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2 Jan 2006

Volume 88, Issue 1, Articles (01xxxx)

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Appl. Phys. Lett. 88, 011112 (2006); http://dx.doi.org/10.1063/1.2161387 (3 pages)

Yoshinori Tanaka, Takashi Asano, Ranko Hatsuta, and Susumu Noda
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Nonradiative recombination effect on photoluminescence decay dynamics in GaInNAs/GaAs quantum wells

Z. Sun, Z. Y. Xu, X. D. Yang, B. Q. Sun, Y. Ji, S. Y. Zhang, H. Q. Ni, and Z. C. Niu

Appl. Phys. Lett. 88, 011912 (2006); http://dx.doi.org/10.1063/1.2161071 (3 pages) | Cited 4 times

Online Publication Date: 4 January 2006

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The influence of nonradiative recombination on the photoluminescence (PL) decay dynamics in GaInNAs/GaAs quantum wells is studied by time-resolved photoluminescence under various excitation intensities. It is found that the PL decay process strongly depends on the excitation intensity. In particular, under the moderate excitation levels the PL decay curves exhibit unusual nonexponential behavior and show a convex shape. By introducing a new parameter of the effective concentration of nonradiative recombination centers into a rate equation, the observed results are well simulated. The cw PL data further demonstrate the nonradiative recombination effect on the optical properties of GaInNAs/GaAs quantum wells.
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78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.67.De Quantum wells

Adatom-assisted structural transformations of fullerenes

In-Ho Lee, Sukky Jun, Hanchul Kim, Sung Youb Kim, and Youngmin Lee

Appl. Phys. Lett. 88, 011913 (2006); http://dx.doi.org/10.1063/1.2161175 (3 pages) | Cited 10 times

Online Publication Date: 4 January 2006

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Microscopic mechanism of autocatalytic structural transformations of fullerenes is investigated by the action-derived molecular dynamics. Dynamic pathways and the corresponding activation energies are obtained for the Stone-Wales transformation in fullerene and the fullerene coalescence, under the presence of extra carbon atoms. The adatom-assisted Stone-Wales transformation is proved to be a highly probable process unit for the structural transformations and annealing treatments of carbon-based graphitic networks. The complex processes of adatom-assisted fullerene coalescence, yielding very low activation energies, are presented.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
64.70.K- Solid-solid transitions
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
61.43.Bn Structural modeling: serial-addition models, computer simulation
81.40.Gh Other heat and thermomechanical treatments

Photoluminescence of Ge(Si) self-assembled islands embedded in a tensile-strained Si layer

M. V. Shaleev, A. V. Novikov, A. N. Yablonskiy, Y. N. Drozdov, D. N. Lobanov, Z. F. Krasilnik, and O. A. Kuznetsov

Appl. Phys. Lett. 88, 011914 (2006); http://dx.doi.org/10.1063/1.2158506 (3 pages) | Cited 7 times

Online Publication Date: 5 January 2006

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We report photoluminescence (PL) studies of Ge(Si) self-assembled islands embedded into a tensile-strained Si layer grown on smooth relaxed Si0.75Ge0.25/Si(001) buffer layers subjected to chemical-mechanical polishing. The intense PL from Ge(Si) islands embedded into a strained Si layer compared to the PL from islands grown on unstrained Si(001) is associated with efficient confinement of electrons in a strained Si layer on the heterojunction with islands. The observed dependence of the island PL peak position on thickness of strained Si layer confirms the validity of the model for real-space indirect optical transition between electrons confined in the strained Si layer, and holes localized in islands.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.55.Hx Other solid inorganic materials

Atomistic modeling of surface alloy ordering and segregation in the Fe–Pt system

Guillermo Bozzolo, Rosa Alejandra Lukaszew, and Jorge E. Garcés

Appl. Phys. Lett. 88, 011915 (2006); http://dx.doi.org/10.1063/1.2158515 (3 pages) | Cited 6 times

