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9 Jun 2008

Volume 92, Issue 23, Articles (23xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 92, 231901 (2008); http://dx.doi.org/10.1063/1.2938921 (3 pages)

N. A. Mara, D. Bhattacharyya, P. Dickerson, R. G. Hoagland, and A. Misra
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Single-crystalline B12As2 on m-plane (1math00) 15R-SiC

Hui Chen, Guan Wang, Michael Dudley, Zhou Xu, J. H. Edgar, Tim Batten, Martin Kuball, Lihua Zhang, and Yimei Zhu

Appl. Phys. Lett. 92, 231917 (2008); http://dx.doi.org/10.1063/1.2945635 (3 pages) | Cited 4 times

Online Publication Date: 13 June 2008

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Single crystal, heteroepitaxial growth of icosahedral B12As2 (IBA, a boride semiconductor) on m-plane 15R-SiC is demonstrated. Previous studies of IBA on other substrates, i.e., (111)Si and (0001)6H-SiC, produced polycrystalline and twinned epilayers. In contrast, single-crystalline and untwinned IBA was achieved on m-plane 15R-SiC. Synchrotron white beam x-ray topography, Raman spectroscopy, and high resolution transmission electron microscopy confirm the high quality of the films. High quality growth is shown to be mediated by ordered nucleation of IBA on (474) substrate facets. This work demonstrates that m-plane 15R-SiC is a good substrate choice to grow high-quality untwinned IBA epilayers for future device applications.
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68.55.ag Semiconductors
78.30.Hv Other nonmetallic inorganics

Ar gas discharge lamp with heated LiF window: A monochromatized light source for photoemission

M. Budke and M. Donath

Appl. Phys. Lett. 92, 231918 (2008); http://dx.doi.org/10.1063/1.2945641 (3 pages) | Cited 1 time

Online Publication Date: 13 June 2008

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We present a simple, inexpensive, and highly effective method for monochromatizing the vacuum ultraviolet light emitted from an Ar gas discharge for use, e.g., in photoemission experiments. By using a slightly heated window of LiF acting as low-pass filter, the emission spectrum of the Ar gas discharge is reduced to the Ar line at 11.62 eV (106.7 nm). The performance of the low-pass filter is demonstrated by photoemission measurements on Cu(111). Furthermore, we compare our light source with an unmonochromatized He gas discharge, which represents the most widely used laboratory photon source in photoemission.
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42.72.Bj Visible and ultraviolet sources
79.60.Bm Clean metal, semiconductor, and insulator surfaces
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Spin injection from Co2MnGa into an InGaAs quantum well

M. C. Hickey, C. D. Damsgaard, S. N. Holmes, I. Farrer, G. A. C. Jones, D. A. Ritchie, C. S. Jacobsen, J. B. Hansen, and M. Pepper

Appl. Phys. Lett. 92, 232101 (2008); http://dx.doi.org/10.1063/1.2938418 (3 pages) | Cited 9 times

Online Publication Date: 9 June 2008

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We have demonstrated spin injection from a full Heusler alloy Co2MnGa thin film into a (100) InGaAs quantum well in a semiconductor light-emitting diode structure at a temperature of 5 K. The detection is performed in the oblique Hanle geometry, allowing quantification of the effective spin lifetime and spin detection efficiency (22±4%). This work builds on existing studies on off-stoichiometric Heusler injectors into similar light-emitting-diode structures. The role of injector stoichiometry can therefore be quantitatively assessed with the result that the spin injection efficiency increases by a factor of approximately 2 as compared with an off-stoichiometric Co2.4Mn1.6Ga injector.
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73.63.Hs Quantum wells
72.25.Dc Spin polarized transport in semiconductors

CO2 detection using polyethylenimine/starch functionalized AlGaN/GaN high electron mobility transistors

C. Y. Chang, B. S. Kang, H. T. Wang, F. Ren, Y. L. Wang, S. J. Pearton, D. M. Dennis, J. W. Johnson, P. Rajagopal, J. C. Roberts, E. L. Piner, and K. J. Linthicum

