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29 Oct 2012

Volume 101, Issue 18, Articles (18xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 183101 (2012); http://dx.doi.org/10.1063/1.4761935 (4 pages)

S. J. Kim, J. J. Lee, H. J. Kang, J. B. Choi, Y.-S. Yu, Y. Takahashi, and D. G. Hasko
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An unusual variation of stability and hardness in molybdenum borides

Yongcheng Liang, Xun Yuan, Zhao Fu, Yuan Li, and Zheng Zhong

Appl. Phys. Lett. 101, 181908 (2012); http://dx.doi.org/10.1063/1.4764547 (5 pages)

Online Publication Date: 2 November 2012

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Molybdenum borides are currently raising great expectations for superhard materials, but their crystal structures and mechanical behaviors are still under discussion. Here, we report an unexpected reduction of stability and hardness from porous hP16-MoB3 and hR18-MoB2 to dense hP20-MoB4 and hR21-Mo2B5, respectively. Furthermore, we demonstrate that this anomalous variation has its electronic origin. These findings not only manifest that the long-recognized hP20-MoB4 (hP3-MoB2) and hR21-Mo2B5 should be hP16-MoB3 and hR18-MoB2, respectively, but also challenge the general design principle for ultrahard materials only pursuing the dense transition-metal borides with high boron content.
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61.66.Fn Inorganic compounds
62.20.Qp Friction, tribology, and hardness
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
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Topological phase transition and unexpected mass acquisition of Dirac fermion in TlBi(S1−xSex)2

Chengwang Niu, Ying Dai, Yingtao Zhu, Jibao Lu, Yandong Ma, and Baibiao Huang

Appl. Phys. Lett. 101, 182101 (2012); http://dx.doi.org/10.1063/1.4764946 (5 pages)

Online Publication Date: 29 October 2012

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Based on first-principles calculations and effective Hamiltonian analysis, we predict a topological phase transition from normal to topological insulators and the opening of a gap without breaking the time-reversal symmetry in TlBi(S1−xSex)2. The transition can be driven by modulating the Se concentration, and the rescaled spin-orbit coupling and lattice parameters are the key ingredients for the transition. For topological surface states, the Dirac cone evolves differently as the explicit breaking of inversion symmetry and the energy band can be opened under asymmetry surface. Our results present theoretical evidence for experimental observations [Xu et al., Science 332, 560 (2011); Sato et al., Nat. Phys. 7, 840 (2011)].
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81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.K- Solid-solid transitions
61.66.Fn Inorganic compounds
71.20.Ps Other inorganic compounds
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.20.At Surface states, band structure, electron density of states

A 2 nm low temperature GaN spacer to improve the transport properties of two-dimensional electron gas in AlGaN/InAlN/AlN/GaN heterostructures

Jieqin Ding, Xiaoliang Wang, Hongling Xiao, Cuimei Wang, Hong Chen, Yang Bi, Qinwen Deng, Jingwen Zhang, and Xun Hou

Appl. Phys. Lett. 101, 182102 (2012); http://dx.doi.org/10.1063/1.4765086 (4 pages)

Online Publication Date: 29 October 2012

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AlGaN layers were grown on InAlN/AlN/GaN heterostructure with various temperatures. The two-dimensional electron gas density and mobility in heterostructure with high temperature AlGaN were deteriorated which is attributed to the reverse polarization field of AlGaN and the degradation of InAlN structural quality and surface morphology. A 2 nm low temperature GaN spacer was inserted to reduce the risk of InAlN degradation. The improved structures demonstrated an increase of two-dimensional electron gas density and mobility compared to the heterostructures without the GaN spacer, which results in the reduction of sheet resistance. Particularly, at 855 °C, an enhancement of mobility in the improved structure indicates that the heterostructure is relatively stable at this temperature. At higher temperature of 920 °C, significant increase of sheet resistance indicates a sharp degradation of InAlN quality.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.20.-r Electron states at surfaces and interfaces

