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7 Feb 2011

Volume 98, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 98, 063101 (2011); http://dx.doi.org/10.1063/1.3551574 (3 pages)

Y. Z. He, H. Li, P. C. Si, Y. F. Li, H. Q. Yu, X. Q. Zhang, F. Ding, K. M. Liew, and X. F. Liu
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InGaN/GaN quantum wells on self-organized faceted GaN islands: Growth and luminescence studies

Z. L. Fang, Y. X. Lin, and J. Y. Kang

Appl. Phys. Lett. 98, 061911 (2011); http://dx.doi.org/10.1063/1.3554421 (3 pages) | Cited 4 times

Online Publication Date: 11 February 2011

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The growth behavior and luminescence properties of InGaN/GaN quantum wells (QW) on in situ self-organized GaN islands of various distinct smooth sidewall faceting are simultaneously investigated and directly compared. The QW thickness is found to be specific polar angle dependent, leading to variations in QW thickness on multifaceting islands. As a result, by color tuning through island shaping and modifications of the InGaN/GaN QWs on the faceted islands, polychromatic emissions are achieved.
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81.07.St Quantum wells
78.67.De Quantum wells
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Realization of optimal bandgaps in solid-solid, solid-air, and hybrid solid-air-solid phononic crystal slabs

Charles M. Reinke, M. F. Su, R. H. Olsson, III, and I. El-Kady

Appl. Phys. Lett. 98, 061912 (2011); http://dx.doi.org/10.1063/1.3543848 (3 pages) | Cited 5 times

Online Publication Date: 11 February 2011

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We investigate the optimal conditions for bandgap formation in square-lattice phononic crystal (PnC) slabs composed of a solid matrix with solid or air inclusions. To ensure sufficient impedance mismatch (key for bandgap formation) and fabrication amenability, silicon and silica were chosen as candidate matrix materials with either air or tungsten inclusions. Solid-solid PnCs were found to exhibit larger bandgaps while relaxing the topological constraints as compared to solid-air PnCs for all but the largest filling fractions. We also demonstrate a hybridized lattice incorporating both air and solid inclusions in the matrix that further relaxes the constraints for realizing wide bandgaps.
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63.20.dd Measurements
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Strain-tunable spin transport in ferromagnetic graphene junctions

Feng Zhai and Lin Yang

Appl. Phys. Lett. 98, 062101 (2011); http://dx.doi.org/10.1063/1.3552716 (3 pages) | Cited 5 times

Online Publication Date: 7 February 2011

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We investigate spin-dependent electronic transport through normal/strained/normal/ferromagnetic/normal graphene junctions. The substrate strain leads to opposite shifts of the K and K′ valleys and thus modulates the orbital motion of Dirac electrons. The energy dependence of this effect together with the exchange splitting can be utilized to design a strain-tunable spin filter.
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72.25.Mk Spin transport through interfaces
73.40.-c Electronic transport in interface structures
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
71.70.Gm Exchange interactions
75.30.Et Exchange and superexchange interactions

The p-type ZnO film realized by a hydrothermal treatment method

Meng Ding, Dongxu Zhao, Bin Yao, Binghui Li, Zhenzhong Zhang, and Dezhen Shen

Appl. Phys. Lett. 98, 062102 (2011); http://dx.doi.org/10.1063/1.3549304 (3 pages) | Cited 10 times

Online Publication Date: 7 February 2011

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Reproducible and high quality N-doped ZnO (ZnO:N) films were achieved by a hydrothermal treatment method. The ZnO:N films exhibited p-type characteristics by means of the Hall-effect and the photoluminescence measurements. At room temperature, the electrical properties of ZnO:N film showed a hole concentration of 1×1016 cm−3 and hole mobility of 8.6 cm2 V−1 s−1. At 83 K two acceptor related emission peaks could be observed located at 3.353 and 3.237 eV, which were assigned to the acceptor-bound exciton and the donor-acceptor pair emissions. This result gave a direct evidence for the generation of the acceptor energy level after the hydrothermal treatment process. Also, a ZnO homojunction diode was fabricated by this method, which displayed a good rectification characteristic at room temperature. This study revealed that the hydrothermal treatment method was effective and practicable in producing p-type ZnO.
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81.05.Dz II-VI semiconductors
78.66.Hf II-VI semiconductors
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
85.30.Kk Junction diodes
78.55.Et II-VI semiconductors
73.61.Ga II-VI semiconductors

