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25 Dec 2006

Volume 89, Issue 26, Articles (26xxxx)

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Appl. Phys. Lett. 89, 263110 (2006); http://dx.doi.org/10.1063/1.2424541 (3 pages)

Ch. Deneke, U. Zschieschang, H. Klauk, and O. G. Schmidt
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True dipole at the indium tin oxide/organic semiconductor interface

Yow-Jon Lin, Jia-huang Hong, Yi-Chun Lien, and Bei-Yuan Liu

Appl. Phys. Lett. 89, 262110 (2006); http://dx.doi.org/10.1063/1.2424646 (3 pages) | Cited 3 times

Online Publication Date: 28 December 2006

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There has been long-standing interest in the development of organic optoelectronic devices. However, the authors find that the previously reported interface-dipole calculations seem to be inaccurate, owing to a persistent neglect of the induced band bending of indium tin oxide (ITO) by coating of organic semiconductors on ITO. In this study, the correlation between the induced band bending of ITO in the presence of organic semiconductors on ITO and the dipole at the interface was examined.
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73.20.At Surface states, band structure, electron density of states
73.30.+y Surface double layers, Schottky barriers, and work functions
79.60.Jv Interfaces; heterostructures; nanostructures
61.50.Lt Crystal binding; cohesive energy

Effect of grain alignment on interface trap density of thermally oxidized aligned-crystalline silicon films

Woong Choi, Jung-Kun Lee, and Alp T. Findikoglu

Appl. Phys. Lett. 89, 262111 (2006); http://dx.doi.org/10.1063/1.2424655 (3 pages)

Online Publication Date: 28 December 2006

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The authors report studies of the effect of grain alignment on interface trap density of thermally oxidized aligned-crystalline silicon (ACSi) films by means of capacitance-voltage (C-V) measurements. C-V curves were measured on metal-oxide-semiconductor (MOS) capacitors fabricated on ⟨001⟩-oriented ACSi films on polycrystalline substrates. From high-frequency C-V curves, the authors calculated a decrease of interface trap density from 2×1012 to 1×1011 cm−2 eV−1 as the grain mosaic spread in ACSi films improved from 13.7° to 6.5°. These results demonstrate the effectiveness of grain alignment as a process technique to achieve significantly enhanced performance in small-grained ( ⩽ 1 μm) polycrystalline Si MOS-type devices.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors

Identification of oxygen and zinc vacancy optical signals in ZnO

T. Moe Børseth, B. G. Svensson, A. Yu. Kuznetsov, P. Klason, Q. X. Zhao, and M. Willander

Appl. Phys. Lett. 89, 262112 (2006); http://dx.doi.org/10.1063/1.2424641 (3 pages) | Cited 115 times

Online Publication Date: 28 December 2006

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Photoluminescence spectroscopy has been used to study single crystalline ZnO samples systematically annealed in inert, Zn-rich and O-rich atmospheres. A striking correlation is observed between the choice of annealing ambient and the position of the deep band emission (DBE) often detected in ZnO. In particular, annealing in O2 results in a DBE at 2.35±0.05 eV, whereas annealing in the presence of metallic Zn results in DBE at 2.53±0.05 eV. The authors attribute the former band to zinc vacancy (VZn) related defects and the latter to oxygen vacancy (VO) related defects. Additional confirmation for the VO and VZn peak identification comes from the observation that the effect is reversible when O- and Zn-rich annealing conditions are switched. After annealing in the presence of ZnO powder, there is no indication for the VZn- or VO-related bands, but the authors observe a low intensity yellow luminescence band peaking at 2.17 eV, probably related to Li, a common impurity in hydrothermally grown ZnO.
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78.55.Et II-VI semiconductors
61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing

Adjustable metal-semiconductor transition of FeS thin films by thermal annealing

Ganhua Fu, Angelika Polity, Niklas Volbers, Bruno K. Meyer, Boris Mogwitz, and Jürgen Janek

Appl. Phys. Lett. 89, 262113 (2006); http://dx.doi.org/10.1063/1.2424663 (3 pages) | Cited 1 time