Online Publication Date: 5 January 2006

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A unified description of Pt segregation in Fe–Pt alloys and alloy ordering after Fe deposition on a Pt substrate is provided. Atomistic modeling using the Bozzolo–Ferrante–Smith quantum approximate method for alloys explains the mechanisms leading to full Pt segregation in the first case and a stable mixed Fe–Pt surface with subsurface ordering in the second.
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64.75.-g Phase equilibria
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling

Effect of Al∕N flux ratio during nucleation layer growth on the microstructure of GaN films grown by molecular-beam epitaxy

Lin Zhou, David J. Smith, D. F. Storm, D. S. Katzer, S. C. Binari, and B. V. Shanabrook

Appl. Phys. Lett. 88, 011916 (2006); http://dx.doi.org/10.1063/1.2162670 (3 pages) | Cited 4 times

Online Publication Date: 5 January 2006

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The microstructure of AlN nucleation layers grown on semi-insulating 4H-SiC substrates by plasma-assisted molecular beam epitaxy has a major effect on subsequent GaN and AlGaN∕GaN film quality and electronic properties. Characterization by transmission electron microscopy shows that the morphology of the GaN films is critically dependent on the Al to active nitrogen flux ratio used during nucleation layer growth. Structures grown with Al∕N flux ratios slightly above approximately 0.98 have many basal-plane stacking faults in the AlN nucleation layer, the GaN∕AlN interfaces are wavy and ill defined, and regions of cubic GaN exist close to the GaN∕AlN interfaces. In comparison, for structures grown with lower Al∕N flux ratios, the AlN nucleation layers have no stacking faults and the GaN∕AlN interfaces are sharp. The impact of these changes in microstructure on the electron Hall mobility and buffer leakage are discussed.
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68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
68.37.Lp Transmission electron microscopy (TEM)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Photorefractive nematic liquid crystals with gain of constant sign under alternating voltage

Tero Kesti and Attilio Golemme

Appl. Phys. Lett. 88, 011917 (2006); http://dx.doi.org/10.1063/1.2159569 (3 pages) | Cited 4 times

Online Publication Date: 5 January 2006

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Two-beam coupling gain of constant sign was observed in hybrid planar/homeotropic nematic cells under a nonbiased square-wave ac field. Charge photogeneration was induced by using one layer of photoconducting polymer. With writing beams of equal intensities, gains up to 6% were observed in ∼ 10 μm thick samples when the amplitude of the applied field was of the order of 1 V μm−1 at 10 Hz. The gain decreased gradually when the frequency was increased, vanishing above 100 Hz.
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42.70.Df Liquid crystals
61.30.-v Liquid crystals
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Gi Light-sensitive materials
42.70.Jk Polymers and organics

Role of intrinsic defects in the electronic and optical properties of α-HgI2

F. Ayres, L. V. C. Assali, W. V. M. Machado, and J. F. Justo

Appl. Phys. Lett. 88, 011918 (2006); http://dx.doi.org/10.1063/1.2159573 (3 pages) | Cited 6 times

Online Publication Date: 5 January 2006

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We investigated the role of intrinsic defects in the electronic and optical properties of mercuric iodide using ab initio methods. The calculations were performed using the total energy all electron methodology, considering full atomic relaxation. We computed the band structure, spin, formation and transition energies, and the dielectric function of isolated iodine and mercury vacancies in several charge states. Our results were compared to available experimental data on photoluminescence and photoplasticity in HgI2. We propose a microscopic model which can explain most of the data on those luminescent centers, unifying experimental results which suggested conflicting conclusions.
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61.72.J- Point defects and defect clusters
71.15.Nc Total energy and cohesive energy calculations
71.20.Ps Other inorganic compounds
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Hx Other solid inorganic materials

Radiative recombination of GaInNP alloys lattice matched to GaAs

M. Izadifard, J. P. Bergman, W. M. Chen, I. A. Buyanova, Y. G. Hong, and C. W. Tu

Appl. Phys. Lett. 88, 011919 (2006); http://dx.doi.org/10.1063/1.2161118 (3 pages) | Cited 7 times

