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Applied Physics Letters Collection


 
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Applied Physics Letters : Crystalline silicon carbide nanocones an...

By: Zhenyu Liu, Lijie Ci, V. Srot, N. Y. Jin-Phillipp, Peter A. van Aken et al

Description: We present the formations of crystalline silicon carbide (SiC) nanocones and heterostructures catalyzed by iron nanoparticles, originally encapsulated in graphite-like carbon shells, via the vapor-liquid-solid process. We propose that the nanocone shape is due to the release of iron nanoparticles from their carbon shells followed by agglomeration, where the increasing size of the iron nanoparticle during SiC growth creates the nanocone shape. The release and...

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Applied Physics Letters : Absence of elastic clamping in quantitat...

By: David A. Scrymgeour and Julia W. P. Hsu

Description: We establish that clamping effects, which limit accurate determination of piezoelectric responses in bulk materials and films using piezoelectric force microscopy (PFM), are not present when measuring discrete nanostructures with radii less than five times the tip radius. This conclusion is established by comparing the piezoelectric response in ZnO rods using two electrode configurations: one with the conducting atomic force microscopy tip acting as the top ...

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Applied Physics Letters : The enhancement of ZnO nanowalls photoco...

By: F. Fang, D. X. Zhao, B. H. Li, Z. Z. Zhang, J. Y. Zhang et al

Description: 10 nm sized hexagonal CdS nanoparticles were decorated on the surface of well-aligned ZnO nanowall through a facile hydrothermal approach. The effects of CdS-cap layer on the optical and photoelectrical properties of ZnO nanowalls have been studied. It was found the CdS acted not only as a passivation layer to suppress the detrimental surface states of ZnO nanowalls, which reduced the deep-level emissions, but also as an interfacial carrier transport layer t...

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Applied Physics Letters : Surface optical Raman modes in InN nanos...

By: Satyaprakash Sahoo, M. S. Hu, C. W. Hsu, C. T. Wu, K. H. Chen et al

Description: Raman spectroscopic investigations are carried out on one-dimensional nanostructures of InN, such as nanowires and nanobelts synthesized by chemical vapor deposition. In addition to the optical phonons allowed by symmetry A1, E1, and E2 (high) modes, two additional Raman peaks are observed around 528 and 560 cm−1 for these nanostructures. Calculations for the frequencies of surface optical (SO) phonon modes in InN nanostructures yield values close to those o...

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Applied Physics Letters : Chemical patterning of Ag(111): Spatiall...

By: S. Günther, R. Reichelt, J. Wintterlin, A. Barinov, T. O. Mentes et al

Description: Low energy electron irradiation of a Ag(111) surface during NO2 adsorption at 300 K induces formation of Ag oxide. Using a spatially confined electron beam, small Ag2O spots could be grown with a sharp, ∼ 100 nm wide, boundary to the nonirradiated metallic surface. Since the structure size will mainly depend on the sharpness of the irradiating electron beam, this process has the potential of a single step nanostructuring process. Temperature treatment offers...

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Applied Physics Letters : Ag-modified silicon nanowires substrate ...

By: Ming-Wang Shao, Ming-Liang Zhang, Ning-Bew Wong, Dorothy Duo-duo Ma, Hui Wang et al

Description: We report a unique substrate for surface-enhanced raman spectroscopy (SERS) based on silver nanoparticles-embedded silicon nanowires (SiNWs). The SiNWs were prepared by thermal evaporation of SiO powder via oxide-assisted growth, oxide removed with HF, and then used to reduce silver ions to form a highly decorated Ag-embedded surface. Such modified SiNWs substrates yielded ultrahigh SERS sensitivity, which could detect 25 μl of 1×10−16M Rhodamine 6G, 1×10−16...

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Applied Physics Letters : ZnO nanowire arrays: Optical scattering ...

