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24 Sep 2012

Volume 101, Issue 13, Articles (13xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 133101 (2012); http://dx.doi.org/10.1063/1.4752467 (5 pages)

Yen Husn Su and Wei-Yu Chen
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Magnetocapacitance of an electrically tunable silicene device

M. Tahir and U. Schwingenschlögl

Appl. Phys. Lett. 101, 132412 (2012); http://dx.doi.org/10.1063/1.4754711 (3 pages) | Cited 2 times

Online Publication Date: 26 September 2012

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Despite their structural similarity, the electronic properties of silicene are fundamentally different from those of well-known graphene due to the strong intrinsic spin orbit interaction and buckled structure of silicene. We address the magnetocapacitance of spin and valley polarized silicene in an external perpendicular magnetic field to clarify the interplay of the spin orbit interaction and the perpendicular electric field. We find that the band gap is electrically tunable and show that the magnetocapacitance exhibits beating at low and splitting of the Shubnikov de Haas oscillations at high magnetic field.
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72.25.Dc Spin polarized transport in semiconductors
81.05.Cy Elemental semiconductors
71.20.Mq Elemental semiconductors
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
72.20.My Galvanomagnetic and other magnetotransport effects

Enhancement of room temperature ferromagnetism in Mn-implanted Si by He implantation

Jihong Chen, Liping Guo, Congxiao Liu, Fengfeng Luo, Tiecheng Li, Zhongcheng Zheng, Shuoxue Jin, and Zheng Yang

Appl. Phys. Lett. 101, 132413 (2012); http://dx.doi.org/10.1063/1.4754712 (4 pages) | Cited 1 time

Online Publication Date: 26 September 2012

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Room temperature ferromagnetism in Mn-implanted p-Si was enhanced dramatically by implantation of He. A 75 nm end-of-range region was found in the sample, with large scale and inhomogeneous damaging but preserved Si lattice periodicity. The end-of-range region shows an intrinsic magnetization of ∼100 emu/cm3. High resolution transmission electron microscopy and x-ray photoelectron spectroscopy measurements indicate that the spin polarization of Si dangling bonds rather than Mn impurity was the major source for the enhanced magnetism.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
79.60.Bm Clean metal, semiconductor, and insulator surfaces
61.72.uf Ge and Si
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors

Platinum thickness dependence of the inverse spin-Hall voltage from spin pumping in a hybrid yttrium iron garnet/platinum system

V. Castel, N. Vlietstra, J. Ben Youssef, and B. J. van Wees

Appl. Phys. Lett. 101, 132414 (2012); http://dx.doi.org/10.1063/1.4754837 (4 pages) | Cited 3 times

Online Publication Date: 26 September 2012

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We show the experimental observation of the platinum thickness dependence in a hybrid yttrium iron garnet/platinum system of the inverse spin-Hall effect from spin pumping, over a large frequency range and for different radio-frequency powers. From the measurement of the voltage at the resonant condition and the resistance of the normal metal layer, a strong enhancement of the ratio of these quantities has been observed, which is not in agreement with previous studies on the NiFe/platinum system. The origin of this behaviour cannot be fully explained by the spin transport model that we have used and is therefore still unclear.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.25.Mk Spin transport through interfaces
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Gg Ferrimagnetics

Giant magnetocaloric effect in magnetically frustrated EuHo2O4 and EuDy2O4 compounds

A. Midya, N. Khan, D. Bhoi, and P. Mandal

Appl. Phys. Lett. 101, 132415 (2012); http://dx.doi.org/10.1063/1.4754849 (4 pages) | Cited 1 time