Polarization spectroscopy of N-polar AlGaN/GaN multi quantum wells grown on vicinal (000math) GaN

S. Keller, N. Pfaff, S. P. DenBaars, and U. K. Mishra

Appl. Phys. Lett. 101, 182103 (2012); http://dx.doi.org/10.1063/1.4764070 (3 pages)

Online Publication Date: 29 October 2012

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Pronounced polarized light emission was observed from N-polar AlGaN/GaN multi quantum wells grown on (000math) GaN with a misorientation of 4° toward the m-direction grown by metal organic chemical vapor deposition. The misoriented (Al,Ga,In)N layers exhibited a high density of surface steps parallel to the 〈11math0〉 direction with step heights between 1 and 2 nm. The corrugated surfaces led to the formation of self organized quantum wire arrays in samples with 2.5 and 3.5 nm thick wells, revealed by a degree of polarization of 0.19 and 0.14, respectively, for light emission at 10 K.
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78.67.De Quantum wells
81.07.St Quantum wells
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors

Tuning hole mobility in InP nanowires

M. Rebello Sousa Dias, A. Picinin, V. Lopez-Richard, S. E. Ulloa, L. K. Castelano, J. P. Rino, and G. E. Marques

Appl. Phys. Lett. 101, 182104 (2012); http://dx.doi.org/10.1063/1.4764902 (4 pages)

Online Publication Date: 1 November 2012

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Transport properties of holes in InP nanowires (NWs) were calculated considering electron-phonon interaction via deformation potentials, the effect of temperature, and strain fields. Using molecular dynamics, we simulate NW structures, the longitudinal optical phonon (LO-phonon) energy renormalization, and lifetime. The valence band ground state changes between light- and heavy-hole character, as the strain fields and the NW size vary. Drastic changes in the mobility arise with the onset of resonance between the LO-phonons and the separation between valence subbands.
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73.61.Ey III-V semiconductors
63.20.kd Phonon-electron interactions
63.22.Gh Nanotubes and nanowires
71.38.-k Polarons and electron-phonon interactions
72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance

Fermi-level unpinning and low resistivity in contacts to n-type Ge with a thin ZnO interfacial layer

Prashanth Paramahans Manik, Ravi Kesh Mishra, V. Pavan Kishore, Prasenjit Ray, Aneesh Nainani, Yi-Chiau Huang, Mathew C. Abraham, Udayan Ganguly, and Saurabh Lodha

Appl. Phys. Lett. 101, 182105 (2012); http://dx.doi.org/10.1063/1.4764909 (5 pages)

Online Publication Date: 1 November 2012

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We report low resistance Ohmic contacts on n-Ge using a thin ZnO interfacial layer (IL) capped with Ti. A 350°C post metallization anneal is used to create oxygen vacancies that dope ZnO heavily n-type (n+). Rectifying Ti/n-Ge contacts become Ohmic with 1000× higher reverse current density after insertion of n+-ZnO IL. Specific resistivity of ∼ 1.4×10−7 Ω cm2 is demonstrated on epitaxial n+-Ge (2.5×1019 cm−3) layers. Low resistance with ZnO IL can be attributed to (a) low barrier height from Fermi-level unpinning, (b) good conduction band alignment between ZnO and Ge, and (c) thin tunneling barrier due to the n+ doping.
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73.40.Ns Metal-nonmetal contacts
61.72.jd Vacancies
61.72.uf Ge and Si
61.72.Cc Kinetics of defect formation and annealing
73.40.Ei Rectification
73.40.Gk Tunneling

Indicators of mobility extraction error in bottom gate CdS metal-oxide-semiconductor field-effect transistors

Ukjin Jung, Young Gon Lee, Jin Ju Kim, Sang Kyung Lee, I. Mejia, A. Salas-Villasenor, Manuel Quevedo-Lopez, and Byoung Hun Lee

Appl. Phys. Lett. 101, 182106 (2012); http://dx.doi.org/10.1063/1.4765067 (3 pages) | Cited 1 time

