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

26 Feb 2001

Volume 78, Issue 9, pp. 1171-1311

Page 1 of 2 Pages Next Page | Jump to Page
back to top
RSS Feeds

Epitaxial growth and optical characterization of InAs/InGaAsP/InP self-assembled quantum dots

Weon G. Jeong, P. Daniel Dapkus, U. H. Lee, J. S. Yim, D. Lee, and B. T. Lee

Appl. Phys. Lett. 78, 1171 (2001); http://dx.doi.org/10.1063/1.1350620 (3 pages) | Cited 23 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Five stacks of InAs quantum dots (QDs) with InGaAsP barriers were grown on (100) InP and luminescence characteristics were analyzed. Cross-sectional transmission electron microscopy shows that small dots with a lateral size of ∼30 nm and a height of ∼3 nm are formed with an areal density of ∼ 5×1010 cm−2. The QDs emit strong photoluminescence (PL) peaks in the range of 1.4–1.6 μm that can be controlled by nominal InAs thickness. The integrated PL intensity from QDs stays very high at room temperature as much as 20% of that at 10 K. At weak excitation, the carrier lifetimes are measured to be almost the same across the whole PL band at low temperature with a value of ∼4 ns and they remain at that value at room temperature. These characteristics strongly evidence that individual QDs are well isolated and have a strong carrier confinement at room temperature. © 2001 American Institute of Physics.
Show PACS
81.05.Ea III-V semiconductors
78.67.Hc Quantum dots
81.07.Ta Quantum dots
78.55.Cr III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.65.Hb Quantum dots (patterned in quantum wells)
73.63.Kv Quantum dots

Effect of nonradiative recombination on light emitting properties of two-dimensional photonic crystal slab structures

Han-Youl Ryu, Jeong-Ki Hwang, Dae-Sung Song, Il-Young Han, Yong-Hee Lee, and Dong-Hoon Jang

Appl. Phys. Lett. 78, 1174 (2001); http://dx.doi.org/10.1063/1.1350901 (3 pages) | Cited 23 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
InGaAsP-based two-dimensional photonic crystal light emitting structures are fabricated by employing wafer fusion and characterized optically. The structure does not contain defect regions and the whole area of the photonic crystal is used for light generation and extraction. The effect of nonradiative recombination is studied as a function of pump power. The relative contribution of surface recombination can be as low as 10% as pump power increases since carrier recombination is dominated by Auger recombination. In spite of the large surface-to-volume ratio of the photonic crystal pattern, over four-fold enhancement of photoluminescence extraction efficiency is observed. © 2001 American Institute of Physics.
Show PACS
42.70.Qs Photonic bandgap materials
73.25.+i Surface conductivity and carrier phenomena
78.55.Cr III-V semiconductors

Thermal resistance and temperature characteristics of GaAs/Al0.33Ga0.67As quantum-cascade lasers

Vincenzo Spagnolo, Mariano Troccoli, Gaetano Scamarcio, Cyrille Becker, Geneviève Glastre, and Carlo Sirtori

Appl. Phys. Lett. 78, 1177 (2001); http://dx.doi.org/10.1063/1.1351850 (3 pages) | Cited 21 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on the determination of thermal resistance, facet temperature profile, and heat flux of GaAs/Al0.33Ga0.67As quantum-cascade lasers operating in pulsed mode, using a microprobe band-to-band photoluminescence technique. The thermal resistance of epilayer-side mounted lasers is ∼30% smaller than that of substrate-side mounted ones. The dependence of the thermal resistance on the injection conditions and its correlation with the output power is also reported. © 2001 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.De Quantum wells

Three-dimensional photonic crystals based on macroporous silicon with modulated pore diameter

