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1 Oct 2012

Volume 101, Issue 14, Articles (14xxxx)

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Appl. Phys. Lett. 101, 141101 (2012); http://dx.doi.org/10.1063/1.4742864 (4 pages)

Po-Hsun Huang, Michael Ian Lapsley, Daniel Ahmed, Yuchao Chen, Lin Wang, and Tony Jun Huang
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Luminescence of free-standing versus matrix-embedded oxide-passivated silicon nanocrystals: The role of matrix-induced strain

Kateřina Kůsová, Lukáš Ondič, Eva Klimešová, Kateřina Herynková, Ivan Pelant, Stanislav Daniš, Jan Valenta, Mathieu Gallart, Marc Ziegler, Bernd Hönerlage, and Pierre Gilliot

Appl. Phys. Lett. 101, 143101 (2012); http://dx.doi.org/10.1063/1.4756696 (5 pages) | Cited 3 times

Online Publication Date: 1 October 2012

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We collect a large number of experimental data from various sources to demonstrate that free-standing (FS) oxide-passivated silicon nanocrystals (SiNCs) exhibit considerably blueshifted emission, by 200 meV on average, compared to those prepared as matrix-embedded (ME) ones of the same size. This is suggested to arise from compressive strain, exerted on the nanocrystals by their matrix, which plays an important role in the light-emission process; this strain has been neglected up to now as opposed to the impact of quantum confinement or surface passivation. Our conclusion is also supported by the comparison of low-temperature behavior of photoluminescence of matrix-embedded and free-standing silicon nanocrystals.
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78.55.Ap Elemental semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
62.25.-g Mechanical properties of nanoscale systems

Physical-gap-channel graphene field effect transistor with high on/off current ratio for digital logic applications

Jeong Hun Mun and Byung Jin Cho

Appl. Phys. Lett. 101, 143102 (2012); http://dx.doi.org/10.1063/1.4756795 (4 pages)

Online Publication Date: 1 October 2012

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We propose and analyze an approach to secure a high on/off current ratio in a graphene field effect transistor (FET) by introducing a physical gap along the channel rather than by attempting to open the energy bandgap of graphene. The device simulation results of the newly proposed device structure reveal highly suppressed off-state current of ∼10−9 A/μm, an on/off current ratio of more than seven orders of magnitude, and a subthreshold slope of 2.23 mV/decade more than a 20-fold reduction relative to the theoretical limitation of conventional metal-oxide-semiconductor FETs.
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85.65.+h Molecular electronic devices
85.30.Tv Field effect devices

Chemical assembly and electrical characteristics of surface-rich topological insulator Bi2Se3 nanoplates and nanoribbons

Robin B. Jacobs-Gedrim, Chris A. Durcan, Nikhil Jain, and Bin Yu

Appl. Phys. Lett. 101, 143103 (2012); http://dx.doi.org/10.1063/1.4756942 (3 pages)

Online Publication Date: 1 October 2012

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We demonstrate synthesis of low-dimensional, surface-rich bismuth selenide nanoplates and nanoribbons through a low-pressure chemical-vapor-deposition method. The single crystalline lattice structure, morphology, and chemical composition of the synthesized nanoplates and nanoribbons are analyzed. As-prepared samples are found to be all n-type doped. Very large surface-to-volume ratios have been achieved in these low-dimensional nanostructures, making them ideal for investigating topological insulator properties. Gate-controlled bismuth selenide nanoplate field-effect transistors are fabricated and basic electrical behavior is characterized.
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81.16.Be Chemical synthesis methods
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
85.30.Tv Field effect devices
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
73.61.Le Other inorganic semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

The influence of radial heterostructuring on carrier dynamics in gallium nitride nanowires

Ayan Kar, Qiming Li, Prashanth C. Upadhya, Min Ah Seo, Jeremy Wright, T. S. Luk, George T. Wang, and Rohit P. Prasankumar

Appl. Phys. Lett. 101, 143104 (2012); http://dx.doi.org/10.1063/1.4756915 (5 pages)

