jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter UniPHY Group iResearch App Facebook

BROWSE VOLUMES

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

15 Feb 2003

Volume 93, Issue 4, pp. 1859-2309

Page 1 of 4 Pages Next Page | Jump to Page
back to top
RSS Feeds

Simulation of optical pulse propagation in a two-dimensional photonic crystal waveguide using a high accuracy finite-difference time-domain algorithm

S. Yamada, Y. Watanabe, Y. Katayama, and J. B. Cole

J. Appl. Phys. 93, 1859 (2003); http://dx.doi.org/10.1063/1.1539542 (6 pages) | Cited 6 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Propagation properties of optical pulses in a two-dimensional photonic crystal with a straight waveguide structure imbedded were examined using a high accuracy finite-difference time-domain (FDTD) algorithm based on nonstandard finite differences. A tunable and significantly large group velocity dispersion was found even for photonic crystal structures as small as 10 unit cells long. Detailed calculations indicated that a very small photonic crystal with an imbedded waveguide can be used to control pulse dispersion, i.e., a just 25 μm long photonic crystal with waveguide can compress a 1% up-chirped pulse to the Fourier transform limit. Further, our FDTD calculations showed excellent agreement with the prediction of photonic band calculations on infinite structures. © 2003 American Institute of Physics.
Show PACS
42.79.Gn Optical waveguides and couplers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
02.70.Bf Finite-difference methods
42.70.Qs Photonic bandgap materials

Two-color optical technique for characterization of x-ray radiation-enhanced electron transport in SiO2

Z. Marka, R. Pasternak, R. G. Albridge, S. N. Rashkeev, S. T. Pantelides, N. H. Tolk, B. K. Choi, D. M. Fleetwood, and R. D. Schrimpf

J. Appl. Phys. 93, 1865 (2003); http://dx.doi.org/10.1063/1.1534904 (6 pages) | Cited 3 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Damage enhanced electron transport, across thin oxides in x-ray irradiated Si/SiO2 samples, was measured via a contactless two-color laser technique. This method involves two steps: (1) optically stimulated electron injection into the oxide and (2) detection of transport, trapping, and recombination rates using time-dependent electric-field-induced second-harmonic generation arising from charge separation at the interface. Measured electron transport rates across an irradiated oxide are found to be substantially higher in comparison to unirradiated oxides. This effect is attributed to the presence of x-ray irradiation-induced defects that act as intermediate trapping sites facilitating enhanced electron tunneling through the oxide. The possible nature of the radiation-induced trapping sites is discussed. © 2003 American Institute of Physics.
Show PACS
73.61.Ng Insulators
78.66.Nk Insulators
61.80.Cb X-ray effects
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.20.Jq Electro-optical effects

Light amplification and lasing in a (meta-phenylene vinylene) copolymer

Hacene Manaa, Fryad Z. Henari, Ahmed Al-Saie, Anna Drury, Takeyuki Kobayashi, and Werner J. Blau

J. Appl. Phys. 93, 1871 (2003); http://dx.doi.org/10.1063/1.1537463 (3 pages) | Cited 3 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on single pass optical gain and lasing measurements on a blue-emitting copolymer, poly(m-phenylene vinylene-co-2,5-dioctyloxy-p-phenylene vinylene) under 0.5 ns pulsed photoexcitation. This soluble copolymer is designed and synthesized for light amplification and lasing applications. Blue photoluminescence is achieved by introduction of the meta linkage of the phenylene rings in the polymer backbone, which reduces the extent of delocalization of π electrons. The large Stokes shift of about 70 nm implies a low reabsorption rate, and leads to easier creation of population inversion and hence to efficient light amplification. A solution of the polymer exhibits amplified spontaneous emission evidenced by spectral narrowing and a superlinear increase of output intensity when it is photoexcited at 337 nm. By means of the variable excitation stripe length method, net gains of 18 and 24 cm−1 are deduced for different pump energies of 71 and 113 μJ, respectively. Moreover, laser emission from the polymer solution is obtained in a simple cavity formed by Fresnel reflections at the cuvette–solution interfaces. A conversion efficiency as high as 27% and a wide tuning range between 470 and 492 nm in solutions are demonstrated. © 2003 American Institute of Physics.
Show PACS
42.70.Hj Laser materials
42.70.Jk Polymers and organics
78.55.Bq Liquids
78.45.+h Stimulated emission
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Differential surface photovoltage spectroscopy characterization of a 1.3 μm InGaAlAs/InP vertical-cavity surface-emitting laser structure