Appl. Phys. Lett. 92, 232102 (2008); http://dx.doi.org/10.1063/1.2937126 (3 pages) | Cited 10 times

Online Publication Date: 10 June 2008

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AlGaN/GaN high electron mobility transistors (HEMTs) functionalized with polyethylenimine/starch were used for detecting CO2 with a wide dynamic range of 0.9%–50% balanced with nitrogen at temperatures from 46 to 220 °C. Higher detection sensitivity to CO2 gas was achieved at higher testing temperatures. At a fixed source-drain bias voltage of 0.5 V, drain-source current of the functionalized HEMTs showed a sublinear correlation upon exposure to different CO2 concentrations at low temperature. The superlinear relationship was at high temperature. The sensor exhibited a reversible behavior and a repeatable current change of 32 and 47 μA with the introduction of 28.57% and 37.5% CO2 at 108 °C, respectively.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.30.Tv Field effect devices

Complementary inverter circuits based on p-SnO2 and n-In2O3 thin film transistors

Dhananjay, Chih-Wei Chu, Chun-Wei Ou, Meng-Chyi Wu, Zhong-Yo Ho, Kuo-Chuan Ho, and Shih-Wei Lee

Appl. Phys. Lett. 92, 232103 (2008); http://dx.doi.org/10.1063/1.2936275 (3 pages) | Cited 9 times

Online Publication Date: 11 June 2008

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Thin film transistors (TFTs) of indium oxide (In2O3) and tin oxide (SnO2) were fabricated on SiO2 gate dielectric using reactive evaporation process. Structural investigation of the films revealed that In2O3 films were polycrystalline in nature with preferred (222) orientation and SnO2 films exhibited amorphous nature. The x-ray photoelectric spectroscopy measurements suggest that SnO2 films were oxygen rich and presume mixed oxidation states of Sn, namely Sn2+ and Sn4+. While the In2O3 based TFTs possess n-type channel conduction, SnO2 based TFTs exhibited anomalous p-type conductivity. Integration of these n- and p-type devices resulted in complementary inverter with a gain of 11.
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84.30.Jc Power electronics; power supply circuits
85.30.Tv Field effect devices

Semiconductor charge transport driven by a picosecond strain pulse

D. R. Fowler, A. V. Akimov, A. G. Balanov, M. T. Greenaway, M. Henini, T. M. Fromhold, and A. J. Kent

Appl. Phys. Lett. 92, 232104 (2008); http://dx.doi.org/10.1063/1.2942389 (3 pages) | Cited 1 time

Online Publication Date: 11 June 2008

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We demonstrate that a picosecond strain pulse can be used to drive an electric current through both thin-film epilayer and heterostructure semiconductor crystals in the absence of an external electric field. By measuring the transient current pulses, we are able to clearly distinguish the effects of the coherent and incoherent components of the acoustic packet. The properties of the strain induced signal suggest a technique for exciting picosecond current pulses, which may be used to probe semiconductor devices.
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73.61.-r Electrical properties of specific thin films
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Postgrowth annealing of GaInAs/GaAs and GaInAsN/GaAs quantum well samples placed in a proximity GaAs box: A simple method to improve the crystalline quality

J. Pakarinen, C. S. Peng, J. Puustinen, P. Laukkanen, V.-M. Korpijärvi, A. Tukiainen, and M. Pessa

Appl. Phys. Lett. 92, 232105 (2008); http://dx.doi.org/10.1063/1.2943157 (3 pages) | Cited 11 times

Online Publication Date: 11 June 2008

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The effects of thermal annealing on GaInAs/GaAs and GaInAsN/GaAs quantum wells, grown by molecular beam epitaxy, were investigated. Optical and structural properties were examined upon annealing when the samples had a 200 nm thick SiO2 cap layer, or were placed in a so-called GaAs box or were left uncapped. The GaAs box gave rise to the strongest photoluminescence without significant blueshift or structural changes at moderate annealing temperature. Capping with SiO2 impaired the samples and caused a more pronounced blueshift for the GaInAs quantum wells than for the GaInAsN ones. These results consolidate our understanding of the blueshift mechanisms.
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81.05.Ea III-V semiconductors
81.07.St Quantum wells
78.67.De Quantum wells
73.63.Hs Quantum wells
61.72.Cc Kinetics of defect formation and annealing
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Broadband electrical detection of spin excitations in Ga0.98Mn0.02As using a photovoltage technique