Direct measurement of the band gap and Fermi level position at InN(11math0)

Ph. Ebert, S. Schaafhausen, A. Lenz, A. Sabitova, L. Ivanova, M. Dähne, Y.-L. Hong, S. Gwo, and H. Eisele

Appl. Phys. Lett. 98, 062103 (2011); http://dx.doi.org/10.1063/1.3553022 (3 pages) | Cited 9 times

Online Publication Date: 7 February 2011

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A nonpolar stoichiometric InN(11math0) surface freshly cleaved inside UHV was investigated by scanning tunneling microscopy and spectroscopy. Due to the absence of intrinsic surface states in the band gap, scanning tunneling spectroscopy yields directly the fundamental bulk band gap of 0.7±0.1 eV. The Fermi energy is pinned 0.3 eV below the conduction band minimum due to cleavage induced defect states. Thus, intrinsic electron accumulation can be excluded for this surface. Electron accumulation is rather an extrinsic effect due to surface contamination or material decomposition, but not an intrinsic material property of InN.
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73.20.At Surface states, band structure, electron density of states
71.20.Nr Semiconductor compounds

Theory of quasiballistic transport through nanocrystalline silicon dots

Nobuya Mori, Hideki Minari, Shigeyasu Uno, Hiroshi Mizuta, and Nobuyoshi Koshida

Appl. Phys. Lett. 98, 062104 (2011); http://dx.doi.org/10.1063/1.3553501 (3 pages) | Cited 3 times

Online Publication Date: 7 February 2011

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A model to describe the underlying physics of high-energy electron emission from a porous silicon diode is presented. The model is based on an atomistic tight-binding method combined with semiclassical Monte Carlo simulation. It well reproduces essential features of experimental findings. An initial acceleration region is shown to play a crucial role in generating quasiballistic electron emission.
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73.23.Ad Ballistic transport
85.30.Kk Junction diodes
73.63.Kv Quantum dots

Metastable properties of Cu(In1−xGax)Se2 with and without sodium

Peter T. Erslev, William N. Shafarman, and J. David Cohen

Appl. Phys. Lett. 98, 062105 (2011); http://dx.doi.org/10.1063/1.3553783 (3 pages) | Cited 5 times

Online Publication Date: 9 February 2011

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We compare the electronic properties of Cu(In1−xGax)Se2 (CIGS, x = 0.3) companion films with standard and nearly absent sodium levels. The films were examined over a wide range of metastable states produced by light-soaking. Admittance spectroscopy revealed that the activation energy of the dominant deep defect (hole trap) decreased monotonically from 300 to 60 meV with light-soaking time for samples with normal sodium, but remained nearly fixed ( ∼ 350 meV) for samples without sodium. Drive-level capacitance profiling indicated that the deep defect densities increased under light-soaking by roughly a factor of 20 for both samples and annealed at identical rates; however, the relative increases between the defect and hole carrier densities were dramatically different.
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71.20.Ps Other inorganic compounds
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Gh Other heat and thermomechanical treatments
71.55.Ak Metals, semimetals, and alloys
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Sub-100-nm negative bend resistance ballistic sensors for high spatial resolution magnetic field detection

A. M. Gilbertson, D. Benstock, M. Fearn, A. Kormányos, S. Ladak, M. T. Emeny, C. J. Lambert, T. Ashley, S. A. Solin, and L. F. Cohen

Appl. Phys. Lett. 98, 062106 (2011); http://dx.doi.org/10.1063/1.3554427 (3 pages)

