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19 Oct 2009

Volume 95, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 162501 (2009); http://dx.doi.org/10.1063/1.3248257 (3 pages)

W. W. Lei, D. Liu, P. W. Zhu, X. H. Chen, Q. Zhao, G. H. Wen, Q. L. Cui, and G. T. Zou
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Dynamics of free carrier absorption in InN layers

S. Nargelas, R. Aleksiejūnas, M. Vengris, T. Malinauskas, K. Jarašiūnas, and E. Dimakis

Appl. Phys. Lett. 95, 162103 (2009); http://dx.doi.org/10.1063/1.3251077 (3 pages) | Cited 2 times

Online Publication Date: 20 October 2009

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Carrier dynamics in highly excited InN epitaxial layers was investigated in the 1550–2440 nm (0.8–0.51 eV) spectral range by using a femtosecond differential transmission technique. A transition from induced bleaching to induced absorption was observed for probing energy of 90 meV below the bandgap of the samples. The decay of the induced free carrier absorption provided the averaged lifetime of the total nonequilibrium carriers. In the carrier density range of Δn = 1018–1020 cm−3, the density-dependent recombination mechanism was attributed to trap-assisted Auger recombination with decay rate 1/τ = BTAARΔn, with BTAAR in the range (4–30)×10−10 cm3 s−1 for layers with different defect densities.
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68.55.ag Semiconductors
71.20.Nr Semiconductor compounds
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.Eq III-V semiconductors
79.20.Fv Electron impact: Auger emission

Band offsets of HfO2/ZnO interface: In situ x-ray photoelectron spectroscopy measurement and ab initio calculation

Q. Chen, M. Yang, Y. P. Feng, J. W. Chai, Z. Zhang, J. S. Pan, and S. J. Wang

Appl. Phys. Lett. 95, 162104 (2009); http://dx.doi.org/10.1063/1.3253420 (3 pages) | Cited 4 times

Online Publication Date: 20 October 2009

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High quality HfO2 dielectrics have been grown on ZnO (0001) substrates. The valence- and conduction-band offsets for HfO2/ZnO (0001) heterojunctions have been determined to be 0.14±0.05 and 2.29±0.05 eV, respectively, by using in situ x-ray photoemission spectroscopy. First-principles calculations show that the valence-band offset at the HfO2/ZnO (0001) interface of the most energetically favorable interface structure is 0.40 eV, which is consistent with the experimental results.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ng Insulators
77.55.-g Dielectric thin films
68.35.Ct Interface structure and roughness
73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
71.15.-m Methods of electronic structure calculations

Electrical resistance switching in Ti added amorphous SiOx

Ting-Yi Lin (林庭誼), Li-Ming Chen (陳力銘), Shih-Ching Chang (張士欽), and Tsung-Shune Chin (金重勳)

Appl. Phys. Lett. 95, 162105 (2009); http://dx.doi.org/10.1063/1.3243983 (3 pages) | Cited 2 times

Online Publication Date: 20 October 2009

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Unipolar switching in electrical resistivity is demonstrated in Ti-doped amorphous SiOx with suitable electrodes. We studied stacks of Al(30 nm)/SiOx/Pt, Cu/SiOx/Pt, Cu/Al(2 nm)/SiOx/Pt, and Pt/SiOx/TiN grown on Ti/SiO2/Si(100) wafer to investigate the effect of metal electrodes. The nature of interface oxides between top electrodes and SiOx, as elucidated by x-ray photoelectron and Auger-electron spectra, was found to manifestly influence switching-ability. A 30 nm Al top electrode leads to thick interfacial Al2O3, which frustrates resistivity switching, while an ultrathin Al between Cu and SiOx alleviates this problem. The Pt/SiOx/TiN stack, designed to avoid interface oxides, is the best showing narrower distribution in operation voltage and cycling more than 500 times.
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73.40.Rw Metal-insulator-metal structures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.60.+g Mixed conductivity and conductivity transitions

Microwave magnetoabsorption in two-dimensional electron systems

Jesús Iñarrea and Gloria Platero

Appl. Phys. Lett. 95, 162106 (2009); http://dx.doi.org/10.1063/1.3254231 (3 pages) | Cited 1 time

