Jump to Content
View Cart
Top 20 Most Read Articles
October 2009
The 20 articles with the most full-text downloads during the month, in descending order.
 |
Appl. Phys. Lett. 95, 013107 (2009); http://dx.doi.org/10.1063/1.3167775 (3 pages) Online Publication Date: 7 July 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
A direct transfer method for fabricating flexible electronics without the assistance of an adhesive layer and stamp is reported in this paper. This rapid and simple method provides an approach for the application of vertically aligned carbon nanotubes (VA-CNTs) on plastic substrates. After transfer, the VA-CNTs maintained their initial orientation in the designed pattern and showed sufficient adhesion to the substrate under extreme bending conditions. The flexible device performed an emission on the transparent substrate and showed a low turn-on of 1.13 V/μm. This VA-CNT-based flexible device, which exhibits electrical resistance sensitive to bending, is also described herein.
|
|||
|
Show PACS
|
|||
|
|
Nanosecond switching in GeTe phase change memory cells Appl. Phys. Lett. 95, 043108 (2009); http://dx.doi.org/10.1063/1.3191670 (3 pages) Online Publication Date: 28 July 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
The electrical switching behavior of GeTe-based phase change memory devices is characterized by time resolved experiments. SET pulses with a duration of less than 16 ns are shown to crystallize the material. Depending on the resistance of the RESET state, the minimum SET pulse duration can even be reduced down to 1 ns. This finding is attributed to the increasing impact of crystal growth upon decreasing switchable volume. Using GeTe or materials with similar crystal growth velocities, hence promises nonvolatile phase change memories with dynamic random access memorylike switching speeds.
|
||||
|
Show PACS
|
||||
|
|
Nonvolatile memory with switching interfacial polar structures of nano Si-in-mesoporous silica Appl. Phys. Lett. 95, 143501 (2009); http://dx.doi.org/10.1063/1.3240888 (3 pages) Online Publication Date: 5 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We show an artificially engineered electret with Si nanocrystals embedded in mesoporous silica for nonvolatile memory. We attribute the polarization to from polar layers lying at the interfaces between one-side bonded Si nanocrystals and mesoporous silica matrix. Under external field, the Si nanocrystals could be displaced in the porechannels causing displaced charge distributions and therefore a field-controllable electric polarization. Nonvolatile memory is demonstrated with a metal-oxide-semiconductor field-effect transistor.
|
|||
|
Show PACS
|
|||
|
|
Self-assembled bioinspired quantum dots: Optical properties Appl. Phys. Lett. 94, 261907 (2009); http://dx.doi.org/10.1063/1.3167354 (3 pages) Online Publication Date: 2 July 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Until now, the wide research field of quantum dots (QDs) focused on inorganic structures. In the present study, we report on quantum confinement phenomena found in peptide nanocrystalline regions formed within self-assembly peptide nanospheres. These bioinspired nanostructures exhibit the optical absorption characteristics of QDs with pronounced luminescence of excitons whose origin is at the UV region. Theoretical estimations based on experimental data show that the radius of the self assembled peptide QDs is 1.3 nm.
|
|||
|
Show PACS
|
|||
|
|
Impact dynamics of water droplets on chemically modified WOx nanowire arrays Appl. Phys. Lett. 95, 153101 (2009); http://dx.doi.org/10.1063/1.3244597 (3 pages) Online Publication Date: 12 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
The effects of surface energy on the wetting transition for impinging water droplets were investigated on the chemically modified WOx nanowire surfaces. We could modify the surface energy of the nanowires through chemisorption of alkyltrichlorosilanes with various carbon chain lengths and also by the ultraviolet-enhanced decomposition of self assembled monolayer molecules. Three surface wetting states could be identified through the balance between antiwetting and wetting pressures. This approach establishes a simple strategy for design of the water-repellent surface to impinging droplets.
|
|||
|
Show PACS
|
|||
|
|
Optical black hole: Broadband omnidirectional light absorber Appl. Phys. Lett. 95, 041106 (2009); http://dx.doi.org/10.1063/1.3184594 (3 pages) Online Publication Date: 27 July 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||
|
Show Abstract
We develop an approach to broad-band omnidirectional light absorption, based on light propagation in a metamaterial structure forming an effective “black hole.” The proposed system does not rely on magnetic response, is nonresonant, and can be fabricated from existing materials.
