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2 Jan 2012

Volume 100, Issue 1, Articles (01xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 100, 013101 (2012); http://dx.doi.org/10.1063/1.3673334 (3 pages)

Patrice Genevet, Nanfang Yu, Francesco Aieta, Jiao Lin, Mikhail A. Kats, Romain Blanchard, Marlan O. Scully, Zeno Gaburro, and Federico Capasso
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Efficiency enhancement of InGaN multi-quantum-well solar cells via light-harvesting SiO2 nano-honeycombs

P. H. Fu, G. J. Lin, C. H. Ho, C. A. Lin, C. F. Kang, Y. L. Lai, K. Y. Lai, and J. H. He

Appl. Phys. Lett. 100, 013105 (2012); http://dx.doi.org/10.1063/1.3673838 (4 pages) | Cited 3 times

Online Publication Date: 4 January 2012

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Periodic sub-wavelength SiO2 nano-honeycombs are fabricated on GaN-based multiple quantum well solar cells by self-assembly polystyrene nanosphere lithography and reactive ion etching. The nano-honeycombs are found to be effective in suppressing the undesired surface reflections over a wide range of wavelengths. Under the illumination of air mass 1.5G solar simulator, conversion efficiency of the solar cell is enhanced by 24.4%. Simulations based on finite-difference time-domain method indicate that the improved performances result from the enhanced optical absorption in the active region due to the reflection suppression and enhanced forward scattering.
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88.40.jm Thin film III-V and II-VI based solar cells
88.40.hj Efficiency and performance of solar cells

Thermal effects on the characteristic Raman spectrum of molybdenum disulfide (MoS2) of varying thicknesses

S. Najmaei, Z. Liu, P. M. Ajayan, and J. Lou

Appl. Phys. Lett. 100, 013106 (2012); http://dx.doi.org/10.1063/1.3673907 (4 pages) | Cited 14 times

Online Publication Date: 4 January 2012

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In this letter, thermal effects on the Raman spectra of molybdenum disulfide with thicknesses ranging from bulk to monolayer were evaluated. We quantitatively determined the laser-induced heating effects on the peak position and the line-width of the Raman spectrum. We found considerable thickness-dependent red-shifts as well as line-width changes for both E2g1 and A1g vibrating modes as laser power was increased. Our results enrich the knowledge of phononic behaviors of this material and demonstrate the important effects of the anharmonic terms in the lattice potential energy.
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78.30.Hv Other nonmetallic inorganics
81.40.Gh Other heat and thermomechanical treatments
63.20.Ry Anharmonic lattice modes
61.50.Lt Crystal binding; cohesive energy
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
61.82.Ms Insulators
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Independent tuning of electron and hole confinement in InAs/GaAs quantum dots through a thin GaAsSbN capping layer

J. M. Ulloa, D. F. Reyes, M. Montes, K. Yamamoto, D. L. Sales, D. González, A. Guzman, and A. Hierro

Appl. Phys. Lett. 100, 013107 (2012); http://dx.doi.org/10.1063/1.3673563 (4 pages) | Cited 4 times

Online Publication Date: 5 January 2012

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The possibility of an independent tuning of the electron and hole confinement in InAs/GaAs quantum dots (QDs) by using a thin GaAsSbN capping layer (CL) is studied. By controlling the Sb and N contents in the quaternary alloy, the band structure of the QDs can be broadly tuned and converted from type-II in the valence band (high Sb contents) to type-I and to type-II in the conduction band (high N contents). Nevertheless, the simultaneous presence of Sb and N is found to induce strain and composition inhomogeneities in the CL and to degrade the photoluminescence of the structure.
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73.21.La Quantum dots
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots

Nano-opto-mechanical actuator driven by gradient optical force

H. Cai, K. J. Xu, A. Q. Liu, Q. Fang, M. B. Yu, G. Q. Lo, and D. L. Kwong

Appl. Phys. Lett. 100, 013108 (2012); http://dx.doi.org/10.1063/1.3673854 (3 pages) | Cited 6 times