André Wirthmann, Xiong Hui, N. Mecking, Y. S. Gui, T. Chakraborty, C.-M. Hu, M. Reinwald, C. Schüller, and W. Wegscheider

Appl. Phys. Lett. 92, 232106 (2008); http://dx.doi.org/10.1063/1.2943280 (3 pages) | Cited 4 times

Online Publication Date: 11 June 2008

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We report on microwave photovoltage and simultaneous magnetotransport measurements in a (Ga, Mn) As film oriented normal to the magnetic field. We detect the ferromagnetic resonance over a broad frequency range of 2–18.5 GHz and determine the spectroscopic g-factor and separate the Gilbert from the inhomogeneous contribution to magnetization relaxation. Temperature dependent measurements below the saturation magnetization indicate that the photovoltage signal can serve as a sensitive tool to study the crystal anisotropy. We demonstrate that the combination of spin dynamics with charge transport is a promising tool to study microstructured ferromagnetic semiconductor samples.
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75.70.Ak Magnetic properties of monolayers and thin films
73.50.Pz Photoconduction and photovoltaic effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Dd Nonmetallic ferromagnetic materials

Temporary transition in suspended carbon nanotubes

Sen-Hong Syue, Hsin-Fu Kuo, Ching-Tung Hsu, Hung-Jen Chen, Uei-Shin Chen, Wen-Kuang Hsu, and Han-Chang Shih

Appl. Phys. Lett. 92, 232107 (2008); http://dx.doi.org/10.1063/1.2943321 (3 pages) | Cited 2 times

Online Publication Date: 11 June 2008

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A semiconducting phase is temporarily present in doped carbon nanotube after field treatment and underlying mechanism involves chemical potential change and EF movement by field induced charge accumulation. Metallic phase re-emerges as accumulated charges are released.
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73.63.Fg Nanotubes
73.61.Cw Elemental semiconductors
61.46.Fg Nanotubes
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
82.60.-s Chemical thermodynamics

Hard x-ray photoemission spectroscopy in wurtzite-type zinc magnesium oxide solid-solution films grown by pulsed-laser deposition

Takeo Ohsawa, Naoki Ohashi, Yutaka Adachi, Isao Sakaguchi, Haruki Ryoken, Kenji Matsumoto, Hajime Haneda, Shigenori Ueda, Hideki Yoshikawa, and Keisuke Kobayashi

Appl. Phys. Lett. 92, 232108 (2008); http://dx.doi.org/10.1063/1.2942393 (3 pages) | Cited 6 times

Online Publication Date: 12 June 2008

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The electronic structure of Zn1−xMgxO alloy thin films was determined by hard x-ray photoemission spectroscopy (HX-PES) and optical transmittance measurements. HX-PES measurements revealed that the binding energies of valence band, Zn 2p, and O 1s levels increased with increasing MgO fraction. The energy shift correlated with a widening of the band gap and change in ionicity of chemical bonds by alloying. The Fermi level in the alloy compounds was found to be close to the bottom of conduction band regardless of the MgO fraction.
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71.20.Nr Semiconductor compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Hf II-VI semiconductors
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
79.60.Dp Adsorbed layers and thin films

Current-voltage characteristics of phase separated La0.5Ca0.5MnO3/Nb–SrTiO3 p-n junction and magnetic tunability

B. T. Xie, Y. G. Zhao, C. M. Xiong, S. Park, and Weida Wu

Appl. Phys. Lett. 92, 232109 (2008); http://dx.doi.org/10.1063/1.2944261 (3 pages) | Cited 4 times