Online Publication Date: 10 February 2011

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We report the magnetic field detection properties of ballistic sensors utilizing the negative bend resistance of InSb/In1−xAlxSb quantum well cross junctions as a function of temperature and geometric size. We demonstrate that the maximum responsivity to magnetic field and its linearity increase as the critical device dimension is reduced. This observation deviates from the predictions of the classical billiard ball model unless significant diffuse boundary scattering is included. The smallest device studied has an active sensor area of 35×35 nm2, with a maximum responsivity of 20 kΩ/T, and a noise-equivalent field of 0.87 μT/math at 100 K.
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07.55.Ge Magnetometers for magnetic field measurements
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Experimental demonstration of In0.53Ga0.47As field effect transistors with scalable nonalloyed source/drain contacts

Jenny Hu, Krishna C. Saraswat, and H.-S. Philip Wong

Appl. Phys. Lett. 98, 062107 (2011); http://dx.doi.org/10.1063/1.3553192 (3 pages) | Cited 5 times

Online Publication Date: 10 February 2011

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We demonstrate the integration of a nonalloyed contact structure developed for III-V semiconductors to the source/drain of an In0.53Ga0.47As metal-oxide-semiconductor field effect transistor (MOSFET) with atomic layer deposition (ALD) Al2O3 high-κ dielectric. This nonalloyed contact utilizes single metals in combination with dielectric dipoles to tune the metal/semiconductor Femi level pinning toward the semiconductor’s band edge for minimal contact resistance and barrier height. The metal/III-V semiconductor effective barrier heights have been reduced by as much as 0.40 eV using SiN and 0.55 eV using Al2O3 dielectrics. With this InGaAs nMOSFET as a starting point, this contact can be applied to other III-V n-type MOSFETs, p-type MOSFETs, and Schottky Barrier field effect transistors.
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85.30.Tv Field effect devices
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Sz Deposition technology

Attainment of low interfacial trap density absent of a large midgap peak in In0.2Ga0.8As by Ga2O3(Gd2O3) passivation

C. A. Lin, H. C. Chiu, T. H. Chiang, T. D. Lin, Y. H. Chang, W. H. Chang, Y. C. Chang, W.-E. Wang, J. Dekoster, T. Y. Hoffmann, M. Hong, and J. Kwo

Appl. Phys. Lett. 98, 062108 (2011); http://dx.doi.org/10.1063/1.3554375 (3 pages) | Cited 14 times

Online Publication Date: 11 February 2011

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The pronounced high interfacial densities of states (Dit) commonly observed around the midgap energy of dielectric/GaAs interfaces are generally considered the culprit responsible for the poor electrical performance of the corresponding inversion-channel metal-oxide-semiconductor field-effect-transistors. In this work, comprehensive Dit spectra as the function of energy [Dit(E)] inside the In0.2Ga0.8As band gap were constructed by using the quasistatic capacitance-voltage and the temperature-dependent conductance method on n- and p-type ultrahigh vacuum (UHV)-Ga2O3(Gd2O3)/In0.2Ga0.8As and atomic-layer-deposited (ALD)-Al2O3/In0.2Ga0.8As metal-oxide-semiconductor capacitors. Unlike the ALD-Al2O3/In0.2Ga0.8As interface giving a Dit spectrum with a high midgap Dit peak, the UHV-Ga2O3(Gd2O3)/In0.2Ga0.8As interface shows a Dit spectrum that monotonically decreases from the valence band to the conduction band with no discernible midgap peak.
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73.20.At Surface states, band structure, electron density of states
73.61.Ey III-V semiconductors
85.30.Tv Field effect devices
81.65.Rv Passivation
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Dynamics of two coupled vortices in a spin valve nanopillar excited by spin transfer torque

N. Locatelli, V. V. Naletov, J. Grollier, G. de Loubens, V. Cros, C. Deranlot, C. Ulysse, G. Faini, O. Klein, and A. Fert

Appl. Phys. Lett. 98, 062501 (2011); http://dx.doi.org/10.1063/1.3553771 (3 pages) | Cited 15 times