Online Publication Date: 21 October 2009

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Magnetoabsorption, microwave-induced resistance oscillations, and zero resistance states in two-dimensional systems are calculated in the framework of the same theory: the microwave driven Larmor orbit model. On one hand, this theory allows to obtain resistance oscillations with multiple peaks, depending on the microwave frequency. On the other hand, it also permits to calculate the microwave magnetoabsorption yielding only one broad peak at the cyclotron resonance condition.
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78.20.Ls Magneto-optical effects
76.40.+b Diamagnetic and cyclotron resonances
78.70.Gq Microwave and radio-frequency interactions

Influence of growth temperature and scandium concentration on piezoelectric response of scandium aluminum nitride alloy thin films

Morito Akiyama, Kazuhiko Kano, and Akihiko Teshigahara

Appl. Phys. Lett. 95, 162107 (2009); http://dx.doi.org/10.1063/1.3251072 (3 pages) | Cited 7 times

Online Publication Date: 21 October 2009

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The authors have investigated the influence of growth temperature and scandium concentration on the piezoelectric response of scandium aluminum nitride (ScxAl1−xN) films prepared by dual reactive cosputtering. The piezoelectric response strongly depends on the growth temperature and scandium concentration. The piezoelectric response of the films prepared at 400 °C gradually increases with increasing scandium concentration. On the other hand, the piezoelectric response of the films prepared at 580 °C drastically decreases and increases in the scandium concentration from 30% to 40%. We think that the drastic change of the piezoelectric response is due to the disordered grain growth.
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77.55.-g Dielectric thin films
81.15.Cd Deposition by sputtering
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Microscopic origin of bipolar resistive switching of nanoscale titanium oxide thin films

Hu Young Jeong, Jeong Yong Lee, Sung-Yool Choi, and Jeong Won Kim

Appl. Phys. Lett. 95, 162108 (2009); http://dx.doi.org/10.1063/1.3251784 (3 pages) | Cited 30 times

Online Publication Date: 21 October 2009

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We report a direct observation of the microscopic origin of the bipolar resistive switching behavior in nanoscale titanium oxide films. Through a high-resolution transmission electron microscopy, an analytical transmission electron microscopy technique using energy-filtering transmission electron microscopy, and an in situ x-ray photoelectron spectroscopy, we demonstrated that the oxygen ions piled up at the top interface by an oxidation-reduction between the titanium oxide layer and the top Al metal electrode. We also found that the drift of oxygen ions during the on/off switching induced the bipolar resistive switching in the titanium oxide thin films.
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68.55.-a Thin film structure and morphology
68.37.Og High-resolution transmission electron microscopy (HRTEM)
79.60.Jv Interfaces; heterostructures; nanostructures
61.72.jd Vacancies

First-principles study of the electronic properties of Ge dangling bonds at (100)Si1−xGex/SiO2 interfaces

M. Houssa, V. V. Afanas’ev, A. Stesmans, G. Pourtois, M. Meuris, and M. M. Heyns

Appl. Phys. Lett. 95, 162109 (2009); http://dx.doi.org/10.1063/1.3253707 (3 pages) | Cited 5 times

Online Publication Date: 22 October 2009

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First-principles calculations of the electronic properties of (100)Si1−xGex/SiO2 structures, with a Ge dangling bond at the interface, are reported. It is found that the defect level associated with this dangling bond approaches the valence band edge of the Si1−xGex substrate as the Si concentration is reduced, mainly due to the narrowing of the energy bandgap of the alloy. These results suggest that these dangling bonds likely behave as acceptor-type defects at Ge-rich (100)Si1−xGex interfaces.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
71.55.-i Impurity and defect levels
81.05.Hd Other semiconductors
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Enhancement of thermoelectric efficiency in oxygen-deficient Sr1−xLaxTiO3−δ ceramics

J. Liu, C. L. Wang, W. B. Su, H. C. Wang, P. Zheng, J. C. Li, J. L. Zhang, and L. M. Mei

Appl. Phys. Lett. 95, 162110 (2009); http://dx.doi.org/10.1063/1.3254219 (3 pages) | Cited 14 times

Online Publication Date: 23 October 2009

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We report that the Seebeck coefficient (S) is remarkably enhanced in oxygen-deficient Sr1−xLaxTiO3−δ ceramics. The S values of all oxygen-deficient samples are larger than those of the near-stoichiometric ones and are temperature-independent at high temperatures, showing a narrow band behavior. This indicates that the introduction of oxygen vacancy changes the density of electronic states around the Fermi energy. The maximum for the figure of merit (ZT) of Sr0.9La0.1TiO3−δ ceramic reaches 0.21 at about 750 K, demonstrating enhancement by a factor of more than 1.3 over that of the near-stoichiometric materials.
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72.20.Pa Thermoelectric and thermomagnetic effects
72.80.Sk Insulators
71.20.Nr Semiconductor compounds
61.72.jd Vacancies

