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29 Sep 2008

Volume 93, Issue 13, Articles (13xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 93, 132101 (2008); http://dx.doi.org/10.1063/1.2988720 (3 pages)

Yueh-Nan Chen and Lukas Gilz
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Electrical properties of Ta-doped SnO2 thin films epitaxially grown on TiO2 substrate

H. Toyosaki, M. Kawasaki, and Y. Tokura

Appl. Phys. Lett. 93, 132109 (2008); http://dx.doi.org/10.1063/1.2993346 (3 pages) | Cited 13 times

Online Publication Date: 30 September 2008

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We report electrical properties of Ta-doped SnO2 (Sn1−xTaxO2) films epitaxially grown on (110) surfaces of rutile TiO2 single crystalline substrates by a pulsed laser deposition method. Due to the large in-plane lattice mismatches (3.0% along [math10] and 7.7% along [001]), the films had almost relaxed crystalline structure. With increasing x, electron density was systematically enhanced to undergo the insulator-metal transition between x = 0.0004 and 0.004. Sn0.95Ta0.05O2 films exhibited the resistivity as low as 1.1×10−4 Ω cm that is comparable to the lowest value for an epitaxial In2O3 film doped with Sn.
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73.61.Le Other inorganic semiconductors
72.20.-i Conductivity phenomena in semiconductors and insulators
68.55.ag Semiconductors

High quality GaN-based Schottky barrier diodes

K. H. Lee, S. J. Chang, P. C. Chang, Y. C. Wang, and C. H. Kuo

Appl. Phys. Lett. 93, 132110 (2008); http://dx.doi.org/10.1063/1.2993353 (3 pages) | Cited 6 times

Online Publication Date: 30 September 2008

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We report the fabrication of GaN-based Schottky barrier diodes with multi-MgxNy/GaN buffer. Compared to conventional devices with a low-temperature GaN buffer, we achieved a six orders of magnitude smaller leakage current. It was also found that effective Schottky barrier height is larger for the proposed device due to the reduction in surface defect density by using the multi-MgxNy/GaN buffer.
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85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Kk Junction diodes
73.30.+y Surface double layers, Schottky barriers, and work functions

Resonant and phonon-assisted tunneling transport through silicon quantum dots embedded in SiO2

B. Berghoff, S. Suckow, R. Rölver, B. Spangenberg, H. Kurz, A. Dimyati, and J. Mayer

Appl. Phys. Lett. 93, 132111 (2008); http://dx.doi.org/10.1063/1.2992057 (3 pages) | Cited 3 times

Online Publication Date: 1 October 2008

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Charge transport through SiO2/Si/SiO2 double-barrier structures (DBSs) and SiO2 single-barrier structures is investigated by low temperature I-V measurements. Resonant tunneling signatures accompanied by a negative differential conductance are observed if silicon quantum dots (Si QDs) are embedded in the amorphous SiO2 matrix. The I-V characteristics are correlated with the morphology of Si QDs extracted from transmission electron microscopy and photoluminescence. Evidence for phonon-assisted tunneling at low voltages has been found in the DBSs. These results show the potential but also the limitation for charge extraction from Si QDs embedded in SiO2.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
78.55.Ap Elemental semiconductors
73.63.Kv Quantum dots
78.67.Hc Quantum dots
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

High temperature electron spin relaxation in bulk GaAs

S. Oertel, J. Hübner, and M. Oestreich

Appl. Phys. Lett. 93, 132112 (2008); http://dx.doi.org/10.1063/1.2993344 (3 pages) | Cited 20 times

Online Publication Date: 1 October 2008

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Temperature and electron density dependent measurements of the electron spin relaxation in bulk GaAs are performed using time- and polarization-resolved photoluminescence spectroscopy. The electron spin relaxation time is dominated in the high temperature regime by the D’yakonov-Perel’ [ M. I. D’yakonov and V. I. Perel’, Sov. Phys. Solid State 13, 3023 (1972) ] spin relaxation mechanism and decreases for negligible electron densities from 42 ps at 300 K to 20 ps at 400 K. The measured spin relaxation times are compared with numerical calculations which include electron-phonon momentum scattering and have no adjustable parameters.
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72.25.Rb Spin relaxation and scattering
72.25.Fe Optical creation of spin polarized carriers
72.25.Dc Spin polarized transport in semiconductors
78.55.Cr III-V semiconductors
78.47.jd Time resolved luminescence