Online Publication Date: 28 December 2006

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FeS polycrystalline thin films were prepared on float glass at 500 °C by radio-frequency reactive sputtering. The influence of vacuum annealing on the metal-semiconductor transition of FeS films was investigated. It has been found that with the increase of the annealing temperature from 360 to 600 °C, the metal-semiconductor transition temperature of FeS films first decreases and then increases, associated with first a reduction and then an enhancement of hysteresis width. The thermal stress is considered to give rise to the abnormal change of the metal-semiconductor transition of the FeS film during annealing.
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73.61.Ng Insulators
81.15.Cd Deposition by sputtering
71.30.+h Metal-insulator transitions and other electronic transitions
81.40.Gh Other heat and thermomechanical treatments
68.60.Bs Mechanical and acoustical properties
68.55.A- Nucleation and growth

Enhanced charge mobility in a molecular hole transporter via addition of redox inactive ionic dopant: Implication to dye-sensitized solar cells

Henry J. Snaith and Michael Grätzel

Appl. Phys. Lett. 89, 262114 (2006); http://dx.doi.org/10.1063/1.2424552 (3 pages) | Cited 35 times

Online Publication Date: 28 December 2006

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Upon the addition of lithium salts to the hole-transporter matrix, 2,2′,7,7′-tetrakis(N,N-di-p-methoxypheny-amine)-9,9′-spirobifluorene (spiro-MeOTAD), the authors observe a 100-fold increase in conductivity through spiro-MeOTAD within a TiO2 mesoporous network. The authors demonstrate this to be a bulk effect and not due to improved injection at the electrodes. By testing “hole-only” diodes of pure spiro-MeOTAD and those doped with lithium salts, the authors calculate that the hole mobility increases from 1.6×10−4 to 1.6×10−3 cm2/V s. The authors discuss the possible mechanisms for this significant enhancement in charge mobility and its implication to the dye-sensitized solar cell operation.
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73.61.Ph Polymers; organic compounds
73.50.Dn Low-field transport and mobility; piezoresistance
72.20.Fr Low-field transport and mobility; piezoresistance
61.72.up Other materials
85.30.Kk Junction diodes
84.60.Jt Photoelectric conversion

Formation mechanism of cerium oxide-doped indium oxide/Ag Ohmic contacts on p-type GaN

Dong-Seok Leem, Tae-Wook Kim, Takhee Lee, Ja-Soon Jang, Young-Woo Ok, and Tae-Yeon Seong

Appl. Phys. Lett. 89, 262115 (2006); http://dx.doi.org/10.1063/1.2424660 (3 pages) | Cited 5 times

Online Publication Date: 28 December 2006

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The authors report on the formation of cerium oxide-doped indium oxide(2.5 nm)/Ag(250 nm) contacts to p-GaN. The contacts become Ohmic with a specific contact resistance of 3.42×10−4 Ω cm2 upon annealing at 530 °C in air. X-ray photoemission spectroscopy (XPS) Ga 3d core levels obtained from the interface regions before and after annealing indicate a large band bending of p-GaN (about 1.7–1.8 eV), namely, an increase of Schottky barrier height. Based on the XPS, secondary ion mass spectroscopy, and capacitance-voltage data, possible transport mechanisms for the annealed contacts are described and discussed.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
61.72.Cc Kinetics of defect formation and annealing
79.60.Jv Interfaces; heterostructures; nanostructures
73.30.+y Surface double layers, Schottky barriers, and work functions
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Quantitative observation and discrimination of AlGaN- and GaN-related deep levels in AlGaN/GaN heterostructures using capacitance deep level optical spectroscopy

A. Armstrong, A. Chakraborty, J. S. Speck, S. P. DenBaars, U. K. Mishra, and S. A. Ringel

Appl. Phys. Lett. 89, 262116 (2006); http://dx.doi.org/10.1063/1.2424670 (3 pages) | Cited 16 times