|
||||
|
Show PACS
|
||||
|
|
A multispectral and polarization-selective surface-plasmon resonant midinfrared detector Appl. Phys. Lett. 95, 161101 (2009); http://dx.doi.org/10.1063/1.3244204 (3 pages) Online Publication Date: 19 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We demonstrate a multispectral polarization sensitive midinfrared dots-in-a-well photodetector utilizing surface-plasmonic resonant elements, with tailorable frequency response and polarization selectivity. The resonant responsivity of the surface-plasmon detector shows an enhancement of up to five times that of an unpatterned control detector. As the plasmonic resonator involves only surface patterning of the top metal contact, this method is independent of light-absorbing material and can easily be integrated with current focal plane array processing for imaging applications.
|
|||
|
Show PACS
|
|||
|
|
Appl. Phys. Lett. 95, 163302 (2009); http://dx.doi.org/10.1063/1.3243986 (3 pages) Online Publication Date: 19 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We evaluate practical power conversion efficiency limits (ηlim) in bulk-heterojunction organic photovoltaic (BHJ OPV) cells and how the field dependence of exciton dissociation affects cell efficiencies. We treat the fill factor limit as a function of the donor-acceptor lowest unoccupied molecular orbital offset energy (ELLO), calculating how this limit varies with decreasing ELLO. We also evaluate OPV external quantum efficiency as a function of wavelength from the optical transmittance and internal quantum efficiency limitations. For a given ELLO, we numerically optimize donor bandgap and ηlim and show that ηlim>10% should be possible for hypothetical OPV systems generating free charge carriers efficiently at ELLO ∼ 0.3–0.4 eV. Current BHJ OPVs with low ELLO values appear to be limited to cell efficiencies of ∼ 5% largely as a consequence of incomplete exciton dissociation.
|
|||
|
Show PACS
|
|||
|
|
Engineering of low-loss metal for nanoplasmonic and metamaterials applications Appl. Phys. Lett. 95, 151102 (2009); http://dx.doi.org/10.1063/1.3237179 (3 pages) Online Publication Date: 12 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We have shown that alloying a noble metal (gold) with another metal (cadmium), which can contribute two electrons per atom to a free electron gas, can significantly improve the metal’s optical properties in certain wavelength ranges and make them worse in the other parts of the spectrum. In particular, in the gold-cadmium alloy we have demonstrated a significant expansion of the spectral range of metallic reflectance to shorter wavelengths. The experimental results and the predictions of the first principles theory demonstrate an opportunity for the improvement and optimization of low-loss metals for nanoplasmonic and metamaterials applications.
|
|||
|
Show PACS
|
|||
|
|
Appl. Phys. Lett. 95, 133303 (2009); http://dx.doi.org/10.1063/1.3242006 (3 pages) Online Publication Date: 1 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||
|
Show Abstract
This work presents an approach for improving the unfavorable vertical composition gradients of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in the photoactive layer of bulk heterojunction solar cells. The proposed method involves simply depositing a thin layer of P3HT on top of poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) prior to the P3HT:PCBM blend is spin coated. The results from photoluminescence and photovoltaic measurements indicate that incorporating this P3HT layer significantly enhances the electron blocking ability of PEDOT:PSS, the efficiency of photoinduced electron transfer and the photocurrent of the device, resulting in an improvement of the power conversion efficiency from 3.98% to 5.05%.
|
||||||||||||||
|
Show PACS
|
||||||||||||||
|
|
Carrier distribution in InGaN/GaN tricolor multiple quantum well light emitting diodes Appl. Phys. Lett. 95, 151103 (2009); http://dx.doi.org/10.1063/1.3244203 (3 pages) Online Publication Date: 12 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Carrier transport in InGaN light emitting diodes has been studied by comparing the electroluminescence (EL) from a set of triple quantum well structures with different indium content in each well, leading to multicolor emission. Both the sequence and width of the quantum wells have been varied. Comparison of the EL spectra reveals the current dependent carrier transport between the quantum wells, with a net carrier flow toward the deepest quantum well.
