Y. Hu, H. Z. Zheng, J. D. Zhang, H. Zhang, F. H. Yang, and Y. P. Zeng

Appl. Phys. Lett. 82, 665 (2003); http://dx.doi.org/10.1063/1.1542929 (3 pages) | Cited 14 times

Online Publication Date: 28 January 2003

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A microcavity structure, containing self-assembled InGaAs quantum dots, is studied by angle-resolved photoluminescence (PL) spectroscopy. A doublet with the splitting energy of 0.5–1.5 nm appears when the detection angle is larger than 35°. This doublet is identified as mode splitting (not the Rabi splitting) by polarization measurements. We find that it is the considerable deviation of the cavity-mode frequency from the central frequency of the stop band that makes the TE and TM cavity modes split more discernibly. The inhomogeneous broadening of quantum dots gives the TE and TM cavity modes a chance to show up simultaneously in the PL spectra. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
81.07.Ta Quantum dots
42.82.Gw Other integrated-optical elements and systems

Polymer-based surface-plasmon-polariton stripe waveguides at telecommunication wavelengths

Thomas Nikolajsen, Kristjan Leosson, Ildar Salakhutdinov, and Sergey I. Bozhevolnyi

Appl. Phys. Lett. 82, 668 (2003); http://dx.doi.org/10.1063/1.1542944 (3 pages) | Cited 147 times

Online Publication Date: 28 January 2003

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Long-range surface-plasmon-polariton (LR–SPP) waveguiding along thin gold stripes embedded in polymer is investigated in the wavelength range of 1510–1620 nm. LR–SPP intensity distributions at the output are measured for different stripe widths and thicknesses. Coupling loss of ∼0.5 dB is achieved when exciting the fundamental LR–SPP mode along 10-nm-thick stripes of 6–10 μm width with a polarization maintaining fiber. LR–SPP propagation loss of 6–8 dB/cm is estimated (at 1550 nm) and attributed to scattering from inhomogeneities of the metal stripe and polymer cladding. © 2003 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
42.82.Bq Design and performance testing of integrated-optical systems
42.70.Jk Polymers and organics
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Lasing properties of GaAs/(Al,Ga)As quantum-cascade lasers as a function of injector doping density

M. Giehler, R. Hey, H. Kostial, S. Cronenberg, T. Ohtsuka, L. Schrottke, and H. T. Grahn

Appl. Phys. Lett. 82, 671 (2003); http://dx.doi.org/10.1063/1.1541099 (3 pages) | Cited 32 times

Online Publication Date: 28 January 2003

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The lasing properties of GaAs/Al0.33Ga0.67As quantum-cascade lasers are investigated as a function of injector doping concentration ns between 2×1011 and 1×1012 cm−2 per period. Lasing is observed for ns ≥ 3.5×1011 cm−2, with optimal lasing properties (minimum of the threshold current and maximum of the modified characteristic temperature) for nopt ≈ 6×1011 cm−2. With increasing ns up to nopt, the lasing energy of 115 meV exhibits first a blueshift to 135 meV, followed by a redshift to 120 meV for higher doping levels. This shift of the lasing energy as a function of ns is discussed in terms of changes in the field distribution, occupation of additional levels above the upper laser level, and electron–electron interactions. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Integrated diffractive terahertz elements

Nikolay S. Stoyanov, T. Feurer, David W. Ward, and Keith A. Nelson

Appl. Phys. Lett. 82, 674 (2003); http://dx.doi.org/10.1063/1.1540241 (3 pages) | Cited 21 times

Online Publication Date: 28 January 2003

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Femtosecond laser machining with high-energy pulses is used for fabrication of diffractive elements in LiNbO3 crystalline samples. This permits terahertz generation, frequency dispersion, detection, and analysis within a single integrated platform that is well suited for applications in terahertz spectroscopy or signal processing. © 2003 American Institute of Physics.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
42.62.Cf Industrial applications
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
42.82.Gw Other integrated-optical elements and systems

Fundamental optical absorption edge of undoped tetragonal zirconium dioxide

C. R. Aita, E. E. Hoppe, and R. S. Sorbello

Appl. Phys. Lett. 82, 677 (2003); http://dx.doi.org/10.1063/1.1543234 (3 pages) | Cited 17 times