Blueshift of intersubband transition wavelength in AlN/GaN multiple quantum wells by low temperature metal organic vapor phase epitaxy using pulse injection method

Jung-Seung Yang, Hassanet Sodabanlu, Masakazu Sugiyama, Yoshiaki Nakano, and Yukihiro Shimogaki

Appl. Phys. Lett. 95, 162111 (2009); http://dx.doi.org/10.1063/1.3254230 (3 pages) | Cited 8 times

Online Publication Date: 23 October 2009

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AlN/GaN multiquantum wells (MQWs) were grown at different growth temperatures via a metal organic vapor phase epitaxy (MOVPE) system using a pulse injection method and their intersubband transition (ISBT) properties were investigated. Strong ISBT at 1.58 μm measured at room temperature was realized with MQWs grown at 770 °C and its absorption properties was the best reported in MOVPE system using GaN buffer layer. Clear blueshift of ISB absorption wavelength by lowering growth temperature was observed, which suggests that interdiffusion within MQWs was suppressed at lower growth temperatures.
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73.21.Fg Quantum wells
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors
78.30.Fs III-V and II-VI semiconductors
78.67.De Quantum wells
66.30.Ny Chemical interdiffusion; diffusion barriers

High-gain photoconductivity in semiconducting InN nanowires

Reui-San Chen, Tsang-Ho Yang, Hsin-Yi Chen, Li-Chyong Chen, Kuei-Hsien Chen, Ying-Jay Yang, Chun-Hsi Su, and Chii-Ruey Lin

Appl. Phys. Lett. 95, 162112 (2009); http://dx.doi.org/10.1063/1.3242023 (3 pages) | Cited 8 times

Online Publication Date: 23 October 2009

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We report on the photoconductivity study of the individual infrared-absorbing indium nitride (InN) nanowires. Temperature-dependent dark conductivity measurement indicates the semiconducting transport behavior of these InN nanowires. An enhanced photosensitivity from 0.3 to 14 is observed by lowering the temperature from 300 to 10 K. A calculated ultrahigh photoconductive gain at around 8×107 at room temperature is obtained from the low-bandgap nitride nanowire under 808 nm excitation.
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73.63.-b Electronic transport in nanoscale materials and structures
72.40.+w Photoconduction and photovoltaic effects
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
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Ferromagnetic Sc-doped AlN sixfold-symmetrical hierarchical nanostructures

W. W. Lei, D. Liu, P. W. Zhu, X. H. Chen, Q. Zhao, G. H. Wen, Q. L. Cui, and G. T. Zou

Appl. Phys. Lett. 95, 162501 (2009); http://dx.doi.org/10.1063/1.3248257 (3 pages) | Cited 13 times

Online Publication Date: 19 October 2009

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Sc-doped AlN (AlN:Sc) sixfold-symmetrical hierarchical nanostructures were grown by direct current (dc) arc discharge plasma method using the direct reaction of Al and Sc metals with N2 gas. Energy-dispersive x-ray spectroscopy, x-ray diffractometry, and Raman spectra analysis clearly showed that Sc was doped in the AlN hierarchical nanostructures. The magnetization curves indicate the existence of room-temperature ferromagnetic behavior. The saturation magnetization and the coercive fields (Hc) of the AlN:Sc nanostructures are about 0.04 emu g−1 and 200 Oe, respectively. The results reveal that Sc is a potential nonmagnetic dopant for preparing diluted magnetic semiconductor nanomaterials.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Tt Fine-particle systems; nanocrystalline materials
78.30.Fs III-V and II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
75.50.Pp Magnetic semiconductors

Saturation magnetization in supersaturated solid solution of Co–Cu alloy

Motohiro Yuasa, Kota Kajikawa, Masataka Hakamada, and Mamoru Mabuchi

Appl. Phys. Lett. 95, 162502 (2009); http://dx.doi.org/10.1063/1.3251795 (3 pages) | Cited 2 times

Online Publication Date: 20 October 2009

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The magnetovolume effect has been investigated using a supersaturated solid solution of a Co–19 at. %Cu alloy processed by electrodeposition. The enhanced saturation magnetization of the Co–Cu alloy was attributed to both metastable fcc Co and lattice expansion. The density functional theory using the CASTEP code revealed that an enhanced magnetic moment due to the magnetovolume effect is obtained in fcc Co, but not in hcp Co.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.80.+q Magnetomechanical effects, magnetostriction
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Pq Electrodeposition, electroplating