Online Publication Date: 12 June 2008

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The authors report the current-voltage characteristics of La0.5Ca0.5MnO3/Nb-SrTiO3 p-n junction. This junction shows remarkable thermal hysteresis, giant negative magnetoresistance (MR), remarkable differences of MR for the zero field cooling and field cooling processes, and memory effect of magnetic field. Magnetic force microscopy studies provide direct evidence of magnetic inhomogeneity in La0.5Ca0.5MnO3 film. These intriguing behaviors of our p-n junction can be explained by the phase separation in La0.5Ca0.5MnO3. This work demonstrates the principle of harnessing phase separation for highly tunable device applications.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.43.Qt Magnetoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Dopant-stress synergy in Si solid-phase epitaxy

N. G. Rudawski, K. S. Jones, and R. Gwilliam

Appl. Phys. Lett. 92, 232110 (2008); http://dx.doi.org/10.1063/1.2945291 (3 pages) | Cited 10 times

Online Publication Date: 12 June 2008

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The influence of dopants on stressed solid-phase epitaxy of Si was studied in B-doped material up to B concentration of ∼ 3.0×1020 cm−3 and stress of 1.0±0.1 GPa. As per the generalized Fermi level shifting model of growth enhancement in the presence of electrically active impurities, it is advanced that application of compressive stress may increase the energy difference between intrinsic Fermi and acceptor levels thus making dopant and stress effects synergistic in growth kinetics.
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61.72.uf Ge and Si
71.55.Cn Elemental semiconductors
81.15.Np Solid phase epitaxy; growth from solid phases
68.55.ag Semiconductors
61.72.sd Impurity concentration

Vertical structure p-type permeable metal-base organic transistors based on N,N′-diphentyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine

Jinying Huang, Mingdong Yi, Dongge Ma, and Ivo A. Hümmelgen

Appl. Phys. Lett. 92, 232111 (2008); http://dx.doi.org/10.1063/1.2944880 (3 pages) | Cited 6 times

Online Publication Date: 12 June 2008

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In this article, vertical structure p-type permeable-base organic transistors were proposed and demonstrated. A hole-type organic semiconductor N,N′-diphentyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine was used as emitter and collector. In the permeable-base transistors, the metal base was formed by firstly coevaporating Al and Ca in vacuum and then annealing at 120 °C for 5 min in air, followed by a thin Al deposition. These devices show a common-base current gain of near 1.0 and a common-emitter current gain of ∼ 270.
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85.30.Pq Bipolar transistors
85.30.Tv Field effect devices
72.80.Le Polymers; organic compounds (including organic semiconductors)
61.72.Cc Kinetics of defect formation and annealing

Characteristics and mechanism of conduction/set process in TiN/ZnO/Pt resistance switching random-access memories

Nuo Xu, Lifeng Liu, Xiao Sun, Xiaoyan Liu, Dedong Han, Yi Wang, Ruqi Han, Jinfeng Kang, and Bin Yu

Appl. Phys. Lett. 92, 232112 (2008); http://dx.doi.org/10.1063/1.2945278 (3 pages) | Cited 64 times

Online Publication Date: 13 June 2008

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The characteristics and mechanism of conduction/set process in TiN/ZnO/Pt-based resistance random access memory devices with stable and reproducible nanosecond bipolar switching behavior were studied. The dependencies of memory behavior on cell area, operating temperature, and frequency indicate that the conduction mechanism in low-resistance states is due to electrons hopping through filament paths. We also identify that the set process is essentially equivalent to a soft dielectric breakdown associated with a polarization effect caused by the migration of space charges under a low electric field stress. The generation/recovery of oxygen vacancies and nonlattice oxygen ions play a critical role in resistance switching.
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84.30.Sk Pulse and digital circuits
77.22.Jp Dielectric breakdown and space-charge effects
77.22.Ej Polarization and depolarization
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Dynamics of magnetization, reversal, and ultrafast demagnetization of TbFeCo amorphous films

Xiaodong Liu, Zhen Xu, Ruixin Gao, Haining Hu, Zhifeng Chen, Zixin Wang, Jun Du, Shiming Zhou, and Tianshu Lai

Appl. Phys. Lett. 92, 232501 (2008); http://dx.doi.org/10.1063/1.2943281 (3 pages) | Cited 6 times