Online Publication Date: 7 February 2011

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We investigate the dynamics of two coupled vortices driven by spin transfer. We are able to independently control with current and perpendicular field and to detect the respective chiralities and polarities of the two vortices. For current densities above J = 5.7×107 A/cm2, a highly coherent signal (linewidth down to 46 kHz) can be observed, with a strong dependence on the relative polarities of the vortices. It demonstrates the interest of using coupled dynamics in order to increase the coherence of the microwave signal. Emissions exhibit a linear frequency evolution with perpendicular field, with coherence conserved even at zero magnetic field.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.70.Gq Microwave and radio-frequency interactions
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.-c Magnetic properties of nanostructures
73.40.Jn Metal-to-metal contacts
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Cross-linking effect on dielectric properties of polypropylene thin films and applications in electric energy storage

Xuepei Yuan and T. C. Mike Chung

Appl. Phys. Lett. 98, 062901 (2011); http://dx.doi.org/10.1063/1.3552710 (3 pages) | Cited 2 times

Online Publication Date: 7 February 2011

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A family of cross-linked polypropylene (x-PP) thin film dielectrics is systematically studied to understand the cross-linking effect on the dielectric properties. Evidently, the butylstyrene (BSt) cross-linkers increase both the dielectric constant (ε) and breakdown strength (E), without increasing energy loss. An x-PP dielectric, with 3.65 mol % BSt cross-linkers, exhibits a ε ∼ 3, which is independent of a wide range of temperatures and frequencies, slim D-E hysteresis loops, high breakdown strength (E = 650 MV/m), narrow breakdown distribution, and reliable energy storage capacity >5 J/cm3 (double that of state-of-the-art biaxially oriented polypropylene capacitors), without showing any increase in energy loss.
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84.32.Tt Capacitors
84.60.Ve Energy storage systems, including capacitor banks
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
77.22.Gm Dielectric loss and relaxation

Direct writing of ferroelectric domains on the x- and y-faces of lithium niobate using a continuous wave ultraviolet laser

H. Steigerwald, Y. J. Ying, R. W. Eason, K. Buse, S. Mailis, and E. Soergel

Appl. Phys. Lett. 98, 062902 (2011); http://dx.doi.org/10.1063/1.3553194 (3 pages) | Cited 2 times

Online Publication Date: 7 February 2011

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Ferroelectric domain reversal has been achieved by scanning a tightly focused, strongly absorbed ultraviolet laser beam across the x- and y-faces of lithium niobate crystals. The domains were investigated by piezoresponse force microscopy. The emergence and width of any domain was found to depend on the scanning direction of the irradiating laser beam with respect to the polar z-axis. Full width and half width domains or no domain formation at all could be achieved for scanning along specific directions. We interpret the results by a direct correlation between the local temperature gradient and the resulting polarization direction.
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77.80.Dj Domain structure; hysteresis
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
79.20.Ds Laser-beam impact phenomena
77.22.Ej Polarization and depolarization

High-resolution core-level photoemission study of CF4-treated Gd2O3(Ga2O3) gate dielectric on Ge probed by synchrotron radiation

T.-W. Pi (皮敦文), M. L. Huang (黃懋霖), W. C. Lee (李威縉), L. K. Chu (朱龍琨), T. D. Lin (林宗達), T. H. Chiang (江宗鴻), Y. C. Wang (王貽樟), Y. D. Wu (吳彥達), M. Hong (洪銘輝), and J. Kwo (郭瑞年)

Appl. Phys. Lett. 98, 062903 (2011); http://dx.doi.org/10.1063/1.3551726 (3 pages) | Cited 3 times

Online Publication Date: 8 February 2011

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High-resolution core-level photoemission analysis using synchrotron radiation was used to investigate the superior electrical performance of aGa2O3(Gd2O3) gate dielectric on Ge(001) after CF4 treatment. Prior to the treatment, a thin germanate-like oxide layer that formed at the interface prevented Ge from diffusing to the surface. The Ge surface retained a small amount of buckled dimers from the as-grown sample. The buckled dimers were quickly removed by CF4 plasma treatment followed by an annealing process, resulting in a more uniform interface than that of the as-grown sample. The detailed interfacial electronic structure for the untreated and treated samples are presented.
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79.60.Jv Interfaces; heterostructures; nanostructures
81.40.Gh Other heat and thermomechanical treatments
68.35.Fx Diffusion; interface formation
52.77.-j Plasma applications