Online Publication Date: 26 September 2012

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We have investigated the magnetic and magnetocaloric properties of EuHo2O4 and EuDy2O4 by magnetization and heat capacity measurements down to 2 K. These compounds undergo a field-induced antiferromagnetic to ferromagnetic transition and exhibit a huge entropy change. For a field change of 0-8 T, the maximum magnetic entropy and adiabatic temperature changes are 30 (25) J kg−1 K−1 and 12.7 (16) K, respectively, and the corresponding value of refrigerant capacity is 540 (415) J kg−1 for EuHo2O4 (EuDy2O4). These magnetocaloric parameters also remain large down to lowest temperature measured and are even larger than that for some of the potential magnetic refrigerants reported in the same temperature range. Moreover, these materials are highly insulating and exhibit no thermal and field hysteresis, fulfilling the necessary conditions for a good magnetic refrigerant in the low-temperature region.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Interface mediated ferromagnetism in bulk CuO/Cu2O composites

Daqiang Gao, Zhipeng Zhang, Zhaolong Yang, and Desheng Xue

Appl. Phys. Lett. 101, 132416 (2012); http://dx.doi.org/10.1063/1.4755766 (4 pages)

Online Publication Date: 26 September 2012

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In this letter, we report the interface-related room temperature ferromagnetism in bulk CuO/Cu2O composites which were synthesized by heat-decomposing or oxidation methods with the CuO and Cu2O as the precursors, respectively. Magnetic measurement results indicate that all the CuO/Cu2O composites show obvious room temperature ferromagnetism, while the samples with the pure CuO and Cu2O phases are paramagnetic. What is more, the ferromagnetism can be tuned by changing the phase rations of the CuO and Cu2O in the composites. The observed ferromagnetism in CuO/Cu2O composites is considered to be related to the interface between CuO and Cu2O phases.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
75.20.Ck Nonmetals
75.50.Dd Nonmetallic ferromagnetic materials

d0 ferromagnetism in undoped n and p-type In2O3 films

Shaohua Sun, Ping Wu, and Pengfei Xing

Appl. Phys. Lett. 101, 132417 (2012); http://dx.doi.org/10.1063/1.4755771 (4 pages) | Cited 2 times

Online Publication Date: 26 September 2012

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Undoped indium oxide films with room temperature d0 ferromagnetism were prepared by radiofrequency magnetron sputtering with different O2/Ar flux ratio. The optical and magnetic properties changed non-monotonously as the oxygen flux increases. A conversion of conductivity from n-type to p-type was observed as the flux ratio reached 15:15. The concordant results in structural, electrical, optical, and magnetic properties suggest that single ionized oxygen and indium vacancies play crucial roles in mediating the ferromagnetism in n and p-type In2O3 films, respectively.
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75.70.Ak Magnetic properties of monolayers and thin films
78.66.Li Other semiconductors
81.15.Cd Deposition by sputtering
75.50.Dd Nonmetallic ferromagnetic materials

Giant tunneling magnetoresistance in epitaxial Co2MnSi/MgO/Co2MnSi magnetic tunnel junctions by half-metallicity of Co2MnSi and coherent tunneling

Hong-xi Liu, Yusuke Honda, Tomoyuki Taira, Ken-ichi Matsuda, Masashi Arita, Tetsuya Uemura, and Masafumi Yamamoto

Appl. Phys. Lett. 101, 132418 (2012); http://dx.doi.org/10.1063/1.4755773 (5 pages) | Cited 1 time

Online Publication Date: 26 September 2012

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Giant tunnel magnetoresistance (TMR) ratios of up to 1995% at 4.2 K and up to 354% at 290 K were obtained for epitaxial Co2MnSi/MgO/Co2MnSi magnetic tunnel junctions (MTJs) featuring a reduced lattice mismatch in the MTJ trilayer by introducing a thin Co2MnSi lower electrode deposited on a Co50Fe50 buffer layer. The obtained giant TMR ratios can be explained by the enhanced contribution of coherent tunneling originating from the increased misfit dislocation spacing at the lower and upper interfaces with a MgO barrier along with the half-metallicity of Co2MnSi electrodes.
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75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