Online Publication Date: 28 January 2003

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The high-frequency optical absorption edge of pure tetragonal ZrO2, isolated in a ZrO2–Al2O3 nanolaminate film structure, was determined using transmission spectrophotometry. The functional dependence of the absorption coefficient on photon energy shows two interband transitions: an initial indirect transition at 5.22 eV (i.e., the band gap) followed by a direct transition at 5.87 eV. The edge structure is associated with O 2p→Zr 4d electron states and discussed in terms of ab initio calculations reported in the literature. © 2003 American Institute of Physics.
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78.40.Ha Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Ps Other inorganic compounds
78.66.Nk Insulators
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

High brightness laser source based on polarization coupling of two diode lasers with asymmetric feedback

Birgitte Thestrup, Mingjun Chi, Bjarne Sass, and Paul Michael Petersen

Appl. Phys. Lett. 82, 680 (2003); http://dx.doi.org/10.1063/1.1540218 (3 pages) | Cited 5 times

Online Publication Date: 28 January 2003

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In this letter, we show that polarization coupling and asymmetric diode-laser feedback can be used to combine two diode-laser beams with low spatial coherence into a single beam with high spatial coherence. The coupled laser source is based on two similar laser systems each consisting of a 1 μm×200 μm broad area laser diode applied with a specially designed feedback circuit. When operating at two times threshold, 50% of the freely running system output power is obtained in a single beam with an M2 beam quality factor of 1.6±0.1, whereas the M2 values of the two freely running diode lasers are 29±1 and 34±1, respectively. © 2003 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

White light-emitting diodes of GaN-based Sr2SiO4:Eu and the luminescent properties

Joung Kyu Park, Mi Ae Lim, Chang Hae Kim, Hee Dong Park, Joon Taik Park, and Se Young Choi

Appl. Phys. Lett. 82, 683 (2003); http://dx.doi.org/10.1063/1.1544055 (3 pages) | Cited 160 times

Online Publication Date: 28 January 2003

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We have synthesized a Eu2+-activated Sr2SiO4 yellow phosphor and investigated an attempt to develop white light-emitting diodes (LEDs) by combining it with a GaN blue LED chip. Two distinct emission bands from the GaN-based LED and the Sr2SiO4:Eu phosphor are clearly observed at 400 nm and at around 550 nm, respectively. These two emission bands combine to give a spectrum that appears white to the naked eye. Our results showed that GaN (400-nm chip)-based Sr2SiO4:Eu exhibits a better luminous efficiency than that of the industrially available product InGaN (460-nm chip)-based YAG:Ce. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.55.Hx Other solid inorganic materials
78.55.Cr III-V semiconductors

Temperature dependence of electron transfer in coupled quantum wells

Amlan Majumdar, K. K. Choi, J. L. Reno, L. P. Rokhinson, and D. C. Tsui

Appl. Phys. Lett. 82, 686 (2003); http://dx.doi.org/10.1063/1.1541094 (3 pages) | Cited 3 times

Online Publication Date: 28 January 2003

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We report on the temperature dependence of electron transfer between coupled quantum wells in a voltage tunable two-color quantum-well infrared photodetector (QWIP). The detection peak of this QWIP switches from 7.1 μm under positive bias to 8.6 μm under negative bias for temperatures T ⩽ 40 K. For T ≥ 40 K, the 7.1 μm peak is present under both bias polarities and increases significantly with T while the 8.6 μm peak decreases correspondingly. We determine the temperature dependence of electron densities in the two QWs from the detector absorption spectra that are deduced using corrugated QWIPs and find that electron transfer is efficient only when thermionic emission is not significant. © 2003 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.)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.30.De Semiconductor-device characterization, design, and modeling
73.20.At Surface states, band structure, electron density of states
73.21.Fg Quantum wells

Photon noise correlations in electrically coupled semiconductor lasers

P. M. Mayer, F. Rana, and R. J. Ram

Appl. Phys. Lett. 82, 689 (2003); http://dx.doi.org/10.1063/1.1539548 (3 pages) | Cited 3 times

Online Publication Date: 28 January 2003

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Measurements of the correlation between the photon noise of two semiconductor lasers sharing a bias circuit are presented. The photon noise of the electrically coupled lasers is found to be correlated by as much as 70%. The photon noise correlations are measured at low frequencies as a function of the bias current for lasers connected in series and in parallel, and for high and low impedance biases. The magnitude and sign of the noise correlations are consistent with theoretical expectations. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.30.De Semiconductor-device characterization, design, and modeling
42.60.Mi Dynamical laser instabilities; noisy laser behavior

