APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

19 May 2008

Volume 92, Issue 20, Articles (20xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 92, 202101 (2008); http://dx.doi.org/10.1063/1.2927379 (3 pages)

Jasmin Aghassi, Matthias H. Hettler, and Gerd Schön
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds

Built-in electric field and large Stokes shift in near-lattice-matched GaN/AlInN quantum wells

G. Franssen, T. Suski, M. Kryśko, A. Khachapuridze, R. Kudrawiec, J. Misiewicz, A. Kamińska, E. Feltin, and N. Grandjean

Appl. Phys. Lett. 92, 201901 (2008); http://dx.doi.org/10.1063/1.2929382 (3 pages) | Cited 6 times

Online Publication Date: 19 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Near-lattice-matched GaN/AlInN quantum wells are investigated by means of contactless electroreflectance (CER) and temperature-dependent photoluminescence (PL). Large Stokes shifts, up to 400 meV, between PL peak energies and CER resonances are identified. This Stokes shift is attributed to large potential profile fluctuations (PPFs) in the AlInN barriers. Further evidence for such PPFs and for the additional influence of QW width fluctuations is provided by temperature-dependent PL measurements, demonstrating large PL halfwidths and clear “S-shape” behavior. The influence of a large Stokes shift on the correct determination of the value of the built-in electric field is discussed, and it is shown that PL measurements may lead to a significant overestimation of the built-in electric field in GaN/AlInN QWs.
Show PACS
78.67.De Quantum wells
78.55.Cr III-V semiconductors
78.20.Jq Electro-optical effects

Nonlinear optical properties of Au nanoparticles colloidal system: Local and nonlocal responses

Rogério F. Souza, Márcio A. R. C. Alencar, Eid C. da Silva, Mario R. Meneghetti, and Jandir M. Hickmann

Appl. Phys. Lett. 92, 201902 (2008); http://dx.doi.org/10.1063/1.2929385 (3 pages) | Cited 18 times

Online Publication Date: 19 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Z-scan revealed thermal and electronic contributions for the nonlinear refractive index of highly stable colloid containing different concentrations of gold nanoparticles. Large enhancement factors were observed for values of n2 and dn/dT of the colloid, due to the presence of the nanoparticles. Our results suggest that thermal effects will play an important role in the development of photonic applications involving nanostructured materials and in the investigation of nonlocal nonlinear phenomena.
Show PACS
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
42.65.-k Nonlinear optics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
82.70.Dd Colloids
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Cubic metallic phase of aluminum hydride showing improved hydrogen desorption

R. H. Scheicher, D. Y. Kim, S. Lebègue, B. Arnaud, M. Alouani, and R. Ahuja

Appl. Phys. Lett. 92, 201903 (2008); http://dx.doi.org/10.1063/1.2931083 (3 pages) | Cited 9 times

Online Publication Date: 19 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on our results calculated from density functional theory and GW of the dehydrogenation properties in a cubic phase of AlH3. The metallic nature of the electronic structure entails a more favorable hydrogen removal energy which is lowered by 75% compared to the insulating hexagonal phase. This remarkable reduction in the Al–H bond strength bears important consequences for feasible applications of AlH3 as an on-board hydrogen storage material for mobile applications. We suggest that the cubic phase could be prepared and stabilized experimentally at ambient pressure by off-board quenching.
Show PACS
61.66.Fn Inorganic compounds
68.43.Nr Desorption kinetics
71.20.Ps Other inorganic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Measuring local lattice polarity in AlN and GaN by high resolution Z-contrast imaging: The case of (0001) and (1math00) GaN quantum dots

Jean-Luc Rouviere, Catherine Bougerol, Benoit Amstatt, Edith Bellet-Almaric, and Bruno Daudin

Appl. Phys. Lett. 92, 201904 (2008); http://dx.doi.org/10.1063/1.2917449 (3 pages) | Cited 7 times