|
|||
|
Show PACS
|
|||
|
|
Appl. Phys. Lett. 86, 121113 (2005); http://dx.doi.org/10.1063/1.1883714 (3 pages) Online Publication Date: 16 March 2005
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We have developed ultrabroadband multiplex coherent anti-Stokes Raman scattering (CARS) microspectroscopy using a coherent supercontinuum in the near-infrared region generated from a photonic crystal fiber. Owing to the ultrabroadband Stokes radiation obtained from the supercontinuum, multiple vibrational modes can be excited simultaneously in the wave-number range of more than 2500 cm−1. A CARS imaging of a lipid vesicle is demonstrated with a high vibrational contrast.
|
|||
|
Show PACS
|
|||
|
|
Ferromagnetic Sc-doped AlN sixfold-symmetrical hierarchical nanostructures Appl. Phys. Lett. 95, 162501 (2009); http://dx.doi.org/10.1063/1.3248257 (3 pages) Online Publication Date: 19 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||
|
Show Abstract
Sc-doped AlN (AlN:Sc) sixfold-symmetrical hierarchical nanostructures were grown by direct current (dc) arc discharge plasma method using the direct reaction of Al and Sc metals with N2 gas. Energy-dispersive x-ray spectroscopy, x-ray diffractometry, and Raman spectra analysis clearly showed that Sc was doped in the AlN hierarchical nanostructures. The magnetization curves indicate the existence of room-temperature ferromagnetic behavior. The saturation magnetization and the coercive fields (Hc) of the AlN:Sc nanostructures are about 0.04 emu g−1 and 200 Oe, respectively. The results reveal that Sc is a potential nonmagnetic dopant for preparing diluted magnetic semiconductor nanomaterials.
|
||||||||||||||
|
Show PACS
|
||||||||||||||
|
|
Emission modification of CdSe quantum dots by titanium dioxide visible logpile photonic crystal Appl. Phys. Lett. 95, 151101 (2009); http://dx.doi.org/10.1063/1.3245309 (3 pages) Online Publication Date: 12 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Air band modes of three-dimensional photonic crystals (3DPCs) have a higher photonic density of states, potentially enabling greater emission enhancement. However, it is challenging to introduce emitters into the “air” region without significantly disturbing the photonic band structure of the PC. Here, we overcome this difficulty by introducing a low refractive index aerogel matrix containing CdSe quantum dots (625 nm peak emission) into a titanium dioxide logpile PC. We observe that the aerogel infiltration indeed preserves the bandstructure. We measure an emission suppression of ∼ 0.25 times inside and an enhancement of approximately three times outside the bandgap with only one vertical unit cell.
|
|||
|
Show PACS
|
|||
|
|
Electric field-dependent charge transport in organic semiconductors Appl. Phys. Lett. 95, 153301 (2009); http://dx.doi.org/10.1063/1.3246160 (3 pages) Online Publication Date: 13 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
An analytical description is elaborated for the variable range hopping conduction mechanism in the presence of temperature and electric fields for quasi-three-dimensional organic semiconductor systems. In the proposed description, it is assumed that the localized states are randomly distributed in energy and space coordinates. The expression for the hopping conductivity is obtained for the Gaussian density of states. The model is applied to the analysis of both temperature and electric field-dependent hopping transport in organic semiconductors. It is shown that the Poole–Frenkel behavior is only valid in medium electric field regime. Moreover, we conclude that the electric field determines whether the temperature dependence of conductivity in organic semiconductors obeys the Arrhenius law.
|
|||
|
Show PACS
|
|||
|
|
Ultraviolet emission from a ZnO rod homojunction light-emitting diode Appl. Phys. Lett. 95, 133124 (2009); http://dx.doi.org/10.1063/1.3243453 (3 pages) Online Publication Date: 2 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||||
|
Show Abstract
Ultraviolet electroluminescence was demonstrated at room temperature from a ZnO rod homojunction light-emitting diode array. The p-type doping was realized by phosphorous (P) ion implantation into defect-free ZnO rods followed by annealing. High resolution transmission electron microscopy shows the lattice compression of annealed single crystalline P-doped ZnO rod compared to the as-grown ZnO rod, suggesting atomically incorporation of P into the ZnO wurtzite structure. p-type doping was confirmed by low temperature photoluminescence spectra and single rod current-voltage characterization.