Online Publication Date: 11 June 2008

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Static and dynamic hysteresis loops of TbFeCo amorphous films are measured by vibrating sample magnetometry (VSM) and magneto-optical Kerr rotation. The static VSM loop shows a faster magnetization reversal than the static Kerr loop does. The dynamic Kerr hysteresis loop in a sinusoidal alternating magnetic field at 1.14 kHz shows a large increase in coercivity with respect to the static coercivity. The ultrafast dynamics of laser-induced demagnetization and magnetization recovery is studied by femtosecond time-resolved polar Kerr rotation spectroscopy, and shows a subpicosecond demagnetization and several hundreds of picosecond magnetization recovery process, which suggests gigahertz writing rate possible.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Jk Magnetization reversal mechanisms
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
78.47.D- Time resolved spectroscopy (>1 psec)

Interesting magnetic behavior from reduced titanium dioxide nanobelts

S. V. Chong, K. Kadowaki, J. Xia, and H. Idriss

Appl. Phys. Lett. 92, 232502 (2008); http://dx.doi.org/10.1063/1.2944141 (3 pages) | Cited 6 times

Online Publication Date: 11 June 2008

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The magnetic behavior of titanium dioxide nanobelts has been investigated with and without Co doping. Room temperature ferromagnetism was observed when the Co-doped anatase TiO2 nanobelts were prepared via vacuum annealing of 2.5 at. % Co-doped titanate nanobelts, while annealing them in air resulted in paramagnetic ordering. Interestingly, by vacuum annealing the undoped titanate nanobelts under the same conditions, superparamagnetic ordering was observed in the resulting anatase TiO2 nanobelts. The electron paramagnetic resonance of this latter sample shows a strong symmetrical signal at g = 2.003 suggesting some sort of exchange interactions among the localized electrons’ spin moments from single electron trapped in oxygen vacancies.
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75.30.Et Exchange and superexchange interactions
61.72.jd Vacancies
75.30.Cr Saturation moments and magnetic susceptibilities
75.20.Ck Nonmetals
61.72.Cc Kinetics of defect formation and annealing
81.16.-c Methods of micro- and nanofabrication and processing

Nano-optics with spin waves at microwave frequencies

Vladislav E. Demidov, Sergej O. Demokritov, Karsten Rott, Patryk Krzysteczko, and Guenter Reiss

Appl. Phys. Lett. 92, 232503 (2008); http://dx.doi.org/10.1063/1.2945000 (3 pages) | Cited 42 times

Online Publication Date: 12 June 2008

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With the recent development in nanoscale patterning techniques, the potential of practical applications of nanometer-size structures for signal processing has been growing continuously. Experimental findings on the manipulation of optical signals in nanostructures have recently given rise to a widely addressed scientific area—subwavelength nano-optics. Here, we demonstrate that spin waves in microscopic ferromagnetic film structures represent a superb object for realization of the principles of nano-optics in the microwave frequency range. We show experimentally that by using the unique properties of spin waves, one can easily channelize, split, and manipulate submicrometer-width spin-wave beams propagating in microscopic magnetic-film waveguides.
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42.79.Gn Optical waveguides and couplers
84.40.-x Radiowave and microwave (including millimeter wave) technology
42.79.Wc Optical coatings
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
75.30.Ds Spin waves
81.16.Rf Micro- and nanoscale pattern formation

Impact of the electrical connection of spin transfer nano-oscillators on their synchronization: an analytical study

B. Georges, J. Grollier, V. Cros, and A. Fert

Appl. Phys. Lett. 92, 232504 (2008); http://dx.doi.org/10.1063/1.2945636 (3 pages) | Cited 17 times

Online Publication Date: 12 June 2008

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We analytically study the impact of an electrical connection of spin transfer nano-oscillators (STNOs) on their synchronization. We demonstrate that the phase dynamics of coupled STNO arrays can be described in the framework of the Kuramoto model. The conditions for successful synchronization of an assembly of STNOs are formulated. Synchronizing an assembly of STNOs appears to be the only solution to make the breakthrough on the emitted output power toward frequency synthesizers. In these potential devices, a large number of STNOs will have to be electrically connected, whatever the coupling mechanisms between oscillators.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
84.40.-x Radiowave and microwave (including millimeter wave) technology
84.30.Ng Oscillators, pulse generators, and function generators

