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22 May 2006

Volume 88, Issue 21, Articles (21xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 211101 (2006); http://dx.doi.org/10.1063/1.2206087 (3 pages)

Kengo Nozaki and Toshihiko Baba
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Improvement of microstructural and optical properties of GaN layer on sapphire by nanoscale lateral epitaxial overgrowth

Y. D. Wang, K. Y. Zang, S. J. Chua, S. Tripathy, H. L. Zhou, and C. G. Fonstad

Appl. Phys. Lett. 88, 211908 (2006); http://dx.doi.org/10.1063/1.2207487 (3 pages) | Cited 13 times

Online Publication Date: 24 May 2006

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Nanoscale lateral epitaxial overgrown (NLEO) GaN layers were investigated for the improvement of microstructural and optical properties of GaN. Nanoporous SiO2 films on the surfaces of GaN/sapphire (0001) were fabricated by inductively coupled plasma etching using anodic alumina templates as etch masks, resulting in an average pore diameter and interpore distance of 60 and 110 nm, respectively. GaN was grown over the nanoporous SiO2 layer using metal organic chemical vapor deposition to realize a continuous and smooth film. NLEO GaN was found to result in a significant reduction of threading dislocation density as characterized by transmission electron microscopy and atomic force microscopy. The threading dislocation density was ∼ 107 cm−2 at the surface of NLEO GaN. The narrower band-edge excitonic transition in photoluminescence spectrum shows a better optical quality in the NLEO GaN film.
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81.05.Ea III-V semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
68.55.A- Nucleation and growth

Ge-modified Si(100) substrates for the growth of 3C-SiC(100)

Ch. Zgheib, L. E. McNeil, P. Masri, Ch. Förster, F. M. Morales, Th. Stauden, O. Ambacher, and J. Pezoldt

Appl. Phys. Lett. 88, 211909 (2006); http://dx.doi.org/10.1063/1.2206558 (3 pages) | Cited 9 times

Online Publication Date: 25 May 2006

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An alternative route to improve the epitaxial growth of 3C-SiC(100) on Si(100) was developed. It consists in covering the silicon wafers with germanium prior to the carbonization step of the silicon substrate. Transmission electron microscopy and μ-Raman investigations revealed an improvement in the residual strain and crystalline quality of the grown 3C-SiC layers comparable to or better than in the case of 3C-SiC grown on silicon on insulator substrates. These beneficial effects were reached by using a Ge coverage in the range of 0.5–1 monolayer.
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81.05.Hd Other semiconductors
68.47.Fg Semiconductor surfaces
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.30.Hv Other nonmetallic inorganics

Optical properties of shuffle dislocations in silicon

S. Pizzini, S. Binetti, A. Le Donne, A. Marzegalli, and J. Rabier

Appl. Phys. Lett. 88, 211910 (2006); http://dx.doi.org/10.1063/1.2206874 (3 pages) | Cited 5 times

Online Publication Date: 25 May 2006

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The radiative recombination processes in dislocated float zone silicon samples deformed under gigapascal stresses were studied by photoluminescence (PL) spectroscopy. The observed shuffle dislocations present a reconstructed core and their generation is accompanied by the introduction of point defects and point defect clusters, whose signature is evident in the PL spectra. A broad band around 1 eV is the only PL feature which could be directly related to shuffle dislocations and it is explained conjecturing strain field induced gap changes, as confirmed by molecular dynamics simulations.
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78.55.Ap Elemental semiconductors
61.72.J- Point defects and defect clusters
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

Photoluminescence at room temperature in disordered Ba0.50Sr0.50(Ti0.80Sn0.20)O3 thin films

I. A. Souza, A. Z. Simões, E. Longo, J. A. Varela, and P. S. Pizani

Appl. Phys. Lett. 88, 211911 (2006); http://dx.doi.org/10.1063/1.2206993 (3 pages) | Cited 5 times

Online Publication Date: 25 May 2006

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Photoluminescence (PL) properties at room temperature of disordered Ba0.50Sr0.50(Ti0.80Sn0.20)O3 (BST:Sn) thin films were obtained by the polymeric precursor method. X-ray diffraction data and corresponding PL properties have been measured using the 488 nm line of an argon ion laser. The PL spectra of the film annealed at 350 °C for 21 h are stronger than those of the film annealed at 350 °C for 28 h, indicating a disorganized structure. The energy band gaps of the crystalline and amorphous BST:Sn thin films were 3.35 and 2.25 eV, respectively. The doped BST thin films also tend to a cubic structure, resulting from TiO6 deformations.
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81.05.Gc Amorphous semiconductors
78.66.Jg Amorphous semiconductors; glasses
78.55.Qr Amorphous materials; glasses and other disordered solids
61.43.Dq Amorphous semiconductors, metals, and alloys
61.72.Cc Kinetics of defect formation and annealing
68.55.-a Thin film structure and morphology