Online Publication Date: 20 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
By using a probe Cs corrected transmission electron microscope, the local lattice polarity, i.e., the local stacking of atoms, in AlN and GaN is determined. The N atomic columns are not directly resolved, but determined from the tunnel positions of the structure. The method is first tested on GaN quantum dots grown on polar (0001) AlN surfaces. Then it is applied to GaN quantum dots grown on nonpolar (1math00) AlN surfaces. In the (11math0) plane, (1math00) GaN dots have an asymmetrical shape and grow faster along the +c = [0001] direction than along −c = [000math].
Show PACS
68.65.Hb Quantum dots (patterned in quantum wells)

Crystal structure and photoluminescence of Mn2+–Mg2+ codoped gamma aluminum oxynitride (γ-AlON): A promising green phosphor for white light-emitting diodes

Rong-Jun Xie, Naoto Hirosaki, Xue-Jian Liu, Takashi Takeda, and Hui-Li Li

Appl. Phys. Lett. 92, 201905 (2008); http://dx.doi.org/10.1063/1.2920190 (3 pages) | Cited 23 times

Online Publication Date: 20 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This letter reports on the crystal structure and luminescence of a green gamma aluminum oxynitride phosphor. This phosphor, codoped with Mn2+ and Mg2+, shows a single cubic spinel phase, with Mn2+ and Mg2+ substituting Al3+ in the tetrahedral sites. It shows a broad emission band centered at 520 nm and a full width at half maximum of 44 nm. The green phosphor exhibits a small thermal quenching and high internal quantum efficiency of 62% under the blue light irradiation, enabling it to be used in high color rendering white light-emitting diodes.
Show PACS
61.66.Fn Inorganic compounds
78.55.Hx Other solid inorganic materials
85.60.Jb Light-emitting devices

Radiative heat transfer between metallic nanoparticles

Pierre-Olivier Chapuis, Marine Laroche, Sebastian Volz, and Jean-Jacques Greffet

Appl. Phys. Lett. 92, 201906 (2008); http://dx.doi.org/10.1063/1.2931062 (3 pages) | Cited 10 times

Online Publication Date: 20 May 2008

Full Text: Read Online (HTML) | Download PDF


See Also: Erratum

Show Abstract
In this letter, we study the radiative heat transfer between two nanoparticles in the near and far fields. We find that the heat transfer is dominated by the electric dipole-dipole interaction for identical dielectric particles and by the magnetic dipole-dipole interaction for identical metallic nanoparticles. We introduce polarizability formulas valid for arbitrary values of the skin depth. While the heat transfer mechanism is different for metallic and dielectric nanoparticles, we show that the distance dependence is the same. However, the dependence of the heat flux on the particle radius is different.
Show PACS
75.30.Cr Saturation moments and magnetic susceptibilities
73.22.-f Electronic structure of nanoscale materials and related systems
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)

Anisotropic optical properties of free and bound excitons in highly strained A-plane ZnO investigated with polarized photoreflectance and photoluminescence spectroscopy

Yoon Sung Nam, Sang Wook Lee, K. S. Baek, S. K. Chang, Jae-Ho Song, Jung-Hoon Song, Seok Kyu Han, Soon-Ku Hong, and Takafumi Yao

Appl. Phys. Lett. 92, 201907 (2008); http://dx.doi.org/10.1063/1.2930683 (3 pages) | Cited 15 times

Online Publication Date: 21 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated the polarization dependence of the near-band-edge photoluminescence and photoreflectance spectra in nonpolar (A-plane) ZnO films under strong biaxial compressive strain. We show that anisotropic strain and the orientation of the nonpolar plane play an important role in determining the polarization selectivity and properties of excitonic transitions. We identified four distinct band-edge transitions at 3.449, 3.420, 3.386, and 3.326 eV. They were identified as E2 and E1 free excitons, E1 excitons bound to a donor, and free-electron-to-bound-hole transition, respectively. Unlike previously reported results on relatively thick nonpolar films, the E1 exciton (lowest energy) was mainly polarized to E⊥c and weakly polarized to E∥c under strong biaxial compressive strain in the 100 nm thick film. The E2 exciton (next higher energy) was exclusively polarized to E∥c. The localization energy of DX is 34 meV, which is much larger than that in polar ZnO, and the DX was not thermally delocalized even at room temperature.
Show PACS
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
78.55.Et II-VI semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Near optical isotropy in noncubic SrI2: Density functional calculations

