Jump to Content
View Cart
Top 20 Most Read Articles
May 2013
The 20 articles with the most full-text downloads during the month, in descending order.
 |
Dexterous manipulation of microparticles using Bessel-function acoustic pressure fields Appl. Phys. Lett. 102, 123508 (2013); http://dx.doi.org/10.1063/1.4798584 (5 pages) Online Publication Date: 29 March 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We show that Bessel-function acoustic pressure fields can be used to trap and controllably position microparticles. A circular, 16-element ultrasound array generates and manipulates an acoustic field within a chamber, trapping microparticles and agglomerates. Changes in the phase of the sinusoidal signals applied to the array elements result in the movement of the Bessel-function pressure field and hence the microparticles. This demonstrates ultrasonic manipulation analogous to holographic optical tweezers. The manipulation limits of the device are explained by the existence of unwanted resonances within the manipulation chamber.
|
|||
|
Show PACS
|
|||
|
|
Local-structure origins of the sustained Curie temperature in (Ba,Ca)TiO3 ferroelectrics Appl. Phys. Lett. 102, 162906 (2013); http://dx.doi.org/10.1063/1.4802996 (5 pages) Online Publication Date: 25 April 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
While the lattice volume in the solid-solution Ba1−xCaxTiO3 decreases with increasing x, the Curie temperature remains unaffected, in contrast to Ba1−xSrxTiO3. We have determined the origin of this phenomenon by comparing the local structures in (Ba,Ca)TiO3 and (Ba,Sr)TiO3. Reverse Monte Carlo refinements of instantaneous atomic positions using simultaneous fitting of multiple types of experimental data (neutron total scattering, X-ray absorption fine structure, patterns of diffuse scattering in electron diffraction) reveal both ferroelectric Ca displacements and their amplification of the Ti off-centering, which mitigate the lattice-volume effects. The activity of Ca is triggered by the anomalously strained Ca-O bonds.
|
|||
|
Show PACS
|
|||
|
|
Tuning magnetic anisotropy in (001) oriented L10 (Fe1−xCux)55Pt45 films Appl. Phys. Lett. 102, 132406 (2013); http://dx.doi.org/10.1063/1.4799651 (4 pages) Online Publication Date: 2 April 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||
|
Show Abstract
We have achieved (001) oriented L10 (Fe1−xCux)55Pt45 thin films, with magnetic anisotropy up to 3.6 × 107 erg/cm3, using atomic-scale multilayer sputtering and post annealing at 400 °C for 10 s. By fixing the Pt concentration, structure and magnetic properties are systematically tuned by the Cu addition. Increasing Cu content results in an increase in the tetragonal distortion of the L10 phase, significant changes to the film microstructure, and lowering of the saturation magnetization and anisotropy. The relatively convenient synthesis conditions, along with the tunable magnetic properties, make such materials highly desirable for future magnetic recording technologies.
|
||||||||||||||
|
Show PACS
|
||||||||||||||
|
|
Ultra-thin perfect absorber employing a tunable phase change material Appl. Phys. Lett. 101, 221101 (2012); http://dx.doi.org/10.1063/1.4767646 (5 pages) Online Publication Date: 26 November 2012
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||
|
Show Abstract
We show that perfect absorption can be achieved in a system comprising a single lossy dielectric layer of thickness much smaller than the incident wavelength on an opaque substrate by utilizing the nontrivial phase shifts at interfaces between lossy media. This design is implemented with an ultra-thin (∼λ/65) vanadium dioxide (VO2) layer on sapphire, temperature tuned in the vicinity of the VO2 insulator-to-metal phase transition, leading to 99.75% absorption at λ = 11.6 μm. The structural simplicity and large tuning range (from ∼80% to 0.25% in reflectivity) are promising for thermal emitters, modulators, and bolometers.
|
||||||||||||||
|
Show PACS
|
||||||||||||||
|
|
Appl. Phys. Lett. 102, 023112 (2013); http://dx.doi.org/10.1063/1.4776707 (4 pages) Online Publication Date: 17 January 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
A high-quality graphene transparent conductive film was fabricated by roll-to-roll chemical vapor deposition (CVD) synthesis on a suspended copper foil and subsequent transfer. While the high temperature required for the CVD synthesis of high-quality graphene has prevented efficient roll-to-roll production thus far, we used selective Joule heating of the copper foil to achieve this. Low pressure thermal CVD synthesis and a direct roll-to-roll transfer process using photocurable epoxy resin allowed us to fabricate a 100-m-long graphene transparent conductive film with a sheet resistance as low as 150 Ω/sq, which is comparable to that of state-of-the-art CVD-grown graphene films.
