Jump to Content
View Cart
Top 20 Most Read Articles
May 2009
The 20 articles with the most full-text downloads during the month, in descending order.
 |
A metallic graphene layer adsorbed with lithium Appl. Phys. Lett. 94, 163115 (2009); http://dx.doi.org/10.1063/1.3126008 (3 pages) Online Publication Date: 24 April 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We found, by density functional calculation, that lithium atoms can be bonded to a graphene layer alternately on both sides by distorting the relative positions of the carbon atoms in the honeycomb lattice. Compared to the recently synthesized graphane by hydrogenation in which each carbon is pulled out of the plane by hydrogen, the carbon is pushed off instead by the attached lithium. And, surprisingly, the counterintuitive structure is a conductor. This should give consequences to its application in lithium storage.
|
|||
|
Show PACS
|
|||
|
|
Resonant spin-filtering in cobalt decorated nanotubes Appl. Phys. Lett. 94, 173103 (2009); http://dx.doi.org/10.1063/1.3120553 (3 pages) Online Publication Date: 28 April 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We study by means of first-principles calculations within the Landauer formalism the transport properties of carbon nanotubes filled with cobalt clusters. We show that in the limit of small cluster sizes, a significant spin polarization of the incoming π−π∗ wave packets can be obtained on a large energy range around the Fermi level. However, in the limit of increasing cluster size, both the spin polarization and total conductance decrease dramatically, suggesting that strategies to limit the diffusion of magnetic adatoms must be found for applications in spintronics.
|
|||
|
Show PACS
|
|||
|
|
Buckling beam micromechanical memory with on-chip readout Appl. Phys. Lett. 94, 183501 (2009); http://dx.doi.org/10.1063/1.3129195 (3 pages) Online Publication Date: 4 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We have used double clamped beams to implement a mechanical memory. Compressive stress is generated by resistive heating of the beams and beyond the buckling limit the bistable regime is accessed. Bits are written by applying lateral electrostatic forces. The state of the beam is read out by measuring the capacitance between beam and electrodes. Two ways to implement a mechanical memory are discussed: compensation of initial beam imperfections and snap through of the postbuckled beam. Although significant relaxation effects are observed, both methods prove reliable over thousands of write cycles.
|
|||
|
Show PACS
|
|||
|
|
Electroluminescent measurement of the internal quantum efficiency of light emitting diodes Appl. Phys. Lett. 94, 181102 (2009); http://dx.doi.org/10.1063/1.3129866 (3 pages) Online Publication Date: 5 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
An experimental method is demonstrated for the determination of internal quantum efficiency (IQE) in III-nitride-based light-emitting diodes (LEDs). LED devices surrounded with an optically absorbing material have been fabricated to limit collected light to photons emitted directly from the quantum wells across a known fraction of the recombination area. The emission pattern for this device configuration was modeled to estimate the extraction efficiency. IQE can then be calculated from the measured input current and output power. This method was applied to c-plane InxGa1−xN-based LEDs emitting at 445 nm. Initial measurements estimate an IQE of 43%±1% at a current density of 7.9 A/cm2.
|
|||
|
Show PACS
|
|||
|
|
Appl. Phys. Lett. 94, 203301 (2009); http://dx.doi.org/10.1063/1.3133902 (3 pages) Online Publication Date: 18 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
We demonstrate low-voltage, solution-processed organic transistors on rough plastic substrates with a carrier mobility over 0.2 cm2/V s, a turn-on voltage of near 0 V, and a record low subthreshold slope of ∼ 80 mV/decade in ambient conditions. These exceptional characteristics are attributed to (1) a device stacking architecture with a conducting polymeric gate and a double layered dielectric composed of low-temperature cross-linked poly(4-vinylphenol), (2) a low interface trap density achieved by modifying the dielectric surface with a phenyl-terminated self-assembled monolayer from 4-phenylbutyltrichlorosilane, and (3) controlled crystallization of a small-molecule organic semiconductor film with favorable charge transport microstructure and a low bulk trap density as deposited by an optimized solution-shearing process. The device performance under different operating voltages was also examined and discussed.