J. Schilling, F. Müller, S. Matthias, R. B. Wehrspohn, U. Gösele, and K. Busch

Appl. Phys. Lett. 78, 1180 (2001); http://dx.doi.org/10.1063/1.1351533 (3 pages) | Cited 59 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on the fabrication and optical characterization of a three-dimensional (3D) photonic crystal on the basis of macroporous silicon. The structure consists of a 2D array of air pores in silicon whose diameter is varied (modulated) periodically with depth. The bandstructure of the resulting 3D hexagonal photonic crystal is calculated and compared with transmission measurements. The described structure allows to adjust the dispersion relation along the pore axis almost independently from the dispersion relation in the plane perpendicular to the pore axis. © 2001 American Institute of Physics.
Show PACS
42.70.Qs Photonic bandgap materials
81.05.Rm Porous materials; granular materials
71.20.Mq Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors

Nonlinear refractive beam shaping by an organic nonlinear absorber

John Robertson, Andrew Smith, Jason Duignan, Philip Milsom, and Grant Bourhill

Appl. Phys. Lett. 78, 1183 (2001); http://dx.doi.org/10.1063/1.1351518 (3 pages) | Cited 6 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The response of organic dyes to laser pulses is typically described solely by nonlinear absorption. Recently, spatial profiles of a nanosecond pulse exiting an organic nonlinear absorber have shown energy redistribution from a Gaussian input profile to a central spike and outer ring. It was suggested that the spike and ring resulted from both nonlinear absorption and nonlinear refraction. In this letter, the role of a thermal nonlinear refraction in beam shaping is demonstrated using single and time-delayed double picosecond pulses. It is concluded that the dynamics of nonlinear absorption and nonlinear refraction must be included to correctly describe the laser-material interaction. © 2001 American Institute of Physics.
Show PACS
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.47.-p Spectroscopy of solid state dynamics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.70.Jk Polymers and organics

Diffraction gratings in polymer-dispersed liquid crystals recorded by means of polarization holographic technique

G. Cipparrone, A. Mazzulla, and G. Russo

Appl. Phys. Lett. 78, 1186 (2001); http://dx.doi.org/10.1063/1.1349867 (3 pages) | Cited 22 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report an observation of holographic gratings recorded exposing a homogeneous mixture of pre-polymer and liquid crystal to a polarization light pattern. This polarization pattern is obtained by a superposition of two waves with orthogonal linear polarization. The idea to use this technique to realize holographic gratings come from the possibility of controlling the liquid crystal alignment inside the droplets, through the photoalignment, during the photoinduced polymerization process. On the contrary, the usual methods of writing diffraction gratings in polymer-dispersed liquid crystals are based on intensity holographic technique that controls the polymerization process. Diffraction gratings, composed of liquid crystal droplets having a particular internal alignment, are observed. © 2001 American Institute of Physics.
Show PACS
42.40.Eq Holographic optical elements; holographic gratings
42.70.Df Liquid crystals
61.30.Pq Microconfined liquid crystals: droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems
82.35.-x Polymers: properties; reactions; polymerization
82.50.-m Photochemistry

Nonvolatile grating in an azobenzene polymer with optimized molecular reorientation

Pengfei Wu, D. V. G. L. N. Rao, B. R. Kimball, M. Nakashima, and B. S. DeCristofano

Appl. Phys. Lett. 78, 1189 (2001); http://dx.doi.org/10.1063/1.1351532 (3 pages) | Cited 6 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We demonstrated a nonvolatile grating using an azobenzene polymer film with polarized two color beams. The reorientation of azobenzene molecules can be optimized when the two color light beams are polarized perpendicularly. The stored information can be read repeatedly without volatility with the same wavelength as the writing beam. © 2001 American Institute of Physics.
Show PACS
42.70.Ln Holographic recording materials; optical storage media
42.70.Jk Polymers and organics
42.40.Eq Holographic optical elements; holographic gratings
61.41.+e Polymers, elastomers, and plastics
42.79.Vb Optical storage systems, optical disks
78.66.Qn Polymers; organic compounds