D. J. Singh

Appl. Phys. Lett. 92, 201908 (2008); http://dx.doi.org/10.1063/1.2936079 (3 pages) | Cited 9 times

Online Publication Date: 22 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report calculations of the electronic structure and optical properties of orthorhombic SrI2. These were done using the Engel–Vosko generalized gradient approximation. We find that the dielectric function and refractive indices are almost isotropic in this noncubic material. This suggests that low cost nonconventional routes for producing SrI2-based scintillators may be practical and, in particular, that ceramic processing may be used.
Show PACS
71.20.Ps Other inorganic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.22.Ch Permittivity (dielectric function)
61.66.Fn Inorganic compounds

Crystal and defect chemistry influences on band gap trends in alkaline earth perovskites

Soonil Lee, William H. Woodford, and Clive A. Randall

Appl. Phys. Lett. 92, 201909 (2008); http://dx.doi.org/10.1063/1.2936091 (3 pages) | Cited 9 times

Online Publication Date: 22 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A number of perovskites with A-site alkaline earth chemistries being Ca, Sr, and Ba, and tetravalent cations including Ce, Zr, and Ti are measured for optical band gap and found to vary systematically with tolerance factor and lattice volume within limits defined by the chemistry of the octahedral site. This paper also focuses on the BaTiO3 system, considering equilibrated nonstoichiometries, and determines the changes in band gap with respect to Ba/Ti ratios. It was found that the optical band gap changes in the solid solution regime and is invariant in the second phase regions, as would be expected. In the cases of Ba/Ti<1.0, the variation in band gap scales with lattice volume, but in the Ba/Ti>1.0 stoichiometries, there is a distinct Urbach tail and the trend with lattice volume no longer holds. It is inferred that the VTi⁗−2VO•• partial Schottky complex controls the band gap trend with Ba-rich nonstoichiometries.
Show PACS
61.66.Fn Inorganic compounds
61.66.Bi Elemental solids
61.66.Dk Alloys
71.20.Ps Other inorganic compounds
78.40.Ha Other nonmetallic inorganics
77.80.-e Ferroelectricity and antiferroelectricity
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Cubic GaN/AlN multiple quantum well photodetector

E. A. DeCuir, Jr., M. O. Manasreh, Elena Tschumak, J. Schörmann, D. J. As, and K. Lischka

Appl. Phys. Lett. 92, 201910 (2008); http://dx.doi.org/10.1063/1.2936279 (3 pages) | Cited 8 times

Online Publication Date: 22 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Photodetectors based on intersubband transitions in molecular beam epitaxially grown cubic GaN/AlN multiple quantum wells were fabricated and tested. The presence of the intersubband transition was confirmed by using the optical absorption technique for structures with different well widths. Samples were polished into waveguide configuration on which the devices were fabricated. The photoresponse spectra were collected in the temperature range of 77–215 K under the influence of small bias voltages. All devices exhibit photovoltaic effect where the photoresponse is observed at zero bias voltage. Theoretical calculations of the intersubband transition were performed and found to be in agreement with the observed results.
Show PACS
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
42.82.Et Waveguides, couplers, and arrays
42.82.Bq Design and performance testing of integrated-optical systems

Thermodynamic trends in the uptake capacity of porous adsorbents on methane and hydrogen

Anutosh Chakraborty, Bidyut Baran Saha, Shigeru Koyama, Kim Choon Ng, and Seong-Ho Yoon

Appl. Phys. Lett. 92, 201911 (2008); http://dx.doi.org/10.1063/1.2918984 (3 pages) | Cited 1 time