|
||||
|
Show PACS
|
||||
|
|
Appl. Phys. Lett. 94, 191102 (2009); http://dx.doi.org/10.1063/1.3133348 (3 pages) Online Publication Date: 11 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
A single-junction germanium solar cell with a photonic crystal nanostructured surface has been developed. The solar cell comprises a Ge p-n junction and an InGaP window layer. The InGaP window layer has been nanopatterned with an extended photonic crystal structure consisting on a triangular lattice of holes with submicronic sizes. Enhancements of the external quantum efficiency of 22% for a wide range of wavelengths and up to a 46% for specific wavelengths have been measured, which implies an increase in photocurrent between 11% and 22%. A clear correlation with the area of photonic crystal patterned has been observed.
|
|||
|
Show PACS
|
|||
|
|
Appl. Phys. Lett. 94, 171109 (2009); http://dx.doi.org/10.1063/1.3126062 (3 pages) Online Publication Date: 29 April 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||
|
Show Abstract
We demonstrate that films of very lossy metal or dielectric, with a thickness of only a few nanometers, can absorb almost all incident radiation when illuminated from the substrate side at the critical angle for total internal reflection. The absorption for s-polarized light approaches 100%, while the absorption for p-polarized light vanishes. We demonstrate this effect by measuring the absorption as a function of the angle of incidence at a wavelength of 775 nm in a 4.5 nm thick NbN film with a dielectric constant ϵNbN = −8.2+31.4i. The measured absorption in this film reaches a maximum of 94%. We discuss the design of a near-unity efficiency single-photon detector for s-polarized light that has a broadband absorption coefficient of >90% for wavelengths from 700 to 1600 nm.
|
||||||||||||
|
Show PACS
|
||||||||||||
|
|
Organic/inorganic hybrid solar cells with vertically oriented ZnO nanowires Appl. Phys. Lett. 94, 173107 (2009); http://dx.doi.org/10.1063/1.3126955 (3 pages) Online Publication Date: 28 April 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||
|
Show Abstract
Hybrid photovoltaic (PV) devices based on copper-phthalocyanine and fullerene combined with ZnO nanowire array as direct charge transport paths were fabricated. The optimized device with ZnO nanowire has a more than fourfold increase in PV performance than the device without nanowire. The former has an open circuit voltage of 0.46 V, a short circuit current of 3.86 mA/cm2, a fill factor of 0.30, and a power conversion efficiency of 0.53%. The hybrid device based on ZnO nanowires with improved PV performance suggests a way for fabrication of PV device with more exciton dissociation interface area and continuous carrier transport paths.
|
||||||||||||||
|
Show PACS
|
||||||||||||||
|
|
Toward photonic crystal based spatial filters with wide angle ranges of total transmission Appl. Phys. Lett. 94, 181101 (2009); http://dx.doi.org/10.1063/1.3127443 (3 pages) Online Publication Date: 5 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Spatial filters with steep switching between wide ranges of total transmission and total reflection can be obtained by using two-dimensional dielectric photonic crystals, which are a few wavelengths thick. The guidelines for engineering bandpass and bandstop filters are given. The flatness of isofrequency contours that are localized around a periphery point of the first Brillouin zone is a necessary but insufficient condition for the existence of wide angle ranges of total transmission at intermediate and large angles of incidence. Such ranges that are wider than 20° are demonstrated.
|
|||
|
Show PACS
|
|||
|
|
Appl. Phys. Lett. 94, 191103 (2009); http://dx.doi.org/10.1063/1.3133358 (3 pages) Online Publication Date: 11 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
UV response of ZnO nanowire nanosensor has been studied under ambient condition. By utilizing Schottky contact instead of Ohmic contact in device fabrication, the UV sensitivity of the nanosensor has been improved by four orders of magnitude, and the reset time has been drastically reduced from ∼ 417 to ∼ 0.8 s. By further surface functionalization with function polymers, the reset time has been reduced to ∼ 20 ms even without correcting the electronic response of the measurement system. These results demonstrate an effective approach for building high response and fast reset UV detectors.