Fibrous nanocomposites with interface stress: Hill’s and Levin’s connections for effective moduli

Tungyang Chen and George J. Dvorak

Appl. Phys. Lett. 88, 211912 (2006); http://dx.doi.org/10.1063/1.2206132 (3 pages) | Cited 13 times

Online Publication Date: 26 May 2006

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We study the macroscopic behavior of solids containing circular cylindrical nanoinclusions of the same size with surface effects prevailing at interfaces. The overall thermomechanical properties of these solids are shown to comply with two sets of exact connections. The first set, similar to Hill’s universal connections, provides two constraints among the three axisymmetric overall elastic moduli. The second set relates the effective coefficients of thermal expansion to the effective moduli, in analogy with Levin’s formula. In contrast to the classical results, the presence of surface effects makes both sets of connections dependent on the absolute size of the nanoinclusions.
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62.25.-g Mechanical properties of nanoscale systems
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
61.72.Qq Microscopic defects (voids, inclusions, etc.)
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
65.40.De Thermal expansion; thermomechanical effects

Room-temperature photoluminescence in structurally disordered SrWO4

M. Anicete-Santos, F. C. Picon, M. T. Escote, E. R. Leite, P. S. Pizani, J. A. Varela, and E. Longo

Appl. Phys. Lett. 88, 211913 (2006); http://dx.doi.org/10.1063/1.2207491 (3 pages) | Cited 17 times

Online Publication Date: 26 May 2006

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Intense and broad visible photoluminescent (PL) band in structurally disordered SrWO4 compounds was observed at room temperature. The polycrystalline scheelite strontium tungstate (SrWO4) samples prepared by the polymeric precursor method at different temperatures of annealing were structurally characterized by x-ray diffraction and Fourier transform Raman spectroscopy measurements. Quantum-mechanical calculations showed that the local disorder in the cluster of the network modifiers Sr has a very important role in the charge transfer. The experimental and theoretical results are in good agreement, indicating that the generation of the intense visible PL band can be related to short-range order-disorder degree in the scheelite structure.
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78.55.Hx Other solid inorganic materials
78.35.+c Brillouin and Rayleigh scattering; other light scattering
81.40.Gh Other heat and thermomechanical treatments
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions

Elucidating the mechanism of transient loss of phosphorus due to interface segregation

R. D. Chang, J. R. Tsai, and L. W. Ho

Appl. Phys. Lett. 88, 211914 (2006); http://dx.doi.org/10.1063/1.2207567 (3 pages)

Online Publication Date: 26 May 2006

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The mechanism of the transient dose loss of phosphorus from silicon was experimentally investigated to understand mechanisms of dopant segregation at a SiO2/Si interface. Phosphorus is lost and then partially recovered during annealing after implantation. The rate of dose recovery depends on the concentration of phosphorus at the silicon surface. Dopant clustering at the interface is proposed to explain the fact that the surface concentration remains nearly constant during dose recovery. When the dose recovery rate decreases with the surface concentration declines, the trapping of dopants by individual interface defects is believed to be the major mechanism of segregation.
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68.35.Dv Composition, segregation; defects and impurities
61.72.S- Impurities in crystals
61.72.Cc Kinetics of defect formation and annealing
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Acoustic charge transport in a n-i-n three terminal device

Marco Cecchini, Giorgio De Simoni, Vincenzo Piazza, Fabio Beltram, H. E. Beere, and D. A. Ritchie

Appl. Phys. Lett. 88, 212101 (2006); http://dx.doi.org/10.1063/1.2206551 (3 pages) | Cited 3 times

Online Publication Date: 22 May 2006

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We present an unconventional scheme for acoustic charge transport devices based on a n-i-n lateral junction as electron injector. We show that surface acoustic waves (SAWs) are able to pick up electrons from a current flowing through the n-i-n junction and steer them towards the Ohmic output contact. Acoustic charge transport was studied at various temperatures, as a function of injector current, voltage bias, and SAW power. The possibility to modulate the acoustoelectric current by means of lateral in-plane gates is also discussed. The main advantage of our approach relies on the possibility to drive the n-i-n injector by means of both voltage and current sources, thus allowing to sample and process voltage and current signals.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Experimental determination of the local geometry around In and In–C complexes in Si