High gain beam compression in new-generation thin-film x-ray waveguides

W. Jark, A. Cedola, S. Di Fonzo, M. Fiordelisi, S. Lagomarsino, N. V. Kovalenko, and V. A. Chernov

Appl. Phys. Lett. 78, 1192 (2001); http://dx.doi.org/10.1063/1.1350956 (3 pages) | Cited 30 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
X-ray waveguides can compress an incident beam for microscopy applications above 8 keV photon energy to sizes smaller than 100 nm in one dimension, a range which is not routinely accessed with other x-ray optics (e.g., Fresnel zone plates). Beryllium, because of its low absorption, is expected to provide the highest intensity gain. Measured gains for a beryllium waveguide of 74 nm thickness exceed values of 100 at 13 and 20 keV photon energy, which is an improvement by an order of magnitude compared to previously reported performances. The same object works also at 8 keV with gain 43. © 2001 American Institute of Physics.
Show PACS
42.79.Gn Optical waveguides and couplers
41.50.+h X-ray beams and x-ray optics
42.79.Wc Optical coatings

Emission spectrum of hard x-rays, generated from iron, copper, and molybdenum targets by subpicosecond KrF laser pulses

N. Takeyasu, Y. Hirakawa, and T. Imasaka

Appl. Phys. Lett. 78, 1195 (2001); http://dx.doi.org/10.1063/1.1342777 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
K-shell emission spectra of iron, copper, and molybdenum in the range of 1.5–20 keV using a 500 fs KrF excimer laser have been observed and are reported herein. © 2001 American Institute of Physics.
Show PACS
78.70.En X-ray emission spectra and fluorescence
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
79.20.Ds Laser-beam impact phenomena
61.82.Bg Metals and alloys

Continuous-wave InGaN multiple-quantum-well laser diodes on copper substrates

William S. Wong, Michael Kneissl, Ping Mei, David W. Treat, Mark Teepe, and Noble M. Johnson

Appl. Phys. Lett. 78, 1198 (2001); http://dx.doi.org/10.1063/1.1350593 (3 pages) | Cited 23 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Continuous-wave (cw) indium-gallium nitride multiple-quantum-well laser diodes (LDs) were transferred from sapphire onto copper substrates using a two-step laser lift-off process. Reduced threshold currents and increased differential quantum efficiencies were measured for LDs on Cu due to a 50% reduction of the thermal impedance. Light output for LDs on Cu was three times greater than comparable LDs on sapphire with a maximum output of 30 mW. CW operation was possible up to heatsink temperatures of 90 °C for LDs on Cu. © 2001 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Pk Continuous operation

Coherent optical control of acoustic phonon oscillations in InGaN/GaN multiple quantum wells

Chi-Kuang Sun, Yue-Kai Huang, Jian-Chin Liang, Amber Abare, and Steven P. DenBaars

Appl. Phys. Lett. 78, 1201 (2001); http://dx.doi.org/10.1063/1.1350598 (3 pages) | Cited 14 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We demonstrate coherent optical control of phonon oscillations using a femtosecond control pulse. The experiments were performed in InGaN/GaN multiple quantum wells. Coherent acoustic phonon oscillations was initiated with an UV femtosecond pulse. The subsequent manipulation, including magnitude and phase, of the coherent acoustic phonon oscillations was achieved using another UV femtosecond pulse by controlling the pulse time delay and intensity. © 2001 American Institute of Physics.
Show PACS
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.67.De Quantum wells
78.55.Cr III-V semiconductors
78.40.Fy Semiconductors

Epitaxial LiNbO3 thin films grown by pulsed laser deposition for optical waveguides

G. Balestrino, S. Martellucci, P. G. Medaglia, A. Paoletti, G. Petrocelli, A. Tebano, A. Tucciarone, F. Gelli, E. Giorgetti, S. Sottini, and L. Tapfer