Low-frequency nanotesla sensitivity in Metglas/piezoelectric/carbon fiber/piezoelectric composites with active tip mass

Chee-Sung Park, Dragan Avirovik, Scott Bressers, and Shashank Priya

Appl. Phys. Lett. 98, 062904 (2011); http://dx.doi.org/10.1063/1.3552970 (3 pages) | Cited 4 times

Online Publication Date: 8 February 2011

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We report nanotesla sensitivity in Metglas/piezoelectric/carbon fiber/piezoelectric laminates with active tip mass operating in the vicinity of second bending mode. The peak magnetoelectric response for the laminate with an active tip mass (1 g) in longitudinal-transversal mode under Hdc = 8 Oe and Hac = 1 Oe was found to be ∼ 1.08 V/cm Oe at 43 Hz (first bending mode) and ∼ 19 V/cm Oe at 511 Hz (second bending mode). At the standard 1 kHz frequency, the maximum resolution of 5 nT was measured under Hac = 0.5 Oe.
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75.85.+t Magnetoelectric effects, multiferroics
77.55.Nv Multiferroic/magnetoelectric films
77.65.-j Piezoelectricity and electromechanical effects

Humidity effects on (001) BaTiO3 single crystal surface water adsorption

D. Y. He, L. J. Qiao, Alex A. Volinsky, Y. Bai, M. Wu, and W. Y. Chu

Appl. Phys. Lett. 98, 062905 (2011); http://dx.doi.org/10.1063/1.3544586 (3 pages) | Cited 6 times

Online Publication Date: 10 February 2011

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Water adsorption on (001) BaTiO3 single crystal surface under varying relative humidity conditions was studied by ab initio calculations and scanning probe microscopy utilizing different operation modes. At 95% relative humidity water droplets nucleated only on c domains, preferential adsorption location for water dipoles. BaTiO3 (001) surface long 65% relative humidity exposure lead to no contrast between a and c domains observed by electrostatic force microscopy. Ab initio calculations confirm that water molecules prefer to adsorb on c domains due to their higher surface energy.
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68.43.Mn Adsorption kinetics
68.43.Bc Ab initio calculations of adsorbate structure and reactions
68.03.Cd Surface tension and related phenomena
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Dynamic ripples in single layer graphene

Y. Z. He, H. Li, P. C. Si, Y. F. Li, H. Q. Yu, X. Q. Zhang, F. Ding, K. M. Liew, and X. F. Liu

Appl. Phys. Lett. 98, 063101 (2011); http://dx.doi.org/10.1063/1.3551574 (3 pages) | Cited 4 times

Online Publication Date: 7 February 2011

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multimedia

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Similar to the water wave on a pond caused by dropping a pebble, the formation of ripples is shown in a single layer graphene (SLG) when it is stroked by a C60 molecule, no matter whether the graphene is plane or corrugated. The controllable ripple in SLG is investigated by molecular dynamics simulations. Noticeable diffraction and interference of the ripples are observed. This study indicates that the ripple propagation in graphene can be used to detect defects.
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61.20.Ja Computer simulation of liquid structure
47.35.Lf Wave-structure interactions
61.48.Gh Structure of graphene

Raman study of interfacial load transfer in graphene nanocomposites

Iti Srivastava, Rutvik J. Mehta, Zhong-Zhen Yu, Linda Schadler, and Nikhil Koratkar

Appl. Phys. Lett. 98, 063102 (2011); http://dx.doi.org/10.1063/1.3552685 (3 pages) | Cited 11 times