Online Publication Date: 22 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A considerable progress has been made for the development of novel porous materials with controlled architectures and surface treatment. An important feature of these adsorbent materials is the maximization of adsorption capacity at Henry’s region. A thermodynamic framework is presented to capture the relationship between the pore specific surface areas with the enthalpy of adsorption. By using this approach, the scientific community can be guided to the development of advanced porous adsorbent and adsorbate pairs. The adsorbents with the highest porous surface areas tend to possess lower isosteric heat of adsorption when storing the methane and hydrogen gases at room temperature.
Show PACS
82.60.-s Chemical thermodynamics
68.35.Md Surface thermodynamics, surface energies
68.43.Mn Adsorption kinetics
81.65.-b Surface treatments
84.60.-h Direct energy conversion and storage

Moderate to large magneto-optical signals in high Tc double perovskites

Hena Das, Molly De Raychaudhury, and T. Saha-Dasgupta

Appl. Phys. Lett. 92, 201912 (2008); http://dx.doi.org/10.1063/1.2936304 (3 pages) | Cited 4 times

Online Publication Date: 22 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using first-principles density functional calculations, we have computed the optical and magneto-optical properties of the Cr-based double perovskite compounds, Sr2CrB′O6 with B′ = W,Re,Os. Our computed magneto-optic spectra show substantially large Kerr rotations of about −2° to −2.5° for Sr2CrWO6 and Sr2CrReO6 and a moderately large Faraday rotation of about −0.25×106 deg/cm in insulating Sr2CrOsO6, indicating possible industrial applications. Our study should motivate experimental investigations in this yet to be explored area of Sr2CrB′O6 compounds.
Show PACS
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.70.-b Superconducting materials other than cuprates
78.20.Ls Magneto-optical effects
71.15.-m Methods of electronic structure calculations
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
74.25.Gz Optical properties

Icosahedral ordering in Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass

X. Hui, H. Z. Fang, G. L. Chen, S. L. Shang, Y. Wang, and Z. K. Liu

Appl. Phys. Lett. 92, 201913 (2008); http://dx.doi.org/10.1063/1.2931702 (3 pages) | Cited 14 times

Online Publication Date: 22 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This paper presents a computational evidence of icosahedral short and medium range ordering in Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass using ab initio molecular dynamics simulation. It is found that 1551, 1541, and 1431 types of bond pairs are pronounced in both the liquid and glass states, resulting in icosahedral coordinate polyhedra at low temperatures. By linking the individual icosahedra through vertex-, edge-, face-, and intercross-shared atoms, icosahedral medium range ordering is formed. The predicted homogenized structure factor and pair correlation function of the glass structure have been confirmed to be in agreement with the experimental results.
Show PACS
61.43.Fs Glasses
61.43.Bn Structural modeling: serial-addition models, computer simulation
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations

Excitation and photoluminescence of pure and Si-doped β-Ga2O3 single crystals

Kiyoshi Shimamura, Encarnación G. Víllora, Takekazu Ujiie, and Kazuo Aoki

Appl. Phys. Lett. 92, 201914 (2008); http://dx.doi.org/10.1063/1.2910768 (3 pages) | Cited 18 times

Online Publication Date: 23 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Excitation and photoluminescence spectra of high purity and Si-doped β-Ga2O3 single crystals are investigated. Emission peaks in the UV and blue wavelength regions are observed. These are excited at two bands, which can be differentiated by polarized light. The features of the spectra are independent of excitation and emission wavelengths in the case of an undoped sample. On the contrary, after Si doping, the blue emission becomes strongly dependent. A model to interpret the characteristics of blue luminescence is proposed.
Show PACS
78.55.Hx Other solid inorganic materials

High strength and utilizable ductility of bulk ultrafine-grained Cu–Al alloys

X. H. An, W. Z. Han, C. X. Huang, P. Zhang, G. Yang, S. D. Wu, and Z. F. Zhang

Appl. Phys. Lett. 92, 201915 (2008); http://dx.doi.org/10.1063/1.2936306 (3 pages) | Cited 21 times