Dominant ultraviolet light emissions in packed ZnO columnar homojunction diodes

Jieying Kong, Sheng Chu, Mario Olmedo, Lin Li, Zheng Yang, and Jianlin Liu

Appl. Phys. Lett. 93, 132113 (2008); http://dx.doi.org/10.1063/1.2992629 (3 pages) | Cited 22 times

Online Publication Date: 2 October 2008

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The growth of Sb-doped p-type ZnO/Ga-doped n-type ZnO homojunction on Si (100) substrate by molecular beam epitaxy led to closely packed vertical ZnO columns with lateral diameters ranging from 100 to 400 nm. Mesa structures were defined and Ohmic contact of both n-type ZnO and p-type ZnO was realized with Au/Ti and Au/NiO, respectively. I-V and C-V curves present typical electrical properties of a diode, indicating that reliable p-type ZnO was formed. Electroluminescence shows dominant ultraviolet emissions with insignificant deep-level related yellow/green band emissions at different drive currents from 60 to 100 mA at room temperature.
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85.30.Kk Junction diodes
85.60.Jb Light-emitting devices

Spin-splitting in an AlxGa1−xN/GaN nanowire for a quantum-ring interferometer

Ikai Lo, Wen-Yuan Pang, Yen-Liang Chen, Yu-Chi Hsu, Jih-Chen Chiang, Wei-Hsin Lin, Wan-Ting Chiu, Jenn-Kai Tsai, and Chun-Nan Chen

Appl. Phys. Lett. 93, 132114 (2008); http://dx.doi.org/10.1063/1.2995866 (3 pages) | Cited 4 times

Online Publication Date: 3 October 2008

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An Al0.18Ga0.82N/GaN heterostructure was used to fabricate a ballistic nanowire with a wire width of 200 nm by focused ion beam. We observed the beating Shubnikov–de Haas oscillations in the nanowire with a spin-splitting energy of (2.4±0.3) meV. Based on the results, we proposed a spin-Hall quantum-ring interferometer made of AlxGa1−xN/GaN nanowires for spintronic applications.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.My Galvanomagnetic and other magnetotransport effects
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Electrical properties of aggregated detonation nanodiamonds

Mose Bevilacqua, Sameer Patel, Aysha Chaudhary, Haitao Ye, and Richard B. Jackman

Appl. Phys. Lett. 93, 132115 (2008); http://dx.doi.org/10.1063/1.2996026 (3 pages) | Cited 6 times

Online Publication Date: 3 October 2008

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Nanometer-scale diamonds formed using a detonation process are an interesting class of diamond materials. Commercially supplied material is highly aggregated with ∼ 5 nm diamond crystals forming particles with micron sizes. Previous models have suggested that nondiamond carbon is incorporated between the crystals, which would reduce the electrical and chemical usefulness of this form of diamond. However, using impedance spectroscopy we have shown that at temperatures below 350 °C the form of detonation nanodiamond being studied is a near to ideal dielectric, implying a full sp3 form. At temperatures above this the surfaces of the diamond crystals may support some nondiamond carbon.
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72.80.Rj Fullerenes and related materials
81.07.Bc Nanocrystalline materials
81.05.U- Carbon/carbon-based materials

Electron scatterings in selectively doped n-AlGaAs/GaAs heterojunctions with high density self-assembled InAlAs antidots

Takuya Kawazu and Hiroyuki Sakaki

Appl. Phys. Lett. 93, 132116 (2008); http://dx.doi.org/10.1063/1.2996414 (3 pages) | Cited 2 times

