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29 Mar 2004

Volume 84, Issue 13, pp. 2223-2459

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Appl. Phys. Lett. 84, 2244 (2004); http://dx.doi.org/10.1063/1.1690471 (3 pages)

David R. Smith, David Schurig, Jack J. Mock, Pavel Kolinko, and Patrick Rye
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Electron mobility in ultrathin silicon-on-insulator layers at 4.2 K

M. Prunnila, J. Ahopelto, and F. Gamiz

Appl. Phys. Lett. 84, 2298 (2004); http://dx.doi.org/10.1063/1.1687980 (3 pages) | Cited 7 times

Online Publication Date: 23 March 2004

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Low temperature mobility measurements of silicon-on-insulator (SOI) metal-oxidefield-effect-transistors are reported. The batch of devices fabricated in this work includes both ultrathin and thick devices for which the SOI film thicknesses are in the ranges of 10–15 nm and 56–61 nm, respectively. The 4.2 K peak mobility of the thick devices is 1.9 m2/V s. The ultrathin devices show mobility degradation at low electron densities where the mobility is also observed to decrease with decreasing the SOI film thickness. The peak mobilities of these devices are in the range of 1.35–1.57 m2/V s. Numerical calculations show that ultrathin devices are in the limit where the electrons are confined by the quantum well defined by gate oxide and buried oxide, which is interpreted to lead to the observed mobility degradation. © 2004 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices

Enhanced thermoelectric figure of merit of CoSb3 via large-defect scattering

X. Shi, L. Chen, J. Yang, and G. P. Meisner

Appl. Phys. Lett. 84, 2301 (2004); http://dx.doi.org/10.1063/1.1687997 (3 pages) | Cited 41 times

Online Publication Date: 23 March 2004

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We have measured the structural, chemical, and transport properties of a series of CoSb3 skutterudite samples modified by fullerene additions of 0, 0.52, 3.28, 3.90, 4.77, and 6.54 mass%. Fullerene is a 60-atom carbon molecule that forms microsize clusters between the grain boundaries of CoSb3. We observed that the dominant scattering mechanism in the electrical transport changes from impurity scattering to grain-boundary scattering near a C60 content of ∼5–6 mass%, and that thermal conductivity decreases with increasing C60 content. A significant increase in the thermoelectric figure of merit is achieved for 6.54 mass% C60 compared to the pure CoSb3. © 2004 American Institute of Physics.
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72.15.Jf Thermoelectric and thermomagnetic effects
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
61.72.Mm Grain and twin boundaries
72.15.Qm Scattering mechanisms and Kondo effect

Tuning the electrical resistivity of pulsed laser deposited TiSiOx thin films from highly insulating to conductive behaviors

D. Brassard, D. K. Sarkar, M. A. El Khakani, and L. Ouellet

Appl. Phys. Lett. 84, 2304 (2004); http://dx.doi.org/10.1063/1.1688999 (3 pages) | Cited 8 times

Online Publication Date: 23 March 2004

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We report on the successful growth of amorphous TiSiOx thin films by means of pulsed-laser ablation of a TiO2/SiO2 composite target in a high-vacuum chamber. The room-temperature resistivity of the TiSiOx films is found to decrease by more than 6 orders of magnitude (i.e., from ∼ 2×104 to 10−2 Ω cm) when their substrate deposition temperature (Td) is increased from 20 to 600 °C. On the other hand, by subjecting these films to a post-deposition annealing at 600 °C in oxygen atmosphere, they become highly insulating with a resistivity level as high as 2×1010 Ω cm, regardless of the Td value. The presence of conductive titanium silicide and titanium sub-oxide local phases in the as-deposited TiSiOx films, as revealed by photoelectron spectroscopy analyses, appears to be the cause of the observed tremendous change in the film resistivity. In particular, it is shown that the resistivity of the TiSiOx films is strongly correlated with their oxygen content. © 2004 American Institute of Physics.
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73.61.Ng Insulators
81.15.Fg Pulsed laser ablation deposition
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
72.60.+g Mixed conductivity and conductivity transitions
79.60.-i Photoemission and photoelectron spectra

A spin metal–oxide–semiconductor field-effect transistor using half-metallic-ferromagnet contacts for the source and drain

Satoshi Sugahara and Masaaki Tanaka

Appl. Phys. Lett. 84, 2307 (2004); http://dx.doi.org/10.1063/1.1689403 (3 pages) | Cited 95 times