Online Publication Date: 5 January 2006

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cw- and time-resolved photoluminescence (PL) spectroscopy is employed to evaluate dominant mechanisms for light emission in GayIn1−yNxP1−x alloys grown by gas source molecular-beam epitaxy on GaAs substrates. Different from other direct band gap dilute nitrides, the low temperature PL emission was shown to be largely attributed to radiative transitions involving spatially separated localized electron-hole pairs. The observed charge separation is tentatively attributed to the long range CuPt ordering promoted by the presence of nitrogen.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.47.-p Spectroscopy of solid state dynamics

Decoration of buried surfaces in Si detected by positron annihilation spectroscopy

R. S. Brusa, C. Macchi, S. Mariazzi, G. P. Karwasz, W. Egger, P. Sperr, and G. Kögel

Appl. Phys. Lett. 88, 011920 (2006); http://dx.doi.org/10.1063/1.2162691 (3 pages) | Cited 4 times

Online Publication Date: 6 January 2006

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The terminations of buried surfaces of two different cavity types (nano- and microcavities) produced in the same He+–H+ co-implanted p-type Si (100) sample annealed at 900 °C, are studied and characterized by positron annihilation spectroscopy. The characterization was carried out by means of three complementary positron techniques: Doppler broadening and coincidence-Doppler broadening spectroscopy with a continuous slow positron beam, and lifetime spectroscopy with a pulsed slow positron beam. It was found that the nanocavities have a pristine surface of Si, while the surfaces of the microcavities, formed below protruding blisters, are oxygen decorated. This case study opens the interesting use of the positron spectroscopy tool in the topical subject of empty space for microelectronics applications.
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61.72.J- Point defects and defect clusters
61.72.Qq Microscopic defects (voids, inclusions, etc.)
71.60.+z Positron states
78.70.Bj Positron annihilation

Photoluminescence and cathodoluminescence analyses of GaN powder doped with Eu

Huaqiang Wu, Carl B. Poitras, Michal Lipson, Michael G. Spencer, Janet Hunting, and Francis J. DiSalvo

Appl. Phys. Lett. 88, 011921 (2006); http://dx.doi.org/10.1063/1.2162667 (3 pages) | Cited 15 times

Online Publication Date: 6 January 2006

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A high yield process to produce gallium nitride (GaN) powder doped with europium (Eu) is presented. Eu is in situ incorporated into GaN powder through the reaction between a molten alloy of Ga and Eu along with NH3 at 1000 °C using Bi as a wetting agent. This procedure provides a method to produce a GaN:Eu phosphor with high yield and low cost. Room temperature photoluminescence (PL) measurements are studied on GaN:Eu powders with different Eu concentrations. The maximum PL intensity is obtained at a Eu concentration of 1.25 at. %. Cathodoluminescence spectra at room temperature exhibit many detailed transitions in the 530–630 nm range.
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78.55.Cr III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
61.72.uj III-V and II-VI semiconductors
81.05.Ea III-V semiconductors

Energy of excitons in CuInS2 single crystals

M. V. Yakushev, A. V. Mudryi, I. V. Victorov, J. Krustok, and E. Mellikov

Appl. Phys. Lett. 88, 011922 (2006); http://dx.doi.org/10.1063/1.2152114 (3 pages) | Cited 9 times

Online Publication Date: 6 January 2006

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High-quality single crystals of CuInS2, grown by the traveling heater method in an indium solvent, were characterized using photoluminescence (PL) and reflectance (RF) at temperatures from 4.2 to 300 K. A number of well-resolved sharp excitonic peaks have been observed in the near-band-edge region of the PL and RF spectra at 4.2 K. The lines at 1.536 and 1.554 eV in the RF spectra were associated with A and (B,C) free-excitonic transitions, respectively. In the PL spectra the A exciton revealed a well-resolved splitting into two peaks at 1.5348 and 1.5361 eV assigned to the lower and upper branches of exciton polariton, respectively. Other sharp lines were assigned to excitons bound at shallow impurities. The experimental temperature variation of the band gap was analyzed using the Bose–Einstein model. Two deeper bands in the PL spectra were identified as free-to-bound optical transitions followed by phonon replicas.
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71.35.-y Excitons and related phenomena
78.55.Hx Other solid inorganic materials
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
71.20.Nr Semiconductor compounds