Online Publication Date: 2 October 2012

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Ultrafast optical pump-probe spectroscopy is used to study the influence of aluminum nitride (AlN) and aluminum gallium nitride (AlGaN) shells on carrier dynamics in radially heterostructured GaN nanowires (NWs). Our experiments reveal longer carrier relaxation times and lower lasing thresholds in NWs passivated with a higher bandgap shell, which can be attributed to a reduction in surface defect state density. We observe that carrier relaxation times vary with the nitride shell material and thickness, likely due to strain from the lattice mismatch between the core and shell materials. Our results demonstrate that radial heterostructuring is a promising route to controlling carrier dynamics in III-nitride NWs.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.Rv Passivation
78.47.J- Ultrafast spectroscopy (<1 psec)
71.55.Eq III-V semiconductors

Polarization-insensitive and wide-angle plasmonically induced transparency by planar metamaterials

Xiaoyang Duan, Shuqi Chen, Haifang Yang, Hua Cheng, Junjie Li, Wenwei Liu, Changzhi Gu, and Jianguo Tian

Appl. Phys. Lett. 101, 143105 (2012); http://dx.doi.org/10.1063/1.4756944 (5 pages) | Cited 1 time

Online Publication Date: 3 October 2012

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We present the design, characterization, and experimental demonstration of a polarization-insensitive wide-angle plasmonically induced transparency (PIT) planar metamaterial (MM) in the near-infrared regime. A four-level plasmonic system is proposed to explain and analyze the forming mechanisms of the PIT planar MM, whose results agree closely with the simulated and experimental results. This shows that the local asymmetrical nanostructure leading to the plasmon-assisted interaction is the key to producing PIT, but it does not mean that PIT cannot be achieved by the whole symmetrical nanostructure. This work offers a further step in developing optical modulation.
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42.70.-a Optical materials
42.25.Ja Polarization
42.60.Fc Modulation, tuning, and mode locking

Highly versatile ultra-low density GaAs quantum dots fabricated by filling of self-assembled nanoholes

D. Sonnenberg, A. Graf, V. Paulava, W. Hansen, and Ch. Heyn

Appl. Phys. Lett. 101, 143106 (2012); http://dx.doi.org/10.1063/1.4756945 (4 pages) | Cited 3 times

Online Publication Date: 3 October 2012

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GaAs quantum dots (QDs) of ultra-low density (ULD) are fabricated by filling of nanoholes in AlGaAs surfaces. The holes are drilled using self-assembled local droplet etching with Al droplets. By precisely controlling the arsenic flux and the substrate temperature, the QD density is reduced down to the 106 cm−2 range uniformly over the whole wafer. The QD size is precisely adjustable via the hole filling level. By this, the optical emission energy of the QDs can be adjusted over a wide energy range of at least 120 meV. The surface visibility of ULD QDs allows their simple integration into lithographic processing.
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81.16.Dn Self-assembly
81.16.Nd Micro- and nanolithography
81.65.Cf Surface cleaning, etching, patterning
61.46.-w Structure of nanoscale materials
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Trapping of diffusing germanium by silicon excess co-implanted into fused silica

D. Barba, J. Demarche, F. Martin, G. Terwagne, and G. G. Ross

Appl. Phys. Lett. 101, 143107 (2012); http://dx.doi.org/10.1063/1.4757291 (4 pages)

Online Publication Date: 3 October 2012

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The trapping of germanium by silicon atoms, successively implanted into fused silica, is evidenced after thermal annealing at 1150 °C. Rutherford backscattering spectroscopy and Raman measurements reveal a linear increase of remaining Ge concentration with the co-implanted Si fluence, accompanied by an increase of the Ge-Ge bond density, respectively. Comparison of Ge concentration profiles with scanning electron microscopy images shows the formation of nanoclusters, resulting from the accumulation of Ge within the region containing a greater concentration of co-implanted Si, whereas nanocavities, indicative of Ge release from nanostructures, are dominant in deeper sample region of lower Si excess concentration.
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66.30.Pa Diffusion in nanoscale solids
78.30.Hv Other nonmetallic inorganics
81.16.-c Methods of micro- and nanofabrication and processing
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.72.up Other materials
61.46.Bc Structure of clusters (e.g., metcars; not fragments of crystals; free or loosely aggregated or loosely attached to a substrate)

Spreading and atomization of droplets on a vibrating surface in a standing pressure field