Online Publication Date: 23 March 2004

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We propose and theoretically analyze a metal–oxide–semiconductor field-effect-transistor (MOSFET) type of spin transistor (spin MOSFET) consisting of a MOS structure and half-metallic-ferromagnet (HMF) contacts for the source and drain. When the magnetization configuration of the HMF source and drain is parallel (antiparallel), highly spin-polarized carriers injected from the HMF source to the channel are transported into (blocked by) the HMF drain, resulting in the magnetization-configuration-dependent output characteristics. Our two-dimensional numerical analysis indicates that the spin MOSFET exhibits high (low) current drive capability in the parallel (antiparallel) magnetization, and that extremely large magnetocurrent ratios can be obtained. Furthermore, the spin MOSFET satisfies other important requirements for “spintronic integrated circuits,” such as high amplification capability, low power-delay product, and low off-current. © 2004 American Institute of Physics.
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85.75.Hh Spin polarized field effect transistors
72.20.Fr Low-field transport and mobility; piezoresistance
85.40.Ls Metallization, contacts, interconnects; device isolation
72.25.Hg Electrical injection of spin polarized carriers
85.30.De Semiconductor-device characterization, design, and modeling

Mn-implanted dilute magnetic semiconductor InP:Mn

Yoon Shon, W. C. Lee, Y. S. Park, Y. H. Kwon, Seung Joo Lee, K. J. Chung, H. S. Kim, D. Y. Kim, D. J. Fu, T. W. Kang, X. J. Fan, Y. J. Park, and H. T. Oh

Appl. Phys. Lett. 84, 2310 (2004); http://dx.doi.org/10.1063/1.1690875 (3 pages) | Cited 17 times

Online Publication Date: 23 March 2004

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Unintentionally doped bulk InP was prepared by the liquid encapsulated Czochralski method and subsequently implanted with various doses of Mn+. The properties of Mn+-implanted InP:Mn were investigated by various measurements. The results of energy dispersive x-ray peaks displayed injected concentrations of Mn of 0.8% and 8.8%, respectively. The results of photoluminescence (PL) measurement showed that optical broad transitions related to Mn appeared near 1.089, 1.144, and 1.185 eV in samples with various doses of Mn+. It was confirmed that the photoluminescence peaks near 1.089, 1.144, and 1.185 eV were Mn-correlated PL bands by the implantation of Mn. Ferromagnetic hysteresis loops measured at 10 K were observed and the temperature-dependent magnetization showed ferromagnetic behavior around 90 K, which almost agreed with the theoretical prediction (Tc ∼ 70 K). © 2004 American Institute of Physics.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.55.Cr III-V semiconductors
81.10.Fq Growth from melts; zone melting and refining
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Electron transport properties in AlGaN/InGaN/GaN double heterostructures grown by metalorganic vapor phase epitaxy

C. X. Wang, K. Tsubaki, N. Kobayashi, T. Makimoto, and N. Maeda

Appl. Phys. Lett. 84, 2313 (2004); http://dx.doi.org/10.1063/1.1690879 (3 pages) | Cited 14 times

Online Publication Date: 23 March 2004

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Electron transport properties in AlGaN/InGaN/GaN double heterostructures have been investigated. Samples were grown by metalorganic vapor phase epitaxy and evaluated using x-ray diffraction and variable temperature Hall effect measurements. Much higher two-dimensional electron gas density of up to 50% has been obtained in AlGaN/InGaN/GaN structure than in a typical AlGaN/GaN structure due to the larger polarization effect while the mobilities are comparable at room temperature and above in these structures, which demonstrates the suitability of an AlGaN/InGaN/GaN structure for high-power device applications. Theoretical simulations were done to investigate the carrier transport mechanism, and they suggest that alloy disorder and interface roughness scattering have a very strong impact on the electron transport properties in AlGaN/InGaN/GaN structures. © 2004 American Institute of Physics.
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81.05.Ea III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.35.Ct Interface structure and roughness
68.55.A- Nucleation and growth
73.61.Ey III-V semiconductors

Dependence of leakage mechanisms on dielectric barrier in Cu–SiOC damascene interconnects

V. C. Ngwan, Chunxiang Zhu, and Ahila Krishnamoorthy

Appl. Phys. Lett. 84, 2316 (2004); http://dx.doi.org/10.1063/1.1688978 (3 pages) | Cited 6 times