Optical and structural changes of silver nanoparticles during photochromic transformation

C. Dahmen, A. N. Sprafke, H. Dieker, M. Wuttig, and G. von Plessen

Appl. Phys. Lett. 88, 011923 (2006); http://dx.doi.org/10.1063/1.2163268 (3 pages) | Cited 15 times

Online Publication Date: 6 January 2006

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Silver nanoparticles embedded in titanium oxide change their color upon irradiation with visible light. Here we investigate the origin of this photochromic effect. The color change is found to result chiefly from a reduction of the optical extinction peak of the photoexcited particle plasmons. From a comparison with x-ray diffraction experiments, we conclude that this reduction is caused by a photoinduced decrease of the mean size of the silver nanocrystals.
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81.07.Bc Nanocrystalline materials
42.70.−a
81.05.Bx Metals, semimetals, and alloys
81.15.Cd Deposition by sputtering
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.16.−c
61.46.−w
81.40.Gh Other heat and thermomechanical treatments
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.82.Rx Nanocrystalline materials
61.82.Bg Metals and alloys
78.68.+m Optical properties of surfaces
78.20.Jq Electro-optical effects
68.37.Lp Transmission electron microscopy (TEM)
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The structure of the SiO2/Si(100) interface from a restraint-free search using computer simulations

Dominik Fischer, Alessandro Curioni, Salomon Billeter, and Wanda Andreoni

Appl. Phys. Lett. 88, 012101 (2006); http://dx.doi.org/10.1063/1.2158520 (3 pages)

Online Publication Date: 3 January 2006

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The structure of the interface between SiO2 and Si(100) is investigated using the replica-exchange method driven by classical molecular dynamics simulations based on ab initio-derived interatomic potentials. Abrupt interfaces are shown to be unstable, whereas a substoichiometric oxide forms at the transition between the two materials that exhibits Si atoms in all three intermediate oxidation states, in agreement with experiment. A number of physical characteristics are found to be consistent with experimental data, including the distribution of Si atoms with different oxidation states, the increase in atom density and the stability of a pseudo-cristobalite pattern at the interface as well as the presence of Si–O–Si bridge bonds between the substrate and the suboxide.
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68.35.Ct Interface structure and roughness
81.65.Mq Oxidation
61.50.Lt Crystal binding; cohesive energy

Enhanced solid-state thermionic emission in nonplanar heterostructures

Zhixi Bian and Ali Shakouri

Appl. Phys. Lett. 88, 012102 (2006); http://dx.doi.org/10.1063/1.2159574 (3 pages) | Cited 10 times

Online Publication Date: 3 January 2006

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Conservation of transverse momentum during thermionic emission from planar structures is a key factor limiting the number of hot electrons emitted and the efficiency of solid-state thermionic energy conversion devices. In this letter, electron emission from nonplanar potential barrier structures is analyzed using a Monte Carlo transport model. Compared to the planar structures, nonplanar tall barriers can achieve much larger emission currents. Although the average energy of the transmitted electrons drops a little, the thermoelectric figure of merit can be increased with a nonplanar barrier structure. The improvement of the thermoelectric properties is attributed to the combined effects of increased effective interface area and reduced probability of total internal reflection at heterostructure interfaces.
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85.80.Fi Thermoelectric devices
79.40.+z Thermionic emission
84.60.Ny Thermionic conversion
72.20.Pa Thermoelectric and thermomagnetic effects
72.20.Ht High-field and nonlinear effects

Transparent indium zinc oxide top cathode prepared by plasma damage-free sputtering for top-emitting organic light-emitting diodes