Single-step fabrication of silicon-cone arrays

G. Wysocki, R. Denk, K. Piglmayer, N. Arnold, and D. Bäuerle

Appl. Phys. Lett. 82, 692 (2003); http://dx.doi.org/10.1063/1.1538347 (2 pages) | Cited 28 times

Online Publication Date: 28 January 2003

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A regular lattice of SiO2 microspheres on a quartz support is used as a microlens system for laser-induced single-step fabrication of arrays of silicon cones on a (100) Si surface. The experiments were performed with single-pulse 248 nm KrF laser radiation. © 2003 American Institute of Physics.
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81.16.Mk Laser-assisted deposition
42.79.Bh Lenses, prisms and mirrors
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Observation of a localized electron beam in large-area microwave discharge

Tibor Terebessy, Milan Širý, Masashi Kando, Jozef Kudela, and Dariusz Korzec

Appl. Phys. Lett. 82, 694 (2003); http://dx.doi.org/10.1063/1.1543250 (3 pages) | Cited 12 times

Online Publication Date: 28 January 2003

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We report on a localized high-density electron beam in large-area microwave discharges in argon. The beam is observed only for certain antenna configurations at gas pressures of about 50 mTorr, and it strongly modifies the radial plasma density profiles. The beam current near the quartz plate is estimated to be ≈140 mA/cm2. © 2003 American Institute of Physics.
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52.80.Pi High-frequency and RF discharges
52.50.Dg Plasma sources
52.25.-b Plasma properties
52.70.Ds Electric and magnetic measurements

Imaging femtosecond laser-induced electronic excitation in glass

Xianglei Mao, Samuel S. Mao, and Richard E. Russo

Appl. Phys. Lett. 82, 697 (2003); http://dx.doi.org/10.1063/1.1541947 (3 pages) | Cited 25 times

Online Publication Date: 28 January 2003

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While substantial progress has been achieved in understanding laser ablation on the nanosecond and picosecond time scales, it remains a considerable challenge to elucidate the underlying mechanisms during femtosecond laser material interactions. We present experimental observations of electronic excitation inside a wide band gap glass during single femtosecond laser pulse (100 fs, 800 nm) irradiation. Using a femtosecond time-resolved imaging technique, we measured the evolution of a laser-induced electronic plasma inside the glass and calculated the electron number density to be on the order of 1019 cm−3. © 2003 American Institute of Physics.
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79.20.Ds Laser-beam impact phenomena
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.47.-p Spectroscopy of solid state dynamics
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
61.43.Fs Glasses
52.38.Mf Laser ablation

Ion densities in an ac metal halide arc discharge

D. Karabourniotis and E. Drakakis

Appl. Phys. Lett. 82, 700 (2003); http://dx.doi.org/10.1063/1.1542684 (3 pages) | Cited 2 times

Online Publication Date: 28 January 2003

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The time-dependent density of mercury ions, sodium ions, and electrons is determined experimentally at the center of a high-pressure mercury discharge with sodium iodide as additive operated on alternating current within transparent quartz tube. The technique used is based on emission lines, and is independent of thermodynamic equilibrium assumptions. The results show that at sinusoidal low-frequency excitation the electrons come mainly from mercury ionization, the electron and mercury-ion densities vary strongly within the ac cycle, whereas the modulation of the sodium-ion density is significantly less pronounced. Results are also obtained assuming thermodynamic equilibrium and compared with the initial ones. © 2003 American Institute of Physics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.25.-b Plasma properties
52.25.Kn Thermodynamics of plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
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Lattice parameters of GaN layers grown on a-plane sapphire: Effect of in-plane strain anisotropy

V. Darakchieva, P. P. Paskov, T. Paskova, E. Valcheva, B. Monemar, and M. Heuken

Appl. Phys. Lett. 82, 703 (2003); http://dx.doi.org/10.1063/1.1542931 (3 pages) | Cited 14 times

Online Publication Date: 28 January 2003

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We have studied GaN films grown on a-plane sapphire by hydride vapor phase epitaxy and metalorganic vapor phase epitaxy. The in-plane lattice parameter was determined from sets of equivalent interplanar distances measured for six different directions in order to examine the effect of strain anisotropy. It is found that, in both types of films, the obtained six values of the in-plane lattice parameter can be grouped around two values. The strain anisotropy is estimated to have different value in the films grown by the two techniques and possible explanations are suggested. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
68.60.Bs Mechanical and acoustical properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Observation of light polarization-dependent structural changes in chalcogenide glasses