Online Publication Date: 23 March 2004

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Leakage mechanisms of low-dielectric constant (low-k) carbon-doped silicon oxide (SiOC) were investigated in Cu damascene structure integrated with amorphous SiC or SiN as Cu diffusion barrier at low electric fields (0–1.36 MV/cm) and various temperatures (25–250 °C). Conduction mechanisms of SiOC integrated with SiC were found to be different from that with SiN. Schottky emission over a barrier height of 0.70 eV at Ta/SiOC interface dominates in SiC–SiOC structures while Poole–Frenkel emission over a trap potential well of 0.69 eV dominates in SiN–SiOC structures. Traps in the SiN/SiOC interface are the main sources of leakage in Cu low-k damascene structures with SiN barrier. © 2004 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
77.22.Ch Permittivity (dielectric function)
68.35.Fx Diffusion; interface formation
73.50.Fq High-field and nonlinear effects

Energy band alignment at the (100)Ge/HfO2 interface

V. V. Afanas’ev and A. Stesmans

Appl. Phys. Lett. 84, 2319 (2004); http://dx.doi.org/10.1063/1.1688453 (3 pages) | Cited 56 times

Online Publication Date: 23 March 2004

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The Ge/HfO2 interface band diagram was directly determined using internal photoemission of electrons and holes from Ge into the Hf oxide. The inferred offsets of the conduction and valence band at the interface, 2.0±0.1 and 3.0±0.1 eV, respectively, suggest the possibility to apply the deposited HfO2 as an insulator on Ge. The post-deposition annealing of the Ge/HfO2 structures in oxygen results in ∼1 eV reduction of the valence band offset attributed to the growth of GeO2 interlayer. © 2004 American Institute of Physics.
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84.32.Tt Capacitors
79.60.Jv Interfaces; heterostructures; nanostructures
68.35.Ct Interface structure and roughness
73.20.At Surface states, band structure, electron density of states
61.72.Cc Kinetics of defect formation and annealing

Temperature dependence of electron impact ionization in In0.53Ga0.47As

C. H. Tan, G. J. Rees, P. A. Houston, J. S. Ng, W. K. Ng, and J. P. R. David

Appl. Phys. Lett. 84, 2322 (2004); http://dx.doi.org/10.1063/1.1691192 (3 pages) | Cited 10 times

Online Publication Date: 23 March 2004

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Monte Carlo is used to model the electric field and temperature dependence of the electron ionization coefficient, α, in In0.53Ga0.47As, using a two-component ionization rate to account for its observed anomalous dependence on the electric field. α is predicted to decrease with temperature at fields above approximately 180 kV/cm, where impact ionization is limited by the high-energy electron population, and to increase with temperature at lower fields, where it is enhanced by the decreasing ionization threshold energy, in agreement with experimental observations. © 2004 American Institute of Physics.
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72.20.Ht High-field and nonlinear effects
72.80.Ey III-V and II-VI semiconductors

Current conduction processes in high-κ Gd0.31Ga0.1O0.59/Ga2O3 gate dielectric stacks on GaAs

A. Chen, M. Passlack, N. Medendorp, and D. Braddock

Appl. Phys. Lett. 84, 2325 (2004); http://dx.doi.org/10.1063/1.1687999 (3 pages) | Cited 6 times

Online Publication Date: 23 March 2004

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Current conduction processes in high-κ (κ = 20.2) Gd0.31Ga0.1O0.59/Ga2O3 dielectric stacks grown on n-type GaAs by molecular beam epitaxy have been investigated. Metal-oxide-semiconductor capacitors have been characterized by current density (j) versus electric field (E) measurements at temperatures ranging from 90 to 450 K. For temperatures T ⩽ 200 K, the high field (4.5 ⩽ E ⩽ 6.2 MV/cm) current is temperature independent and a Fowler–Nordheim tunneling slope of 1.75 eV3/2 is obtained. Frenkel–Poole emission is found to dominate at temperatures of 300 K and above at moderate electric fields (1.3 ⩽ E ⩽ 2.2 MV/cm). For Frenkel–Poole emission, a barrier height of 1.1 eV and a dynamic dielectric constant of 7.95 is derived from ln(j/E) vs 1/T and ln(j/E) vs E1/2 plots, respectively. © 2004 American Institute of Physics.
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77.55.-g Dielectric thin films
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.20.Ht High-field and nonlinear effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
84.32.Tt Capacitors