F. d’Acapito, Y. Shimizu, S. Scalese, M. Italia, P. Alippi, and S. Grasso

Appl. Phys. Lett. 88, 212102 (2006); http://dx.doi.org/10.1063/1.2206703 (3 pages)

Online Publication Date: 22 May 2006

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The electrical properties of dopants in Si are of primary importance for the realization of electronic devices. Indium represents a promising p-type dopant whose electrical properties are improved by codoping with C. From theoretical studies In and C are expected to pair in the Si matrix in order to lower the strain energy. In this contribution we provide the first direct experimental determination of the sites of In and In–C complexes in Si.
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71.55.Cn Elemental semiconductors

p-type electrical conduction in α-AgGaO2 delafossite thin films

K. A. Vanaja, R. S. Ajimsha, A. S. Asha, and M. K. Jayaraj

Appl. Phys. Lett. 88, 212103 (2006); http://dx.doi.org/10.1063/1.2204757 (3 pages) | Cited 5 times

Online Publication Date: 23 May 2006

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Thin films of delafossites of α-AgGaO2 were prepared on α-Al2O3 (0001) and on Si (100) single crystal substrates by pulsed laser deposition. The films have a band gap of 4.12 eV and a transparency of more than 50% in the visible region. The electrical conductivity at 300 K was 3.2×10−4 S cm−1. The positive sign of Seebeck coefficient (+70 μV K−1) demonstrated the p-type conduction in the films. Transparent p-n heterojunctions on a glass substrate having a structure glass/ITO/n-ZnO/p-AgGaO2 were fabricated. The ratio of forward to reverse current was more than 100 in the range of −2 to +2 V.
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73.61.Le Other inorganic semiconductors
73.50.Lw Thermoelectric effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Secondary emission of strain-induced dopant contrast in the source/drain regions of metal-oxide-semiconductor devices

Wen-Chu Hsiao, Chuan-Pu Liu, and Ying-Lang Wang

Appl. Phys. Lett. 88, 212104 (2006); http://dx.doi.org/10.1063/1.2207216 (3 pages) | Cited 2 times

Online Publication Date: 24 May 2006

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Secondary electron (SE) imaging with scanning electron microscopy has been used for two-dimensional dopant profiling. However, the mechanism of dopant contrast is still not yet understood. Here we propose another significant contribution from interface strain for the source/drain regions in p- and n-type metal-oxide-semiconductor (MOS) devices. The results show that the width of the dopant profile by SE imaging agrees well with the strain profile by dark-field technique with transmission electron microscopy. We demonstrate that the dopant contrast of the p-MOS device by SE imaging is higher than a test wafer by 45%. The enhanced SE signals for both p-MOS and n-MOS devices are caused by band bending through CoSi2-induced strain.
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85.30.De Semiconductor-device characterization, design, and modeling
85.30.Tv Field effect devices

Electric field control of magnetization dynamics in ZnMnSe/ZnBeSe diluted-magnetic-semiconductor heterostructures

M. K. Kneip, D. R. Yakovlev, M. Bayer, T. Slobodskyy, G. Schmidt, and L. W. Molenkamp

Appl. Phys. Lett. 88, 212105 (2006); http://dx.doi.org/10.1063/1.2206681 (3 pages) | Cited 3 times

Online Publication Date: 24 May 2006

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We show that the magnetization dynamics in diluted magnetic semiconductors can be controlled separately from the static magnetization by means of an electric field. The spin-lattice relaxation (SLR) time of magnetic Mn2+ ions was tuned by two orders of magnitude by a gate voltage applied to n-type modulation-doped (Zn,Mn)Se/(Zn,Be)Se quantum wells. The effect is based on providing an additional channel for SLR by a two-dimensional electron gas (2DEG). The static magnetization responsible for the giant Zeeman spin splitting of excitons was not influenced by the 2DEG density.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Pp Magnetic semiconductors
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)

Dynamical spin separation induced by spin-dependent type-II band alignment in a diluted magnetic double quantum well

T. Koyama, K. Kayanuma, I. Souma, A. Murayama, and Y. Oka

Appl. Phys. Lett. 88, 212106 (2006); http://dx.doi.org/10.1063/1.2207488 (3 pages) | Cited 3 times