Han-Ki Kim, Kyu-Sung Lee, and J. H. Kwon

Appl. Phys. Lett. 88, 012103 (2006); http://dx.doi.org/10.1063/1.2159577 (3 pages) | Cited 41 times

Online Publication Date: 3 January 2006

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We report on plasma damage-free sputtering of an indium zinc oxide (IZO) top cathode layer for top-emitting organic light-emitting diodes (TOLEDs) by using a box cathode sputtering (BCS) technique. A sheet resistance of 42.6 Ω/cm and average transmittance above 88% in visible range were obtained even in IZO layers deposited by BCS at room temperature. The TOLED with the IZO top cathode layer shows electrical characteristics and lifetime comparable to a TOLED with only thermally evaporated Mg–Ag cathode. In particular, it is shown that the TOLED with the IZO top cathode film shows very low leakage current density of 1×10−5 mA cm2 at reverse bias of −6 V. This suggests that there is no plasma damage caused by the bombardment of energetic particles during IZO sputtering using the BCS system.
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82.45.Fk Electrodes
73.61.Ng Insulators
78.66.Nk Insulators
81.15.Cd Deposition by sputtering
52.77.-j Plasma applications
85.60.Jb Light-emitting devices

Improved thermally stable ohmic contacts on p-GaN based on W2B

L. Voss, Rohit Khanna, S. J. Pearton, F. Ren, and I. Kravchenko

Appl. Phys. Lett. 88, 012104 (2006); http://dx.doi.org/10.1063/1.2161806 (3 pages) | Cited 6 times

Online Publication Date: 4 January 2006

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The annealing temperature (25–800 °C) dependence of ohmic contact characteristics on p-GaN using a W2B/Ti/Au metallization scheme deposited by sputtering are reported. The contacts are rectifying in the as-deposited condition but become ohmic for annealing at ≥ 500 °C. A minimum specific contact resistivity of 1.7×10−3 Ω cm−2 was obtained after annealing at 800 °C for 60 s. Higher annealing temperatures produced sharp increases in the resistivity of the GaN and irreproducible contact properties. However, the contact morphology was similar over the entire annealing range used here. Auger electron spectroscopy profiling showed the onset of Ti out-diffusion through the Au at 500 °C. By 800 °C the Ti was almost completely removed to the surface, where it became oxidized. These boride-based contacts have superior thermal stability to the more common Ni/Au, whose morphology degrades significantly above 500 °C.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
68.47.Fg Semiconductor surfaces
61.72.Cc Kinetics of defect formation and annealing
79.20.Fv Electron impact: Auger emission
81.65.Mq Oxidation

Fermi-level depinning for low-barrier Schottky source/drain transistors

Daniel Connelly, Carl Faulkner, P. A. Clifton, and D. E. Grupp

Appl. Phys. Lett. 88, 012105 (2006); http://dx.doi.org/10.1063/1.2159096 (3 pages) | Cited 37 times

Online Publication Date: 4 January 2006

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By imposing an ultrathin insulator between low-work function metals and silicon, the Schottky barrier of the junction can be substantially reduced, decreasing junction resistance. With this approach, low-Schottky-barrier metal source/drain (S/D) transistors with Mg and Yb as S/D metals are demonstrated.
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85.30.Tv Field effect devices
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts

Effect of current crowding on void propagation at the interface between intermetallic compound and solder in flip chip solder joints

Lingyun Zhang, Shengquan Ou, Joanne Huang, K. N. Tu, Stephen Gee, and Luu Nguyen

Appl. Phys. Lett. 88, 012106 (2006); http://dx.doi.org/10.1063/1.2158702 (3 pages) | Cited 46 times

Online Publication Date: 4 January 2006

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We propose a kinetic model to describe a pancake-type void propagation in flip chip solder joints due to current crowding in electromigration. The divergence of the vacancy fluxes at the interface between the solder and Cu6Sn5 leads to void formation and propagation along the interface between them. Based on the continuity condition, the void growth velocity is calculated. The theoretical calculations are in reasonable agreement with the experimental results.
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61.72.Qq Microscopic defects (voids, inclusions, etc.)
66.30.Qa Electromigration
66.30.Lw Diffusion of other defects