Online Publication Date: 7 February 2011

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We tracked the strain-sensitive characteristic Raman G-band shift of graphene platelets in polydimethyl-siloxane (PDMS) nanocomposites revealing the filler-to-matrix interactions. We obtained large debonding strains of ∼ 7% for graphene in PDMS, with the peak shift rate with strain being ∼ 2.4 cm−1/composite strain % in comparison to single-walled carbon nanotube composites, where a relatively low rate of ∼ 0.1 cm−1/composite strain % was obtained, suggesting enhanced load-transfer effectiveness for graphene. A surprising observation was that for large strains (>1.5%) the graphene fillers went into compression under uniaxial tensile deformation and vice versa. We propose that this effect is related to the high mobility of the PDMS chains at room temperature.
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78.67.Sc Nanoaggregates; nanocomposites
81.05.uj Diamond/nanocarbon composites
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
78.30.-j Infrared and Raman spectra

All-printed infrared sensor based on multiwalled carbon nanotubes

A. Gohier, A. Dhar, L. Gorintin, P. Bondavalli, Y. Bonnassieux, and C. S. Cojocaru

Appl. Phys. Lett. 98, 063103 (2011); http://dx.doi.org/10.1063/1.3552686 (3 pages) | Cited 6 times

Online Publication Date: 7 February 2011

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This contribution deals with all-printed infrared sensors fabricated using multiwalled carbon nanotubes deposited on a flexible polyimide substrate. A high responsivity of up to 1.2 kV/W is achieved at room temperature in ambient air. We evidence a strong dependence of the device transduction mechanism on the surrounding atmosphere, which can be attributed to bolometric effect interference with water molecule desorption upon irradiation.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Kt Nanotube devices
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
81.07.De Nanotubes

Direct current dielectric barrier discharges under voltages below the ionization potential of neutrals in electrode systems with one-dimensional nanostructures

Zhongyu Hou, Weimin Zhou, Yanyan Wang, and Bingchu Cai

Appl. Phys. Lett. 98, 063104 (2011); http://dx.doi.org/10.1063/1.3552709 (3 pages) | Cited 3 times

Online Publication Date: 7 February 2011

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We experimentally investigate the characteristics of dielectric barrier discharges in an electrode system with one-dimensional nanostructures of gap size at micrometer scale. Evidence of quasistationary direct current discharges in air has been observed under the applied voltage several times lower than the first ionization potential of O2. The results qualitatively agree with the hypothesis on the ionization mechanism of stepwise inelastic collisions within a metastable pool, which is populated through field excitation and inelastic impact between the neutrals and the nanostructures.
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52.80.-s Electric discharges
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.Fi Transport properties
52.25.Jm Ionization of plasmas

Amplified spontaneous emission from core and shell transitions in CdSe/CdS nanorods fabricated by seeded growth

Roman Krahne, Margherita Zavelani-Rossi, Maria Grazia Lupo, Liberato Manna, and Guglielmo Lanzani

Appl. Phys. Lett. 98, 063105 (2011); http://dx.doi.org/10.1063/1.3549298 (3 pages) | Cited 3 times

Online Publication Date: 8 February 2011

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We studied the optical properties of core-shell CdSe/CdS nanorods with various lengths and core diameters that were fabricated by wet chemical synthesis using the seeded growth method. We investigated the optical emission from thin films consisting of dense nanorod arrays, where we observed amplified spontaneous emission from states related either to the CdSe core or to the CdS shell depending on the nanorod’s length. The optical gain of the nanorods was studied by transient absorption experiments and we found optical gain for the core and shell states of short rods, whereas for long rods, the optical gain of the core was quenched by defect states and we observed optical gain solely from the states of the shell material.
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81.07.Bc Nanocrystalline materials
68.55.ag Semiconductors
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
78.55.Et II-VI semiconductors

π junction transition in InAs self-assembled quantum dot coupled with SQUID

S. Kim, R. Ishiguro, M. Kamio, Y. Doda, E. Watanabe, D. Tsuya, K. Shibata, K. Hirakawa, and H. Takayanagi

Appl. Phys. Lett. 98, 063106 (2011); http://dx.doi.org/10.1063/1.3552715 (3 pages) | Cited 2 times