Online Publication Date: 5 January 2012

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In this letter, a nanoscale opto-mechanical actuator driven by gradient optical force is designed and demonstrated. The nanoscale actuator can achieve a maximum displacement of 67 nm with a response time of 94.5 ns. The optical force is estimated as 1.01 pN/μm/mW in C-band operating wavelengths. The device is fabricated on silicon-on-insulator wafer using standard dry etching processes. Compared with traditional microelectromechanical systems actuators driven by electrostatic force, the nanoscale opto-mechanical actuator has the advantages of high resolution of actuation, nanoscale displacement, and fast operating speed. It has potential applications in optical signal processing, chemical, and biological sensing.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
85.60.Bt Optoelectronic device characterization, design, and modeling

X-ray luminescence of CdTe quantum dots in LaF3:Ce/CdTe nanocomposites

Marius Hossu, Zhongxin Liu, Mingzhen Yao, Lun Ma, and Wei Chen

Appl. Phys. Lett. 100, 013109 (2012); http://dx.doi.org/10.1063/1.3674313 (3 pages) | Cited 2 times

Online Publication Date: 5 January 2012

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CdTe quantum dots have intense photoluminescence but exhibit almost no x-ray luminescence. However, intense x-ray luminescence from CdTe quantum dots is observed in LaF3:Ce/CdTe nanocomposites. This enhancement in the x-ray luminescence of CdTe quantum dots is attributed to the energy transfer from LaF3:Ce to CdTe quantum dots in the nanocomposites. The combination of LaF3:Ce nanoparticles and CdTe quantum dots makes LaF3:Ce/CdTe nanocomposites promising scintillators for radiation detection.
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78.55.Et II-VI semiconductors
73.21.La Quantum dots
78.67.Hc Quantum dots
78.67.Sc Nanoaggregates; nanocomposites
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Atomic scale investigation of the abnormal transport properties in bilayer graphene nanoribbon

Yong-Jun Li, Ming-Da Li, Jian-Shuang Liu, Qing-Qing Sun, Peng Zhou, Peng-Fei Wang, Shi-Jin Ding, and David Wei Zhang

Appl. Phys. Lett. 100, 013110 (2012); http://dx.doi.org/10.1063/1.3673324 (3 pages)

Online Publication Date: 5 January 2012

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We investigate the transport properties of bilayer AA-stacking zigzag graphene nanoribbons (bi-zGNRs) and observe abnormal I-V characteristics which are sensitive to the number of carbon chains across the ribbons. Combining the chirality selective rule of Dirac electrons in graphene and the symmetry of eigenstates, we attribute the abnormal current behavior to the chirality mismatch of energy states. The mismatch causes the suppression of transmission pathways between two electrodes which lead to saturated current with increasing bias for certain ribbons.
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72.80.Vp Electronic transport in graphene
73.61.Wp Fullerenes and related materials
61.48.Gh Structure of graphene
72.20.Fr Low-field transport and mobility; piezoresistance

Manipulating the size distribution of supported gold nanostructures

A. Sundar, R. A. Hughes, P. Farzinpour, K. D. Gilroy, G. A. Devenyi, J. S. Preston, and S. Neretina

Appl. Phys. Lett. 100, 013111 (2012); http://dx.doi.org/10.1063/1.3675569 (4 pages) | Cited 4 times

Online Publication Date: 6 January 2012

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Gold nanostructures, with a wide size distribution, are confined between a metal foil and the oxide substrate upon which they were formed. When heated the surface energy gradient between the oxide and foil results in a net migration of gold atoms from the nanostructure to the foil. With time, the nanostructures show a size reduction and a narrowed size distribution. The narrowing results from the formation of foil contact points with only the largest nanostructures, a characteristic which leaves small nanostructures intact while consuming larger ones. Also demonstrated is the size reduction of arrayed gold structures to nanoscale dimensions.
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61.46.-w Structure of nanoscale materials
81.40.Gh Other heat and thermomechanical treatments
65.40.gp Surface energy