J. S. Liang, S. D. Wang, Y. S. Huang, L. Malikova, Fred H. Pollak, J. P. Debray, R. Hoffman, A. Amtout, and R. A. Stall

J. Appl. Phys. 93, 1874 (2003); http://dx.doi.org/10.1063/1.1538323 (5 pages) | Cited 6 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated a 1.3 μm InGaAlAs/InP vertical-cavity surface-emitting laser (VCSEL) structure using angle- and temperature-dependent wavelength-modulated differential surface photovoltage spectroscopy (DSPS). The DSPS measurements as functions of incident angle and temperature have been carried out in the ranges 0°⩽θ⩽60° and 300 K⩽T⩽420 K, respectively. Angle-dependent reflectance (R) and surface photovoltage spectroscopy (SPS) measurements have also been performed to illustrate the superior features of the DSPS technique. The differential surface photovoltage (DSPV) and SPV spectra exhibit both the fundamental conduction to heavy-hole excitonic transition of quantum well and cavity mode (CM) plus a rich interference pattern related to the mirror stacks, whereas in the R spectra only the CM and interference features are clearly visible. The energies of the excitonic transition and CM are accurately determined from the DSPV spectra. By changing the angle of incidence in the DSPS measurements the energy positions of the CM and distributed Bragg reflector features show a blueshift while the excitonic transition remains unchanged. At a fixed incident angle, the energy positions of the excitonic feature and CM show a different rate of redshift with increasing temperature, with the latter at a much slower pace. The results demonstrate considerable potential of DSPS for the nondestructive characterization of the VCSEL structures. © 2003 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
73.63.Hs Quantum wells
78.67.De Quantum wells
73.50.Pz Photoconduction and photovoltaic effects
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.Fg Quantum wells
73.25.+i Surface conductivity and carrier phenomena
78.30.Fs III-V and II-VI semiconductors

Resonant cavity enhancement in heterojunction GaAs/AlGaAs terahertz detectors

D. G. Esaev, S. G. Matsik, M. B. M. Rinzan, A. G. U. Perera, H. C. Liu, and M. Buchanan

J. Appl. Phys. 93, 1879 (2003); http://dx.doi.org/10.1063/1.1539918 (5 pages) | Cited 15 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The room-temperature absorption and reflection spectra in the range of 5–100 μm (3–60 THz) for multilayer heterojunction interfacial work function internal photoemission (HEIWIP) GaAs/AlGaAs far-infrared (FIR) detectors are presented. Calculated results based on the free carrier absorption and interaction with optical phonons are found to be in good agreement with the experimental results. Experimental responsivity spectra demonstrate the expected maxima from the absorption measurements due to resonant cavity effects. It is shown that the resonance cavity architecture enhances the performance of the FIR HEIWIP detectors and further improvement is proposed through the use of n++ and p++ bottom contact layers or doped substrates. © 2003 American Institute of Physics.
Show PACS
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
85.60.Gz Photodetectors (including infrared and CCD detectors)
78.30.Fs III-V and II-VI semiconductors
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Theoretical study of radiation effects on GaAs/AlGaAs and InGaAsP/InP quantum-well lasers

O. Gilard

J. Appl. Phys. 93, 1884 (2003); http://dx.doi.org/10.1063/1.1539919 (5 pages) | Cited 5 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Radiation hardness assurance of light emitters such as laser diodes is a primary concern before using such devices in space. In this article, both gallium arsenide (GaAs) and indium phosphide (InP) based laser diodes are theoretically analyzed from a radiation hardness point of view. It has been found that InP based lasers are less sensitive to radiation than GaAs lasers. We will also demonstrate that threshold carrier density is the key parameter to consider when assessing the radiation sensitivity of laser diodes. © 2003 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
61.82.Fk Semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
61.80.Jh Ion radiation effects
68.65.Fg Quantum wells

Anisotropic refractive-index change in silica glass induced by self-trapped filament of linearly polarized femtosecond laser pulses

Kazuhiro Yamada, Wataru Watanabe, Junji Nishii, and Kazuyoshi Itoh

J. Appl. Phys. 93, 1889 (2003); http://dx.doi.org/10.1063/1.1534910 (4 pages) | Cited 12 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Permanent refractive-index change can be induced by a self-trapped filament of intense ultrashort laser pulses in silica glass. We investigated the dependence of refractive-index change on polarization of incident laser pulses. As the region of refractive-index change can be selectively etched by hydrofluoric acid (HF), we first polished the sample and etched the cross section of the regions. The HF-etched cross section of refractive-index change that was induced by linearly polarized pulses was seen to be elliptical when observed with a scanning-electron microscope. By polarimetric analysis of diffraction from gratings fabricated by polarized ultrashort laser pulses, the index ellipsoid of refractive-index change was confirmed to be uniaxial and negative. © 2003 American Institute of Physics.
Show PACS
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
79.20.Ds Laser-beam impact phenomena
61.82.Ms Insulators
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.43.Fs Glasses
back to top
RSS Feeds