Appl. Phys. Lett. 78, 1204 (2001); http://dx.doi.org/10.1063/1.1350903 (3 pages) | Cited 9 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have grown good-quality epitaxial LiNbO3 thin films on (0001) sapphire substrates using a pulsed laser deposition technique. The growth conditions permitted us to deposit c-axis oriented films avoiding the problem of the LiNb3O8 Li-deficient phase. The chemical composition of thin films was investigated by secondary ion mass spectrometry and resulted to coincide with the target composition. Guided propagation was demonstrated at 632 and 488 nm with thin films (∼1200 Å). © 2001 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
81.15.Fg Pulsed laser ablation deposition
42.79.Gn Optical waveguides and couplers
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Close-to-ideal device characteristics of high-power InGaAs/GaAs quantum dot lasers

R. L. Sellin, Ch. Ribbat, M. Grundmann, N. N. Ledentsov, and D. Bimberg

Appl. Phys. Lett. 78, 1207 (2001); http://dx.doi.org/10.1063/1.1350596 (3 pages) | Cited 94 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Close-to-ideal device characteristics of high-power InGaAs/GaAs quantum-dot lasers are achieved by the application of an annealing and growth interruption step at 600 °C after the deposition of the dots. The transparency current is reduced to below 20 A/cm2 at room temperature. The internal differential quantum efficiency is increased from below 50% to above 90% by improvement of the barrier material and subsequent reduction of leakage current. A peak power of 3.7 W at 1140 nm lasing wavelength in pulsed operation at room temperature is demonstrated. © 2001 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Low propagation losses of an Er:Y2O3 planar waveguide grown by alternate-target pulsed laser deposition

M. B. Korzenski, Ph. Lecoeur, B. Mercey, P. Camy, and J.-L. Doualan

Appl. Phys. Lett. 78, 1210 (2001); http://dx.doi.org/10.1063/1.1347026 (3 pages) | Cited 25 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on waveguiding properties in epitaxial Er:Y2O3 films grown by pulsed-laser deposition on sapphire [0001] substrate. Characterization of the as-grown films by x-ray diffraction, atomic force microscopy, and Rutherford backscattering revealed that the films were highly crystalline and textured along the [111] direction and possessed an average surface roughness of 2 nm for a 0.69-μm-thick film. The investigation of the emission spectra confirms the proper structural position for the Er3+ ions in the Y2O3 matrix and that the films guide optical waves along the entire length (5 mm) of the film yielding a propagation loss of <1 dB/cm at 800 nm. © 2001 American Institute of Physics.
Show PACS
42.82.Et Waveguides, couplers, and arrays
81.15.Fg Pulsed laser ablation deposition
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
68.35.B- Structure of clean surfaces (and surface reconstruction)
back to top
RSS Feeds

Critical cooling rate and thermal stability of Zr–Ti–Cu–Ni–Be alloys

Theodore A. Waniuk, Jan Schroers, and William L. Johnson

Appl. Phys. Lett. 78, 1213 (2001); http://dx.doi.org/10.1063/1.1350624 (3 pages) | Cited 67 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The critical cooling rate as well as the thermal stability are measured for a series of alloys in the Zr–Ti–Cu–Ni–Be system. Upon cooling from the molten state with different rates, alloys with compositions ranging along a tie line from (Zr70Ti30)55(Ni39Cu61)25Be20 to (Zr85Ti15)55(Ni57Cu43)22.5Be27.5 show a continuous increase in the critical cooling rate to suppress crystallization. In contrast, thermal analysis of the same alloys shows that the undercooled liquid region, the temperature difference between the glass transition temperature and the crystallization temperature, is largest for some compositions midway between the two endpoints, revealing that glass forming ability does not correlate with thermal stability. The relationship between the composition-dependent glass forming ability and thermal stability is discussed with reference to a chemical decomposition process. © 2001 American Institute of Physics.
Show PACS
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
61.43.Fs Glasses

Electronic and chemical passivation of hexagonal 6H–SiC surfaces by hydrogen termination