Online Publication Date: 28 December 2006

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Deep levels were observed using capacitance deep level optical spectroscopy (DLOS) in an AlGaN/GaN heterostructure equivalent to that of a heterojunction field effect transistor. Band gap states were assigned to either the AlGaN or GaN regions by comparing the DLOS spectra in accumulation and pinch-off modes, where the former reflects both AlGaN- and GaN-related defects, and the latter emphasizes defects residing in the GaN. A band gap state at Ec−3.85 eV was unambiguously identified with the AlGaN region, and deep levels at Ec−2.64 eV and Ec−3.30 eV were associated with the GaN layers. Both the AlGaN and GaN layers exhibited additional deep levels with large lattice relaxation. The influence of deep levels on the two-dimensional electron gas sheet charge was estimated using a lighted capacitance-voltage method.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.55.Eq III-V semiconductors
71.20.Nr Semiconductor compounds

Near-field scanning optical microscopy and time-resolved optical characterization of epitaxial lateral overgrown c-plane and a-plane GaN

Ü. Özgür, X. Ni, Y. Fu, H. Morkoç, and H. O. Everitt

Appl. Phys. Lett. 89, 262117 (2006); http://dx.doi.org/10.1063/1.2424677 (3 pages) | Cited 5 times

Online Publication Date: 29 December 2006

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Epitaxial lateral overgrowth (ELO) was employed for both c-plane and a-plane GaN layers on sapphire, and a more pronounced optical improvement was observed for the a-plane GaN as evidenced by the significantly increased band edge photoluminescence (PL). Room temperature near-field scanning optical microscopy studies explicitly showed enhanced optical quality in the wing regions of the overgrown GaN due to reduced density of dislocations, and for the a-plane ELO GaN sample the wings and the windows were clearly discernible from PL mapping. Time-resolved PL measurements revealed biexponential decays with time constants that were significantly enhanced for the a-plane ELO GaN (τ1 = 0.08 ns, τ2 = 0.25 ns) when compared to the non-ELO control sample but were still much shorter than those for the c-plane ELO GaN (τ1 = 0.26 ns, τ2 = 0.90 ns).
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78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.55.Cr III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

p-type conductivity and donor-acceptor pair emission in Cd1−xFexS dilute magnetic semiconductors

X. J. Wu, D. Z. Shen, Z. Z. Zhang, J. Y. Zhang, K. W. Liu, B. H. Li, Y. M. Lu, D. X. Zhao, and B. Yao

Appl. Phys. Lett. 89, 262118 (2006); http://dx.doi.org/10.1063/1.2425028 (3 pages) | Cited 5 times

Online Publication Date: 29 December 2006

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Cd1−xFexS thin films with different Fe contents were grown on c-plane sapphire by low-pressure metal organic chemical vapor deposition. The resistivity of the thin films was found to increase with the addition of more Fe contents into the Cd1−xFexS thin films by elevating the growth temperature, which was attributed to the ionization of holes from trivalent Fe ions. High density Fe doping eventually reversed the conductivity of Cd1−xFexS thin film from n to p type. With increasing Fe content, the band-to-band transition at 2.5 eV was suppressed while the emission from the donor-acceptor pairs at 2.0–2.4 eV finally dominated the photoluminescence spectra.
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81.05.Dz II-VI semiconductors
73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors
75.50.Pp Magnetic semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
78.55.Et II-VI semiconductors

Photocurrent and transmission spectroscopy of direct-gap interband transitions in Ge/SiGe quantum wells

S. Tsujino, H. Sigg, G. Mussler, D. Chrastina, and H. von Känel

Appl. Phys. Lett. 89, 262119 (2006); http://dx.doi.org/10.1063/1.2425032 (3 pages) | Cited 26 times

Online Publication Date: 29 December 2006

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The authors studied the direct-gap interband transitions in strain-compensated Ge/SiGe quantum wells grown by low energy plasma enhanced chemical vapor deposition. A series of excitonic interband absorptions from the quantized hole states to the quantized electronic states at the Γ7c− edge in the Ge wells is observed up to room temperature by photocurrent and transmission spectroscopy. The results are compared with theory. At low temperature, the quantum confined Stark effect is demonstrated in a Schottky diode geometry.
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78.66.Db Elemental semiconductors and insulators
73.63.Hs Quantum wells
78.67.De Quantum wells
72.40.+w Photoconduction and photovoltaic effects
73.21.Fg Quantum wells

Hysteresis mechanism in pentacene thin-film transistors with poly(4-vinyl phenol) gate insulator