Equilibrium magnetic states in individual hemispherical permalloy caps

Robert Streubel, Volodymyr P. Kravchuk, Denis D. Sheka, Denys Makarov, Florian Kronast, Oliver G. Schmidt, and Yuri Gaididei

Appl. Phys. Lett. 101, 132419 (2012); http://dx.doi.org/10.1063/1.4756708 (3 pages) | Cited 2 times

Online Publication Date: 28 September 2012

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The magnetization distributions in individual soft magnetic permalloy caps on non-magnetic spherical particles with sizes ranging from 50 to 800 nm are investigated. We experimentally visualize the magnetic structures at the resolution limit of the x-ray magnetic circular dichroism photoelectron emission microscopy (XMCD-PEEM). By analyzing the so-called tail contrast in XMCD-PEEM, the spatial resolution is significantly enhanced, which allowed us to explore magnetic vortices and their displacement on curved surfaces. Furthermore, cap nanostructures are modeled as extruded hemispheres to determine theoretically the phase diagram of equilibrium magnetic states. The calculated phase diagram agrees well with the experimental observations.
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75.75.-c Magnetic properties of nanostructures
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
79.60.Bm Clean metal, semiconductor, and insulator surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
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Effects of microwave annealing on electrical enhancement of amorphous oxide semiconductor thin film transistor

Li-Feng Teng, Po-Tsun Liu, Yuan-Jou Lo, and Yao-Jen Lee

Appl. Phys. Lett. 101, 132901 (2012); http://dx.doi.org/10.1063/1.4754627 (4 pages) | Cited 1 time

Online Publication Date: 24 September 2012

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By using microwave annealing technology instead of thermal furnace annealing, this work elucidates the electrical characteristics of amorphous InGaZnO thin film transistor (a-IGZO TFT) with a carrier mobility of 13.5 cm2/Vs, threshold voltage of 3.28 V, and subthreshold swing of 0.43 V/decade. This TFT performance with microwave annealing of 100 s is well competitive with its counterpart with furnace annealing at 450 °C for 1 h. A physical mechanism for the electrical improvement is also deduced. Owing to its low thermal budget and selective heating to materials of interest, microwave annealing is highly promising for amorphous oxide in semiconductor TFT manufacturing.
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85.30.Tv Field effect devices
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Self-assembled NaNbO3-Nb2O5 (ferroelectric-semiconductor) heterostructures grown on LaAlO3 substrates

Zhiguang Wang, Yanxi Li, Bo Chen, Ravindranath Viswan, Jie-Fang Li, and D. Viehland

Appl. Phys. Lett. 101, 132902 (2012); http://dx.doi.org/10.1063/1.4754713 (4 pages)

Online Publication Date: 24 September 2012

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We deposited NaNbO3 (NNO)-Nb2O5 (NO) self-assembled heterostructures on LaAlO3 (LAO) to form ferroelectric-semiconductor vertically integrated nanostructures. The NNO component formed as nanorods embedded in a NO matrix. X-ray diffraction confirmed epitaxial growth of both NNO and NO phases. Phase distribution was detected by scanning electron microscopy. The NNO/NO volume ratio was strongly dependent on the deposition temperature due to the volatility of sodium. Piezoelectric force microscopy revealed a good piezoelectric response in the NNO component with a piezoelectric coefficient of D33 ≈ 12 pm/V, with SrRuO3 (SRO) acting as bottom electrode. The current-voltage characterization of NNO-NO/SRO-LAO showed a typical diode rectifying behavior.
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81.16.Dn Self-assembly
77.84.Ek Niobates and tantalates
73.40.Ei Rectification
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.65.-j Piezoelectricity and electromechanical effects
77.80.-e Ferroelectricity and antiferroelectricity

Giant electrocaloric effect in ferroelectric poly(vinylidenefluoride-trifluoroethylene) copolymers near a first-order ferroelectric transition