N. Sieber, B. F. Mantel, Th. Seyller, J. Ristein, L. Ley, T. Heller, D. R. Batchelor, and D. Schmeißer

Appl. Phys. Lett. 78, 1216 (2001); http://dx.doi.org/10.1063/1.1351845 (3 pages) | Cited 32 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Hydrogenation of 6H–SiC (0001) and (000math) is achieved by high-temperature hydrogen treatment. Both surfaces show a low-energy electron diffraction pattern representative of unreconstructed surfaces of extremely high crystallographic order. On SiC(0001), hydrogenation is confirmed by the observation of sharp Si–H stretching modes. The absence of surface band bending for n- and p-type samples is indicative of electronically passivated surfaces with densities of charged surface states in the gap of below 7×1010 cm−2 for p-type and 1.7×1012 cm−2 for n- type samples, respectively. Even after two days in air, the surfaces show no sign of surface oxide in x-ray photoelectron spectroscopy. © 2001 American Institute of Physics.
Show PACS
81.65.Rv Passivation
81.05.Hd Other semiconductors
68.35.Dv Composition, segregation; defects and impurities
73.20.At Surface states, band structure, electron density of states

Effective compliant substrate for low-dislocation relaxed SiGe growth

Y. H. Luo, J. L. Liu, G. Jin, J. Wan, K. L. Wang, C. D. Moore, M. S. Goorsky, C. Chih, and K. N. Tu

Appl. Phys. Lett. 78, 1219 (2001); http://dx.doi.org/10.1063/1.1351520 (3 pages) | Cited 20 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An effective compliant substrate was fabricated for the growth of high-quality relaxed SiGe templates, by synthesizing a 20% B2O3 concentration borosilicate glass (BSG) in the silicon on insulator wafers. Substrates with 5%, 10%, and 20% B2O3 were used for 150 nm Si0.75Ge0.25 epitaxy. Double-axis x-ray diffraction measurements determined the relaxation and composition of the Si1−xGex layers. Cross-sectional transmission electron microscopy was used to observe the lattice of the SiGe epilayer and the Si substrate, dislocation density, and distribution. Raman spectroscopy was combined with step etch to study the samples. The strain sharing effect of the 20% BSG substrate was demonstrated. Thus, we concluded that this compliant substrate is a highly promising candidate for the growth of low-dislocation relaxed SiGe layers. © 2001 American Institute of Physics.
Show PACS
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.05.Hd Other semiconductors
78.66.Li Other semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.Nq Composition and phase identification

Spatial variation of luminescence in thick GaN films

F. Bertram, S. Srinivasan, F. A. Ponce, T. Riemann, J. Christen, and R. J. Molnar

Appl. Phys. Lett. 78, 1222 (2001); http://dx.doi.org/10.1063/1.1350594 (3 pages) | Cited 9 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The spatial variation of the optical properties of hydride vapor-phase epitaxial GaN layers of various thickness has been studied using scanning cathodoluminescence microscopy. A strong improvement of these properties with film thickness is observed in plan view. Cross-sectional studies show a strong redshift of the luminescence in the vicinity of the substrate within a typical thickness of about 2 μm, reflecting a high local impurity content. Above this initial growth region, a strong blueshift is observed up to the energy of fully relaxed high-purity GaN, indicating vertical strain relaxation as well as depletion of residual donors. This is accompanied by a sharp increase in the lateral spectral homogeneity, indicative of a significant improvement in crystalline quality. © 2001 American Institute of Physics.
Show PACS
78.66.Fd III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.60.Bs Mechanical and acoustical properties

Effect of hydrogen on the photoluminescence of Si nanocrystals embedded in a SiO2 matrix

S. Cheylan and R. G. Elliman

Appl. Phys. Lett. 78, 1225 (2001); http://dx.doi.org/10.1063/1.1338492 (3 pages) | Cited 33 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Hydrogen passivation of Si nanocrystals is shown to result in a redshift of photoluminescence (PL) emission spectra, as well as the more commonly observed intensity increase. The shift is reversible, with spectra returning to their unpassivated values as hydrogen is removed from the samples by annealing. The magnitude of the redshift also depends on the implant fluence employed for nanocrystal synthesis, increasing with increasing fluence or particle size. These data are shown to be consistent with a model in which larger crystallites are assumed to contain a greater number of nonradiative defects, i.e., the number of nonradiative defects is assumed to scale with the surface area or volume of a nanocrystal. Hydrogen passivation then results in a disproportionate increase in emission from larger crystallites, giving rise to an apparent redshift in the composite PL emission spectrum. © 2001 American Institute of Physics.
Show PACS
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Ap Elemental semiconductors
61.82.Rx Nanocrystalline materials
61.46.-w Structure of nanoscale materials
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors

Self-assembled metallic dots and antidots: Epitaxial Co on Ru(0001)

Chengtao Yu, Dongqi Li, J. Pearson, and S. D. Bader

Appl. Phys. Lett. 78, 1228 (2001); http://dx.doi.org/10.1063/1.1351522 (3 pages) | Cited 19 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have grown ∼ 1–420 nm thick epitaxial Co wedges on Ru(0001) with molecular-beam epitaxy at 350 °C and characterized them with atomic force microscopy. A metal-on-metal growth mode was observed where three-dimensional islands (dots) or a flat film network with holes (antidots) in truncated pyramidal shapes exist below or above ∼ 20 nm, respectively. The top of the islands and the rim of the holes are flat with a roughness of ∼0.3 nm, and the lateral sizes of these dots/antidots, ∼ 102 nm, tend to be uniform. We suggest that this self-assembled growth be mainly driven by strain. © 2001 American Institute of Physics.
Show PACS
68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
68.37.Ps Atomic force microscopy (AFM)

Ab initio study of substitutional nitrogen in GaAs

W. Orellana and A. C. Ferraz

Appl. Phys. Lett. 78, 1231 (2001); http://dx.doi.org/10.1063/1.1351524 (3 pages) | Cited 11 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We investigate the atomic geometry, formation energies, and electronic structure of nitrogen occupying both arsenic and gallium sites in GaAs (NAs and NGa) using first-principles total-energy calculations. We find that both neutral defects induce impurity-like empty levels in the band gap acting as acceptors. While NAs shows a s-like a1 level in the middle of the band gap, NGa shows a p-like t2 level close to the bottom of the conduction band. The gap level of NAs gives theoretical support for the experimentally observed band-edge redshift on the GaAsN alloy for a N concentration ∼3%. Strong inward relaxations preserving the Td symmetry characterize the NAs equilibrium geometry in all the charge states investigated. In contrast, NGa exhibits a structural metastability in neutral charge state and Jahn–Teller off-center distortions in negative charge states forming a negative-U center. Formation energies of competing NAs and NGa defects are also discussed. © 2001 American Institute of Physics.
Show PACS
71.55.Eq III-V semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Nc Total energy and cohesive energy calculations

Evidence for negatively charged vacancy defects in 6H-SiC after low-energy proton implantation

D. T. Britton, M.-F. Barthe, C. Corbel, A. Hempel, L. Henry, P. Desgardin, W. Bauer-Kugelmann, G. Kögel, P. Sperr, and W. Triftshäuser

Appl. Phys. Lett. 78, 1234 (2001); http://dx.doi.org/10.1063/1.1350961 (3 pages) | Cited 19 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have used pulsed-slow-positron-beam-based positron lifetime spectroscopy to investigate the nature of acceptors and charge states of vacancy-type defects in low-energy proton-implanted 6H-SiC(H). We can infer from the temperature dependence of the lifetime spectra that neutral and negatively charged vacancy clusters exist in the track region. Depending on annealing, they give rise to positron lifetimes of 257±2, 281±4, and 345±2 ps, respectively. The 281 ps cluster likely has an ionization level near the middle of the band gap. By comparison with theory, the 257 and 280 ps are identified as (VC–VSi)2 and (VC–VSi)3 clusters, respectively. In addition, other acceptors of ionic type act as strong trapping centers at low temperature (T<150 K). Neutral monovacancy-like complexes are also detected with a lifetime of 160±2 after 900 °C annealing. © 2001 American Institute of Physics.
Show PACS
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.J- Point defects and defect clusters
78.70.Bj Positron annihilation
61.72.up Other materials
61.72.Cc Kinetics of defect formation and annealing
71.55.Ht Other nonmetals