Online Publication Date: 24 May 2006

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Dynamical spin separation is demonstrated in a magnetic double quantum well composed of a diluted magnetic semiconductor well (MW) and a nonmagnetic well (NMW). Excitonic photoluminescence of the type-II transition between an electron in the NMW and a down-spin heavy hole (hh) in the MW is induced with an increase in the magnetic field. A type-I transition involving an up-spin hh inside the NMW is simultaneously observed. Therefore, the hh spins are concluded to be spatially separated, which is sustained by a low hh-spin injection time of 500 ps from the NMW to the MW.
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75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
73.21.Fg Quantum wells
75.50.Pp Magnetic semiconductors
72.25.Dc Spin polarized transport in semiconductors
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
78.67.De Quantum wells

Ultralow resistance Si-containing Ti/Al/Mo/Au Ohmic contacts with large processing window for AlGaN/GaN heterostructures

Fitih M. Mohammed, Liang Wang, and Ilesanmi Adesida

Appl. Phys. Lett. 88, 212107 (2006); http://dx.doi.org/10.1063/1.2206127 (3 pages) | Cited 13 times

Online Publication Date: 25 May 2006

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We report on the electrical and microstructural characterization of Si-containing Ti/Al/Mo/Au contacts for AlGaN/GaN heterostructures. Excellent Ohmic contact formation with contact resistance and specific contact resistivity as low as 0.12 Ω mm and 3.8×10−7 Ω cm2, respectively, have been obtained by the optimization of Si distribution in the metallization. The presence of Si strongly affects the Ohmic performance and microstructural makeup of the annealed contacts. Greater enhancement in Ohmic performance is achieved when optimized amount of Si is dispersed throughout the metallization.
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73.40.Ns Metal-nonmetal contacts
85.40.Ls Metallization, contacts, interconnects; device isolation
85.30.Tv Field effect devices
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Cg Contact resistance, contact potential
61.72.Cc Kinetics of defect formation and annealing

Direct observation of photoinduced charge redistribution of WO3–TiO2 double layer nanocomposite films by photoassisted Kelvin force microscopy

S. J. Wang, G. Cheng, X. H. Jiang, Y. C. Li, Y. B. Huang, and Z. L. Du

Appl. Phys. Lett. 88, 212108 (2006); http://dx.doi.org/10.1063/1.2207498 (3 pages) | Cited 12 times

Online Publication Date: 25 May 2006

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The microscopic photoinduced charge redistribution between heterogeneous semiconductor nanofilms of WO3 and TiO2 double layers (written as WO3–TiO2 nanocomposite films) was directly observed using Kelvin probe force microscopy (KFM) coupled with an UV light source. Under illumination the surface potential morphologies of WO3–TiO2 nanocomposite films changed from 162 to 592 mV, which was associated with the photoinduced charge transfer between WO3 and TiO2 nanoparticles due to the energy level alignment between them. This improved technique of photoassisted KFM was presented to visualize the photoinduced charge transfer between different semiconductor nanoparticles on microscopic scale.
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73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors

Multiple and virtual photon processes in radiation-induced magnetoresistance oscillations in two-dimensional electron systems

X. L. Lei and S. Y. Liu

Appl. Phys. Lett. 88, 212109 (2006); http://dx.doi.org/10.1063/1.2207499 (3 pages) | Cited 15 times

Online Publication Date: 25 May 2006

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Recently discovered new structures and zero-resistance states outside the well-known oscillations are demonstrated to arise from multiphoton assisted processes, by a detailed analysis of microwave photoresistance in two-dimensional electron systems under enhanced radiation. The concomitant resistance dropping and the peak narrowing observed in the experiments are also reproduced. We show that the radiation-induced suppression of average resistance comes from virtual photon effect and exists throughout the whole magnetic field range.
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73.63.-b Electronic transport in nanoscale materials and structures
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.20.My Galvanomagnetic and other magnetotransport effects

Site-specific dopant profiling in a scanning electron microscope using focused ion beam prepared specimens

P. Kazemian, A. C. Twitchett, C. J. Humphreys, and C. Rodenburg

Appl. Phys. Lett. 88, 212110 (2006); http://dx.doi.org/10.1063/1.2207552 (3 pages) | Cited 7 times