Online Publication Date: 3 October 2008

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The scattering processes of two-dimensional electrons are studied in selectively doped n-AlGaAs/GaAs heterojunctions where high density InAlAs anti dots are embedded in the vicinity of the GaAs channel. Mobilities μ are measured as a function of the electron concentrations Ns in two samples where the In1−xAlxAs antidots are grown with different Al contents (x ∼ 0.75 and 0.5). It is found that the Ns dependence of μ is strongly dependent on the Al content x of the embedded InAlAs dots, although their shapes and densities are almost same. The experimental data are well explained by theoretical models based on the surface profiles of the InAlAs dot layers.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.72.U- Doping and impurity implantation
73.21.La Quantum dots

Epitaxial ferromagnetic Fe3Si/Si(111) structures with high-quality heterointerfaces

K. Hamaya, K. Ueda, Y. Kishi, Y. Ando, T. Sadoh, and M. Miyao

Appl. Phys. Lett. 93, 132117 (2008); http://dx.doi.org/10.1063/1.2996581 (3 pages) | Cited 17 times

Online Publication Date: 3 October 2008

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To develop silicon-based spintronic devices, we have explored high-quality ferromagnetic Fe3Si/silicon (Si) structures. Using low-temperature molecular beam epitaxy at 130 °C, we realize the epitaxial growth of ferromagnetic Fe3Si layers on Si(111) with an abrupt interface, and the grown Fe3Si layer has the ordered DO3 phase. Measurements of magnetic and electrical properties for the Fe3Si/Si(111) yield a magnetic moment of ∼ 3.16μB/f.u. at room temperature and a rectifying Schottky-diode behavior with the ideality factor of ∼ 1.08, respectively.
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73.40.Ns Metal-nonmetal contacts
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.30.Cr Saturation moments and magnetic susceptibilities
73.40.Ei Rectification
85.30.Kk Junction diodes
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
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Room temperature ferromagnetism in Mn-doped CdS nanorods

Savas Delikanli, Shuli He, Yueling Qin, Peihong Zhang, Hao Zeng, Hongwang Zhang, and Mark Swihart

Appl. Phys. Lett. 93, 132501 (2008); http://dx.doi.org/10.1063/1.2982583 (3 pages) | Cited 13 times

Online Publication Date: 2 October 2008

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Mn-doped CdS nanorods synthesized by solution phase chemistry demonstrate robust ferromagnetic properties at and above room temperature. The nanorods show large coercivity, possibly originating from the shape anisotropy. The hysteresis measurements reveal strong temperature dependence. Possible origin of the ferromagnetism is discussed.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Pp Magnetic semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
81.07.-b Nanoscale materials and structures: fabrication and characterization
75.30.Gw Magnetic anisotropy
75.50.Tt Fine-particle systems; nanocrystalline materials

Atomic-scale chemical analyses of niobium oxide/niobium interfaces via atom-probe tomography

Kevin E. Yoon, David N. Seidman, Claire Antoine, and Pierre Bauer

Appl. Phys. Lett. 93, 132502 (2008); http://dx.doi.org/10.1063/1.2987483 (3 pages) | Cited 9 times

Online Publication Date: 2 October 2008

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Niobium is the metal of choice for superconducting radio-frequency cavities for the future International Linear Collider. We present the results of atomic-scale characterization of the oxidation of niobium utilizing local-electrode atom-probe tomography employing picosecond laser pulsing. Laser pulsing is utilized to prevent a tip from fracturing as a buried niobium oxide/niobium interface is dissected on an atom-by-atom basis. The thickness of niobium oxide is about 15 nm, the root-mean-square chemical roughness is 0.4 nm, and the composition is close to Nb2O5, which is an insulator, with an interstitial oxygen concentration profile in Nb extending to a depth of 12 nm.
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68.35.Ct Interface structure and roughness
81.65.Mq Oxidation
61.72.jj Interstitials