Online Publication Date: 1 November 2012

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Widely varying mobility values of CdS metal-oxide-semiconductor field-effect transistors have been reported in the literature (μ = 1–48 cm2/Vs). Sulfide vacancies in CdS channel generated by an incomplete post deposition anneal are found to be the origin of scattered mobility values. The presence of sulfide vacancies can be easily diagnosed by simple electrical measurements checking a strong channel length dependence of mobility and an abrupt drain current increase due to the carrier ionization at sulfur vacancies.
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85.30.Tv Field effect devices
61.72.jd Vacancies
72.80.Ey III-V and II-VI semiconductors
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Positive colossal magnetoresistance observed in Co doped amorphous carbon/silicon heterostructures

Y. C. Jiang and J. Gao

Appl. Phys. Lett. 101, 182401 (2012); http://dx.doi.org/10.1063/1.4765648 (4 pages)

Online Publication Date: 1 November 2012

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Heterostructures of Co-doped amorphous carbon (Co-C)/silicon were fabricated by growing Co-C films on n-type Si substrates using pulsed laser deposition. The heterostructures exhibited a positive colossal magnetoresistance (CMR) effect over a temperature range of 55-240 K. The magnetoresistance (MR) for the reverse bias voltage reached around 270% at 5 T, whereas the MR under a forward bias was 7% only. Besides, the transmission electron microscopy results demonstrate that Co atoms tended to be aggregated at Co-C/Si interface. The Co aggregation in the interface may be a possible origin of the positive CMR effect.
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75.47.Gk Colossal magnetoresistance
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth

Electrical excitation and detection of magnetic dynamics with impedance matching

D. Fang, T. D. Skinner, H. Kurebayashi, R. P. Campion, B. L. Gallagher, and A. J. Ferguson

Appl. Phys. Lett. 101, 182402 (2012); http://dx.doi.org/10.1063/1.4764519 (4 pages)

Online Publication Date: 2 November 2012

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Motivated by the prospects of increased measurement bandwidth, improved signal to noise ratio, and access to the full complex magnetic susceptibility we develop a technique to extract microwave voltages from our high resistance ( ∼ 10kΩ) (Ga,Mn)As microbars. We drive magnetization precession with microwave frequency current, using a mechanism that relies on the spin orbit interaction. A capacitively coupled λ/2 microstrip resonator is employed as an impedance matching network, enabling us to measure the microwave voltage generated during magnetisation precession.
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81.05.Ea III-V semiconductors
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Pp Magnetic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Growth and characterization of n-type electron-induced ferromagnetic semiconductor (In,Fe)As

Pham Nam Hai, Le Duc Anh, Shyam Mohan, Tsuyoshi Tamegai, Masaya Kodzuka, Tadakatsu Ohkubo, Kazuhiro Hono, and Masaaki Tanaka

Appl. Phys. Lett. 101, 182403 (2012); http://dx.doi.org/10.1063/1.4764947 (5 pages) | Cited 1 time

Online Publication Date: 2 November 2012

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We show that by introducing isoelectronic iron (Fe) magnetic impurities and Beryllium (Be) double-donor atoms into InAs, it is possible to grow an n-type ferromagnetic semiconductor (FMS) with the ability to control ferromagnetism by both Fe and independent carrier doping by low-temperature molecular-beam epitaxy. We demonstrate that (In,Fe)As doped with electrons behaves as an n-type electron-induced FMS. This achievement opens the way to realize spin-devices such as spin light-emitting diodes or spin field-effect transistors, as well as helps to understand the mechanism of carrier-mediated ferromagnetism in FMSs.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.60.Jb Light-emitting devices
85.75.Hh Spin polarized field effect transistors
61.72.uj III-V and II-VI semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors

Design of remnant magnetization FeCoV films as compact, heatless neutron spin rotators