|
|||
|
Show PACS
|
|||
|
|
Effect of illumination intensity and temperature on open circuit voltage in organic solar cells Appl. Phys. Lett. 94, 183505 (2009); http://dx.doi.org/10.1063/1.3129194 (3 pages) Online Publication Date: 6 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
The effect of illumination intensity and temperature on open circuit voltage (Voc) in organic photovoltaic devices has been investigated. Voc is observed to saturate at high illumination intensities. The illuminated J-V characteristics at different intensities intersect the dark characteristic at a single point. This intersection point is shown to be equal to the built-in voltage (Vbi) in the sample. A reduction in temperature shows increment in saturated Voc. This increment in saturated Voc is attributed to the variation of Vbi with temperature. A model has been presented that explains the observed behavior of Vbi at different temperatures.
|
|||
|
Show PACS
|
|||
|
|
The grain boundary related p-type conductivity in ZnO films prepared by ultrasonic spray pyrolysis Appl. Phys. Lett. 94, 192101 (2009); http://dx.doi.org/10.1063/1.3134486 (3 pages) Online Publication Date: 11 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Intrinsic p-type ZnO thin film was fabricated on sapphire substrate by ultrasonic spray pyrolysis, the p-type ZnO film is achieved using O2 as the carrier gas, with a resistivity of 2.18 Ω cm−1, a carrier concentration of 1.10×1016 cm−3, and a high Hall mobility of 261 cm2/V s. The scanning capacitance microscopy images and annealing the p-type ZnO indicate that the absorbed oxygen in the grain boundary (GB) aroused the p-type conductivity, and the high Hall mobility of the p-type ZnO film own to the quasi-two-dimensional hole gas, which was induced by the negatively charged interface states in the GBs.
|
|||
|
Show PACS
|
|||
|
|
Appl. Phys. Lett. 94, 183301 (2009); http://dx.doi.org/10.1063/1.3124660 (3 pages) Online Publication Date: 5 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
High field-effect mobility organic thin-film transistors with nanoparticle polymer composite/polymer bilayer insulators were fabricated. A device composed of a polyvinylphenol (PVP) insulator filled with barium strontium titanate (BST) nanoparticles and coated with a thin polystyrene film was found to exhibit a field-effect mobility (1.2 cm2 V−1 s−1 for a pentacene device) and a field-induced current that are superior to those of devices with only a PVP insulator or a BST-filled PVP insulator. These improvements in the performance are due to an increase in the capacitance and a reduction in the interface roughness of the insulator.
|
|||
|
Show PACS
|
|||
|
|
Enhancement of light absorption in a quantum well by surface plasmon polariton Appl. Phys. Lett. 94, 191106 (2009); http://dx.doi.org/10.1063/1.3137186 (3 pages) Online Publication Date: 14 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We investigate analytically the degree to which the absorption of light in a single quantum well can be enhanced in the proximity of a structured metallic surface and show that the wavelength at which the maximum enhancement of about one order of magnitude is attained depends on metal loss and the initial absorption in a quantum well.
|
|||
|
Show PACS
|
|||
|
|
Resistive switching in nanostructured thin films Appl. Phys. Lett. 94, 202107 (2009); http://dx.doi.org/10.1063/1.3134484 (3 pages) Online Publication Date: 20 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
Planar capacitor structures based on granular films composed of nanometric ferromagnetic grains embedded in an insulating Al2O3 matrix can switch between a high-conductance and a low-conductance state. The switching properties are induced by a forming process. The ON/OFF resistance ratio is as high as 104 under an electrical field of only 15 kV/m. This resistive switching is accompanied by a capacitive switching between two well-defined voltage-independent states, a behavior that is not readily explained by the filamentary type of conduction.