|
|||
|
Show PACS
|
|||
|
|
Appl. Phys. Lett. 102, 103504 (2013); http://dx.doi.org/10.1063/1.4795717 (4 pages) Online Publication Date: 13 March 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
We introduce an ac-transconductance method to profile the gate oxide traps in a HfO2 gated AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors (MOS-HEMTs) that can exchange carriers with metal gates, which in turn causes changes in analog and pulsed channel currents. The method extracts energy and spacial distributions of the oxide and interface traps under the gate from the frequency dependence of ac transconductance. We demonstrate the method using MOS-HEMTs with gate oxides that were annealed at different temperatures.
|
||||
|
Show PACS
|
||||
|
|
Band alignment in SnS thin-film solar cells: Possible origin of the low conversion efficiency Appl. Phys. Lett. 102, 132111 (2013); http://dx.doi.org/10.1063/1.4801313 (3 pages) Online Publication Date: 4 April 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Tin sulfide is an attractive absorber material for low-cost thin-film solar cells. Despite the ideal physical properties of bulk SnS, the photovoltaic conversion efficiencies achieved in devices to date have been no greater than 2%. Assessment of the valence band energy of the stable orthorhombic phase of SnS reveals a low ionisation potential (4.7 eV) in comparison to typical absorber materials (CdTe, CuInSe2, and Cu2ZnSnS4). A band mis-alignment is therefore predicted with commonly used back contact and buffer layers. Alternative configurations are proposed that should improve device performance.
|
|||
|
Show PACS
|
|||
|
|
Continuous-wave terahertz system with a 60 dB dynamic range Appl. Phys. Lett. 86, 204104 (2005); http://dx.doi.org/10.1063/1.1935032 (3 pages) Online Publication Date: 13 May 2005
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We have developed a high-performance continuous-wave terahertz imaging system based on photomixing. The emitter and detector are driven by compact, unstabilized, single-mode diode lasers. The all-optoelectronic, homodyne detection scheme yields both amplitude and phase information, and with careful optimization and matching of both emitter and receiver, a 60 dB dynamic range, at 0.53 THz, can be routinely achieved. This replicates the performance of established pulsed THz imagers at this frequency.
|
|||
|
Show PACS
|
|||
|
|
Novel millimeter‐wave near‐field resistivity microscope Appl. Phys. Lett. 68, 1579 (1996); http://dx.doi.org/10.1063/1.116685 (3 pages)
Full Text:
|
Download PDF
|
||
|
Show Abstract
We demonstrate a technique for contactless mapping of resistivity or dielectric constant of surfaces and films with a spatial resolution better than 100 μm. This technique may be used for the nondestructive testing of semiconducting wafers, conducting polymers, oxide superconductors, and printed circuits. The principle of operation consists of the scanning of a tiny millimeter‐wave antenna at a very small height above an inhomogeneous conducting surface and measuring the intensity and phase of the reflected (transmitted) wave. We use a specially designed resonant slit antenna and achieve subwavelength spatial resolution of λ/50. © 1996 American Institute of Physics. |
|||
|
Show PACS
|
|||
|
|
Bandgap engineering of ZnSnP2 for high-efficiency solar cells Appl. Phys. Lett. 100, 251911 (2012); http://dx.doi.org/10.1063/1.4730375 (3 pages) Online Publication Date: 22 June 2012
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
ZnSnP2, an absorber material for solar cells, transitions from an ordered chalcopyrite to a disordered sphalerite structure at high temperatures. We investigate the electronic structure of both phases, combining a screened hybrid density functional with the special quasi-random structure method. We predict a bandgap reduction of 0.95 eV between the ordered and fully disordered materials. Experimental reports are consistent with partial disorder. Tuning of the order parameter would lead to a family of ZnSnP2 phases with bandgaps ranging from 0.75 eV to 1.70 eV, thus providing graded solar cell absorbers from a single material system.