Selective domain wall depinning by localized Oersted fields and Joule heating

Dennis Ilgaz, Mathias Kläui, Lutz Heyne, Olivier Boulle, Fabian Zinser, Stephen Krzyk, Mikhail Fonin, Ulrich Rüdiger, Dirk Backes, and Laura J. Heyderman

Appl. Phys. Lett. 93, 132503 (2008); http://dx.doi.org/10.1063/1.2990629 (3 pages) | Cited 7 times

Online Publication Date: 2 October 2008

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Using low temperature magnetoresistance measurements, the possibility to selectively move a domain wall locally by applying current pulses through a Au nanowire adjacent to a permalloy element is studied. We find that the domain wall depinning field is drastically modified with increasing current density due to the Joule heating and the Oersted field of the current, and controlled motion due to the Oersted field without any externally applied fields is achieved. By placing the domain wall at various distances from the Au wire, we determine the range of the Joule heating and the Oersted field and both effects can be separated.
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75.60.Ch Domain walls and domain structure
72.15.Gd Galvanomagnetic and other magnetotransport effects
72.15.Jf Thermoelectric and thermomagnetic effects

Current-perpendicular-to-plane transport properties of polycrystalline Fe3O4/α-Fe2O3 heterostructures

W. B. Mi, E. Y. Jiang, and H. L. Bai

Appl. Phys. Lett. 93, 132504 (2008); http://dx.doi.org/10.1063/1.2993223 (3 pages) | Cited 2 times

Online Publication Date: 2 October 2008

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Current-perpendicular-to-plane transport properties of sputtered polycrystalline Fe3O4/α-Fe2O3 heterostructures were investigated. A rectifying behavior was observed. The voltage shift increases linearly with temperature and turns from negative to positive at 230 K. The current-dependent magnetoresistance (MR) changes from negative to positive in the temperature range of 230–260 K. The largest negative MR is −32% at 230 K, and the positive MR at 305 K reaches 80% at 1.0 mA. The characteristic MR is thought to be caused by the rectifying effect and band structure at the Fe3O4/α-Fe2O3 interface.
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73.40.Ei Rectification
75.50.Gg Ferrimagnetics
75.20.Ck Nonmetals
72.25.Mk Spin transport through interfaces

Observation of a high negative spin polarization at the Fe/MgO(100) surface oxidized at room temperature

M. Kurahashi, X. Sun, S. Entani, and Y. Yamauchi

Appl. Phys. Lett. 93, 132505 (2008); http://dx.doi.org/10.1063/1.2995995 (3 pages) | Cited 6 times

Online Publication Date: 2 October 2008

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Spin polarization of an Fe/MgO(100) surface oxidized at room temperature has been analyzed with a spin-polarized metastable helium beam, which is an extremely surface sensitive spin probe, under high magnetic fields (0–50 kOe). The spin polarization of the Fe surface, although it initially decays with oxygen exposure, increases at >20 L (1 L = 10−6 Torr sec) and becomes comparable to that observed for a clean Fe surface at >100 L. The polarization is negative and especially high at around the Fermi level. This may be understood if we assume the formation of Fe3O4.
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72.25.Mk Spin transport through interfaces
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.25.Ba Spin polarized transport in metals
75.50.Bb Fe and its alloys

Ferromagnetism induced by defect complex in Co-doped ZnO

En-Zuo Liu, Yan He, and J. Z. Jiang

Appl. Phys. Lett. 93, 132506 (2008); http://dx.doi.org/10.1063/1.2995997 (3 pages) | Cited 21 times

Online Publication Date: 2 October 2008

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The effect of Al donor and O vacancy (VO) on the magnetic properties of Co-doped ZnO has been studied by first-principles calculations. It is found that only Al donor cannot induce ferromagnetism (FM) in Co-doped ZnO but can provide additional electrons, which results in the enhancement of Fermi level. The presence of VO makes the Co empty 3d-t2g minority state broadened, and a t2g-VO hybrid level at the conduction band minimum forms. The combination of Al donor and VO results in a charge transfer to the Co empty 3d-t2g minority states, which induces a strong carrier-mediated FM interaction. Our results give an explanation for the controversial magnetic properties of (Co, Al)-codoped ZnO reported in the literature.
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71.20.Nr Semiconductor compounds
61.72.jd Vacancies
71.15.-m Methods of electronic structure calculations
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials

On the possibility of ferromagnetism in carbon-doped anatase TiO2

Kesong Yang, Ying Dai, Baibiao Huang, and Myung-Hwan Whangbo

Appl. Phys. Lett. 93, 132507 (2008); http://dx.doi.org/10.1063/1.2996024 (3 pages) | Cited 47 times

Online Publication Date: 2 October 2008

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To see if ferromagnetism can occur in C-doped anatase TiO2, we performed first-principles calculations for a number of C-doped structures in which C atoms substitute O atoms. Our study shows that each C has spin-polarized 2p states in the band gap generating a magnetic moment of 2.0μB. The magnetic coupling between doped C atoms is substantial leading to either antiferromagnetism or ferromagnetism when the C⋯C distance lies between 3–4 Å. A strong ferromagnetic coupling occurs when the two C atoms form a slightly bent C–Ti–C unit by replacing two oxygen atoms at the opposite vertices of a TiO6 octahedron.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Cc Other ferromagnetic metals and alloys
75.50.Pp Magnetic semiconductors
71.15.-m Methods of electronic structure calculations
71.20.Nr Semiconductor compounds

Fast computation of magnetostatic fields by nonuniform fast Fourier transforms

Evaggelos Kritsikis, Jean-Christophe Toussaint, Olivier Fruchart, Helga Szambolics, and Liliana Buda-Prejbeanu

Appl. Phys. Lett. 93, 132508 (2008); http://dx.doi.org/10.1063/1.2995850 (3 pages) | Cited 1 time

Online Publication Date: 3 October 2008

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The bottleneck of micromagnetic simulations is the computation of the long-ranged magnetostatic fields. This can be tackled on regular N-node grids with fast Fourier transforms in time N log N, whereas the geometrically more versatile finite element methods (FEMs) are bounded to N4/3 in the best case. We report the implementation of a nonuniform fast Fourier transform algorithm, which brings a N log N convergence to FEM, with no loss of accuracy in the results.
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75.40.Mg Numerical simulation studies
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
02.30.Uu Integral transforms
02.70.Dh Finite-element and Galerkin methods
02.60.Lj Ordinary and partial differential equations; boundary value problems
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Polarization switching using single-walled carbon nanotubes grown on epitaxial ferroelectric thin films

P. Paruch, A.-B. Posadas, M. Dawber, C. H. Ahn, and P. L. McEuen

Appl. Phys. Lett. 93, 132901 (2008); http://dx.doi.org/10.1063/1.2985815 (3 pages) | Cited 10 times

Online Publication Date: 29 September 2008

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We have directly grown single-walled carbon nanotubes on epitaxial BaTiO3 thin films, fabricating prototype carbon nanotube-ferroelectric devices. We demonstrate polarization switching using the nanotube as a local electric field source and compare the results to switching with an atomic force microscopy tip. The observed variation of domain growth rates in the two cases agrees with the changes in electric field intensity at the ferroelectric surface.
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81.07.De Nanotubes
77.80.Fm Switching phenomena
77.55.-g Dielectric thin films
77.22.Ej Polarization and depolarization

High mobility HfO2-based In0.53Ga0.47As n-channel metal-oxide-semiconductor field effect transistors using a germanium interfacial passivation layer

Hyoung-Sub Kim, Injo Ok, Feng Zhu, M. Zhang, S. Park, J. Yum, H. Zhao, Prashant Majhi, Domingo I. Garcia-Gutierrez, Niti Goel, W. Tsai, C. K. Gaspe, M. B. Santos, and Jack C. Lee

Appl. Phys. Lett. 93, 132902 (2008); http://dx.doi.org/10.1063/1.2990645 (3 pages) | Cited 3 times