|
||||
|
Show PACS
|
||||
|
|
Many-body effects on terahertz quantum well detectors Appl. Phys. Lett. 94, 201101 (2009); http://dx.doi.org/10.1063/1.3134485 (3 pages) Online Publication Date: 19 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Many-body effects have been investigated in the design of terahertz quantum well photon detectors. A large discrepancy between the theoretical and experimental photoresponse peak positions exist without considering the many-body interactions. The calculated results agree with the experimental data quantitatively with including the exchange-correlation and depolarization effects within the local density approximation. Our numerical results show that it is a must to consider the many-body interactions for designing the quantum well detectors for the terahertz region.
|
|||
|
Show PACS
|
|||
|
|
Auger recombination rates in nitrides from first principles Appl. Phys. Lett. 94, 191109 (2009); http://dx.doi.org/10.1063/1.3133359 (3 pages) Online Publication Date: 15 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We report Auger recombination rates for wurtzite InGaN calculated from first-principles density-functional and many-body-perturbation theory. Two different mechanisms are examined—inter- and intra-band recombination—that affect different parts of the emission spectrum. In the blue to green spectral region and at room temperature the Auger coefficient can be as large as 2×10−30 cm6 s−1; in the infrared it is even larger. Since Auger recombination scales with the cubic power of the free-carrier concentration it becomes an important nonradiative loss mechanism at high current densities. Our results indicate that Auger recombination may be responsible for the loss of quantum efficiency that affects InGaN-based light emitters.
|
|||
|
Show PACS
|
|||
|
|
Appl. Phys. Lett. 94, 193302 (2009); http://dx.doi.org/10.1063/1.3134490 (3 pages) Online Publication Date: 12 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
We report all-polymer solar cells (PSCs) based on a polymer blend of poly[3-(10-n-octyl-3-phenothiazine-vinylene)thiophene-co-2,5-thiophene] as donor and poly[1,4-dioctyloxyl-p-2,5-dicyanophenylenevinylene] as acceptor. Strong photoluminescence quenching is observed in the polymer blend indicating the photoinduced charge transfer occurs between the two polymers. The power conversion efficiency of the PSC was improved from 0.41% to 0.8% after 120 °C postannealing, under the illumination of AM 1.5, 100 mW/cm2. We attribute the improved efficiency to better morphological features of the photoactive layer after thermal annealing.
|
||||
|
Show PACS
|
||||
|
|
Graphene nanoribbon as a negative differential resistance device Appl. Phys. Lett. 94, 173110 (2009); http://dx.doi.org/10.1063/1.3126451 (3 pages) Online Publication Date: 29 April 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We present a theoretical study on electronic structure and elastic transport properties of armchair graphene nanoribbon based junctions by using density functional theory calculations and nonequilibrium Green’s function technique. The I-V characteristics of various junctions are examined, which all exhibit robust negative differential resistance (NDR) phenomena. It is found that such NDR behaviors originate from the interaction between the narrow density of states of the doped leads and the discrete states in the scattering region.
|
|||
|
Show PACS
|
|||
|
|
Surface plasmon resonances of optical antenna atomic force microscope tips Appl. Phys. Lett. 94, 171107 (2009); http://dx.doi.org/10.1063/1.3116145 (3 pages) Online Publication Date: 29 April 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
A method for fabricating optical antennas on atomic force microscope probes using focused ion beam modification is described. We numerically demonstrate that these optical antenna probes provide a large near field intensity enhancement when illuminated at their resonant wavelengths. We experimentally measure the plasmon resonant wavelengths of probes with various lengths. Both simulation and experiment indicate that the resonant wavelength redshifts with increasing antenna length. We anticipate that the optical antenna tips could be used for mapping the field distributions of nanophotonic devices or for high spatial resolution spectroscopy.
|
|||
|
Show PACS
|
|||
This Publication
Scitation
Google Scholar
PubMed