Conductance quantization and the 0.7×2e2/h conductance anomaly in one-dimensional hole systems

R. Danneau, W. R. Clarke, O. Klochan, A. P. Micolich, A. R. Hamilton, M. Y. Simmons, M. Pepper, and D. A. Ritchie

Appl. Phys. Lett. 88, 012107 (2006); http://dx.doi.org/10.1063/1.2161814 (3 pages) | Cited 28 times

Online Publication Date: 5 January 2006

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We have studied ballistic transport in a one-dimensional (1D) channel formed using surface gate techniques on a back-gated, high-mobility, bilayer two-dimensional hole system. At millikelvin temperatures, robust conductance quantization is observed in the quantum wire formed in the top layer of the bilayer system, without the gate instabilities that have hampered previous studies of 1D hole systems. Using source drain bias spectroscopy, we have measured the 1D subband spacings, which are 5–10 times smaller than in comparable GaAs electron systems, but 2–3 times larger than in previous studies of 1D holes. We also report the first observation of the anomalous conductance plateau at G = 0.7×2e2/h in a 1D hole system.
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73.21.Hb Quantum wires
73.63.Nm Quantum wires
81.07.Vb Quantum wires
72.15.Nj Collective modes (e.g., in one-dimensional conductors)
73.23.Ad Ballistic transport
73.20.At Surface states, band structure, electron density of states

Visible spectrum light-emitting transistors

F. Dixon, R. Chan, G. Walter, N. Holonyak, M. Feng, X. B. Zhang, J. H. Ryou, and R. D. Dupuis

Appl. Phys. Lett. 88, 012108 (2006); http://dx.doi.org/10.1063/1.2158704 (3 pages) | Cited 4 times

Online Publication Date: 5 January 2006

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Visible radiative recombination in the base layer of AlGaInP/InGaP light-emitting transistors (LETs) is reported. For this form of transistor, which previously has not existed, and with an emitter area of 100×100 μm2, we demonstrate a current gain β (β ≡ ΔIC/ΔIB) of 3.5 for the device operating in the common-emitter configuration. The LET In0.49Ga0.51P base recombination radiation is centered in the visible at λ = 650 nm (red emission).
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85.60.Jb Light-emitting devices
85.30.Tv Field effect devices

Comparison of Ti/Al/Pt/Au and Ti/Au Ohmic contacts on n-type ZnCdO

Jau-Jiun Chen, Soohwan Jang, F. Ren, S. Rawal, Yuanjie Li, Hyun-Sik Kim, D. P. Norton, S. J. Pearton, and A. Osinsky

Appl. Phys. Lett. 88, 012109 (2006); http://dx.doi.org/10.1063/1.2161927 (3 pages) | Cited 1 time

Online Publication Date: 5 January 2006

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A comparison of Ti/Au and Ti/Al/Pt/Au Ohmic contacts on n-type Zn0.05Cd0.95O layers grown on ZnO buffer layers on GaN/sapphire templates showed a minimum contact resistivity of 2.3×10−4 Ω cm2 at 500 °C anneal temperature for Ti/Al/Pt/Au and 1.6×10−4 Ω cm2 at 450 °C for Ti/Al. The morphology of the Ti/Al/Pt/Au contacts showed much better thermal stability and remained smooth until at least 450 °C, whereas the Ti/Au contacts show a reacted appearance after 350 °C anneals. Auger electron spectroscopy depth profiling of the contact schemes as a function of anneal temperature suggests that the formation of TiOx phases that induce oxygen vacancies in the ZnCdO are responsible for the improved contact resistance after annealing in both types of metal schemes.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
61.72.Cc Kinetics of defect formation and annealing
68.35.Ct Interface structure and roughness
79.20.Fv Electron impact: Auger emission
61.72.J- Point defects and defect clusters