|
||||
|
Show PACS
|
||||
|
|
Appl. Phys. Lett. 102, 053901 (2013); http://dx.doi.org/10.1063/1.4789855 (5 pages) Online Publication Date: 4 February 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
SnS is a promising earth-abundant material for photovoltaic applications. Heterojuction solar cells were made by vapor deposition of p-type tin(II) sulfide, SnS, and n-type zinc oxysulfide, Zn(O,S), using a device structure of soda-lime glass/Mo/SnS/Zn(O,S)/ZnO/ITO. A record efficiency was achieved for SnS-based thin-film solar cells by varying the oxygen-to-sulfur ratio in Zn(O,S). Increasing the sulfur content in Zn(O,S) raises the conduction band offset between Zn(O,S) and SnS to an optimum slightly positive value. A record SnS/Zn(O,S) solar cell with a S/Zn ratio of 0.37 exhibits short circuit current density (Jsc), open circuit voltage (Voc), and fill factor (FF) of 19.4 mA/cm2, 0.244 V, and 42.97%, respectively, as well as an NREL-certified total-area power-conversion efficiency of 2.04% and an uncertified active-area efficiency of 2.46%.
|
|||
|
Show PACS
|
|||
|
|
Planar junctionless transistor with non-uniform channel doping Appl. Phys. Lett. 102, 133505 (2013); http://dx.doi.org/10.1063/1.4801443 (3 pages) Online Publication Date: 5 April 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
We propose a planar junctionless transistor (JLT) in silicon-on-insulator (SOI) with non-uniform channel doping in vertical direction to improve the ON to OFF drain current ratio. In single gate JLT in SOI, a thin device layer is depleted in the off-state from the top of the layer and the leakage current flows through bottom of the device layer, and the leakage current depends on the device layer thickness. We show that the decrease of doping in vertical direction suppresses the leakage current flowing through the bottom of the device by decreasing conductivity at the bottom of the device layer.
|
||||
|
Show PACS
|
||||
|
|
A theoretical study on thermoelectric properties of graphene nanoribbons Appl. Phys. Lett. 94, 263107 (2009); http://dx.doi.org/10.1063/1.3171933 (3 pages) Online Publication Date: 30 June 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We investigate the thermoelectric properties of graphene nanoribbons (GNRs) by solving atomistic electron and phonon transport equations in the nonequilibrium Green’s function formalism. The dependence of thermopower on temperature and chemical potential is compared to that of graphene, which shows the important role of quasi-one-dimensional geometry in determining the thermoelectric properties of a GNR. The edge roughness and lattice vacancy are found to increase the thermopower but decrease the thermoelectric ZT factor because the decrease in the electronic conductance outweighs the decrease in the thermal conductance and the increase in the thermopower.
|
|||
|
Show PACS
|
|||
|
|
Photo-origami—Bending and folding polymers with light Appl. Phys. Lett. 100, 161908 (2012); http://dx.doi.org/10.1063/1.3700719 (5 pages) Online Publication Date: 20 April 2012
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Photo-origami uses the dynamic control of the molecular architecture of a polymer by a combination of mechanical and non-contact optical stimuli to design and program spatially and temporally variable mechanical and optical fields into a material. The fields are essentially actuators, embedded in the material at molecular resolution, designed to enable controllable, sequenced, macroscopic bending and folding to create three-dimensional material structures. Here, we demonstrate, through a combination of theory, simulation-based design, synthesis, and experiment, the operative phenomena and capabilities of photo-origami that highlight its potential as a powerful, and potentially manufacturable, approach to create three-dimensional material structures.
|
|||
|
Show PACS
|
|||
|
|
Highly efficient charge transfer in nanocrystalline Si:H solar cells Appl. Phys. Lett. 102, 133101 (2013); http://dx.doi.org/10.1063/1.4795940 (4 pages) Online Publication Date: 1 April 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We demonstrate that in nanostructured films of nanocrystalline silicon imbedded in a hydrogenated amorphous silicon matrix, carriers generated in the amorphous region are transported out of this region and therefore do not recombine in the amorphous phase. Electron paramagnetic resonance (EPR) and photoluminescence (PL) measurements show that the EPR and PL from the amorphous phase are rapidly quenched as the volume fraction of Si nanocrystals exceeds about 30 vol. %. We propose the use of similar structures to dramatically increase the open circuit voltages in solar cell devices.