The LaFe11.2Co0.7Si1.1Cx carbides for magnetic refrigeration close to room temperature

Mohamed Balli, Daniel Fruchart, and Damien Gignoux

Appl. Phys. Lett. 92, 232505 (2008); http://dx.doi.org/10.1063/1.2939098 (3 pages) | Cited 17 times

Online Publication Date: 13 June 2008

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The influence of carbon on the structural, magnetic, and magnetocaloric properties of LaFe11.2Co0.7Si1.1Cx compounds was investigated. The Curie temperature increases with increasing the carbon content. The maximum magnetic entropy changes under a magnetic field change of 5 T are about 14.5, 9.8, and 8.3 J/kg K for x = 0.1, 0.2, and 0.3, respectively. A composite material based on LaFe11.2Co0.7Si1.1Cx was proposed for magnetic systems using Ericsson cycle for refrigeration close to room temperature. The obtained entropy change of the composite remains approximately constant in this temperature range.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Neutron diffraction study of hexagonal manganite YMnO3, HoMnO3, and ErMnO3 epitaxial films

I. Gélard, C. Dubourdieu, S. Pailhès, S. Petit, and Ch. Simon

Appl. Phys. Lett. 92, 232506 (2008); http://dx.doi.org/10.1063/1.2943276 (3 pages) | Cited 12 times

Online Publication Date: 13 June 2008

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The antiferromagnetic phase transition in epitaxial RMnO3 (R = Y,Ho,Er) films of thickness 450–500 nm was investigated by neutron diffraction by recording the intensity variation of magnetic reflections as a function of temperature. For YMnO3 and ErMnO3, the Néel temperature for the Mn3+ ions ordering is of 66 and 68 K, respectively. For HoMnO3, the magnetic 011 reflection, which normally appears in bulk, is very weak and thus the onset of the Mn3+ ordering is not clearly observed; at 50 K there is a magnetic phase transition, which temperature corresponds to the reorientation temperature in bulk HoMnO3.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Ee Antiferromagnetics
68.55.jd Thickness

Room-temperature ferromagnetism in the Co-doped Ba0.5Sr0.5TiO3 thin films

L. B. Luo, Y. G. Zhao, H. F. Tian, J. J. Yang, H. Y. Zhang, J. Q. Li, J. J. Ding, B. He, S. Q. Wei, and C. Gao

Appl. Phys. Lett. 92, 232507 (2008); http://dx.doi.org/10.1063/1.2945282 (3 pages) | Cited 13 times

Online Publication Date: 13 June 2008

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The authors report the room-temperature ferromagnetism in the epitaxial thin films of 3% Co-doped Ba0.5Sr0.5TiO3 (CBSTO) grown by pulsed laser deposition. These films show the single phase character with Co dopants in the +2 state. More interestingly, ferromagnetic and ferroelectric transitions were observed at 570 and 150 K, respectively. The CBSTO films also show the exchange bias effect manifested by the negative shift and training effect of the hysteresis loops at 5 K. This work demonstrates that ferromagnetism can be induced in the ferroelectric materials, which is significant for shedding light on the mechanism of dopant induced ferromagnetism in insulators and applications.
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75.70.Ak Magnetic properties of monolayers and thin films
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.80.+q Magnetomechanical effects, magnetostriction
77.55.-g Dielectric thin films
77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
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Piezoelectricity enhancement in ferroelectric ceramics due to orientation

K. P. Jayachandran, J. M. Guedes, and H. C. Rodrigues

Appl. Phys. Lett. 92, 232901 (2008); http://dx.doi.org/10.1063/1.2940215 (3 pages) | Cited 4 times