Online Publication Date: 25 May 2006

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Site-specific dopant profiling across a silicon p-n junction has been performed in the scanning electron microscope (SEM) on samples prepared using focused ion beam (FIB) milling. The results are compared with the dopant contrast obtained after using non-site-specific cleaving and tripod polishing of specimens. FIB milling generates a damaged surface layer which reduces the dopant contrast observed in the SEM using secondary electron imaging. These results show that two dimensional dopant contrast can be observed from FIB-prepared membranes, thereby extending the application of SEM dopant profiling to the examination of complex nanometer-scale device structures for which site selection is essential.
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61.72.S- Impurities in crystals
79.20.Hx Electron impact: secondary emission

Theoretical study of electron transport in boron nanotubes

Kah Chun Lau, Ravindra Pandey, Ranjit Pati, and Shashi P. Karna

Appl. Phys. Lett. 88, 212111 (2006); http://dx.doi.org/10.1063/1.2207570 (3 pages) | Cited 15 times

Online Publication Date: 25 May 2006

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The electron transport in single-walled boron nanotube (BNT) is studied using the Landauer-Büttiker [ R. Landauer, J. Phys.: Condens: Matter 1, 8099 (1989) ; M. Büttiker, Phys. Rev. Lett. 57, 1761 (1986) ] multichannel approach in conjunction with the tight-binding method. In the range of the calculated length (1–5.0 nm) of the tubes, the calculations predict a ballistic transport in BNT and find a relatively low resistance for BNTs as compared to that of the single-walled carbon nanotubes (CNTs) of comparable length. A lower resistance in the case of BNT than the CNT may be attributed to electron-deficient nature of boron characterized by the presence of two-center, and multicenter bonds in the former.
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73.63.Fg Nanotubes
72.20.Ht High-field and nonlinear effects

Reliability of thermally oxidized SiO2/4H-SiC by conductive atomic force microscopy

Patrick Fiorenza and Vito Raineri

Appl. Phys. Lett. 88, 212112 (2006); http://dx.doi.org/10.1063/1.2207991 (3 pages) | Cited 10 times

Online Publication Date: 26 May 2006

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The dielectric breakdown (BD) kinetics of silicon dioxide (SiO2) thin films thermally grown on 4H-SiC was determined by comparison between I-V measurements on large area (up to 1.96×10−5 cm2) metal-oxide-semiconductor structures and conductive atomic force microscopy (C-AFM). C-AFM clearly images the weak breakdown single spots under constant voltage stresses. The stress time on the single C-AFM tip dot was varied from 2.5×10−3 to 1×10−1 s. The density of BD spots, upon increasing the stress time, exhibits an exponential trend. The Weibull slope and the characteristic time of the dielectric BD events have been determined by direct measurements at nanometer scale allowing to demonstrate that the percolative model is valid for thermal oxide on 4H-SiC.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.22.Jp Dielectric breakdown and space-charge effects
68.37.Ps Atomic force microscopy (AFM)
73.61.Ng Insulators
81.65.Mq Oxidation

Evenly curved two-dimensional electron systems in rolled-up Hall bars

S. Mendach, O. Schumacher, H. Welsch, Ch. Heyn, W. Hansen, and M. Holz

Appl. Phys. Lett. 88, 212113 (2006); http://dx.doi.org/10.1063/1.2206135 (3 pages) | Cited 17 times

Online Publication Date: 26 May 2006

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We present evenly curved two-dimensional electron systems in Hall-bar geometry. Expanding the method of self-rolling strained layers to fragile thickness modulated layer systems enables us to roll-up complete Hall-bar geometries into microscrolls. These structures represent model systems for the investigation of transport phenomena in sinusoidally modulated magnetic fields. The sinusoidal shape of the modulation and the tunability of the modulation phase are illustrated by comparing finite element calculations with transport data in the classical regime. Furthermore, we demonstrate the tunability of the carrier density in our structures using rolled-in metal gates.
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72.20.-i Conductivity phenomena in semiconductors and insulators
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Field emission from reconstructed heavily phosphorus-doped homoepitaxial diamond (111)

Takatoshi Yamada, Ken Okano, Hisato Yamaguchi, Hiromitsu Kato, Shin-ichi Shikata, and Christoph E. Nebel

Appl. Phys. Lett. 88, 212114 (2006); http://dx.doi.org/10.1063/1.2206552 (3 pages) | Cited 13 times