P. Deepu, Saptarshi Basu, Abhishek Saha, and Ranganathan Kumar

Appl. Phys. Lett. 101, 143108 (2012); http://dx.doi.org/10.1063/1.4757567 (5 pages) | Cited 1 time

Online Publication Date: 4 October 2012

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We report the first observation and analytical model of deformation and spreading of droplets on a vibrating surface under the influence of an ultrasonic standing pressure field. The standing wave allows the droplet to spread, and the spreading rate varies inversely with viscosity. In low viscosity droplets, the synergistic effect of radial acoustic force and the transducer surface acceleration also leads to capillary waves. These unstable capillary modes grow to cause ultimate disintegration into daughter droplets. We find that using nanosuspensions, spreading and disintegration can be prevented by suppressing the development of capillary modes and subsequent break-up.
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68.08.Bc Wetting
82.70.Kj Emulsions and suspensions
66.20.-d Viscosity of liquids; diffusive momentum transport
62.10.+s Mechanical properties of liquids
62.60.+v Acoustical properties of liquids

Development of knife-edge ridges on ion-bombarded surfaces

Miranda Holmes-Cerfon, Wei Zhou, Andrea L. Bertozzi, Michael P. Brenner, and Michael J. Aziz

Appl. Phys. Lett. 101, 143109 (2012); http://dx.doi.org/10.1063/1.4755838 (5 pages)

Online Publication Date: 4 October 2012

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We demonstrate in both laboratory and numerical experiments that ion bombardment of a modestly sloped surface can create knife-edge like ridges with extremely high slopes. Small pre-fabricated pits expand under ion bombardment, and the collision of two such pits creates knife-edge ridges. Both laboratory and numerical experiments show that the pit propagation speed and the precise shape of the knife edge ridges are universal, independent of initial conditions, as has been predicted theoretically. These observations suggest a method of fabrication in which a surface is pre-patterned so that it dynamically evolves to a desired target pattern made of knife-edge ridges.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.65.-b Surface treatments
68.35.bd Metals and alloys
61.80.Jh Ion radiation effects

Resistive switching in a GaOx-NiOx p-n heterojunction

K. Zheng, J. L. Zhao, X. W. Sun, V. Q. Vinh, K. S. Leck, R. Zhao, Y. G. Yeo, L. T. Law, and K. L. Teo

Appl. Phys. Lett. 101, 143110 (2012); http://dx.doi.org/10.1063/1.4757761 (5 pages)

Online Publication Date: 5 October 2012

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We report a unidirectional bipolar resistive switching in an n-type GaOx/p-type NiOx heterojunction fabricated by magnetron sputtering at room temperature. The resistive switching behavior coincides with the switching between Ohmic conduction (low resistance) and rectifying behavior (high resistance) of the heterojunction diode. Under external electric field, electromigrated intrinsic defects, such as oxygen vacancies and oxygen ions, accumulate at the pn junction interface and modify the interface barrier, forming or rupturing the filamentary paths between n-GaOx and p-NiOx, leading to the switching between Ohmic and diode characteristics of the device. The device shows good endurance, retention performance, and scaling capability, signaling the potential of a diode-structured resistive switching device for non-volatile memory applications.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Cd Deposition by sputtering
84.30.Sk Pulse and digital circuits
61.72.jd Vacancies
68.55.ag Semiconductors
66.30.Qa Electromigration

Field-effect diode based on electron-induced Mott transition in NdNiO3

W. L. Lim, E. J. Moon, J. W. Freeland, D. J. Meyers, M. Kareev, J. Chakhalian, and S. Urazhdin

Appl. Phys. Lett. 101, 143111 (2012); http://dx.doi.org/10.1063/1.4757865 (4 pages)

Online Publication Date: 5 October 2012

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We studied an electron-induced metal-insulator transition in a two-terminal device based on oxide NdNiO3. In our device, the NdNiO3 is electrostatically doped by the voltage applied between the terminals, resulting in an asymmetric conductivity with respect to the bias polarity. The asymmetry is temperature-dependent and is most significant near the metal-insulator transition. The I-V characteristics exhibit a strong dependence both on the thermal history and the history of the applied voltage bias. Our two-terminal device represents a simple and efficient route for studies of the effect of electron doping on the metal-insulator transition.
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85.30.Tv Field effect devices
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