Online Publication Date: 10 June 2008

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A continuum model simulation, explicitly incorporating anisotropic grain-level features, based on homogenization of materials predicts an enhancement of piezoelectricity in ferroelectric ceramics better than oriented single crystals. Incorporation of randomness in the orientation of polarization associated with the grains is demonstrated to offer great prospect in the design of ceramic ferroelectric materials such as BaTiO3.
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77.65.-j Piezoelectricity and electromechanical effects
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Dielectrophoretic trapping of suspended particles by selective pyroelectric effect in lithium niobate crystals

Simonetta Grilli and Pietro Ferraro

Appl. Phys. Lett. 92, 232902 (2008); http://dx.doi.org/10.1063/1.2943319 (3 pages) | Cited 14 times

Online Publication Date: 10 June 2008

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We have developed a dielectrophoretic approach for trapping suspended dielectric particles. The electric forces were produced by using the pyroelectric effect in periodically poled lithium niobate substrates. Complex electric field distributions can be built up through an appropriate control of the temperature and the particles can be distributed according to the geometry of the reversed ferroelectric domain structure. The electrode-less configuration makes the technique easier to accomplish compared to conventional dielectrophoretic devices, with interesting possibilities of applications in the field of biology and biomedicine.
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87.50.ch Electrophoresis/dielectrophoresis and other mechanical effects
81.40.Jj Elasticity and anelasticity, stress-strain relations

Local probing of relaxation time distributions in ferroelectric polymer nanomesas: Time-resolved piezoresponse force spectroscopy and spectroscopic imaging

Brian J. Rodriguez, Stephen Jesse, Jihee Kim, Stephen Ducharme, and Sergei V. Kalinin

Appl. Phys. Lett. 92, 232903 (2008); http://dx.doi.org/10.1063/1.2942390 (3 pages) | Cited 9 times

Online Publication Date: 11 June 2008

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Time-resolved piezoresponse force spectroscopy (TR-PFS) and spectroscopic imaging are developed to probe the spatial variability of relaxation behavior in nanoscale ferroelectric materials and structures. TR-PFS was applied to study polarization dynamics in polyvinylidine fluoride and trifluoroethylene nanomesas. We demonstrate that polarization relaxation in ferroelectric polymers is slow even on the ∼ 10 nm length scale of piezoresponse force microscopy (PFM) signal generation. Furthermore, the relaxation times are found to be nonuniform within the nanomesa, indicative of a complex internal structure. The applicability of TR-PFM for studies of polarization dynamics in ferroelectric polymers and relaxors is discussed.
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77.55.-g Dielectric thin films
77.84.Jd Polymers; organic compounds
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Gm Dielectric loss and relaxation
77.22.Ej Polarization and depolarization
77.65.-j Piezoelectricity and electromechanical effects

Demonstration of enhancement-mode GaAs metal-insulator-semiconductor field effect transistor with channel inversion using Si3N4 as gate dielectric

J. F. Zheng, W. Tsai, W. P. Li, X. W. Wang, and T. P. Ma

Appl. Phys. Lett. 92, 232904 (2008); http://dx.doi.org/10.1063/1.2943148 (3 pages) | Cited 3 times

Online Publication Date: 11 June 2008

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We report n-channel enhancement-mode GaAs metal-insulator-semiconductor Field Effect Transistors (MISFETs) with ∼ 6 nm equivalent oxide thickness of molecular-and-atomic (MAD) depositioned Si3N4 as the gate dielectric. The GaAs based MISFETs were fabricated using a gate-first process that preserved the channel inversion characteristic in MIS capacitor structures [ W. P. Li, X. W. Wang, Y. X. Liu, and T. P. Ma, Appl. Phys. Lett. 90, 193503 (2007) ]. The channel inversion characteristics of the GaAs MIS capacitors, measured by the quasistatic C-V (capacitor-voltage) technique, were well maintained throughout the entire fabrication process with temperatures up to 800 °C. C-V hysteresis as small as 100 mV was achieved. The Si3N4-gated GaAs MISFETs clearly demonstrated the enhancement-mode, gate-modulated Id-Vd transfer characteristics with channel inversion.
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85.30.Tv Field effect devices
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