By: Ramón Tena-Zaera, Jamil Elias, and Claude Lévy-Clément

Description: Arrays of ZnO nanowires with different lengths (0.5–2 μm) and diameters (100–330 nm) were electrodeposited to study the influence of the nanowire dimensions on light scattering. The nanowire length and diameter were found to be major parameters in modifying the intensity and the wavelength of the scattered radiation, respectively. A significant scattering for the whole visible wavelength range was attained in arrays of ZnO nanowires of ∼ 1.5 μm in length and...

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Applied Physics Letters : Multilevel sensitization of Er3+ in low-...

By: Oleksandr Savchyn, Ravi M. Todi, Kevin R. Coffey, and Pieter G. Kik

Description: The dynamics of Er3+ excitation in low-temperature-annealed Si-rich SiO2 are studied. It is demonstrated that Si-excess-related indirect excitation is fast (transfer time τtr<27 ns) and occurs into higher lying Er3+ levels as well as directly into the first excited state (4I13/2). By monitoring the time-dependent Er3+ emission at 1535 nm, the multilevel nature of the Er3+ sensitization is shown to result in two types of excitation of the 4I13/2 state: a fast...

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Applied Physics Letters : Effect of viscosity of base fluid on the...

By: Tsung-Han Tsai, Long-Sheng Kuo, Ping-Hei Chen, and Chin-Ting Yang

Description: This study aims to investigate the effect of viscosity of the base fluid on the thermal conductivity of nanofluids in which Fe3O4 nanoparticles are suspended in the base fluid composed of diesel oil and polydimethylsiloxane. Viscosity of the base fluid is varied by changing the volumetric fractions between both fluids. The measured thermal conductivity of nanofluids gradually approaches the value predicted by the Maxwell equation by increasing the viscosity....

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Applied Physics Letters : Determining the optimum pentacene channe...

By: Sung-jin Mun, Jeong-M. Choi, Kwang H. Lee, Kimoon Lee, and Seongil Im

Description: We report that the optimum pentacene channel thickness is dependent on the surface energy state of its dielectric substrate. Pentacene thin-film transistor (TFT) with hydrophobic substrate displays a peak linear mobility at an optimum channel thickness of 50 nm, below or above which the linear mobility decreases. In contrast, the linear mobility of the TFT with hydrophilic substrate monotonically increases until the channel thickness decreases to 15 nm. Acco...

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Applied Physics Letters : A flexible organic pentacene nonvolatile...

By: Ming-Feng Chang, Po-Tsung Lee, S. P. McAlister, and Albert Chin

Description: We report a pentacene thin film transistor nonvolatile memory fabricated on a flexible polyimide substrate. This device shows a low program/erase voltage of 12 V, a speed of 1/100 ms, an initial memory window of 2.4 V, and a 0.78 V memory window after 48 h. This has been achieved by using a high-κ dielectric as charge trapping, blocking, and tunneling gate insulator layers.

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Applied Physics Letters : Multilayered solid-state organic laser f...

By: K. Yamashita, A. Arimatsu, N. Takeuchi, M. Takayama, K. Oe et al

Description: This paper describes an organic dye-doped polymeric laser with a multilayered structure of active waveguides. Using the technique of photonanoimprint lithography, organic active-waveguide layers with distributed-feedback cavities and a polymeric intermediate cladding layer were stacked on a silica substrate. Under optical pumping, lasing oscillations at 427 and 636 nm, which correspond to the Bragg reflection wavelengths in the respective active waveguides, ...

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Applied Physics Letters : High performance ambient processed inver...

By: Steven K. Hau, Hin-Lap Yip, Hong Ma, and Alex K.-Y. Jen

Description: The performance of inverted bulk-heterojunction solar cells with zinc oxide nanoparticles as the electron selective contact is compared to those modified with a fullerene self-assembled monolayer (C60-SAM). The devices modified with a C60-SAM show very significant improvement in conversion efficiencies compared to unmodified devices leading to efficiencies as high as 4.9%. This is due to enhanced electronic coupling of the inorganic/organic interface from th...

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Applied Physics Letters : Organic heterostructure device with nonv...