Gang Chen, Himanshu Jain, Miroslav Vlcek, Syed Khalid, Jun Li, David A. Drabold, and Stephen R. Elliott

Appl. Phys. Lett. 82, 706 (2003); http://dx.doi.org/10.1063/1.1541942 (3 pages) | Cited 33 times

Online Publication Date: 28 January 2003

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The atomistic origin of photoinduced vector (polarization-dependent) phenomena in As–Se films is determined by extended x-ray absorption fine structure with in situ exposure to polarized laser light. A vector structural change is observed directly for any material: there is an expansion of the nearest-neighbor distance around the Se atoms, the magnitude of which depends on the direction of light polarization; the effect around As atoms is relatively smaller. The results point to the origin of scalar as well as vector changes in properties, which either persist after the light is removed, or exist only when light is incident on the sample. © 2003 American Institute of Physics.
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61.43.Fs Glasses
68.55.-a Thin film structure and morphology
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
78.70.Dm X-ray absorption spectra

Elastic instability of nanomechanical beams

S. M. Carr and M. N. Wybourne

Appl. Phys. Lett. 82, 709 (2003); http://dx.doi.org/10.1063/1.1539924 (3 pages) | Cited 19 times

Online Publication Date: 28 January 2003

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We report on elastic instability of nanomechanical SiO2 beams with widths 20 nm<d<110 nm and lengths 5 μm<L<10 μm. The beams are fabricated from a silicon substrate with a 500 nm thermal oxide layer. After release from the silicon substrate by reactive ion etching the beams buckle due to the residual Si/SiO2 strain. The measured buckling displacements of the beams are compared with the predictions of nonlinear continuum elasticity theory. We observe a continuous buckling transition, qualitatively different than the critical transition predicted by Euler buckling theory, which we attribute to system asymmetry. Finally, we determine the effective potential energy of the fundamental buckling mode. © 2003 American Institute of Physics.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.07.Bc Nanocrystalline materials
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
61.46.-w Structure of nanoscale materials
46.32.+x Static buckling and instability

Compensation mechanisms in low-temperature-grown Ga1−xMnxAs investigated by scanning tunneling spectroscopy

G. Mahieu, P. Condette, B. Grandidier, J. P. Nys, G. Allan, D. Stiévenard, Ph. Ebert, H. Shimizu, and M. Tanaka

Appl. Phys. Lett. 82, 712 (2003); http://dx.doi.org/10.1063/1.1522821 (3 pages) | Cited 20 times

Online Publication Date: 28 January 2003

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Ga1−xMnxAs layers with Mn composition of up to 6.2% are investigated by cross-sectional scanning tunneling microscopy and spectroscopy. We identify in the tunneling spectra contributions from MnGa− acceptor states, compensating AsGa2+ donor states, and additional compensating donor states, which we suggest to be Mni2+ interstitials. On basis of the observed Fermi level shift and a charge carrier compensation analysis, we deduce the concentration of Mni2+ interstitials. Furthermore, scanning tunneling microscopy images suggest an inhomogeneous distribution of Mn dopant atoms. © 2003 American Institute of Physics.
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71.55.Eq III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.20.Nr Semiconductor compounds
61.72.J- Point defects and defect clusters
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.50.Pp Magnetic semiconductors

Atomic-scale strain field and In atom distribution in multiple quantum wells InGaN/GaN

K. Watanabe, N. Nakanishi, T. Yamazaki, J. R. Yang, S. Y. Huang, K. Inoke, J. T. Hsu, R. C. Tu, and M. Shiojiri

Appl. Phys. Lett. 82, 715 (2003); http://dx.doi.org/10.1063/1.1542930 (3 pages) | Cited 29 times

Online Publication Date: 28 January 2003

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We present an atomic-scale structural and compositional analysis of ultrathin layers in multiple quantum well InGaN/GaN, by high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). A high-quality HAADF STEM image processed by two-dimensional smoothing and deconvolution provides precise atomic-column positions and clear contrast, thereby allowing us to map the strain field and In atom distribution in successive GaN and InGaN layers. We conclude from these maps that there is a local fluctuation of In atoms in the InGaN layers and the In-rich regions, considered as quantum dots, cause large expansion only along the [0001] direction. © 2003 American Institute of Physics.
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68.65.Fg Quantum wells
68.37.Lp Transmission electron microscopy (TEM)
07.05.Pj Image processing