Optical feedback mechanisms in laser induced growth of carbon nanotube forests

M. C. D. Bock, R. Denk, C. T. Wirth, P. Goldberg-Oppenheimer, S. Hofmann, and J. J. Baumberg

Appl. Phys. Lett. 100, 013112 (2012); http://dx.doi.org/10.1063/1.3670328 (3 pages)

Online Publication Date: 6 January 2012

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We study optical feedback mechanisms occurring during growth of multi-walled carbon nanotube forests on transparent substrates. Growth is realised via laser-induced chemical vapour deposition using iron nanoparticle catalysts. In situ Raman and reflection spectroscopy employed clearly distinguish three growth phases. In the initial seed phase, growth of carbon nanostructures increases the laser absorption and this feedback enables growth of radially orientated carbon nanotubes. Understanding the laser interaction with the growing nanostructure holds the key towards controlled growth and opens up new routes to nanostructure and nanodevice design and fabrication.
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81.16.Mk Laser-assisted deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.07.De Nanotubes
78.67.Ch Nanotubes
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
42.62.-b Laser applications

Quantum transport of Au-S-S-Au nanoscale junctions

Jing-Xin Yu, Xiang-Rong Chen, Stefano Sanvito, and Yan Cheng

Appl. Phys. Lett. 100, 013113 (2012); http://dx.doi.org/10.1063/1.3665614 (4 pages) | Cited 2 times

Online Publication Date: 6 January 2012

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Transport in S2 molecules sandwiched between Au electrodes is investigated with a combination of density functional theory and the non-equilibrium Green’s function method. We consider four different configurations and find that their conductances are related to the details of the bonding geometry. When S2 connects to pyramidal-shaped electrodes at the top site, the transmission is governed by a resonance and is strongly affected by the bias. In contrast, the transport of the remaining three configurations is through several closely spaced broad molecular orbitals, and the transmission coefficient is almost flat around the Fermi level.
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85.65.+h Molecular electronic devices
85.35.-p Nanoelectronic devices

Electrical transport in suspended and double gated trilayer graphene

Tymofiy Khodkov, Freddie Withers, David Christopher Hudson, Monica Felicia Craciun, and Saverio Russo

Appl. Phys. Lett. 100, 013114 (2012); http://dx.doi.org/10.1063/1.3675337 (3 pages) | Cited 9 times

Online Publication Date: 6 January 2012

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We present a fabrication process for high quality suspended and double gated trilayer graphene devices. The electrical transport measurements in these transistors reveal a high charge carrier mobility (higher than 20 000 cm2/Vs) and ballistic electric transport on a scale larger than 200 nm. We report a particularly large on/off ratio of the current in ABC-stacked trilayers, up to 250 for an average electric displacement of −0.08 V/nm, compatible with an electric field induced energy gap. The high quality of these devices is also demonstrated by the appearance of quantum Hall plateaus at magnetic fields as low as 500 mT.
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85.65.+h Molecular electronic devices
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Changing inter-molecular spin-orbital coupling for generating magnetic field effects in phosphorescent organic semiconductors

Liang Yan, Ming Shao, Carlos F. O. Graeff, Ivo Hummelgen, Dongge Ma, and Bin Hu

Appl. Phys. Lett. 100, 013301 (2012); http://dx.doi.org/10.1063/1.3673561 (3 pages) | Cited 1 time

Online Publication Date: 3 January 2012

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Phosphorescent organic semiconductors normally show negligible magnetic field effects in electronic and optic responses. These phenomena have been generally attributed to strong spin-orbital coupling which can dominate internal spin-dephasing process as compared with applied magnetic field. This paper reports both positive and negative magnetocurrents from phosphorescent organic semiconductors through dissociation and charge-reaction channels when the intermolecular spin-orbital coupling is changed based on materials mixing. Our experimental results indicate that inter-molecular spin-orbital coupling is essentially responsible for the generation of magnetic field effects in phosphorescent organic semiconductors.
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71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
78.55.Kz Solid organic materials
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Nanostructured barbed wire architecturing of organic conducting material blends by electrospinning