M. O. Abutaleb, D. A. Pushin, M. G. Huber, C. F. Majkrzak, M. Arif, and D. G. Cory

Appl. Phys. Lett. 101, 182404 (2012); http://dx.doi.org/10.1063/1.4765069 (4 pages)

Online Publication Date: 2 November 2012

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We introduce a design of a neutron spin rotator for applications with space and temperature constraints. These passive devices employ remnant magnetization FeCoV thin films and can be tuned experimentally to achieve arbitrary rotation of an incident neutron with a known spin state. Polarized neutron reflectometry measurements are reported for FeCoV monolayer films at thicknesses of 0.5 μm and 5.3 μm to characterize the depth-dependent vector magnetization in the films. Results for a prototype set of film rotators are presented, and the stray field near such films is characterized.
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75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Distribution of switching fields in magnetic granular materials

O. Hovorka, J. Pressesky, G. Ju, A. Berger, and R. W. Chantrell

Appl. Phys. Lett. 101, 182405 (2012); http://dx.doi.org/10.1063/1.4765085 (5 pages)

Online Publication Date: 2 November 2012

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We present analytical calculations and kinetic Monte-Carlo modeling of rate-dependent behavior of switching field distributions (SFDs) in an ensemble of Stoner-Wohfarth particles, assuming distributions of anisotropies and volumes, and thermal activation included by the Néel-Brown theory. By applying probabilistic arguments, we show that the SFD can be self-consistently separated into the contribution from distributions of intrinsic properties of particles and the (irreducible) contribution resulting solely from thermal fluctuations, which is shown to become a significant effect at sweep rates relevant to the recording process. This provides a unifying framework for systematic analysis of different classes of systems.
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75.40.Mg Numerical simulation studies
75.50.Ss Magnetic recording materials
75.50.Tt Fine-particle systems; nanocrystalline materials
75.78.Jp Ultrafast magnetization dynamics and switching
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Gw Magnetic anisotropy

Tunable bandgap and ferromagnetism in sputtered epitaxial Sn1−xMgxO2 thin films

Baozeng Zhou, Ping Wu, and Wei Zhou

Appl. Phys. Lett. 101, 182406 (2012); http://dx.doi.org/10.1063/1.4765346 (5 pages)

Online Publication Date: 2 November 2012

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Room-temperature magnetic behavior and tunable bandgap of epitaxial Sn1−xMgxO2 films were investigated. The Mg dopants can enhance the ferromagnetism and the largest saturation magnetization of 7.0 emu/cm3 has been observed in Sn0.94Mg0.06O2 film which has the narrowest bandgap. The ferromagnetism decreases with further doping but increases in Sn0.84Mg0.16O2 film after air annealing at 700 °C. The ferromagnetism is likely due to the double exchange mechanism through the p-p interaction. Mg interstitials can irreversibly transform to Mg substitutions by thermal treatment. The generated oxide alloys will decrease the optical bandgap and ferromagnetism of the samples.
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71.20.Nr Semiconductor compounds
75.30.Et Exchange and superexchange interactions
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films

Sub-micron mapping of GHz magnetic susceptibility using scanning transmission x-ray microscopy

Cheng Cheng and William E. Bailey

Appl. Phys. Lett. 101, 182407 (2012); http://dx.doi.org/10.1063/1.4765663 (4 pages)

Online Publication Date: 2 November 2012

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We report submicron imaging ( ∼ 0.75 μm resolution) of complex magnetic susceptibility in a micron-size ferromagnetic heterostructure using time-resolved scanning transmission x-ray microscopy. The real and imaginary parts of the susceptibility are extracted from the phase and amplitude of the small-angle (<20°) rotational response of the local magnetization under microwave excitation. Frequency-dependent response patterns were observed in an incompletely saturated bilayer element. The technique is extensible to higher frequencies (to ∼ 10 GHz), better spatial resolution, and layer-specific measurement.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
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Multiplexed dispersive readout of superconducting phase qubits

Yu Chen, D. Sank, P. O'Malley, T. White, R. Barends, B. Chiaro, J. Kelly, E. Lucero, M. Mariantoni, A. Megrant, C. Neill, A. Vainsencher, J. Wenner, Y. Yin, A. N. Cleland, et al.