Xinyu Li, Xiao-Shi Qian, Haiming Gu, Xiangzhong Chen, S. G. Lu, Minren Lin, Fred Bateman, and Q. M. Zhang

Appl. Phys. Lett. 101, 132903 (2012); http://dx.doi.org/10.1063/1.4756697 (4 pages) | Cited 4 times

Online Publication Date: 26 September 2012

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We present directly measured electrocaloric effect (ECE) from the poly(vinylidenefluoride-trifluoroethylene) 65/35 mol. % copolymer. The data reveal a large difference in the ECE between that measured in applying and in removing the electric field. The difference is significantly reduced by modifying the copolymer with 20 Mrad of high energy electron irradiation. Moreover, an isothermal entropy change ΔSint = 160 J kg−1 K−1 and an adiabatic temperature change ΔTint = 35 °C can be induced in the irradiated copolymer. These results demonstrate the promise of achieving a significant ECE in ferroelectric polymers near first-order ferroelectric-paraelectric transition where multiple intermediate phases can exist.
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77.70.+a Pyroelectric and electrocaloric effects
77.80.B- Phase transitions and Curie point

Phase transitions and domain evolution in (Pb, La)(Zr, Sn, Ti)O3 single crystal

Yuanyuan Li, Qiang Li, Qingfeng Yan, Yiling Zhang, Xiaoqing Xi, Xiangcheng Chu, and Wenwu Cao

Appl. Phys. Lett. 101, 132904 (2012); http://dx.doi.org/10.1063/1.4755759 (4 pages)

Online Publication Date: 27 September 2012

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Antiferroelectric (Pb, La)(Zr, Sn, Ti)O3 (PLZST) single crystal has been grown and characterized. From dielectric measurements, x-ray diffraction analysis, and in situ observation of domain structures, we found two first-order phase transitions during heating from room temperature to 250 °C: orthorhombic (O) → rhombohedral (R) → cubic. Coexistence of O and R phases, with the R phase region strongly restricted inside the O phase matrix, has been observed within a broad temperature range above 123 °C. In addition, much denser domain walls appeared in the PLZST crystal when the O-R transition takes place.
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81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
81.40.Gh Other heat and thermomechanical treatments
64.70.K- Solid-solid transitions
77.80.B- Phase transitions and Curie point
61.66.Fn Inorganic compounds
77.80.Dj Domain structure; hysteresis

Polarization screening in polymer ferroelectric films: Uncommon bulk mechanism

E. Mikheev, I. Stolichnov, A. K. Tagantsev, and N. Setter

Appl. Phys. Lett. 101, 132905 (2012); http://dx.doi.org/10.1063/1.4754146 (4 pages)

Online Publication Date: 27 September 2012

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Charge compensation at the interface is a fundamental phenomenon determining the operation conditions of thin-film devices incorporating ferroelectrics. The underlying mechanisms have been thoroughly addressed in perovskite ferroelectrics where the charge compensation originates from injection through the interface-adjacent layer. Here, we demonstrate that polarization screening in the polymer ferroelectric polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) films can be dominated by charge injection through the bulk, unlike ferroelectric oxides. The experimental evidence relies on polarization imprint under applied field and time-dependence of the dielectric constant. A linearized electrostatic model correctly accounts for the observed trends and links their occurrence to the unique properties of P(VDF-TrFE).
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84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

The intrinsic electrical breakdown strength of insulators from first principles

Y. Sun, S. A. Boggs, and R. Ramprasad

Appl. Phys. Lett. 101, 132906 (2012); http://dx.doi.org/10.1063/1.4755841 (5 pages)