Sumeet R. Mishra, K. Ranjith, S. K. Swathi, and Praveen C. Ramamurthy

Appl. Phys. Lett. 100, 013302 (2012); http://dx.doi.org/10.1063/1.3673620 (4 pages) | Cited 1 time

Online Publication Date: 3 January 2012

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In this study, fibers of barbed wire structure were obtained by electrospinning blend of organic conducting crystalline material and polyethylene oxide. Thermal and structural characterization of the blend fibers has been carried out to study the fiber characteristics. An increase in crystallinity in the electrospun fibers was observed and was attributed to both electrospinning process as well as addition of organic conducting crystalline material. A mechanism for the formation of this barbed wire structure has also been proposed.
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81.16.-c Methods of micro- and nanofabrication and processing
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
81.07.Gf Nanowires
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Reduction of charge injection barrier by 1-nm contact oxide interlayer in organic field effect transistors

Peter Darmawan, Takeo Minari, Akichika Kumatani, Yun Li, Chuan Liu, and Kazuhito Tsukagoshi

Appl. Phys. Lett. 100, 013303 (2012); http://dx.doi.org/10.1063/1.3673842 (3 pages) | Cited 5 times

Online Publication Date: 3 January 2012

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The enhancement of the charge injection process by the insertion of an ultrathin (∼1 nm) contact oxide interlayer (COI) at the metal/organic material interface in organic field effect transistors (OFETs) is reported. Six different oxides were used as COI, and Al2O3 was found to exhibit the highest OFET mobility with a reduction in the average contact resistance (Rc) from 19.9 to 1.9 kΩ·cm. Photoelectron yield spectroscopy analysis revealed that the insertion of COI increases the work function of an Au contact and reduces the charge injection barrier at the interface, which lowers Rc and, therefore, results in enhanced device performance.
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85.30.Tv Field effect devices
FREE

Self-assembly of C60 monolayer on epitaxially grown, nanostructured graphene on Ru(0001) surface

G. Li, H. T. Zhou, L. D. Pan, Y. Zhang, J. H. Mao, Q. Zou, H. M. Guo, Y. L. Wang, S. X. Du, and H.-J. Gao

Appl. Phys. Lett. 100, 013304 (2012); http://dx.doi.org/10.1063/1.3673830 (4 pages) | Cited 4 times

Online Publication Date: 4 January 2012

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C60 molecules adsorbed on graphene/Ru(0001) substrate were investigated by scanning tunneling microscopy (STM) at 5 K. On high quality substrates, C60 molecules adopt a commensurate growth mode, leading to formation of a supramolecular structure with perfect periodicity and few defects. On under-annealed substrates with imperfections and domains, the molecules form the same closely packed hexagonal structures in spite of underlying corrugations, disorders or steps, indicating a weak molecule-substrate interaction—a conclusion that is also supported by DFT calculations. This system may be beneficial to the fabrication of carbon based devices and of other types of organic functional overlayers.
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81.16.Dn Self-assembly
81.05.ub Fullerenes and related materials
68.43.Fg Adsorbate structure (binding sites, geometry)
81.07.Bc Nanocrystalline materials
68.43.Mn Adsorption kinetics
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
FREE

Optical microcavities with a thiol-functionalized gold nanoparticle polymer thin film coating

Ce Shi, Hong Seok Choi, and Andrea M. Armani

Appl. Phys. Lett. 100, 013305 (2012); http://dx.doi.org/10.1063/1.3673872 (3 pages) | Cited 2 times