Appl. Phys. Lett. 101, 182601 (2012); http://dx.doi.org/10.1063/1.4764940 (4 pages)

Online Publication Date: 1 November 2012

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We introduce a frequency-multiplexed readout scheme for superconducting phase qubits. Using a quantum circuit with four phase qubits, we couple each qubit to a separate lumped-element superconducting readout resonator, with the readout resonators connected in parallel to a single measurement line. The readout resonators and control electronics are designed so that all four qubits can be read out simultaneously using frequency multiplexing on the one measurement line. This technology provides a highly efficient and compact means for reading out multiple qubits, a significant advantage for scaling up to larger numbers of qubits.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)

Absence of boron aggregates in superconducting silicon confirmed by atom probe tomography

K. Hoummada, F. Dahlem, T. Kociniewski, J. Boulmer, C. Dubois, G. Prudon, E. Bustarret, H. Courtois, D. Débarre, and D. Mangelinck

Appl. Phys. Lett. 101, 182602 (2012); http://dx.doi.org/10.1063/1.4760261 (4 pages)

Online Publication Date: 1 November 2012

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Superconducting boron-doped silicon films prepared by gas immersion laser doping (GILD) technique are analyzed by atom probe tomography. The resulting three-dimensional chemical composition reveals that boron atoms are incorporated into crystalline silicon in the atomic percent concentration range, well above their solubility limit, without creating clusters or precipitates at the atomic scale. The boron spatial distribution is found to be compatible with local density of states measurements performed by scanning tunneling spectroscopy. These results combined with the observations of very low impurity level and of a sharp two-dimensional interface between doped and undoped regions show that the Si:B material obtained by GILD is a well-defined random substitutional alloy endowed with promising superconducting properties.
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74.78.-w Superconducting films and low-dimensional structures
42.62.-b Laser applications
64.75.Bc Solubility
61.72.uf Ge and Si
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Evaluation and modeling of lanthanum diffusion in TiN/La2O3/HfSiON/SiO2/Si high-k stacks

Z. Essa, C. Gaumer, A. Pakfar, M. Gros-Jean, M. Juhel, F. Panciera, P. Boulenc, C. Tavernier, and F. Cristiano

Appl. Phys. Lett. 101, 182901 (2012); http://dx.doi.org/10.1063/1.4764558 (5 pages) | Cited 1 time

Online Publication Date: 29 October 2012

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In this study, TiN/La2O3/HfSiON/SiO2/Si gate stacks with thick high-k (HK) and thick pedestal oxide were used. Samples were annealed at different temperatures and times in order to characterize in detail the interaction mechanisms between La and the gate stack layers. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurements performed on these samples show a time diffusion saturation of La in the high-k insulator, indicating an La front immobilization due to LaSiO formation at the high-k/interfacial layer. Based on the SIMS data, a technology computer aided design (TCAD) diffusion model including La time diffusion saturation effect was developed.
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66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Rt Time of flight mass spectrometry
77.55.df For silicon electronics
61.72.Cc Kinetics of defect formation and annealing

Ultra-sensitive magnetoelectric microcantilever at a low frequency

Dong Gun Lee, Sung Man Kim, Yong Kyung Yoo, Jun Hyun Han, Dong Won Chun, Yu-Chan Kim, Jinseok Kim, Kyo Seon Hwang, Tae Song Kim, Won Woo Jo, Hyungsuk Kim, Seung-Ho Song, and Jeong Hoon Lee

Appl. Phys. Lett. 101, 182902 (2012); http://dx.doi.org/10.1063/1.4764944 (4 pages)