Formation and structure of inverted hexagonal pyramid defects in multiple quantum wells InGaN/GaN

K. Watanabe, J. R. Yang, S. Y. Huang, K. Inoke, J. T. Hsu, R. C. Tu, T. Yamazaki, N. Nakanishi, and M. Shiojiri

Appl. Phys. Lett. 82, 718 (2003); http://dx.doi.org/10.1063/1.1542683 (3 pages) | Cited 27 times

Online Publication Date: 28 January 2003

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We have determined the structure of inverted hexagonal pyramid defects (IHPs) in multiple quantum wells InGaN/GaN by high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM). HAADF STEM images reveal definitely that the IHP nucleates at a threading dislocation and grows in the form of a thin six-walled structure with InGaN/GaN {10math1} layers. It has been found that IHPs start even at In-rich dots under adverse growth conditions. © 2003 American Institute of Physics.
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68.65.Fg Quantum wells
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Lp Transmission electron microscopy (TEM)
61.72.Lk Linear defects: dislocations, disclinations

Random anisotropy and domain-wall pinning process in the magnetic properties of rapidly quenched Nd60Fe30Al10

A. Bracchi, K. Samwer, S. Schneider, and J. F. Löffler

Appl. Phys. Lett. 82, 721 (2003); http://dx.doi.org/10.1063/1.1544430 (3 pages) | Cited 13 times

Online Publication Date: 28 January 2003

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The magnetic properties and microstructure of glassy Nd60Fe30Al10 splat-quenched samples have been investigated by small-angle neutron scattering, Mössbauer spectroscopy, and vibrating sample magnetometry. The presence of chemical inhomogeneities in the amorphous sample is evidenced by small-angle neutron scattering which indicates a complex network of atom clusters with an average diameter of 15 nm. These results are confirmed by the magnetization measurements which show the coexistence of two magnetic phases with different ordering temperatures and indicate phases separation in rapidly quenched Nd60Fe30Al10 samples. Magnetic neutron scattering analysis reveals magnetic correlation volumes in the ferromagnetic phase of about 34 nm in diameter. Random anisotropy and a domain-wall pinning process within the two phases are discussed to explain the magnetic properties of amorphous Nd60Fe30Al10. © 2003 American Institute of Physics.
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75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure
75.50.Kj Amorphous and quasicrystalline magnetic materials
76.80.+y Mössbauer effect; other γ-ray spectroscopy
61.43.Fs Glasses
81.05.Kf Glasses (including metallic glasses)
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
64.75.-g Phase equilibria
75.50.Bb Fe and its alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Vv High coercivity materials
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Plasmons of a two-dimensional electron gas in the presence of spin orbit interaction

W. Xu

Appl. Phys. Lett. 82, 724 (2003); http://dx.doi.org/10.1063/1.1541098 (3 pages) | Cited 26 times

Online Publication Date: 28 January 2003

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A theoretical study of the collective excitation associated with plasmon modes is presented for a two-dimensional electron gas in the presence of spin orbit (SO) interaction induced by the Rashba effect. In such a case, the plasmon excitation can be achieved via intra- and inter-SO electronic transitions. As a result, three branches of the plasmon oscillations can be observed. It is found that inter-SO plasmons depend strongly on sample parameters and, at a long-wavelength limit, are optic-like, in contrast to intra-SO ones. The interesting features of these plasmon modes are examined. © 2003 American Institute of Physics.
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73.21.Fg Quantum wells
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

SmxNd1−xNiO3 thin-film solid solutions with tunable metal–insulator transition synthesized by alternate-target pulsed-laser deposition

Andrea Ambrosini and Jean-François Hamet

Appl. Phys. Lett. 82, 727 (2003); http://dx.doi.org/10.1063/1.1541116 (3 pages) | Cited 21 times

Online Publication Date: 28 January 2003

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Thin-film solid solutions of SmxNd1−xNiO3 were synthesized on NdGaO3 substrates by pulsed-laser deposition using alternating NdNiO3 and SmNiO3 targets. The films were characterized by x-ray diffraction and variable-temperature four-probe conductivity measurements. The films grow in the {100}pseudocubic direction. There is a nearly linear increase of the metal–insulator transition from 199 K for x = 0 to 378 K for x = 1, with the composition corresponding to x = 0.6 displaying a transition near room temperature. © 2003 American Institute of Physics.
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72.60.+g Mixed conductivity and conductivity transitions
81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology

Spin wave resonance in Ga1−xMnxAs

S. T. B. Goennenwein, T. Graf, T. Wassner, M. S. Brandt, M. Stutzmann, J. B. Philipp, R. Gross, M. Krieger, K. Zürn, P. Ziemann, A. Koeder, S. Frank, W. Schoch, and A. Waag

Appl. Phys. Lett. 82, 730 (2003); http://dx.doi.org/10.1063/1.1539550 (3 pages) | Cited 45 times

Online Publication Date: 28 January 2003

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We report ferromagnetic resonance experiments on Ga1−xMnxAs thin films. For the dc magnetic field perpendicular to the sample plane, we observe up to eight distinct resonances, which we attribute to spin wave modes. To account for the spacing of the resonances, we infer a linear gradient in the magnetic properties, which is ascribed to a linear variation of the uniaxial magnetic anisotropy with film thickness. Values of D = (1±0.4)×10−9 Oe cm2 for the spin stiffness and JMnMn ≈ 1 meV for the exchange integral between Mn spins are obtained. © 2003 American Institute of Physics.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.30.Gw Magnetic anisotropy
75.30.Et Exchange and superexchange interactions
75.70.Ak Magnetic properties of monolayers and thin films

ZnO-based transparent thin-film transistors

R. L. Hoffman, B. J. Norris, and J. F. Wager

Appl. Phys. Lett. 82, 733 (2003); http://dx.doi.org/10.1063/1.1542677 (3 pages) | Cited 483 times

Online Publication Date: 28 January 2003

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Highly transparent ZnO-based thin-film transistors (TFTs) are fabricated with optical transmission (including substrate) of ∼75% in the visible portion of the electromagnetic spectrum. Current–voltage measurements indicate n-channel, enhancement-mode TFT operation with excellent drain current saturation and a drain current on-to-off ratio of ∼ 107. Threshold voltages and channel mobilities of devices fabricated to date range from ∼10 to 20 V and ∼0.3 to 2.5 cm2/V s, respectively. Exposure to ambient light has little to no observable effect on the drain current. In contrast, exposure to intense ultraviolet radiation results in persistent photoconductivity, associated with the creation of electron-hole pairs by ultraviolet photons with energies greater than the ZnO band gap. Light sensitivity is reduced by decreasing the ZnO channel layer thickness. One attractive application for transparent TFTs involves their use as select-transistors in each pixel of an active-matrix liquid-crystal display. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
73.50.Pz Photoconduction and photovoltaic effects
72.20.Fr Low-field transport and mobility; piezoresistance
72.40.+w Photoconduction and photovoltaic effects

In situ Mg surface treatment of p-type GaN grown by ammonia-molecular-beam epitaxy for efficient Ohmic contact formation

H. Tang, J. A. Bardwell, J. B. Webb, S. Rolfe, Y. Liu, S. Moisa, and I. Sproule

Appl. Phys. Lett. 82, 736 (2003); http://dx.doi.org/10.1063/1.1543233 (3 pages) | Cited 10 times

Online Publication Date: 28 January 2003

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The pronounced effect of in situ Mg surface treatment of p-type GaN grown by ammonia-molecular-beam epitaxy on Ohmic contact formation is reported. The surface of the Mg-doped p-type GaN layer was held at the growth temperature following the growth, and exposed to a Mg beam under a NH3 flow for 15 min. With such a treatment, a specific contact resistance in the low 10−4 Ω cm2 was obtained with as-deposited Ni/Au contacts and without any ex situ treatment. In contrast, contacts on similar p-type layers without such an in situ treatment were highly rectifying even after annealing. A surface Fermi level shift as a result of the in situ treatment was observed by x-ray photoemission studies, and is ascribed, together with the high surface doping concentration, to be the mechanisms behind the effective Ohmic contact formation. © 2003 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
81.65.-b Surface treatments
73.40.Cg Contact resistance, contact potential
73.20.At Surface states, band structure, electron density of states
61.72.Cc Kinetics of defect formation and annealing
79.60.Jv Interfaces; heterostructures; nanostructures
61.72.S- Impurities in crystals
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