Online Publication Date: 26 May 2006

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We report about field emission from reconstructed phosphorus-doped diamond surfaces. In order to reconstruct the surface, annealing at 950 °C for 60 min in a high vacuum system has been applied. Field emission shows the lowest threshold field for the reconstructed surface of 16 V/μm, while the threshold fields for oxidized and hydrogen-terminated surface are 28 and 44 V/μm, respectively. A model is introduced to discuss these results, which takes into account effective electron affinities and tunneling of electrons from conduction band and donor levels.
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81.05.Cy Elemental semiconductors
68.47.Fg Semiconductor surfaces
79.70.+q Field emission, ionization, evaporation, and desorption
71.55.Cn Elemental semiconductors
73.61.Cw Elemental semiconductors
81.65.Mq Oxidation

Temperature dependence of the resistance of magnetic tunnel junctions with MgO barrier

X. Kou, J. Schmalhorst, A. Thomas, and G. Reiss

Appl. Phys. Lett. 88, 212115 (2006); http://dx.doi.org/10.1063/1.2206680 (3 pages) | Cited 15 times

Online Publication Date: 26 May 2006

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The temperature dependent tunneling resistance of magnetic tunnel junctions with MgO barriers was characterized. In the junctions prepared by magnetron sputtering, the tunnel magnetoresistance decreases with increasing temperature. Various contributions to the tunnel conductance are discussed using different models. Not only the direct elastic tunneling contributes to the temperature dependence of tunnel magnetoresistance, but also the assisted, spin-independent tunneling plays an important role in determining the temperature dependent behavior in our magnetic tunneling junctions. The process is further investigated assuming magnon and phonon assisted tunneling and compared to junctions with alumina tunnel barrier.
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75.47.Np Metals and alloys
75.30.Ds Spin waves
72.25.Ba Spin polarized transport in metals

Field-effect modulation of the transport properties of nondoped SrTiO3

Keisuke Shibuya, Tsuyoshi Ohnishi, Takayuki Uozumi, Taisuke Sato, Mikk Lippmaa, Masashi Kawasaki, Kiyomi Nakajima, Toyohiro Chikyow, and Hideomi Koinuma

Appl. Phys. Lett. 88, 212116 (2006); http://dx.doi.org/10.1063/1.2207502 (3 pages) | Cited 19 times

Online Publication Date: 26 May 2006

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We have fabricated SrTiO3 (100) single crystal field-effect transistors with amorphous and epitaxial CaHfO3 gate insulator layers. The devices with amorphous insulator layers showed nearly temperature independent behavior. The transistors with epitaxial interfaces exhibited a large improvement over the amorphous devices. The field-effect mobility was found to increase at low temperature, reaching 35 cm2/V s at 50 K. This result shows that the carriers accumulated by the field effect on the SrTiO3 side of the gate interface behaved as would be expected for electron-doped SrTiO3. An insulator-metal transition, induced by field-effect doping, was observed in epitaxial SrTiO3-based transistors.
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85.30.Tv Field effect devices
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Deep trench etching combining aluminum thermomigration and electrochemical silicon dissolution

G. Gautier, L. Ventura, R. Jérisian, S. Kouassi, C. Leborgne, B. Morillon, and M. Roy

Appl. Phys. Lett. 88, 212501 (2006); http://dx.doi.org/10.1063/1.2206120 (3 pages) | Cited 1 time

Online Publication Date: 22 May 2006

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A micromachining technique for silicon deep anisotropic etching and isolating porous silicon structures is developed. This original method combines aluminum thermomigration and silicon electrochemical etching. In this way, we have generated high aspect ratio trenches and porous silicon isolating regions as well, through the entire thickness of the wafer. In order to evaluate our method, we performed etching rate measurements varying the current density. A maximum value of 22 μm/min has been already measured. The interest of the method in terms of cost and structures diversity is also justified.
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85.40.Ls Metallization, contacts, interconnects; device isolation
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.65.Cf Surface cleaning, etching, patterning

Magnetoresistance switch effect in a multiferroic Fe3O4/BaTiO3 bilayer

M. Ziese, A. Bollero, I. Panagiotopoulos, and N. Moutis

Appl. Phys. Lett. 88, 212502 (2006); http://dx.doi.org/10.1063/1.2206121 (3 pages) | Cited 17 times

Online Publication Date: 22 May 2006

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Multiferroic bilayers composed of a magnetite (Fe3O4) and a BaTiO3 layer show nonlinear current-voltage characteristics in current perpendicular to plane configuration. The magnetoresistance of the bilayers is strongly bias dependent and can be switched from negative at low bias to positive at large bias. It is shown that these effects do not arise from charge-carrier modulation in the magnetite layer by an electric field effect. Therefore both the nonlinear transport characteristics and the switchable magnetoresistance are attributed to interfacial transport phenomena.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.Pq Other materials
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