Magnetic force microscopy analysis of magnetization reversal in exchange-biased Co/CoO nanostructure arrays

S. Y. Suck, V. Neu, U. Wolff, S. Bahr, O. Bourgeois, and D. Givord

Appl. Phys. Lett. 95, 162503 (2009); http://dx.doi.org/10.1063/1.3248240 (3 pages) | Cited 3 times

Online Publication Date: 20 October 2009

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Asymmetry in the magnetization reversal processes of exchange bias Co/CoO rectangular nanodot arrays is revealed by magnetic force microscopy. One-step switching is found along the descending branch of the hysteresis cycle whereas rotational or multidomain processes are involved along the ascending branch. From a statistical analysis of the environment of each dot during reversal, it is concluded that dipolar interactions do not significantly influence the magnetization reversal processes.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Jk Magnetization reversal mechanisms
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure
75.30.Et Exchange and superexchange interactions
75.75.-c Magnetic properties of nanostructures

Tunable steady-state domain wall oscillator with perpendicular magnetic anisotropy

A. Bisig, L. Heyne, O. Boulle, and M. Kläui

Appl. Phys. Lett. 95, 162504 (2009); http://dx.doi.org/10.1063/1.3238314 (3 pages) | Cited 12 times

Online Publication Date: 22 October 2009

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We theoretically study domain wall oscillations upon the injection of a dc current through a geometrically constrained wire with perpendicular magnetic anisotropy. The frequency spectrum of the oscillation can be tuned by the injected current density and additionally by the application of an external magnetic field. Our analytical calculations are supported by micromagnetic simulations based on the Landau–Lifshitz–Gilbert equation. The simple concept of our localized steady-state oscillator might prove useful as a nanoscale microwave generator with possible applications in telecommunications or for rf-assisted writing in magnetic hard drives.
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75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure
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Growth and properties of chemical solution deposited BiInO3–PbTiO3 films

S. W. Ko, H. G. Yeo, and S. Trolier-McKinstry

Appl. Phys. Lett. 95, 162901 (2009); http://dx.doi.org/10.1063/1.3250165 (3 pages) | Cited 3 times

Online Publication Date: 19 October 2009

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The dielectric, ferroelectric, and piezoelectric properties of chemical solution deposited xBiInO3–(1−x)PbTiO3 (0.10 ≤ x ≤ 0.35) thin films on platinized silicon substrates were investigated. Using a PbTiO3 seed layer, phase pure xBiInO3–(1−x)PbTiO3 (0.10 ≤ x ≤ 0.35) thin films were prepared. For a 470 nm thick 0.15BiInO3–0.85PbTiO3 film, the room temperature permittivity was 650, while the dielectric loss tangent was below 2%. The coercive field and remanent polarization were 73 kV/cm and 22 μC/cm2, respectively. The ferroelectric transition temperatures of the xBiInO3–(1−x)PbTiO3 (x = 0.10–0.20) films were all in excess of 550 °C. For x = 0.15, the e31,f piezoelectric coefficient was −2.7 C/m2.
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77.55.-g Dielectric thin films
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
77.65.Bn Piezoelectric and electrostrictive constants
77.22.Gm Dielectric loss and relaxation
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Reliability properties of metal-oxide-semiconductor capacitors using LaAlO3 high-k dielectric

Lingyen Yeh, Ingram Yin-Ku Chang, Chun-Heng Chen, and Joseph Ya-Min Lee

Appl. Phys. Lett. 95, 162902 (2009); http://dx.doi.org/10.1063/1.3250242 (3 pages)

Online Publication Date: 19 October 2009

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In this study, metal-oxide-semiconductor (MOS) capacitors with high dielectric constant LaAlO3 film were fabricated. Furthermore, the characteristic time-to-breakdown, TBD, of the MOS capacitors was investigated. The TBD was measured and the corresponding Weibull slopes, β, of the MOS capacitors with various LaAlO3 thicknesses were calculated. In addition, a modified percolation model was proposed to consider the extrinsic factors of breakdown. These extrinsic factors were described by an equivalent reduction of the path-to-breakdown, tex, in the model. Using this model, the calculated tex of the MOS capacitor was 5.8 nm.
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84.32.Tt Capacitors
85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Influence of dc-bias on phase stability in Mn-doped Na0.5Bi0.5TiO3-5.6 at. %BaTiO3 single crystals