Online Publication Date: 8 February 2011

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We report the transport measurements on the InAs self-assembled quantum dots (SAQDs) which have a unique structural zero-dimensionality, coupled to a superconducting quantum interference device (SQUID). Owing to the SQUID geometry, we directly observe a π phase shift in the current phase relation and the negative supercurrent indicating π junction behavior by not only tuning the energy level of SAQD by back-gate but also controlling the coupling between SAQD and electrodes by side-gate. Our results inspire the future quantum information devices which can link optical, spin, and superconducting state.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.25.Dq Superconducting quantum interference devices (SQUIDs)
81.05.Ea III-V semiconductors
73.63.Kv Quantum dots
81.16.Dn Self-assembly

Influence of gas rarefaction on the lateral resolution achievable by thermocapillary patterning

Nan Liu and Sandra M. Troian

Appl. Phys. Lett. 98, 063107 (2011); http://dx.doi.org/10.1063/1.3551535 (3 pages)

Online Publication Date: 8 February 2011

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Molten polymer nanofilms subject to a large transverse thermal gradient can undergo a thermocapillary instability leading to the growth of nanopillar arrays on the cooler side. The array pitch can be estimated from the fastest growing wavelength from linear stability analysis. Here we quantify the influence of gas rarefaction on thermal conduction for cases in which the gas layer thickness above the film approaches dimensions of the molecular mean free path. For experimentally relevant parameters, rarefaction increases the pitch by as much as 65%, an important consideration for noncontact three-dimensional structure formation by thermocapillary lithography.
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47.85.md Polymer processing flows
47.57.Ng Polymers and polymer solutions
47.55.nb Capillary and thermocapillary flows
47.50.Gj Instabilities
47.45.Dt Free molecular flows
81.16.Rf Micro- and nanoscale pattern formation

Stability and electronic structure of bilayer graphone

J. Zhou, Q. Wang, Q. Sun, and P. Jena

Appl. Phys. Lett. 98, 063108 (2011); http://dx.doi.org/10.1063/1.3555431 (3 pages) | Cited 2 times

Online Publication Date: 9 February 2011

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Stability, reconstruction, and electronic structure of a bilayer graphone have been studied, where the most stable configuration undergoes a (1×2) surface reconstruction. An energy barrier of 1.83 eV separates this structure from the nonbonded state. The stability of the reconstructed bilayer at room temperature is confirmed by both frequency calculation and molecular dynamics simulation. Unlike the graphone sheet, the bilayer graphone is nonmagnetic but remains metallic due to the existence of delocalized π orbital on the zigzag sp2 carbon chains, which are stable against Peierls instability. The metallicity is also stable under gate external electric field.
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71.20.Tx Fullerenes and related materials; intercalation compounds
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
68.35.bp Fullerenes
71.30.+h Metal-insulator transitions and other electronic transitions

Motional modes in bulk powder and few-molecule clusters of tris(8-hydroxyquinoline aluminum) and their relation to spin dephasing

Lopamudra Das, Jennette Mateo, Saumil Bandyopadhyay, Supriyo Bandyopadhyay, Jarrod D. Edwards, and John Anderson

Appl. Phys. Lett. 98, 063109 (2011); http://dx.doi.org/10.1063/1.3554753 (3 pages) | Cited 1 time

Online Publication Date: 10 February 2011

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The ensemble averaged spin dephasing rate of localized electrons in the organic molecule tris(8-hydroxyquinoline aluminum) or Alq3 has been found to be significantly larger in bulk powder than in single- or few-molecule clusters confined within 1–2 nm sized nanocavities [ B. Kanchibotla et al., Phys. Rev. B 78, 193306 (2008)] . To understand this observation, we have compared the midinfrared absorption spectra of bulk powder and single- or few-molecule clusters. It appears that molecules have additional vibrational modes in bulk powder possibly due to multimerization. Their coupling with spin may be responsible for the increased spin dephasing rate in bulk powder.
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78.30.Jw Organic compounds, polymers
36.40.-c Atomic and molecular clusters
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Ea Infrared spectra
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