Effects of interlayer and annealing on chemical states of HfO2 gate insulators studied by photoemission spectroscopy

S. Toyoda, J. Okabayashi, H. Kumigashira, M. Oshima, K. Ono, M. Niwa, K. Usuda, and G. L. Liu

Appl. Phys. Lett. 84, 2328 (2004); http://dx.doi.org/10.1063/1.1689393 (3 pages) | Cited 31 times

Online Publication Date: 23 March 2004

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We have performed photoemission spectroscopy of high-k gate insulators HfO2/HfSiON/Si to investigate the interlayer formation by Hf metal predeposition and the annealing effect systematically. Comparing the line shapes of core-level photoemission spectra for two systems with and without Hf-metal predeposition, we found that Hf-metal predeposition effectively reduces the growth of interface layer. Hf 4f core-level spectra revealed that the annealing at 1000 °C for both samples causes the formation of the metallic Hf and Hf-silicide clusters. Surface morphology was also observed by atomic force microscopy. © 2004 American Institute of Physics.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
77.22.Ch Permittivity (dielectric function)
73.20.Fz Weak or Anderson localization
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)
81.40.Gh Other heat and thermomechanical treatments

Terahertz emission by plasma waves in 60 nm gate high electron mobility transistors

W. Knap, J. Lusakowski, T. Parenty, S. Bollaert, A. Cappy, V. V. Popov, and M. S. Shur

Appl. Phys. Lett. 84, 2331 (2004); http://dx.doi.org/10.1063/1.1689401 (3 pages) | Cited 85 times

Online Publication Date: 23 March 2004

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We report on the resonant, voltage tunable emission of terahertz radiation (0.4–1.0 THz) from a gated two-dimensional electron gas in a 60 nm InGaAs high electron mobility transistor. The emission is interpreted as resulting from a current driven plasma instability leading to oscillations in the transistor channel (Dyakonov–Shur instability). © 2004 American Institute of Physics.
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85.30.Tv Field effect devices
72.20.Fr Low-field transport and mobility; piezoresistance
72.30.+q High-frequency effects; plasma effects
85.30.De Semiconductor-device characterization, design, and modeling

Organic phototransistor based on intramolecular charge transfer in a bifunctional spiro compound

Tobat P. I Saragi, Robert Pudzich, Thomas Fuhrmann, and Josef Salbeck

Appl. Phys. Lett. 84, 2334 (2004); http://dx.doi.org/10.1063/1.1690110 (3 pages) | Cited 65 times

Online Publication Date: 23 March 2004

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We report on the fabrication of organic phototransistors based on the spiro-conjugated molecule 2,7-bis-(N,N′-diphenylamino)-2′,7′-bis(biphenyl-4-yl)-9,9′-spirobifluorene. Intramolecular charge transfer leads to an increase in charge carrier density, providing the amplification effect. The sensitivity is better than 1 A/W for ultraviolet light at 370 nm, making the device interesting for sensor applications. © 2004 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions

Thickness-dependent metal–insulator transition in V2O3 ultrathin films

Qiang Luo, Qinlin Guo, and E. G. Wang

Appl. Phys. Lett. 84, 2337 (2004); http://dx.doi.org/10.1063/1.1690107 (3 pages) | Cited 13 times

Online Publication Date: 23 March 2004

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In this study, V2O3 ultrathin films about 5–20 nm thick were prepared on Al2O3 (0001) substrates through a reactive evaporation process. Auger electron spectroscopy and x-ray photoelectron spectroscopy have been used in situ to characterize their compositions and chemical states. Electric resistance measurements show that V2O3 films transform from metallic to semiconducting with the decrease of film thickness, which results from the a1g level rising because the lattice mismatch between the substrate and the film expands the c/a parameter ratio. No temperature-induced metal–insulator transition (like that in bulk V2O3) was observed in V2O3 thin films at low temperature. We conclude that stress plays a major role in suppressing the temperature-induced metal–insulator transition. © 2004 American Institute of Physics.
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71.30.+h Metal-insulator transitions and other electronic transitions
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
79.60.-i Photoemission and photoelectron spectra
79.20.Fv Electron impact: Auger emission
73.61.Ng Insulators
72.80.Sk Insulators

Polarization-induced electron island in semiconductor grain placed into pyroelectric matrix