Online Publication Date: 1 November 2012

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Here, we propose the device platform of energy domain transfer using a magnetoelectric microcantilever. By incorporating Tb0.3Dy0.7Fe1.9 (Terfenol-D) magnetostrictive materials onto a Pb(Zr0.52Ti0.48)O3 (PZT) piezoelectric microcantilever, we demonstrated energy conversion from the magnetic to the electric domain. By measuring the charge signal from a PZT layer under variable dc magnetic field at constant 60 Hz AC magnetic field, we acquired the magnetoelectric coefficient of 24.4 V/cm·Oe. The proposed magnetoelectric microcantilever enables the generation of a minimum detectable DC magnetic field up to 1 × 10−12 T at off-resonance.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Fully developed contact angle change of a droplet in liquid actuated by dielectric force

Chih-Cheng Yang, Lin Yang, C. Gary Tsai, Patrick Hongchang Jou, and J. Andrew Yeh

Appl. Phys. Lett. 101, 182903 (2012); http://dx.doi.org/10.1063/1.4759112 (4 pages) | Cited 1 time

Online Publication Date: 2 November 2012

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The non-saturation phenomenon of contact angle change of a nonconductive droplet in an immiscible dielectric liquid with iso-density is demonstrated using the dielectric force due to the difference of the two dielectric constants. The concentric electrode design permits the dielectric force exerted at various contact angles. The droplet fully develops from 22° to 176° (nearly spherical) in contact angle as the voltages tuned from 0 to 215 Vrms. The contact angle change was found to behave almost linearly with respect to voltage by experiments. The dielectric force in the liquid/liquid interface was further simulated at the aspects of energy distribution, force distribution, and electric fields, found in a good agreement with experimental results.
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68.03.Cd Surface tension and related phenomena
77.22.Ch Permittivity (dielectric function)
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One electron-based smallest flexible logic cell

S. J. Kim, J. J. Lee, H. J. Kang, J. B. Choi, Y.-S. Yu, Y. Takahashi, and D. G. Hasko

Appl. Phys. Lett. 101, 183101 (2012); http://dx.doi.org/10.1063/1.4761935 (4 pages)

Online Publication Date: 29 October 2012

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A one electron-based operating half-adder, the smallest arithmetic block, has been implemented on silicon-on-insulator structure whose basic element is a nanoscale single-electron transistor (SET) with two symmetrical side-wall gates. Grayscale contour plots of the resulting cell output voltages exhibit the Coulomb blockade-induced periodic alternating high/low features. Their voltage transfer characteristics display typical Sum and Carry-Out functions for binary, multi-valued (MV), and binary-MV mixed input voltages. Moreover, the half-adder function converts into a subtraction mode by adjusting control gates of the SET element. This flexible multi-valued cell provides an arithmetic block for the SET MV logic family of high density integration, operating with ultra-low power.
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84.30.Sk Pulse and digital circuits
85.35.Gv Single electron devices

Primary energy dependence of secondary electron emission from graphene adsorbed on Ni(111)

P. Riccardi, A. Cupolillo, M. Pisarra, A. Sindona, and L. S. Caputi

Appl. Phys. Lett. 101, 183102 (2012); http://dx.doi.org/10.1063/1.4765053 (4 pages) | Cited 3 times

Online Publication Date: 29 October 2012

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We measured energy distribution and yields of electrons emitted from graphene adsorbed on a Ni(111) surface under the impact of 200–1200 eV electrons. The adsorption of graphene results in significant changes of the spectra of emitted electrons but not of the total emission yields. The electronic structure of the graphitic overlayer determines the final states of excited electrons transported by collision cascade from the bulk of the substrate.
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79.20.Hx Electron impact: secondary emission
73.22.Pr Electronic structure of graphene
68.43.Mn Adsorption kinetics

Electrostatics and electrical transport in semiconductor nanowire Schottky diodes

Cheng-Han Hsu, Qiaoming Wang, Xin Tao, and Yi Gu

Appl. Phys. Lett. 101, 183103 (2012); http://dx.doi.org/10.1063/1.4765653 (5 pages) | Cited 2 times