Online Publication Date: 27 September 2012

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A first principles quantum-mechanical method for estimating intrinsic breakdown strength of insulating materials has been implemented based on an average electron model which assumes that the breakdown occurs when the average electron energy gain from the electric field exceeds the average energy loss to phonons. The approach is based on density functional perturbation theory and on the direct integration of electronic scattering probabilities over all possible final states, with no adjustable parameters. The computed intrinsic breakdown field for several prototypical materials compares favorably with available experimental data. This model also provides physical insight into the material properties that affect breakdown.
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77.22.Jp Dielectric breakdown and space-charge effects
63.20.kd Phonon-electron interactions

The adsorption-controlled growth of LuFe2O4 by molecular-beam epitaxy

Charles M. Brooks, Rajiv Misra, Julia A. Mundy, Lei A. Zhang, Brian S. Holinsworth, Kenneth R. O'Neal, Tassilo Heeg, Willi Zander, J. Schubert, Janice L. Musfeldt, Zi-Kui Liu, David A. Muller, Peter Schiffer, and Darrell G. Schlom

Appl. Phys. Lett. 101, 132907 (2012); http://dx.doi.org/10.1063/1.4755765 (4 pages) | Cited 2 times

Online Publication Date: 28 September 2012

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We report the growth of single-phase (0001)-oriented epitaxial films of the purported electronically driven multiferroic, LuFe2O4, on (111) MgAl2O4, (111) MgO, and (0001) 6H-SiC substrates. Film stoichiometry was regulated using an adsorption-controlled growth process by depositing LuFe2O4 in an iron-rich environment at pressures and temperatures where excess iron desorbs from the film surface during growth. Scanning transmission electron microscopy reveals reaction-free film-substrate interfaces. The magnetization increases rapidly below 240 K, consistent with the paramagnetic-to-ferrimagnetic phase transition of bulk LuFe2O4. In addition to the ∼0.35 eV indirect band gap, optical spectroscopy reveals a 3.4 eV direct band gap at the gamma point.
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75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.85.+t Magnetoelectric effects, multiferroics
68.43.Mn Adsorption kinetics
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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Nanoantenna-like properties of sea-urchin shaped ZnO as a nanolight filter

Yen Husn Su and Wei-Yu Chen

Appl. Phys. Lett. 101, 133101 (2012); http://dx.doi.org/10.1063/1.4752467 (5 pages) | Cited 1 time

Online Publication Date: 24 September 2012

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A light scattering peak of ZnO rods is presented at 543.2 nm. The radiation peaks of ZnO nanospines correspond to 496.6 nm and 630.6 nm due to the breaking of the symmetry of the ZnO rods. The radiation peaks of sea-urchin shaped ZnO was observed and confirmed by utilizing the dipole approximation. Sea-urchin shaped ZnO can tune and then filter different frequencies of light by utilizing incident light to illuminate at the different positions of sea-urchin shaped ZnO which works like a nanolight filter device and has potential applications in photonic computers, bio-light emission device, and solar cells.
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78.66.Hf II-VI semiconductors
42.79.Ci Filters, zone plates, and polarizers
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Electrical and optical properties of vanadium dioxide containing gold nanoparticles deposited by pulsed laser deposition

J.-C. Orlianges, J. Leroy, A. Crunteanu, R. Mayet, P. Carles, and C. Champeaux

Appl. Phys. Lett. 101, 133102 (2012); http://dx.doi.org/10.1063/1.4754708 (4 pages) | Cited 1 time

Online Publication Date: 24 September 2012

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Nanostructured vanadium dioxide is one of the most interesting and studied member of the vanadates family performing a reversible transition from an insulating state to a metallic state associated with a structural transition when heated above a temperature of 68 °C. On the other hand, noble metal nanoparticles (NPs) support localized surface plasmon resonance which causes selective absorption bands in the visible and near-IR regions. The purpose of this letter is to study structural, optical, and electrical properties of vanadium dioxide thin films containing gold nanoparticles synthetized using pulsed laser deposition process. Thus, we have performed x-ray diffraction, optical transmission, and four point probe electrical measurements to investigate the nanocomposite properties versus its temperature. Interestingly, we have observed switching behavior for VO2 film containing gold NPs with a resistivity contrast of four orders of magnitude and a decrease of its transition temperature.
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73.61.Ng Insulators
78.66.Nk Insulators
81.15.Fg Pulsed laser ablation deposition
81.16.-c Methods of micro- and nanofabrication and processing
64.70.K- Solid-solid transitions
68.55.A- Nucleation and growth