Online Publication Date: 4 January 2012

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Polymer coatings endow ultra-high-Q dielectric resonators with nonlinear properties, impacting numerous applications. However, minimal research combining microcavities with polymer-nanoparticle coatings to tune or tailor the optical properties of the system has been performed. One challenge is maintaining the high performance of the optical device while in the presence of nanoparticles. In the present work, a toroidal microcavity is coated with a polymethylmethacrylate thin film containing thiol-functionalized gold nanoparticles. The thiol-functionalization ensures that the nanoparticles are uniformly distributed throughout the film. The quality factors of these devices are above 5 × 106 and are in good agreement with the theoretical predictions.
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42.79.Wc Optical coatings
42.70.Jk Polymers and organics
FREE

Impact of unbalanced charge transport on the efficiency of normal and inverted solar cells

J. D. Kotlarski and P. W. M. Blom

Appl. Phys. Lett. 100, 013306 (2012); http://dx.doi.org/10.1063/1.3663860 (3 pages) | Cited 2 times

Online Publication Date: 5 January 2012

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In a normal solar cell, most charge carriers are generated close to the anode, such that electrons have to travel a longer distance as compared to the holes. In an inverted solar cell, holes have to travel a longer distance. We use a combined optical and electronic model to simulate the effect of unbalanced transport on the efficiency of normal and inverted single and tandem solar cells. When the electrons are ten times more mobile than the holes, the efficiency for a single cell with a thickness of 250 nm drops from 7.5% to 4.5% when changing from a normal to an inverted structure. For opposite mobility ratio, the inverted structure clearly outperforms the normal structure.
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88.40.hj Efficiency and performance of solar cells
FREE

Can morphology tailoring improve the open circuit voltage of organic solar cells?

Biswajit Ray, Mark S. Lundstrom, and Muhammad A. Alam

Appl. Phys. Lett. 100, 013307 (2012); http://dx.doi.org/10.1063/1.3672221 (3 pages) | Cited 8 times

Online Publication Date: 5 January 2012

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While the effect of interfacial morphology on the short circuit current (ISC) of organic photovoltaic devices (OPVs) is well known, its impact on open circuit voltage (VOC) and fill-factor (FF) are less clear. Since the output power of a solar cell Pout = ISCVOCFF, such understanding is critical for designing high-performance, morphology-engineered OPVs. In this letter, we provide an explicit analytical proof that any effort to radically improve VOC by tailoring bulk heterojunction morphology is futile, because any increase in ISC due to larger interface area is counterbalanced by corresponding increase in recombination current, so that the upper limit of VOCBHJ cannot exceed that of the corresponding planar heterojunction devices, i.e., VOCBHJ ≤ VOCPHJ. We discuss the implication of this VOC-constraint on the efficiency optimization of organic solar cells.
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88.40.jr Organic photovoltaics
88.40.hj Efficiency and performance of solar cells
FREE

Surface plasmon-enhanced electroluminescence in organic light-emitting diodes incorporating Au nanoparticles

Y. Xiao, J. P. Yang, P. P. Cheng, J. J. Zhu, Z. Q. Xu, Y. H. Deng, S. T. Lee, Y. Q. Li, and J. X. Tang

Appl. Phys. Lett. 100, 013308 (2012); http://dx.doi.org/10.1063/1.3675970 (4 pages) | Cited 5 times

Online Publication Date: 6 January 2012

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Surface plasmon-enhanced electroluminescence (EL) in an organic light-emitting diode is demonstrated by incorporating the synthesized Au nanoparticles (NPs) in the hole injection layer of poly(3,4-ethylene dioxythiophene):polystyrene sulfonic acid. An increase of ∼25% in the EL intensity and efficiency are achieved for devices with Au NPs, whereas the spectral and electrical properties remain almost identical to the control device. Time-resolved photoluminescence spectroscopy reveals that the EL enhancement is ascribed to the increase in spontaneous emission rate due to the plasmonic near-field effect induced by Au NPs.
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85.60.Jb Light-emitting devices
78.55.-m Photoluminescence, properties and materials
FREE