|
|||
|
Show PACS
|
|||
|
|
Flexible solid-state paper based carbon nanotube supercapacitor Appl. Phys. Lett. 100, 104103 (2012); http://dx.doi.org/10.1063/1.3691948 (4 pages) Online Publication Date: 7 March 2012
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
This paper presents a flexible solid-state supercapacitor of high energy density. The electrodes of the supercapacitor are made of porous and absorbent cotton paper coated with single-wall carbon nanotubes. To ensure all solid-state configuration, a solid-state polymer-based electrolyte (poly (vinyl alcohol)/phosphoric acid) is used. The as-fabricated supercapacitor can be charged to over 3 V. It has high specific capacitance and high energy density of 115.8301 F/g carbon and 48.8587 Wh/kg carbon. Its performance is comparable to that of commercial supercapacitors, which need to utilize liquid electrolytes. Flexible solid-state supercapacitors offer several significant advantages for use in hybrid electric vehicles.
|
|||
|
Show PACS
|
|||
|
|
Tunable giant magnetic anisotropy in amorphous SmCo thin films Appl. Phys. Lett. 102, 162402 (2013); http://dx.doi.org/10.1063/1.4802908 (4 pages) Online Publication Date: 23 April 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
SmCo thin films have been grown by magnetron sputtering at room temperature with a composition of 2–35 at. % Sm. Films with 5 at. % or higher Sm are amorphous and smooth. A giant tunable uniaxial in-plane magnetic anisotropy is induced in the films which peaks in the composition range 11–22 at. % Sm. This cross-over behavior is not due to changes in the atomic moments but rather the local configuration changes. The excellent layer perfection combined with highly tunable magnetic properties make these films important for spintronics applications.
|
|||
|
Show PACS
|
|||
|
|
Photoactive self-assembled monolayers for optically switchable organic thin-film transistors Appl. Phys. Lett. 102, 203301 (2013); http://dx.doi.org/10.1063/1.4804595 (4 pages) Online Publication Date: 20 May 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
We investigate the photoconductive and photovoltaic effects in organic thin-film transistors with thin hybrid dielectrics composed of aluminum oxide and self-assembled monolayers (SAMs). By using SAM molecules with an electro-optical functionality tuning of the photoinduced charge transfer at the interface of semiconductor and SAM upon illumination with laser light can be achieved. Control of the threshold voltage by the SAM composition enables the optical operation of the transistors without applying a gate voltage and affects the dynamics of photoinduced charge transfer.
|
||||
|
Show PACS
|
||||
|
|
Temperature-induced ductile-to-brittle transition of bulk metallic glasses Appl. Phys. Lett. 102, 171901 (2013); http://dx.doi.org/10.1063/1.4803170 (4 pages) Online Publication Date: 29 April 2013
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Uniaxial tensile and uniaxial compressive tests for Zr-based bulk metallic glasses (BMGs) were conducted at room and cryogenic temperatures, respectively. It was observed that both the change of macroscopic fracture mode from ductile shear fracture to brittle normal tensile fracture and microscopic fracture feature from micron-scaled vein patterns to nano-scaled dimples with decreasing test temperatures were identified, indicating a significant ductile-to-brittle transition (DBT) behavior. The mechanism of DBT behavior was revealed by the competition between the intrinsic critical shear strength τ0 and critical tensile strength σ0 at different temperatures.
|
|||
|
Show PACS
|
|||
|
|
Effect of dislocations on electron mobility in AlGaN/GaN and AlGaN/AlN/GaN heterostructures Appl. Phys. Lett. 101, 262102 (2012); http://dx.doi.org/10.1063/1.4773510 (4 pages) Online Publication Date: 26 December 2012
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||
|
Show Abstract
AlxGa1−xN/GaN (x = 0.06, 0.12, 0.24) and AlGaN/AlN/GaN heterostructures were grown on 6 H-SiC, GaN-on-sapphire, and free-standing GaN, resulting in heterostructures with threading dislocation densities of ∼2 × 1010, ∼5 × 108, and ∼5 × 107 cm−2, respectively. All growths were performed under Ga-rich conditions by plasma-assisted molecular beam epitaxy. Dominant scattering mechanisms with variations in threading dislocation density and sheet concentration were indicated through temperature-dependent Hall measurements. The inclusion of an AlN interlayer was also considered. Dislocation scattering contributed to reduced mobility in these heterostructures, especially when sheet concentration was low or when an AlN interlayer was present.
|
||||||||||||||
|
Show PACS
|
||||||||||||||
This Publication
Scitation
Google Scholar
PubMed