Band gap engineering based on MgxZn1−xO and CdyZn1−yO ternary alloy films

T. Makino, Y. Segawa, M. Kawasaki, A. Ohtomo, R. Shiroki, K. Tamura, T. Yasuda, and H. Koinuma

Appl. Phys. Lett. 78, 1237 (2001); http://dx.doi.org/10.1063/1.1350632 (3 pages) | Cited 229 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We describe the structural and optical properties of II–VI oxide alloys, MgxZn1−xO and CdyZn1−yO, grown by pulsed-laser deposition. Single-phase alloyed films of (Mg,Zn)O and (Cd,Zn)O with c-axis orientations were epitaxially grown on sapphire (0001) substrates. The maximum magnesium and cadmium concentrations (x=0.33 and y=0.07, respectively) were significantly larger than the thermodynamic solubility limits. The band gap energies systematically changed from 3.0 (y = 0.07) to 4.0 eV (x = 0.33) at room temperature. The photoluminescence peak energy deduced at 4.2 K could be tuned from 3.19 to 3.87 eV by using Cd0.07Zn0.93O and Mg0.33Zn0.67O at both ends, respectively. The lattice constants of the a axis were monotonically increasing functions of the concentrations of both alloys. The exciton–phonon coupling strength was determined in Cd0.01Zn0.99O grown on a lattice-matched ScAlMgO4 substrate. © 2001 American Institute of Physics.
Show PACS
78.66.Hf II-VI semiconductors
68.55.-a Thin film structure and morphology
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
63.20.kk Phonon interactions with other quasiparticles

Influence of intraband transitions on the electron thermoreflectance response of metals

Andrew N. Smith and Pamela M. Norris

Appl. Phys. Lett. 78, 1240 (2001); http://dx.doi.org/10.1063/1.1351523 (3 pages) | Cited 26 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ultrashort pulsed lasers have repeatedly been demonstrated as effective tools for the observation of transport properties on atomistic time and length scales. Transient thermoreflectance scans of a Au thin film taken using a 200 fs pulsed laser are compared to the parabolic two step model using both the assumption of a linear relationship between reflectance and temperature and using an intraband reflectance model. In this study, the incident photon energy was less than the interband transition energy, therefore the thermoreflectance response is primarily due to intraband transitions. The intraband transitions are influenced by the electron and lattice temperatures through the electron collisional frequency. © 2001 American Institute of Physics.
Show PACS
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
78.66.Bz Metals and metallic alloys
78.47.-p Spectroscopy of solid state dynamics
63.20.K- Phonon interactions

Uniform deposition of ultrathin polymer films on the surfaces of Al2O3 nanoparticles by a plasma treatment

Donglu Shi, S. X. Wang, Wim J. van Ooij, L. M. Wang, Jiangang Zhao, and Zhou Yu

Appl. Phys. Lett. 78, 1243 (2001); http://dx.doi.org/10.1063/1.1352700 (3 pages) | Cited 44 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Surface modification of nanoparticles will present great challenges due to their extremely small dimensions, high surface areas, and high surface energies. In this research, we demonstrate the uniform deposition of ultrathin polymer films of 2 nm on the surfaces of alumina nanoparticles. The deposited film can also be tailored to multilayers. Time-of-flight secondary ion mass spectroscopy was used to confirm the pyrrole thin film on the nanoparticle surfaces. Using such a nanocoating, it is possible to alter the intrinsic properties of materials that cannot be achieved by conventional methods and materials. © 2001 American Institute of Physics.
Show PACS
68.55.A- Nucleation and growth
61.41.+e Polymers, elastomers, and plastics
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
81.65.-b Surface treatments
52.77.-j Plasma applications
82.35.-x Polymers: properties; reactions; polymerization
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
Page 1 of 2 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close