Extended spectral response in organic photomultiple photodetectors using multiple near-infrared dopants

Shao-Tang Chuang, Shang-Chieh Chien, and Fang-Chung Chen

Appl. Phys. Lett. 100, 013309 (2012); http://dx.doi.org/10.1063/1.3675573 (3 pages)

Online Publication Date: 6 January 2012

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We demonstrate highly sensitive polymer photodetectors (OPDs) with spectral response extending from the ultraviolet to the near-infrared (NIR) region (∼1200 nm). After doping two NIR dopants, high external quantum efficiencies (∼5500%) and high responsivities (23.0 A/W) are achieved under a low reverse bias (−3.7 V). The high gains could be attributed to unbalanced carrier transport in the photoactive layer arising from the electron traps at the NIR dopants. This approach allows the ready preparation of OPDs exhibiting broad spectral responses and high quantum efficiencies simultaneously.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
FREE

Efficient polymer solar cell employing an oxidized Ni capped Al:ZnO anode without the need of additional hole-transporting-layer

T. L. Chen, R. Betancur, D. S. Ghosh, Jordi Martorell, and V. Pruneri

Appl. Phys. Lett. 100, 013310 (2012); http://dx.doi.org/10.1063/1.3673843 (3 pages) | Cited 1 time

Online Publication Date: 6 January 2012

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We show that an effective transparent electrode for bulk-heterostructure organic solar cells (OSCs) can be produced by uniformly depositing a few nm of Ni on a film of aluminum-doped zinc oxide (AZO). After deposition, the Ni capping layer is O2 plasma treated to form a bilayer of Ni/NiO, as it is evidenced by x-ray photoelectron spectroscopy analysis. The oxidized Ni capped AZO electrode can act as anode and hole-transporting-layer in OSCs, providing an enhancement in transparency, environmental stability, and injection/collection of charges. The S-shaped feature of the IV curve for the OSC using AZO electrodes in conjunction with NiO transporting layer is not present in the case of the proposed electrode structure, clearly indicating the significant role of the Ni metallic interlayer in reducing the energy barrier. The relevant role played by the Ni was further confirmed when a NiO layer was deposited on top of the AZO/Ni bilayer. In that case, the S-shape was not present while a 90% photo-conversion efficiency relative to the ITO/NiO cell was achieved.
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88.40.jr Organic photovoltaics
88.40.hj Efficiency and performance of solar cells
FREE

Barrierless hole injection through sub-bandgap occupied states in organic light emitting diodes using substoichiometric MoOx anode interfacial layer

Maria Vasilopoulou, Leonidas C. Palilis, Dimitra G. Georgiadou, Stella Kennou, Ioannis Kostis, Dimitris Davazoglou, and Panagiotis Argitis

Appl. Phys. Lett. 100, 013311 (2012); http://dx.doi.org/10.1063/1.3673283 (4 pages) | Cited 8 times

Online Publication Date: 6 January 2012

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In this letter, highly efficient hole injection was demonstrated in hole only devices based on organic semiconductors with different highest occupied molecular orbital level and transport properties. The barrierless hole injection was achieved by using a substoichiometric MoOx thin film (consisting of 65% Mo+6 and 35% Mo+5) as a higly effective anode interfacial layer. The current in these devices was found to be space charge limited, achieved due to the formation of highly efficient anode ohmic contact via the excellent band alignment through occupied gap states at the ITO/MoOx and MoOx/organic semiconductor modified interface. Quite remarkably, the efficiency of hole injection was found to be almost independent of the MoOx thickness, which is indicative of perfect band alignment at the anode interface.
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85.60.Jb Light-emitting devices
FREE

Role of n-dopant based electron injection layer in n-doped organic light-emitting diodes and its simple alternative

Young Wook Park, Jin Hwan Choi, Tae Hyun Park, Eun Ho Song, Hakkoo Kim, Hyun Jun Lee, Se Joong Shin, Byeong-Kwon Ju, and Won Jun Song