V. Yu. Kachorovskii and M. S. Shur

Appl. Phys. Lett. 84, 2340 (2004); http://dx.doi.org/10.1063/1.1691197 (3 pages) | Cited 7 times

Online Publication Date: 23 March 2004

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We consider the electron distribution in an n-type semiconductor grain inserted into a pyroelectric matrix. We show that for typical values of parameters, the electric field induced in the grain by the pyroelectric spontaneous polarization is very strong and cannot be screened by the electrons in the grain. This field removes the electrons from donors and leads to the formation of a two-dimensional electron island on the surface of the grain with the size much smaller than the grain size. This effect can be used for creation of small two-dimensional quantum dots. © 2004 American Institute of Physics.
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77.22.Ej Polarization and depolarization
73.21.La Quantum dots

Electron counting of single-electron tunneling current

T. Fujisawa, T. Hayashi, Y. Hirayama, H. D. Cheong, and Y. H. Jeong

Appl. Phys. Lett. 84, 2343 (2004); http://dx.doi.org/10.1063/1.1691491 (3 pages) | Cited 20 times

Online Publication Date: 23 March 2004

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Single-electron tunneling through a quantum dot is detected by means of a radio-frequency single-electron transistor. Poisson statistics of single-electron tunneling events are observed from frequency domain measurements, and individual tunneling events are detected in the time-domain measurements. Counting tunneling events gives an accurate current measurement in the saturated current regime, where electrons tunnel into the dot only from one electrode and tunnel out of the dot only to the other electrode. © 2004 American Institute of Physics.
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73.63.Kv Quantum dots
73.23.Hk Coulomb blockade; single-electron tunneling
73.40.Gk Tunneling

Ultrafast control of electronic motion in quantum-well structures

A. Matos-Abiague and J. Berakdar

Appl. Phys. Lett. 84, 2346 (2004); http://dx.doi.org/10.1063/1.1691191 (3 pages) | Cited 8 times

Online Publication Date: 23 March 2004

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An ultrashort half-cycle pulse (HCP) is a fast (<1 ps) unipolar pulse, followed by a much longer ( ∼ 100 ps) and weaker unipolar pulse of opposite polarity. We show that such pulses can be utilized to localize, within femtoseconds, and control, for picoseconds, the electronic motion in a AlxGa1−xAs based symmetric double quantum well. The results are obtained by (i) deriving analytically for a model system the type of HCPs that lead to a fast and sustainable localization of a desirable final electron state and (ii) by solving numerically exactly the time-dependent Schrödinger equation for the quantum-well structure in the presence of the HCPs. © 2004 American Institute of Physics.
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73.21.Fg Quantum wells
73.20.Fz Weak or Anderson localization

Electrical characterization of phosphorus-doped n-type homoepitaxial diamond layers by Schottky barrier diodes

Mariko Suzuki, Hiroaki Yoshida, Naoshi Sakuma, Tomio Ono, Tadashi Sakai, and Satoshi Koizumi

Appl. Phys. Lett. 84, 2349 (2004); http://dx.doi.org/10.1063/1.1695206 (3 pages) | Cited 21 times

Online Publication Date: 23 March 2004

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Temperature-dependent current–voltage (I–V), capacitance–voltage (C–V) measurements, and frequency-dependent C–V measurements have been carried out to investigate electrical properties of phosphorus (P)-doped n-type homoepitaxial diamond layers. We have fabricated lateral dot-and-plane (with ring-shaped-gap) Schottky barrier diodes. Frequency-dependent capacitance measurements revealed the existence of a deep donor level. C–V measurements deduced that the net donor concentration was 6.2×1017 cm−3 and the corresponding built-in potential was 4.0 eV, when the P concentration was 8.3×1017 cm−3. Phosphorus electrical activity was 0.75 in the P-doped diamond layer. The carrier thermal activation energy (the donor level) was evaluated to be 0.6 eV from the relation between the net donor concentration and the carrier concentration. © 2004 American Institute of Physics.
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85.30.Kk Junction diodes
73.61.Cw Elemental semiconductors
73.30.+y Surface double layers, Schottky barriers, and work functions
61.72.S- Impurities in crystals
71.55.Cn Elemental semiconductors
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Modification of critical current density of MgB2 films irradiated with 200 MeV Ag ions

S. R. Shinde, S. B. Ogale, J. Higgins, R. J. Choudhary, V. N. Kulkarni, T. Venkatesan, H. Zheng, R. Ramesh, A. V. Pogrebnyakov, S. Y. Xu, Qi Li, X. X. Xi, J. M. Redwing, and D. Kanjilal