Wenwei Ge, Hu Cao, Jiefang Li, D. Viehland, Qinhui Zhang, and Haosu Luo

Appl. Phys. Lett. 95, 162903 (2009); http://dx.doi.org/10.1063/1.3253412 (3 pages) | Cited 15 times

Online Publication Date: 20 October 2009

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Mn-doped Na0.5Bi0.5TiO3-5.6 at. %BaTiO3 (Mn:NBT-5.6%BT) single crystals were grown by a top-seeded solution growth method. Tetragonal and rhombohedral phases were found to coexist in the as-grown condition. The dielectric and structural properties were studied as a function of temperature under dc electrical bias. An induced phase stability change from rhombohedral to tetragonal phases occurred under an electric-field applied along the 〈001〉 direction.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Bn Piezoelectric and electrostrictive constants
81.10.Dn Growth from solutions
61.72.up Other materials
77.22.Ch Permittivity (dielectric function)
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Influence of bin time and excitation intensity on fluorescence lifetime distribution and blinking statistics of single quantum dots

Der-Hau Lee, Chi-Tsu Yuan, M. Tachiya, and Jau Tang

Appl. Phys. Lett. 95, 163101 (2009); http://dx.doi.org/10.1063/1.3236772 (3 pages) | Cited 3 times

Online Publication Date: 19 October 2009

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In this study of single CdSe/ZnS quantum dots in a polymethyl methacrylate (PMMA) matrix, we report narrowing of fluorescence lifetime distribution with increased bin time or excitation intensity mostly due to statistical variance of photon counts per bin and Auger relaxation. We also observed saturation for the excitation intensity dependence of the exponential bending rate for the blinking statistics for quantum dots in PMMA but not on glass.
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78.67.Hc Quantum dots
78.55.Et II-VI semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots

Suspended metal wire array as a thermoacoustic sound source

A. O. Niskanen, J. Hassel, M. Tikander, P. Maijala, L. Grönberg, and P. Helistö

Appl. Phys. Lett. 95, 163102 (2009); http://dx.doi.org/10.1063/1.3249770 (3 pages) | Cited 9 times

Online Publication Date: 19 October 2009

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multimedia

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We demonstrate that a suspended metal wire array can be used to produce high-pressure sound waves over a wide spectrum using the thermoacoustic effect. We fabricated air-bridge arrays containing up to 2×105 wires covering an area of a few square centimeters. The supporting silicon wafer was isotropically plasma etched to release the wires thereby avoiding heat contact with the substrate. Sound pressure levels reaching 110 dB at a distance of 8 cm were demonstrated near 40 kHz in free field. The devices are also able to reproduce music and speech. They have potential for applications especially in the ultrasound range.
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07.64.+z Acoustic instruments and equipment
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect

Thermal conductivity of graphene nanoribbons

Zhixin Guo, Dier Zhang, and Xin-Gao Gong

Appl. Phys. Lett. 95, 163103 (2009); http://dx.doi.org/10.1063/1.3246155 (3 pages) | Cited 54 times

Online Publication Date: 20 October 2009

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We have investigated the thermal conductivity of graphene nanoribbons (GNRs) with different edge shapes as a function of length, width, and strain using nonequilibrium molecular dynamics method. The initial GNR for the functional variations has dimensions of 2×11 nm2. Strong length dependence of thermal conductivity is obtained, indicating high thermal conductivities of GNRs, which is consistent with the experimental results for graphene. A tensile/compressive uniaxial strain can remarkably decrease the thermal conductivity of GNR.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep

Stretching induced Hall current and conductance anisotropy in graphene

A. R. Wright and C. Zhang

Appl. Phys. Lett. 95, 163104 (2009); http://dx.doi.org/10.1063/1.3251074 (3 pages) | Cited 3 times

Online Publication Date: 20 October 2009

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We evaluate the effect of stretching on the optical conductance of graphene. It is found that the low energy (Dirac regime) isotropy that leads to the “universal conductance” is lost. More significantly, due to the loss of C3 symmetry, a nonzero Hall conductance emerges for stretching along chiral directions, reaching a maximum at a stretching angle of 45°, and being as high as σ0 = e2/4ℏ at van Hove singular point for bond angle changes of about 2°. Our results indicate that the optical properties of graphene can be tuned by a weak mechanical deformation.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
73.63.-b Electronic transport in nanoscale materials and structures
73.20.At Surface states, band structure, electron density of states
81.05.U- Carbon/carbon-based materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.40.Lm Deformation, plasticity, and creep
72.20.My Galvanomagnetic and other magnetotransport effects