Appl. Phys. Lett. 100, 013312 (2012); http://dx.doi.org/10.1063/1.3674960 (4 pages)

Online Publication Date: 6 January 2012

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We investigate the enhancement mechanism of the electroluminescence (EL) of alkali metal based n-doped organic light-emitting diodes (OLEDs). The dual role of the n-dopant (carrier transport and lowering of the injection barrier) induces a trade-off. When the electron transport layer (ETL) is optimally doped by the n-dopant for the highest conductivity, the amount of n-dopant at the ETL/cathode interface is insufficient to form enough chemical bonds with the cathode for efficient carrier injection. This insufficient amount of n-dopant limits the carrier injection properties. To solve this problem, we demonstrated that the addition of an electron injection layer (EIL) comprised of the n-dopant could increase its presence at the interface and, thereby, improve the carrier injection properties and, consequently, the EL efficiency. Moreover, simply using an alkali-metal alloy (rather than co-deposition) on the n-doped ETL as a cathode, instead of using the additional EIL, greatly improves the EL efficiency of the OLEDs. The alkali-metal alloy cathode increased the interfaced states at the ETL/cathode. The proposed model was confirmed by x-ray photoemission spectroscopy experiments on the alkali-metal n-dopant/electrode interface.
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85.60.Jb Light-emitting devices
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Effects of nitrogen doping on device characteristics of InSnO thin film transistor

Chang Eun Kim and Ilgu Yun

Appl. Phys. Lett. 100, 013501 (2012); http://dx.doi.org/10.1063/1.3673556 (3 pages) | Cited 3 times

Online Publication Date: 3 January 2012

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The effects of nitrogen doping on the performance of InSnO thin film transistor were investigated. When the nitrogen was doped in the InSnO channel, device characteristics such as turn-on voltage, subthreshold swing, field effect mobility, and on/off current ratio were enhanced. The N2 insertion in the deposition process decreased the density of the interface trap states and enhanced the crystallinity of the InSnO channel layer. These results indicate that device characteristics can be improved by nitrogen doping in the deposition process.
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85.30.Tv Field effect devices

Perfect spin-filter and highly spin-polarized current in a quantum network device

Hua-Hua Fu and Kai-Lun Yao

Appl. Phys. Lett. 100, 013502 (2012); http://dx.doi.org/10.1063/1.3673840 (3 pages) | Cited 3 times

Online Publication Date: 3 January 2012

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We report a design to realize perfect spin-filter and highly spin-polarized current in a quantum network device composed of multiple quantum dots (QDs). By producing an energy difference between the site energy of the upper QDs and down ones, the linear conductance spectra present well-defined insulating bands with very steep edges due to the Fano antiresonance in some suitable conditions. Considering a Zeeman splitting, highly to 100% spin-polarized windows appear in the conductance spectra, which makes the network device can be used as a perfect spin filter to generate completely spin-polarized current. This idea opens a practical way to prompt other similar configures of the network to realize perfect spin-filter.
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85.30.-z Semiconductor devices

Frequency splitting of the main mode in a microelectromechanical resonator due to coupling with an anchor resonance

Lauri Lipiäinen, Antti Jaakkola, Kimmo Kokkonen, and Matti Kaivola

Appl. Phys. Lett. 100, 013503 (2012); http://dx.doi.org/10.1063/1.3673558 (3 pages) | Cited 1 time

Online Publication Date: 4 January 2012

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We present an experimental study of the frequency scaling of the main, square-extensional mode in a piezoelectrically actuated plate resonator. The studied set consists of resonators of different plate sizes with identical anchors. The behavior of the square-extensional mode is analyzed using electrical impedance measurements and optical characterization of the mechanical vibration fields. The results reveal a detrimental anchor effect, where for certain plate sizes the square-extensional mode branch is split into two due to a coupled oscillation of the resonator plate and the anchors.
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07.10.Cm Micromechanical devices and systems
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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