Appl. Phys. Lett. 84, 2352 (2004); http://dx.doi.org/10.1063/1.1687982 (3 pages) | Cited 21 times

Online Publication Date: 23 March 2004

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The effect of 200 MeV Ag ion irradiation on the temperature and field dependence of critical current density (JC) of high quality MgB2 thin films is studied. Substantial increase in JC is observed over a certain field range for the film irradiated at a dose of 1012 ions/cm2. Our analysis suggests that columnar defects are not formed under irradiation conditions used in these studies, which correspond to an electronic energy loss of about 16 keV/nm. Defects clusters are likely to be responsible for the observed improvement in JC.© 2004 American Institute of Physics.
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74.25.Sv Critical currents
61.80.Jh Ion radiation effects
61.72.-y Defects and impurities in crystals; microstructure
74.78.-w Superconducting films and low-dimensional structures

Magneto-optical properties of a highly transparent cadmium ferrite-based magnetic fluid

A. F. Bakuzis, K. Skeff Neto, P. P. Gravina, L. C. Figueiredo, P. C. Morais, L. P. Silva, R. B. Azevedo, and O. Silva

Appl. Phys. Lett. 84, 2355 (2004); http://dx.doi.org/10.1063/1.1690497 (3 pages) | Cited 28 times

Online Publication Date: 23 March 2004

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The magneto-optical properties of a highly stable ionic magnetic fluid sample containing CdFe2O4 nanoparticles were investigated using static magnetic birefringence, zero-field optical transmissivity, and transmission electron microscopy. From our measurements we found that the transmittivity and the birefringence of the CdFe2O4-based sample is several times greater than a typical magnetic fluid sample (γ-Fe2O3 based), giving this magnetic material great potential for magneto-optics applications. We also found that the birefringence can be increased by several orders of magnitude, allowing full manipulation of the observed negative differential transmitted optical intensity feature. © 2004 American Institute of Physics.
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78.20.Ls Magneto-optical effects
75.50.Mm Magnetic liquids
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Gg Ferrimagnetics

Large positive magnetoresistance in nonstoichiometric NiMnSb thin films on silicon

W. R. Branford, S. K. Clowes, M. H. Syed, Y. V. Bugoslavsky, S. Gardelis, J. Androulakis, J. Giapintzakis, C. E. A. Grigorescu, A. V. Berenov, S. B. Roy, and L. F. Cohen

Appl. Phys. Lett. 84, 2358 (2004); http://dx.doi.org/10.1063/1.1691172 (3 pages) | Cited 12 times

Online Publication Date: 23 March 2004

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We report a systematic study of the transport properties of pulsed-laser-deposited NiMnSb films on silicon as a function of film thickness. A low-temperature upturn is observed in the resistivity for film thicknesses of 130 nm and below. The resistivity minimum corresponds to the maximum in the positive magnetoresistance for all samples. As the film thickness decreases, the magnitude of both the resistivity upturn and the magnetoresistance increase. There is no feature associated with the upturn in the low-field Hall resistivity, which becomes systematically more electron dominated as the film thickness decreases and the temperature increases. This has implications for the use of NiMnSb as a spin injector for spintronic applications. The positive magnetoresistance of the 5 nm sample is greater than 100% at 200 K in 8 T. Further enhancement of the magnetoresistance occurs for field parallel, rather than perpendicular, to the film surface. The magnetoresistance behavior is compared to various model systems, including the band-gap tuning found in the silver chalcogenides, disorder-induced weak localization, and the emerging class of “bad metal” ferromagnets. © 2004 American Institute of Physics.
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75.50.Cc Other ferromagnetic metals and alloys
73.61.At Metal and metallic alloys
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.47.Np Metals and alloys
71.20.Be Transition metals and alloys
72.15.Gd Galvanomagnetic and other magnetotransport effects

Magnetic domain structure of a La0.7Sr0.3MnO3 (001) surface observed by a spin-polarized scanning electron microscope

M. Konoto, T. Kohashi, K. Koike, T. Arima, Y. Kaneko, Y. Tomioka, and Y. Tokura

Appl. Phys. Lett. 84, 2361 (2004); http://dx.doi.org/10.1063/1.1690463 (3 pages) | Cited 14 times