Tuning the inherent magnetoresistance of InSb thin films

Tong Zhang, J. J. Harris, W. R. Branford, Y. V. Bugoslavsky, S. K. Clowes, L. F. Cohen, A. Husmann, and S. A. Solin

Appl. Phys. Lett. 88, 012110 (2006); http://dx.doi.org/10.1063/1.2162666 (3 pages) | Cited 3 times

Online Publication Date: 6 January 2006

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We have investigated the 300 K inherent magnetoresistance of undoped InSb epilayers grown on GaAs(001) by molecular-beam epitaxy. The magnetoresistance of these films can be described well using a simplified model that incorporates gradation of properties away from the InSb/GaAs interface and the interplay between conduction and impurity bands. Although there is no significant intrinsic contribution in InSb bulk crystalline (001) materials due to its isotropic Fermi surface and mobility tensor, the linear and quadratic terms in the magnetoresistance as well as the overall magnitude can be tuned by varying the film thickness from 100 to 2000 nm.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.05.Ea III-V semiconductors
73.20.At Surface states, band structure, electron density of states
73.61.Ey III-V semiconductors
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Nonlinear characteristics of a superconducting receiver

M. I. Salkola

Appl. Phys. Lett. 88, 012501 (2006); http://dx.doi.org/10.1063/1.2159101 (3 pages) | Cited 3 times

Online Publication Date: 3 January 2006

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Superconducting filter technology enables highly selective and sensitive base-station receivers for wireless communications. The performance analysis of a superconducting receiver, which is inherently a nonlinear system, is simplified by introducing the concept of an effective frequency response. With this approach, superconducting filters are shown to be ideal for applications that require steep rejection at the edges of a communication band. In contrast, filter nonlinearities decrease the order of the effective frequency response of a cascaded bandpass filter, thus reducing its stop-band rejection.
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84.40.Ua Telecommunications: signal transmission and processing; communication satellites
84.30.Vn Filters
85.25.-j Superconducting devices

Significant improvement of activation energy in MgB2/Mg2Si multilayer films

Y. Zhao, S. X. Dou, M. Ionescu, and P. Munroe

Appl. Phys. Lett. 88, 012502 (2006); http://dx.doi.org/10.1063/1.2159572 (3 pages) | Cited 5 times

Online Publication Date: 3 January 2006

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We obtained a MgB2/Mg2Si multilayer structure by sequentially switching a stoichiometric MgB2 target and a Si target during off-axis pulsed-laser deposition. The transmission-electron-microscopic cross-sectional image of the resulting film exhibits a layered structure with each MgB2 layer being 40–50 nm thick and the Mg2Si interlayers about 5 nm thick. A clearly enhanced anisotropy in the irreversibility lines and the vortex activation energy was observed. Pinning and the flux flow activation energy are significantly increased in parallel applied fields.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.78.Fk Multilayers, superlattices, heterostructures
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)

Acoustomagnetic pulse experiments in LiNbO3/Mn12 hybrids

J. M. Hernandez, P. V. Santos, F. Macià, A. García-Santiago, and J. Tejada

Appl. Phys. Lett. 88, 012503 (2006); http://dx.doi.org/10.1063/1.2158705 (3 pages) | Cited 4 times

Online Publication Date: 3 January 2006

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Show Abstract
We report here on the influence of surface acoustic waves (SAWs) on the magnetization of a Mn12-acetate single crystal. The crystal was mounted on the surface of a piezoelectric LiNbO3 substrate containing an interdigital transducer for the excitation of SAWs. The magnetization of the crystal was measured using a rf superconducting quantum interference device with a time resolution of 1 μs. The piezoelectric material was excited by SAW pulses of different frequencies produced by applying microwave pulses to the transducer. Our data show that molecular magnets onto the LiNbO3 surface can be used as very sensitive detectors of the SAW frequency and intensity.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
75.80.+q Magnetomechanical effects, magnetostriction
68.35.Iv Acoustical properties
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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