|
||||||||||||||||
|
Show PACS
|
||||||||||||||||
|
|
Appl. Phys. Lett. 95, 131107 (2009); http://dx.doi.org/10.1063/1.3236752 (3 pages) Online Publication Date: 29 September 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
We demonstrate electrically pumped laser light emission in the visible (red) spectral range using self-assembled InP quantum dots embedded in a microcavity mesa realized by monolithically grown high-reflectivity AlGaAs distributed Bragg reflectors. We used common semiconductor laser processing steps to fabricate stand-alone index-guided vertical-cavity surface-emitting lasers with oxide apertures for optical wave-guiding and electrical current constriction. Ultra-low threshold of around 10 A/cm2 and room temperature lasing were demonstrated. Additionally, the temperature independence of the threshold current, which was predicted in theory for quantum dot lasers, is displayed.
|
|||
|
Show PACS
|
|||
|
|
Appl. Phys. Lett. 95, 131102 (2009); http://dx.doi.org/10.1063/1.3236776 (3 pages) Online Publication Date: 28 September 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||||||||||||
|
Show Abstract
Pulsed infrared photocurrent spectroscopy is used to investigate deep levels in highly resistive metal organic chemical vapor deposition-grown, magnesium-doped aluminum gallium nitride metal-semiconductor-metal test structures in the range of aluminum fraction from x = 0.0 to x = 0.52. Some background level of photocurrent is observed at all infrared pump wavelengths between 1.35 and 4.0 μm. The photocurrent decay time is a decreasing function of aluminum fraction. A peak photocurrent energy is observed for each aluminum fraction. With increasing aluminum fraction, the peak blueshifts and narrows.
|
||||||||||||||||||||||||
|
Show PACS
|
||||||||||||||||||||||||
|
|
Appl. Phys. Lett. 95, 143102 (2009); http://dx.doi.org/10.1063/1.3240403 (3 pages) Online Publication Date: 5 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
The authors report a simple site selective growth for producing interconnecting suspended graphene on SiO2/Si substrate. The outcome of the process depends on the thickness of the catalyst (Ni) and process ambient on SiO2/Si wafer by low pressure fast heating chemical-vapor deposition at 820 °C for periods from 30 s to 10 min. Raman spectroscopy revealed that the graphene grown on the substrate consists of from 1 to <20 layers, with the number of layers depending on the thickness of the catalyst (Ni). Also, the thickness of Ni catalyst determines whether the graphite layers (GLs) are grown in a suspended form or adhered to the substrate. The possibility of producing qualified as-grown GL supported on a wafer without further processing, such as transferring to another substrate, should contribute to further scientific research and development of graphene.
|
|||
|
Show PACS
|
|||
|
|
Impact of dye interlayer on the performance of organic photovoltaic devices Appl. Phys. Lett. 95, 153303 (2009); http://dx.doi.org/10.1063/1.3243991 (3 pages) Online Publication Date: 13 October 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
The influences of buffer interlayer at the donor/acceptor interface on the open circuit voltage (VOC) of typical copper phthalocyanine (CuPc)/C60 organic photovoltaic devices are studied. Six fluorescent dyes with progressively increasing ionization potentials (IP) were used to investigate the factors influencing the VOC. The short-circuit current and fill factor of CuPc/C60 device incorporating dye interlayer are lower than those of standard bilayer device. On the other hand, the VOC increases linearly with the IP of dye material and falls off when the IP is equal to or greater than 5.6 eV, in which the energy offset between the highest occupied molecular orbitals at the interlayer/C60 heterojunction is smaller than the C60 exciton binding energy. The findings underscore the importance of energy offsets in photovoltaic responses.
|
|||
|
Show PACS
|
|||
This Publication
Scitation
Google Scholar
PubMed