Online Publication Date: 23 March 2004

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The magnetization vector distribution at a cleaved surface of La0.7Sr0.3MnO3 (001) crystal has been quantitatively analyzed by using a newly developed low-temperature spin-polarized scanning electron microscope. The magnetic structure essentially consists of two kinds of domains, where magnetizations are parallel or antiparallel to the [110] direction with no surface-normal component. The rhombus-shaped domains range from a few to several tens of micrometers across. The domain structure can be considered to be made by laying down the magnetization from the out-of-surface-plane easy axis to the surface plane to reduce the magnetostatic energy without forming closure domains. © 2004 American Institute of Physics.
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75.60.Ch Domain walls and domain structure
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Magnetic anisotropy and structure of epitaxial permalloy films sputter-deposited on Nb(110)

R. Loloee, S. Urazhdin, W. P. Pratt, H. Geng, and M. A. Crimp

Appl. Phys. Lett. 84, 2364 (2004); http://dx.doi.org/10.1063/1.1691176 (3 pages) | Cited 4 times

Online Publication Date: 23 March 2004

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Epitaxial Permalloy™ (Py) thin films sputter-deposited onto epitaxial Nb with and without a Cu buffer layer have been investigated. Transmission electron microscopy was used to characterize the morphology of the Nb/Py/Cu and Nb/Cu/Py multilayers. Rotational magnetization measurements indicated significant differences in the magnetic anisotropy of the films. A phenomenological model taking into account uniaxial anisotropy agree well with the data, and provides a simple method for determinating the anisotropy strength. The correlations between the crystal structures and the magnetic properties are discussed. © 2004 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
75.30.Gw Magnetic anisotropy
68.55.-a Thin film structure and morphology
68.37.Lp Transmission electron microscopy (TEM)

Structural, magnetic, and transport properties of thin films of the Heusler alloy Co2MnSi

L. J. Singh, Z. H. Barber, Y. Miyoshi, Y. Bugoslavsky, W. R. Branford, and L. F. Cohen

Appl. Phys. Lett. 84, 2367 (2004); http://dx.doi.org/10.1063/1.1690868 (3 pages) | Cited 33 times

Online Publication Date: 23 March 2004

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Thin films of Co2MnSi have been grown on a-plane sapphire substrates from three elemental targets by dc magnetron cosputtering. These films are single phase, have a strong (110) texture, and a saturation magnetization of 4.95μB/formula unit at 10 K. Films grown at the highest substrate temperature of 715 K showed the lowest resistivity (47 μΩ cm at 4.2 K) and the lowest coercivity (18 Oe). The spin polarization of the transport current was found to be of the order of 54% as determined by point contact Andreev reflection spectroscopy. A decrease in saturation magnetization with a decrease in film thickness and different transport behavior in thinner films indicate graded disorder in these films grown on nonlattice matched substrates. © 2004 American Institute of Physics.
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81.15.Cd Deposition by sputtering
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.47.Np Metals and alloys
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films

Control of resistance of a magnetoresistive manganite by spin injection

T. Ono, A. Kogusu, S. Morimoto, S. Nasu, A. Masuno, T. Terashima, and M. Takano

Appl. Phys. Lett. 84, 2370 (2004); http://dx.doi.org/10.1063/1.1690877 (3 pages) | Cited 6 times

Online Publication Date: 23 March 2004

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We report a spin-injection effect found for a manganite using a specially fabricated sample. A wire of La0.7Sr0.3MnO3 was patterned by means of focused ion beam etching, and the center was subsequently lightly irradiated with Ga+ ions. The ferromagnetic Curie temperature was reduced locally by the irradiation from TC to TC′, and thus a sequential ferromagnetic/paramagnetic/ferromagnetic structure was realized along the wire between TC and TC′. The injection of spin-polarized current from the ferromagnetic manganite into the paramagnetic part rendered the latter ferromagnetic and more conductive. This can be explained by assuming the suppression of spin fluctuation in the paramagnet by the spins injected. © 2004 American Institute of Physics.
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75.50.Dd Nonmetallic ferromagnetic materials
75.20.Ck Nonmetals
72.20.My Galvanomagnetic and other magnetotransport effects
75.47.Gk Colossal magnetoresistance
75.47.Lx Magnetic oxides
75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
61.80.Jh Ion radiation effects
81.65.Cf Surface cleaning, etching, patterning
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
72.25.Hg Electrical injection of spin polarized carriers
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