By: Frank Lindner, Karsten Walzer, and Karl Leo

Description: Recently, several memory devices based on organic semiconductors were reported. In most cases, single organic layers were employed, and the switching mechanisms were not fully understood. Here, we report on a novel device structure based on electrically doped organic heterostructures showing highly stable memory behavior. The organic layers are embedded between a bottom indium tin oxide and a top metal contact and form a quantum well-like structure. The devi...

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Applied Physics Letters : Reduced hole mobility due to the presenc...

By: J. Y. Song, N. Stingelin, W. P. Gillin, and T. Kreouzis

Description: The hole mobility in poly-(3-hexylthiophene) samples is measured by the dark injection transient technique in both hole only and ambipolar devices. By applying a small offset bias prior to the voltage step, electronic excited states are generated in the ambipolar but not in the hole only devices. The presence of excited states reduces the room temperature hole mobility (typically 5×10−5 cm2 V−1 s−1) by as much as 15% compared to that measured without offset,...

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Applied Physics Letters : The effect of aluminum oxide incorporati...

By: Monica Sawkar-Mathur, Ya-Chuan Perng, Jun Lu, Hans-Olof Blom, John Bargar et al

Description: Hafnium aluminate thin films were synthesized by atomic layer deposition (ALD) to assess the effect of aluminum oxide incorporation on the dielectric/Ge interfacial properties. In these HfxAlyOz thin films, the Hf to Al cation ratio was effectively controlled by changing the ratio of hafnium oxide to aluminum oxide ALD cycles, while their short range order was changed upon increasing aluminum oxide incorporation, as observed by extended x-ray absorption fine...

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Applied Physics Letters : Field emission from graphene based compo...

By: Goki Eda, H. Emrah Unalan, Nalin Rupesinghe, Gehan A. Amaratunga, and Manish Chhowalla

Description: Field emission from graphene is challenging because the existing deposition methods lead to sheets that lay flat on the substrate surface, which limits the field enhancement. Here we describe a simple and general solution based method for the deposition of field emitting graphene/polymer composite thin films. The graphene sheets are oriented at some angles with respect to the substrate surface leading to field emission at low threshold fields ( ∼ 4 V μm−1). ...

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Applied Physics Letters : Subwavelength imaging of acoustic waves ...

By: Zhaojian He, Feiyan Cai, Yiqun Ding, and Zhengyou Liu

Description: In this letter, the subwavelength imaging of acoustic waves is reported based on a mechanism that the evanescent modes of a source are canalized by the Bloch modes of a two-dimensional phononic crystal that served as the lens. The phononic crystal was designed to have a thickness that meets the condition of Fabry–Pérot resonance in order to enhance wave transmission and hence to improve imaging performance. Numerical simulations demonstrated that for a point...

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Applied Physics Letters : Performance comparison of Pb(Zr0.52Ti0.4...

By: Hengky Chandrahalim, Sunil A. Bhave, Ronald Polcawich, Jeff Pulskamp, Daniel Judy et al

Description: This paper provides a quantitative comparison and explores the design space of lead zirconium titanate (PZT)–only and PZT-on-silicon length-extensional mode resonators for incorporation into radio frequency microelectromechanical system filters and oscillators. We experimentally measured the correlation of motional impedance (RX) and quality factor (Q) with the resonators’ silicon layer thickness (tSi). For identical lateral dimensions and PZT-layer thicknes...

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Applied Physics Letters : Reduced boron lateral ion channeling in ...

By: W. S. Lau, Peizhen Yang, V. Ho, B. K. Lim, S. Y. Siah et al

Description: The on-current of p-channel transistors fabricated on (100) Si substrate can be easily increased by switching from ⟨110⟩ to ⟨100⟩ channel orientation because of faster hole transport. In this paper, we pointed out that there is also a reduction in the gate-to-source/drain overlap, resulting in an increase in the effective channel length for p-channel transistors. Our experimental observation can be explained by a reduction in boron lateral ion channeling due to this switch.

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