Cheon An Lee, Dong-Wook Park, Keum-Dong Jung, Byung-ju Kim, Yoo Chul Kim, Jong Duk Lee, and Byung-Gook Park

Appl. Phys. Lett. 89, 262120 (2006); http://dx.doi.org/10.1063/1.2425042 (3 pages) | Cited 28 times

Online Publication Date: 29 December 2006

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The hysteresis mechanism is studied in pentacene organic thin-film transistors (OTFTs) with poly(4-vinyl phenol) (PVP) gate insulator by examining OTFTs with an oxide/PVP double layer gate insulator. The oxide thickness affects the direction of the hysteresis as well as its magnitude. This result can be explained on the basis of the charge injection and trapping mechanism rather than slow polarization or ion migration. The hysteresis occurs mainly due to the charges which could be injected from the gate electrode and trapped in the PVP. As the thickness of the oxide layer is increased, the gate charge injection is blocked and the effect of the charges from the channel increases.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Intrinsic crystalline-to-amorphous transition above 400 °C in plasma-deposited Si thin films

Toshihiro Kamei

Appl. Phys. Lett. 89, 262121 (2006); http://dx.doi.org/10.1063/1.2426905 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2006

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There has been long debate concerning why microcrystalline Si formation is disrupted at a deposition temperature above around 400 °C: is it due to the loss of surface hydrogen coverage or to the incorporation of oxygen impurities? The authors reduced the atmospheric concentration of such impurities as O, C, and N in this work by using an ultraclean plasma deposition apparatus and demonstrate that microcrystalline Si films showed improved crystallinity at a deposition temperature of 350 °C, resulting in a mobility of 5. As the deposition temperature was raised to 450 °C, however, the Raman spectrum shows an amorphous structure of the film under such clean conditions. According to secondary ion mass spectrometry, the O, C, and N concentrations in this film were as low as 1017, 1016, and 1017 cm−3, respectively, demonstrating that the crystalline-to-amorphous transition around 400 °C should be intrinsic under the present conditions and may be correlated with thermal hydrogen desorption on a film-growing surface.
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81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
68.55.A- Nucleation and growth
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
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Magnetostriction studies in an antiferromagnetic polycrystalline Mn42Fe58 alloy

W. Y. Peng and J. H. Zhang

Appl. Phys. Lett. 89, 262501 (2006); http://dx.doi.org/10.1063/1.2405850 (3 pages) | Cited 5 times

Online Publication Date: 26 December 2006

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Magnetostriction “jump” effect often occurs in ferromagnetic materials. However, in this letter, the jump effect is observed in antiferromagnetic face-centered-cubic austenitic polycrystalline Mn42Fe58 alloy at room temperature. The magnetostriction under an applied field of 1.0 T is 169 ppm parallel to the field. The jump magnetostriction of −581 ppm, which is antiparallel to the field, is obtained when the sample is subjected to the compressive stress of 1.52 MPa. The relation between the magnetostriction and the field strength is discussed.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Ee Antiferromagnetics
62.50.-p High-pressure effects in solids and liquids
81.40.Vw Pressure treatment

Enhancement of exchange coupling between GaMnAs and IrMn with self-organized Mn(Ga)As at the interface

H. T. Lin, Y. F. Chen, P. W. Huang, S. H. Wang, J. H. Huang, C. H. Lai, W. N. Lee, and T. S. Chin

Appl. Phys. Lett. 89, 262502 (2006); http://dx.doi.org/10.1063/1.2410234 (3 pages) | Cited 6 times

Online Publication Date: 26 December 2006

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An atomically flat and uniform reaction layer of Mn(Ga)As was found to self-organize at the (Ga,Mn)As/IrMn interface by postannealing. The Mn(Ga)As layer exhibits strong ferromagnetic characteristics up to the measured 300 K. In particular, the manifested horizontal shift of field-cooled hysteresis loops shows a clear signature of exchange bias attributable to the exchange coupling between IrMn and Mn(Ga)As. Implication from composition analyses, exchange-bias effect, and thickness dependence of the Mn(Ga)As layer versus annealing conditions is also discussed.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing

Structural and magnetic properties of epitaxial thin films of the ordered double perovskite La2CoMnO6

H. Z. Guo, A. Gupta, T. G. Calvarese, and M. A. Subramanian

Appl. Phys. Lett. 89, 262503 (2006); http://dx.doi.org/10.1063/1.2422878 (3 pages) | Cited 22 times

Online Publication Date: 26 December 2006

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Epitaxial thin films of the ordered ferromagnetic double perovskite La2CoMnO6 have been grown on (001)-oriented SrTiO3 substrates by pulsed laser deposition. X-ray photoemission spectroscopy analysis suggests that the Mn and Co ions are primarily in the 4+ and 2+ valence states. Magnetic measurements indicate the presence of two phases: a majority and a minority ferromagnetic phase with transition temperatures of 230 and 80 K, respectively. A spin-glass-type magnetic behavior is also indicated for the films based on time-dependent measurements. The spin-glass behavior likely arises from a competition between ferromagnetic and antiferromagnetic interactions because of local disorder, even in films grown under optimal conditions.
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75.70.Ak Magnetic properties of monolayers and thin films
68.55.-a Thin film structure and morphology
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Lk Spin glasses and other random magnets
75.50.Ee Antiferromagnetics
81.15.Fg Pulsed laser ablation deposition

Vacancy induced structural and magnetic transition in MnCo1−xGe

Jian-Tao Wang, Ding-Sheng Wang, Changfeng Chen, O. Nashima, T. Kanomata, H. Mizuseki, and Y. Kawazoe

Appl. Phys. Lett. 89, 262504 (2006); http://dx.doi.org/10.1063/1.2424273 (3 pages) | Cited 13 times

Online Publication Date: 26 December 2006

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The authors report ab initio total energy calculations on the first-order structural transition of the ferromagnetic MnCo1−xGe(0.00 ⩽ x ⩽ 0.25) intermetallic compound. They show that increasing Co vacancies induce a transition from an orthorhombic structure at 0 ⩽ x ⩽ 0.08 to a hexagonal structure at x>0.08. A concomitant high-to-low moment magnetic transition and a large magnetovolume effect occur due to the change of the symmetry and the resulting coupling distance between the magnetic atoms. These results provide an excellent account for the experimental results and reveal the crucial role of the Co vacancies in determining the relative structural stability and the magnetic properties of MnCo1−xGe.
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64.70.K- Solid-solid transitions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.72.J- Point defects and defect clusters
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.50.Cc Other ferromagnetic metals and alloys

Prospects for detection of spin accumulation using submicron planar Andreev array spectroscopy

F. Magnus, K. A. Yates, B. Morris, Y. Miyoshi, Y. Bugoslavsky, L. F. Cohen, G. Burnell, M. G. Blamire, and P. W. Josephs-Franks

Appl. Phys. Lett. 89, 262505 (2006); http://dx.doi.org/10.1063/1.2424279 (3 pages) | Cited 4 times

Online Publication Date: 27 December 2006

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Andreev spectroscopy can be employed to measure transport spin polarization. Planar Andreev devices have an advantage over point-contact Andreev spectroscopy as they offer greater control over interface quality and the possibility of spatially resolved information about spin polarization using submicron Andreev junction arrays. The authors compare the performance of Pb point contacts onto Cu and Co with that of large area and submicron planar junctions and singularly connected nanoarrays. Planar structures compare favorably to point contacts although the fabrication method influences extracted parameters. The authors find that submicron planar junction reproducibility does not adversely affect the prospects for developing arrays for detection of spin accumulation.
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74.50.+r Tunneling phenomena; Josephson effects
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.F- Transport properties

Strain induced magnetic anisotropy in highly epitaxial CoFe2O4 thin films

W. Huang, J. Zhu, H. Z. Zeng, X. H. Wei, Y. Zhang, and Y. R. Li

Appl. Phys. Lett. 89, 262506 (2006); http://dx.doi.org/10.1063/1.2424444 (3 pages) | Cited 31 times