Online Publication Date: 29 September 2008

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The electrical characteristics of HfO2-based n-channel metal-oxide-semiconductor field effect transistors (MOSFETs) and metal-oxide-semiconductor capacitors (MOSCAPs) on high indium content In0.53Ga0.47As channel layers are presented. N-channel MOSFETs with a germanium (Ge) interfacial passivation layer (IPL) show maximum mobility 3186 cm2/V s from split capacitance-voltage (C-V) method and the normalized drain current (to the channel length of 1 μm) of 753 mA/mm at Vg = Vth+2 V and Vd = 2 V. On the contrary, MOSFETs without a Ge IPL or with high temperature post-metal annealing (PMA) exhibit inferior characteristics. MOSCAPs on n-type In0.53Ga0.47As layers demonstrate excellent C-V characteristics including low C-V frequency dispersion and low dielectric leakage current.
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85.30.Tv Field effect devices
84.32.Tt Capacitors

Hardening of the ferroelectric soft mode in SrTiO3 thin films

Ikufumi Katayama, Hiroshi Shimosato, Dhanvir Singh Rana, Iwao Kawayama, Masayoshi Tonouchi, and Masaaki Ashida

Appl. Phys. Lett. 93, 132903 (2008); http://dx.doi.org/10.1063/1.2991442 (3 pages) | Cited 12 times

Online Publication Date: 30 September 2008

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We have studied the origin of soft-mode hardening in SrTiO3 thin films using broadband terahertz time-domain spectroscopy. We measured the dielectric dispersions in the terahertz region of as-deposited, O2 annealed, and high-temperature annealed SrTiO3 thin films deposited on MgO and La0.3Sr0.7Al0.65Ta0.35O3 substrates. The results show that the ferroelectric soft mode softens dramatically by the high-temperature annealing. We also measure x-ray diffractions and atomic force microscope images and conclude that the hardening of the ferroelectric soft mode in the thin films is determined by the grain size of each crystalline domain which is enlarged by the high-temperature annealing due to remelting.
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77.55.-g Dielectric thin films
77.80.B- Phase transitions and Curie point
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Size effects on thin film ferroelectrics: Experiments on isolated single crystal sheets

L. W. Chang, M. McMillen, F. D. Morrison, J. F. Scott, and J. M. Gregg

Appl. Phys. Lett. 93, 132904 (2008); http://dx.doi.org/10.1063/1.2990760 (3 pages) | Cited 20 times

Online Publication Date: 1 October 2008

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Thin lamellae were cut from bulk single crystal BaTiO3 using a focused ion beam microscope. They were then removed and transferred onto single crystal MgO substrates, so that their functional properties could be measured independent of the original host bulk ferroelectric. The temperature dependence of the capacitance of these isolated single crystal films was found to be strongly bulklike, demonstrating a sharp Curie anomaly, as well as Curie–Weiss behavior. In addition, the sudden change in the remanent polarization as a function of temperature at TC was characteristic of a first order phase change. The work represents a dramatic improvement on that previously published by Saad et al. [J. Phys.: Condens. Matter 16, L451 (2004) ], as critical shortcomings in the original specimen geometry, involving potential signal contributions from bulk BaTiO3, have now been obviated. That the functional properties of single crystal thin film lamellae are comparable to bulk, and not like those of conventionally deposited heterogeneous thin film systems, has therefore been confirmed.
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77.55.-g Dielectric thin films
77.22.Ej Polarization and depolarization
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point

Temperature characteristics and development of field-induced phase transition in relaxor ferroelectric Pb(Mg1/3Nb2/3)0.87Ti0.13O3 ceramics

J. Peräntie, J. Hagberg, A. Uusimäki, and H. Jantunen

Appl. Phys. Lett. 93, 132905 (2008); http://dx.doi.org/10.1063/1.2993345 (3 pages) | Cited 7 times