Implications of nanostructuring on the thermoelectric properties in half-Heusler alloys

A. Bhardwaj, D. K. Misra, J. J. Pulikkotil, S. Auluck, A. Dhar, and R. C. Budhani

Appl. Phys. Lett. 101, 133103 (2012); http://dx.doi.org/10.1063/1.4754570 (5 pages) | Cited 1 time

Online Publication Date: 25 September 2012

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High energy ball milled Zr0.25Hf0.75NiSn alloys subjected to spark plasma sintering show an enhanced thermoelectric figure of merit in comparison with its normal bulk material synthesized by arc-melting process. The enhancement is due to increase in Seebeck coefficient with simultaneous decrease in thermal conductivity which follows due to increase in the cell volume. Theoretical calculations find that volume expansion facilitates band narrowing effects leading to high Seebeck coefficient and that decreasing orbital overlap which results in weak bonding leads to dampening the phonon propagation in addition to the interface scattering of phonons from phase boundaries.
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72.15.Jf Thermoelectric and thermomagnetic effects
81.16.-c Methods of micro- and nanofabrication and processing
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.20.Wk Machining, milling
61.46.-w Structure of nanoscale materials
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys

Feedback cooling of cantilever motion using a quantum point contact transducer

M. Montinaro, A. Mehlin, H. S. Solanki, P. Peddibhotla, S. Mack, D. D. Awschalom, and M. Poggio

Appl. Phys. Lett. 101, 133104 (2012); http://dx.doi.org/10.1063/1.4754606 (5 pages)

Online Publication Date: 25 September 2012

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We use a quantum point contact (QPC) as a displacement transducer to measure and control the low-temperature thermal motion of a nearby micromechanical cantilever. The QPC is included in an active feedback loop designed to cool the cantilever's fundamental mechanical mode, achieving a squashing of the QPC noise at high gain. The minimum achieved effective mode temperature of 0.2 K and the displacement resolution of 10−11 m/math are limited by the performance of the QPC as a one-dimensional conductor and by the cantilever-QPC capacitive coupling.
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07.07.Mp Transducers
07.10.Cm Micromechanical devices and systems
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Detecting single molecules inside a carbon nanotube to control molecular sequences using inertia trapping phenomenon

Z. L. Hu, Gustaf Mårtensson, Murali Murugesan, Yifeng Fu, Xingming Guo, and Johan Liu

Appl. Phys. Lett. 101, 133105 (2012); http://dx.doi.org/10.1063/1.4754617 (4 pages)

Online Publication Date: 25 September 2012

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Here we show the detection of single gas molecules inside a carbon nanotube based on the change in resonance frequency and amplitude associated with the inertia trapping phenomenon. As its direct implication, a method for controlling the sequence of small molecule is then proposed to realize the concept of manoeuvring of matter atom by atom in one dimension. The detection as well as the implication is demonstrated numerically with the molecular dynamics method. It is theoretically assessed that it is possible for a physical model to be fabricated in the very near future.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Protocols for characterising quantum transport through nano-structures

Sudeshna Sen and N. S. Vidhyadhiraja

Appl. Phys. Lett. 101, 133106 (2012); http://dx.doi.org/10.1063/1.4754620 (5 pages) | Cited 2 times

Online Publication Date: 25 September 2012

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In this work, we have analysed the exact closed-form solutions for transport quantities through a mesoscopic region which may be characterised by a polynomial functional of resonant transmission functions. These are then utilized to develop considerably improved protocols for parameters relevant for quantum transport through molecular junctions and quantum dots. The protocols are shown to be experimentally feasible and should yield the parameters at much higher resolution than the previously proposed ones.
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73.23.-b Electronic transport in mesoscopic systems