Online Publication Date: 29 October 2012

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The electrostatics and electrical transport characteristics in semiconductor nanowire Schottky diodes are studied using three-dimensional finite-element simulations. From the simulations, the dependences of the depletion region width on the bias and the doping level are found to deviate significantly from the relations in the bulk Schottky model, indicating different electrostatic properties in nanowire Schottky junctions. Furthermore, simulations of the current-voltage relation, which is corroborated by experimental measurements, demonstrate that the standard analytical model is not sufficient to describe current-voltage characteristics in nanowire Schottky diodes. An important implication is that the commonly used analytical model is not valid for extracting the ideality factor and the Schottky barrier height. These findings suggest that numerical simulations are critical to evaluating nanoscale device performance and guiding device development efforts.
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85.30.Kk Junction diodes
02.70.Dh Finite-element and Galerkin methods

Spectral patterns underlying polarization-enhanced diffractive interference are distinguishable by complex trigonometry

Drew DeJarnette, Justin Norman, and D. Keith Roper

Appl. Phys. Lett. 101, 183104 (2012); http://dx.doi.org/10.1063/1.4764943 (5 pages)

Online Publication Date: 1 November 2012

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Superpositioned modes from scatterers in periodic arrays that prescribe spectral interference patterns are distinguishable using an analytic description. Interference arising from irradiation of ordered lattices with polarizable components yields far-field spectral patterns in which extraordinary features appear at resonant frequencies associated with lattice geometry. Organization of nanostructures utilizing these features has been limited by complexity of electrodynamic descriptions for coupling between these plasmon resonance energies and diffracted spectral modes. The trigonometric description shows how changing lattice constant and incident wavelength to adjust coupling between phase-dependent constructive interference and isometric values of plasmonic gold nanostructure polarizability results in extraordinary spectral features.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
02.70.Bf Finite-difference methods

Large room-temperature quantum linear magnetoresistance in multilayered epitaxial graphene: Evidence for two-dimensional magnetotransport

Ram Sevak Singh, Xiao Wang, Wei Chen, Ariando, and Andrew T. S. Wee

Appl. Phys. Lett. 101, 183105 (2012); http://dx.doi.org/10.1063/1.4765656 (5 pages)

Online Publication Date: 1 November 2012

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We report magnetoresistance (MR) properties from room temperature (300 K) to 2 K in multilayered epitaxial graphene (EG) prepared on C-face of SiC substrate. A large (∼50%) and linear MR is observed at 300 K, which is distinctively different from other carbon materials. This linear MR is attributed to the two-dimensional (2D) transport in the material as inferred from our angular dependence magnetotransport experiments. Furthermore, negative MR behaviour at a low field regime for temperatures ≤20 K is recognised as a weak localization in EG. This study underlines the potential of exploiting multilayered EG on C-face SiC for room temperature magneto-electronic device applications.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Vp Electronic transport in graphene

A suspended nanogap formed by field-induced atomically sharp tips

Jun Hyun Han, Kyung Song, Shankar Radhakrishnan, Sang Ho Oh, and Chung Hoon Lee

Appl. Phys. Lett. 101, 183106 (2012); http://dx.doi.org/10.1063/1.4764562 (3 pages)

Online Publication Date: 2 November 2012

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Show Abstract
A sub-nanometer scale suspended gap (nanogap) defined by electric field-induced atomically sharp metallic tips is presented. A strong local electric field (>109 V/m) across micro/nanomachined tips facing each other causes the metal ion migration in the form of dendrite-like growth at the cathode. The nanogap is fully isolated from the substrate eliminating growth mechanisms that involve substrate interactions. The proposed mechanism of ion transportation is verified using real-time imaging of the metal ion transportation using an in situ biasing in transmission electron microscope (TEM). The configuration of the micro/nanomachined suspended tips allows nanostructure growth of a wide variety of materials including metals, metal-oxides, and polymers.
Show PACS
71.20.Be Transition metals and alloys
73.63.Bd Nanocrystalline materials
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
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