Online Publication Date: 1 October 2008

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Ferroelectric phase inducing threshold electric field Eth and its temperature dependence were determined in relaxor ferroelectric 0.87Pb(Mg1/3Nb2/3)O3−0.13PbTiO3 (PMN–13PT) ceramics by measuring dielectric response on a dc field pulse. Evolution of the induced ferroelectricity was observed by means of polarization measurements. An inducing threshold field was found to have a minimum of Eth,min = 1.55 kV/cm at T = −5 °C. In contrast to pure PMN, which shows a minimum threshold field near the depolarization temperature, the temperature of the minimum threshold field differs by an amount of ΔT = 23 °C from the depolarization temperature Tdp = 18 °C in PMN-13PT.
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77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.22.Ej Polarization and depolarization

Observation of magnetoelectric coupling in Bi0.7Dy0.3FeO3 thin films at room temperature

V. R. Palkar and K. Prashanthi

Appl. Phys. Lett. 93, 132906 (2008); http://dx.doi.org/10.1063/1.2994692 (3 pages) | Cited 16 times

Online Publication Date: 2 October 2008

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Spatial coexistence of ferroelectric and magnetic domains in micrometer scale is confirmed by multimode scanning probe microscopy of pulsed laser deposited Bi0.7Dy0.3FeO3 thin films. The observed change in ferroelectric polarization with applied magnetic field proves the coupling between magnetic and ferroelectric order parameters. Moreover, the alignment of magnetic domains with externally applied electric field further confirms the presence of coupling in this system. Remarkably, the effect persists even after the electric field is removed, thereby implying an electric field induced magnetic hysteresis phenomenon in the magnetic domain structure. The results suggest an in-principle usability of this system for multifunctional applications.
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75.80.+q Magnetomechanical effects, magnetostriction
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Kw Domain structure (including magnetic bubbles and vortices)
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization

Bandgap engineering of tunnel oxide with multistacked layers of Al2O3/HfO2/SiO2 for Au-nanocrystal memory application

Yun-Shan Lo, Ke-Chih Liu, Jyun-Yi Wu, Cheng-Hao Hou, and Tai-Bor Wu

Appl. Phys. Lett. 93, 132907 (2008); http://dx.doi.org/10.1063/1.2995862 (3 pages) | Cited 14 times

Online Publication Date: 2 October 2008

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Charge storage characteristics of metal-oxide-semiconductor (MOS) structure containing Au nanocrystals on tunnel oxide composed of triply stacked SiO2, HfO2, and Al2O3 layers were studied. Significantly high charge injection and detrapping efficiency for program and erase operations along with a satisfactory long-term charge retention were obtained from the above MOS structure. It is attributed to the bandgap engineering of tunnel oxide with a multistacked concave barrier, from which the effective thickness of the tunneling barrier can be greatly reduced under a moderate bias, while a thick and high barrier is retained for charge retention.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
84.30.Sk Pulse and digital circuits
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films

Effects of unequally biaxial misfit strains on polarization phase diagrams in embedded ferroelectric thin layers: Phase field simulations

Ping-Li Liu, Jie Wang, Tong-Yi Zhang, Yulan Li, Long-Qing Chen, Xing-Qiao Ma, Wu-Yang Chu, and Li-Jie Qiao

Appl. Phys. Lett. 93, 132908 (2008); http://dx.doi.org/10.1063/1.2975161 (3 pages) | Cited 2 times

Online Publication Date: 3 October 2008

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Show Abstract
Phase field simulations were conducted to investigate the effects of unequally biaxial misfit strains on domain stability diagrams and equilibrium domain structures in an epitaxial ferroelectric PbTiO3 thin layer, which is sandwiched in a nonferroelectric medium. The simulations reveal a multidomain structure in the layer and allow constructing “misfit strain-misfit strain” and “temperature-misfit strain” phase diagrams. It is found that unequally biaxial misfit strains may lead to the presence of a single tetragonal variant, either a-domains or b-domains, which do not exist if the misfit strains are equally biaxial.
Show PACS
77.80.B- Phase transitions and Curie point
77.80.Dj Domain structure; hysteresis
77.55.-g Dielectric thin films
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