Online Publication Date: 27 December 2006

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Cobalt ferrite (CoFe2O4) thin films were epitaxially grown on (001) SrTiO3 and (001) MgO by laser molecular beam epitaxy. Microstructural studies indicate that the CoFe2O4 grown on (001) SrTiO3 with compressive strain are c-oriented island growth mode with rough surface morphology, whereas the films on (001) MgO with tensile strain become c oriented with layer-by-layer mode. Magnetic property studies reveal that the compressive strained CoFe2O4 films on (001) SrTiO3 can significantly enhance out-of-plane magnetization (190 emu/cm3) with a large coercivity (3.8 kOe). In contrast, the tensile strained CoFe2O4 films on (001) MgO exhibit weak magnetic anisotropy. These results suggest that strong magnetic anisotropy is highly dependent on the lattice mismatch induced strain.
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75.50.Gg Ferrimagnetics
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.60.Bs Mechanical and acoustical properties
68.35.B- Structure of clean surfaces (and surface reconstruction)

Dynamics of vortex core switching in ferromagnetic nanodisks

Q. F. Xiao, J. Rudge, B. C. Choi, Y. K. Hong, and G. Donohoe

Appl. Phys. Lett. 89, 262507 (2006); http://dx.doi.org/10.1063/1.2424673 (3 pages) | Cited 41 times

Online Publication Date: 28 December 2006

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Dynamics of magnetic vortex core switching in nanometer-scale Permalloy disk, having a single vortex ground state, was investigated by micromagnetic modeling. When an in-plane magnetic field pulse with an appropriate strength and duration is applied to the vortex structure, additional two vortices, i.e., a circular and an antivortex, are created near the original vortex core. Sequentially, the vortex-antivortex pair annihilates. A spin wave is created at the annihilation point and propagated through the entire element; the relaxed state for the system is the single vortex state with a switched vortex core.
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75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.30.Ds Spin waves
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.50.Bb Fe and its alloys
75.50.Tt Fine-particle systems; nanocrystalline materials

Improvement of magnetic properties of granular perpendicular recording media by using a fcc nonmagnetic intermediate layer with stacking faults

Atsushi Hashimoto, Shin Saito, Norikazu Itagaki, and Migaku Takahashi

Appl. Phys. Lett. 89, 262508 (2006); http://dx.doi.org/10.1063/1.2424280 (3 pages) | Cited 10 times

Online Publication Date: 28 December 2006

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Various binary systems are investigated as face-centered cubic (fcc) bases for the nonmagnetic intermediate layer (NMIL) in granular perpendicular recording media. Loss of stacking order on the (111) plane in fcc NMIL is found to enhance the perpendicular magnetic anisotropy energy (KuRL) of the overlying medium. One persuasive reason for this enhancement is the preferred epitaxial growth of magnetic grains on only the (111) atomic terrace of the fcc NMIL due to collapse of the sixfold symmetry of (math11), (1math1), and (11math) atomic terraces of the fcc NMIL.
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75.50.Ss Magnetic recording materials
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Gw Magnetic anisotropy
61.72.Nn Stacking faults and other planar or extended defects

Trends in spin-transfer-driven magnetization dynamics of CoFe/AlO/Py and CoFe/MgO/Py magnetic tunnel junctions

G. Finocchio, G. Consolo, M. Carpentieri, A. Romeo, B. Azzerboni, L. Torres, and L. Lopez-Diaz

Appl. Phys. Lett. 89, 262509 (2006); http://dx.doi.org/10.1063/1.2425017 (3 pages) | Cited 16 times

Online Publication Date: 28 December 2006

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A spin-polarized current is able to excite magnetization dynamics in nanomagnets. A detailed theoretical study of dynamics in low and high field regimes in AlO and MgO magnetic tunnel junctions (MTJs) is presented, considering the maximum value of the applied current which comes from the breakdown voltage of the tunnel barrier. In low field regime, dynamics with a well-defined peak in frequency is observed. In high field regime, AlO MTJ presents the same behavior, while the magnetization in the MgO MTJ shows chaotic motion with a noisy spectrum. Lastly, an effect of the presence of a pinhole in the tunnel barrier is discussed.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.25.Mk Spin transport through interfaces
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Interfacial and quantum well effects on ac magnetotransport of La0.7Sr0.3MnO3/La1.4Sr1.6Mn2O7 composites