Thermal boundary resistance at the graphene-oil interface

Deepthi Konatham and Alberto Striolo

Appl. Phys. Lett. 95, 163105 (2009); http://dx.doi.org/10.1063/1.3251794 (3 pages) | Cited 17 times

Online Publication Date: 20 October 2009

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In this work, using molecular dynamics simulations, we demonstrate that it is possible to significantly reduce the Kapitza resistance [ P. L. Kapitza, J. Phys. (USSR) 4, 181 (1941) ] at the graphene sheet-liquid octane interface by appropriately functionalizing the graphene sheets. The key concept is that the functional groups, to be effective, must show vibrational modes compatible with those of the organic matrix. Because functionalizing graphene sheets at their edges should not compromise their exceptional intrinsic thermal-transport properties, our results suggest a practical recipe for manufacturing high-thermal-transport polymeric nanocomposites.
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68.35.Ja Surface and interface dynamics and vibrations

Number sensitive detection and direct imaging of dipolar coupled magnetic nanoparticles by tunnel magnetoresistive sensors

C. Albon, A. Weddemann, A. Auge, D. Meißner, K. Rott, P. Jutzi, and A. Hütten

Appl. Phys. Lett. 95, 163106 (2009); http://dx.doi.org/10.1063/1.3253410 (3 pages) | Cited 5 times

Online Publication Date: 20 October 2009

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The suitability of magnetic tunnel junctions for the detection of magnetic nanoparticles is related to their scalability onto the nanoscale size regime without a significant loss of sensitivity. Elliptically shaped MgO based tunnel magnetoresistance sensors are used to provide a sharp detection of 14 nm Co nanoparticles. The measured signal is related to the degree of coverage of the sensor area by a nanoparticle layer. Moreover, the nanoparticles magnetostatic interaction on the sensor surface is clearly distinguished by the presence of a coercitive field in the detected signal. Experimentally obtained results are compared to theoretical models.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.55.-w Magnetic instruments and components
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Tt Fine-particle systems; nanocrystalline materials
75.47.-m Magnetotransport phenomena; materials for magnetotransport

Controllable local modification of fractured Nb-doped SrTiO3 surfaces

TeYu Chien, Tiffany S. Santos, Matthias Bode, Nathan P. Guisinger, and John W. Freeland

Appl. Phys. Lett. 95, 163107 (2009); http://dx.doi.org/10.1063/1.3254184 (3 pages) | Cited 9 times

Online Publication Date: 21 October 2009

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Nanoscale surface modification of a fractured Nb-doped SrTiO3 surface is demonstrated in a controlled way by scanning tunneling microscopy. By applying positive voltage pulses, holes can be created and the width and depth of the hole can be controlled by selecting the appropriate bias and pulse duration. The process shows a threshold condition for creation of the holes and change in the local electronic density of state consistent with exposure of the underlying TiO2 layer by removal of SrO. By applying negative bias, the hole can be partially refilled from the transfer of adsorbates on the tip.
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68.35.Gy Mechanical properties; surface strains
62.20.mm Fracture
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
73.20.At Surface states, band structure, electron density of states
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Dual nonlinear dielectric resonance and nesting microwave absorption peaks of hollow cobalt nanochains composites with negative permeability

Xiao-Ling Shi, Mao-Sheng Cao, Jie Yuan, and Xiao-Yong Fang

Appl. Phys. Lett. 95, 163108 (2009); http://dx.doi.org/10.1063/1.3250170 (3 pages) | Cited 33 times

Online Publication Date: 21 October 2009

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The permittivity and permeability behaviors of the hollow cobalt nanochains composites have been investigated in 2–18 GHz. The permittivity presents two dielectric resonance peaks at about 12.3 and 14.5 GHz, respectively, which mainly results from the cooperative consequence of the hollow structure and the one-dimensional structure of the as-synthesized Co nanochains. The negative permeability behavior within 12.3–18 GHz is attributed to radiation of the magnetic energy according to the as-established equivalent circuit model. Two strong absorption peaks of the composites nest at the resonance frequencies due to the effect of the dual nonlinear dielectric resonance and the negative permeability behavior.
Show PACS
77.22.Ch Permittivity (dielectric function)
81.16.-c Methods of micro- and nanofabrication and processing
61.46.-w Structure of nanoscale materials
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