Direct visualization method of the atomic structure of light and heavy atoms with double-detector Cs-corrected scanning transmission electron microscopy

Yasutoshi Kotaka

Appl. Phys. Lett. 101, 133107 (2012); http://dx.doi.org/10.1063/1.4756783 (5 pages) | Cited 1 time

Online Publication Date: 27 September 2012

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The advent of Cs-corrected scanning transmission electron microscopy (STEM) has advanced the observation of atomic structures in materials and nanotechnology devices. High-angle annular dark-field (HAADF)-STEM using an annular detector visualizes heavy elements as bright spots at atomic resolution that can be observed with the Z-contrast technique. In this study, the atomic column of light elements is directly observed as bright spots by middle-angle bright-field (MABF)-STEM imaging. Therefore, a double-detector STEM imaging method was developed, exploiting the advantage of both MABF-STEM and HAADF-STEM to maximum, which consists of multiple exposures of simultaneously observed MABF- and HAADF-STEM images in red-green-blue color.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Information processing with a single multifunctional nanofluidic diode

Patricio Ramirez, Mubarak Ali, Wolfgang Ensinger, and Salvador Mafe

Appl. Phys. Lett. 101, 133108 (2012); http://dx.doi.org/10.1063/1.4754845 (4 pages) | Cited 2 times

Online Publication Date: 27 September 2012

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We show that a multifunctional nanofluidic diode, based on a single pH-sensitive polymeric pore, can be used for different information processing tasks. This fact should permit a significant simplification of the logic circuitry in physico-chemical processors. The inputs are the pH values in the external solutions and the applied potential difference (voltage). The output is the electrical pore conductance. As a proof of concept, different logic and arithmetic computational functions are demonstrated.
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84.30.Sk Pulse and digital circuits
85.35.-p Nanoelectronic devices

Synchrotron x-ray modification of nanoparticle superlattice formation

Chenguang Lu, Austin J. Akey, and Irving P. Herman

Appl. Phys. Lett. 101, 133109 (2012); http://dx.doi.org/10.1063/1.4752239 (3 pages) | Cited 1 time

Online Publication Date: 27 September 2012

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The synchrotron x-ray radiation used to perform small angle x-ray scattering (SAXS) during the formation of three-dimensional nanoparticle superlattices by drop casting nanoparticle solutions affects the structure and the local crystalline order of the resulting films. The domain size decreases due to the real-time SAXS analysis during drying and more macroscopic changes are visible to the eye.
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78.70.Ck X-ray scattering
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
68.65.Cd Superlattices
81.16.-c Methods of micro- and nanofabrication and processing

InGaP-based InGaAs quantum dot solar cells with GaAs spacer layer fabricated using solid-source molecular beam epitaxy

T. Sugaya, A. Takeda, R. Oshima, K. Matsubara, S. Niki, and Y. Okano

Appl. Phys. Lett. 101, 133110 (2012); http://dx.doi.org/10.1063/1.4755757 (4 pages) | Cited 1 time

Online Publication Date: 27 September 2012

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We report InGaP-based multistacked InGaAs quantum dot (QD) solar cells with GaAs spacer layers. We obtain a highly stacked and well-aligned InGaAs QD structure with GaAs spacer layers in an InGaP matrix grown by solid-source molecular beam epitaxy. The photoluminescence intensity of the InGaAs QDs in the InGaP matrix increases as the number of QD layers increases, which indicates the growth of a high-quality InGaP-based multistacked InGaAs QD structure. The short-circuit current density and the conversion efficiency of the InGaP-based QD solar cells increase as the number of InGaAs QD layers increases.
Show PACS
88.40.J- Types of solar cells
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots
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