C. Y. Hsu, Hsiung Chou, B. Y. Liao, and J. C. A. Huang

Appl. Phys. Lett. 89, 262510 (2006); http://dx.doi.org/10.1063/1.2422880 (3 pages) | Cited 5 times

Online Publication Date: 29 December 2006

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The field-dependent complex impedance (CI) spectroscopy is employed to clarify the origins of ac magnetoimpedance (MI) effects at room temperature near the conduction threshold of [La0.67Sr0.33MnO3(113)]1−x/[La1.67Sr1.33Mn2O7(327)]x composites. The field-dependent CI spectra in 113-327 granular composites are further transformed to field-dependent magnetoconductance (MC) spectra. The frequency-dependent high-field and low-field MC spectra can be well interpreted by including the trap-state contributions in 113-327 interfaces and 327 grain boundaries, together with the leakage-region-induced spin-dependent quantum well state effect. The principle of this work could be applied to study the magnetoresistance and MI effects of magnetic granular composites.
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75.47.Lx Magnetic oxides
73.63.Hs Quantum wells
73.43.Qt Magnetoresistance
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.Mm Grain and twin boundaries

Observation of magnetism in the nanoscale amorphous ruthenium clusters prepared by ion beam mixing

W. C. Wang, Y. Kong, X. He, and B. X. Liu

Appl. Phys. Lett. 89, 262511 (2006); http://dx.doi.org/10.1063/1.2425037 (3 pages) | Cited 3 times

Online Publication Date: 29 December 2006

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A unique composite of nanoscale amorphous Ru clusters embedded in the amorphous Ru/Ta matrix was observed in the Ru/Ta multilayered films upon ion irradiation. It was found that the magnetic moment of the Ru nanoclusters varied with cluster size, i.e., when the diameter of the clusters changed from 1 to 5 nm, the magnetic moment decreased from 0.24μB (parallel) and 0.27μB (vertical) to 0μB and 0μB, respectively, according well with the prediction from ab initio calculations.
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75.75.-c Magnetic properties of nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Cr Saturation moments and magnetic susceptibilities
61.46.Bc Structure of clusters (e.g., metcars; not fragments of crystals; free or loosely aggregated or loosely attached to a substrate)
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
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Mechanism of leakage current reduction of tantalum oxide capacitors by postmetallization annealing

W. S. Lau, K. K. Khaw, Taejoon Han, and Nathan P. Sandler

Appl. Phys. Lett. 89, 262901 (2006); http://dx.doi.org/10.1063/1.2408645 (3 pages) | Cited 6 times

Online Publication Date: 26 December 2006

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In this letter, the authors will point out that defect states related to impurities or structural defects in tantalum oxide capacitors can be passivated by hydrogen during postmetallization anneal (PMA) while oxygen vacancies are enhanced by PMA such that some will observe a decrease while other may observe an increase in the leakage current after PMA. The PMA process can be tuned such that the hydrogen passivation of defect states dominates over the enhancement of oxygen vacancies, resulting in significant leakage current reduction.
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84.32.Tt Capacitors
81.65.Rv Passivation
85.40.Ls Metallization, contacts, interconnects; device isolation

Strain distribution in epitaxial SrTiO3 thin films

Z. Y. Zhai, X. S. Wu, Z. S. Jiang, J. H. Hao, J. Gao, Y. F. Cai, and Y. G. Pan

Appl. Phys. Lett. 89, 262902 (2006); http://dx.doi.org/10.1063/1.2424282 (3 pages) | Cited 10 times

Online Publication Date: 27 December 2006

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The lattice strain distributions of epitaxial SrTiO3 films deposited on LaAlO3 were investigated by in situ x-ray diffraction at the temperature range of 25–300 K, grazing incident x-ray diffraction, and high resolution x-ray diffraction. The nearly linear temperature dependence of the out-of-plane lattice constant of SrTiO3 was observed in the measured temperature range. The depth distribution of the lattice strain at room temperature for SrTiO3 films includes the surface layer, strained layer, and interface layer.
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68.60.Bs Mechanical and acoustical properties
61.66.Fn Inorganic compounds
68.55.-a Thin film structure and morphology
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