Online Publication Date: 23 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Lack of plasticity is the main drawback for nearly all ultrafine-grained (UFG) materials, which restricts their practical applications. Bulk UFG Cu–Al alloys have been fabricated by using equal channel angular pressing technique. Its ductility was improved to exceed the criteria for structural utility while maintaining a high strength by designing the microstructure via alloying. Factors resulting in the simultaneously enhanced strength and ductility of UFG Cu–Al alloys are the formation of deformation twins and their extensive intersections facilitating accumulation of dislocations.
Show PACS
81.40.Lm Deformation, plasticity, and creep
62.20.fq Plasticity and superplasticity
62.20.fk Ductility, malleability
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
81.10.Fq Growth from melts; zone melting and refining

Dielectric degradation mechanism for copper interconnects capped with CoWP

T. L. Tan, C. L. Gan, A. Y. Du, C. K. Cheng, and J. P. Gambino

Appl. Phys. Lett. 92, 201916 (2008); http://dx.doi.org/10.1063/1.2929388 (3 pages) | Cited 2 times

Online Publication Date: 23 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Time-dependent dielectric breakdown (TDDB) reliability of CoWP-capped copper/SiO2 interconnect structures are observed to be better than conventional SiN-capped structures. The activation energy for TDDB (Ea) is higher for CoWP-capped structures (0.66–0.84 eV) as compared to SiN-capped ones (0.47 eV), and is comparable to the Ea for intrinsic breakdown of SiO2. The TDDB degradation mechanism in CoWP-capped structures is postulated to be dominated by the properties of the intrametal dielectric, as opposed to being influenced by the properties of dielectric cap and associated interfaces. The presence of the dielectric cap lowers the Ea and increases leakage by Poole–Frenkel emission.
Show PACS
85.40.Ls Metallization, contacts, interconnects; device isolation
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
77.22.Jp Dielectric breakdown and space-charge effects

Melt-dispersion mechanism for fast reaction of aluminum particles: Extension for micron scale particles and fluorination

Valery I. Levitas, Michelle L. Pantoya, and Kyle W. Watson

Appl. Phys. Lett. 92, 201917 (2008); http://dx.doi.org/10.1063/1.2936855 (3 pages) | Cited 7 times

Online Publication Date: 23 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The theoretically predicted relationship for the relative flame rate versus relative particle size based on the melt dispersion mechanism (MDM), which was previously confirmed for oxidation of 40–120 nm diameter aluminum particles, is found to be in agreement with experiments for 1–3 μm diameter Al particles and fluorination. The main physical parameters for MDM (pressure in molten particle, cavitation threshold, and nanoclusters’ velocity) have been estimated for micron scale particles. The results suggest parameters that could be controlled during particle synthesis that would enable micron scale Al particles to react and achieve the performance of nanoscale Al particles.
Show PACS
82.30.Nr Association, addition, insertion, cluster formation
36.40.Sx Diffusion and dynamics of clusters

Raman spectra of epitaxial graphene on SiC(0001)

J. Röhrl, M. Hundhausen, K. V. Emtsev, Th. Seyller, R. Graupner, and L. Ley

Appl. Phys. Lett. 92, 201918 (2008); http://dx.doi.org/10.1063/1.2929746 (3 pages) | Cited 95 times

Online Publication Date: 23 May 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present Raman spectra of epitaxial graphene layers grown on 6math×6math reconstructed silicon carbide surfaces during annealing at elevated temperature. In contrast to exfoliated graphene a significant phonon hardening is observed. We ascribe that phonon hardening to a minor part to the known electron transfer from the substrate to the epitaxial layer, and mainly to mechanical strain that builds up when the sample is cooled down after annealing. Due to the larger thermal expansion coefficient of silicon carbide compared to the in-plane expansion coefficient of graphite this strain is compressive at room temperature.
Show PACS
78.66.Db Elemental semiconductors and insulators
78.30.Am Elemental semiconductors and insulators
61.72.Cc Kinetics of defect formation and annealing
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
68.60.Bs Mechanical and acoustical properties
68.60.Wm Other nonelectronic physical properties
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close