Determination of gas temperature in an open-air atmospheric pressure plasma torch from resolved plasma emission

James M. Williamson and Charles A. DeJoseph

J. Appl. Phys. 93, 1893 (2003); http://dx.doi.org/10.1063/1.1536736 (6 pages) | Cited 9 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The resolved emission spectrum of an open-air atmospheric pressure plasma torch was recorded with a 0.5 m spectrometer and CCD camera. The plasma emission under these conditions was found to be dominated by continuum radiation and emission from species, which obscured large portions of the N2 second positive emission spectrum. Despite these difficulties, the gas temperature of the torch could be determined from a fit of partially resolved N2+ first negative vibrational transitions and a blackbody fit to the continuum radiation. The vibrational temperature, determined from a Boltzmann plot, was 4300±900 K while the blackbody radiation temperature was 4400±400 K. To check these gas temperature determinations, measured spectra over selected spectral regions were compared with spectral simulations using N2+ first negative emission, N2 second positive emission, and a blackbody. Best agreement between measured and simulated spectra was with blackbody temperature, rotational temperature, and vibrational temperature set to 4400 K. © 2003 American Institute of Physics.
Show PACS
52.75.Hn Plasma torches
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Ion energy distribution functions of vacuum arc plasmas

Eungsun Byon and André Anders

J. Appl. Phys. 93, 1899 (2003); http://dx.doi.org/10.1063/1.1539535 (8 pages) | Cited 29 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The velocity distribution function of vacuum arc ions can be measured by a time-of-flight technique. The measuring principle makes use of the well-justified assumption that the ion drift velocity from the cathode spot region to a collector is approximately constant. It is shown that the negative time derivative of the collector current is directly proportional to the ion distribution function provided that the time-averaged emission of ions from cathode spots is constant until the arc is rapidly switched off. In the experiment, arc termination took about 700 ns, which is much faster than the decay of the ion current measured at the collector placed more than 2 m from the cathode. The experimental distribution functions for most cathode materials show one large peak with a tail and one or more small peaks at higher ion velocities. The typical peak position is at about 104 m/s, with the precise values being material specific. The distribution functions for some materials exhibit not one but several peaks. No conclusive answer can be given about the nature of these peaks. Arguments are presented that the peaks are not caused by different charge states or plasma contamination but rather are due to insufficiently averaged source fluctuations and/or acceleration by plasma instabilities. © 2003 American Institute of Physics.
Show PACS
52.80.Vp Discharge in vacuum
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.25.Dg Plasma kinetic equations
52.70.Nc Particle measurements
52.25.Fi Transport properties
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

Characterization of neutral, positive, and negative species in a chlorine high-density surface-wave plasma

L. Stafford, J. Margot, M. Chaker, and O. Pauna

J. Appl. Phys. 93, 1907 (2003); http://dx.doi.org/10.1063/1.1538313 (7 pages) | Cited 10 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This article reports an experimental study of the influence of the plasma parameters on the concentration of neutral and ion species in a chlorine high-density plasma sustained by surface waves. The investigation focuses on the dependence of the concentrations of Cl, Cl2, Cl+, Cl2+, Cl−, and electrons on the gas pressure in the 0.1 to 10 mTorr range, and on the intensity of a confinement magnetic field. The results show that a high dissociation degree (up to 90%) can be achieved even with a very modest power level (250 W, power density of about 2 mW/cm3), provided the pressure is low enough (i.e., less than 1 mTorr). It was also found that Cl+ is the main positive ion and that electrons are the main negative charge carrier at lower pressure. When the gas pressure is higher than a few mTorr, Cl2+ becomes dominant with Cl− as the negative charge carrier. The behavior of the positive ion and neutral species concentrations is compared to the results of a simple model based on creation–losses rate equations for the various species. It is shown that for a given magnetic field intensity, there is a critical pressure above which diffusion can be neglected in comparison with ion–ion recombination and charge transfer. © 2003 American Institute of Physics.
Show PACS
52.25.Kn Thermodynamics of plasmas
52.70.-m Plasma diagnostic techniques and instrumentation
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
back to top
RSS Feeds

Analysis of single- and two-photon-excited green emission spectra of thin-film cadmium sulfide

B. Ullrich, S. Yano, R. Schroeder, and H. Sakai

J. Appl. Phys. 93, 1914 (2003); http://dx.doi.org/10.1063/1.1537459 (4 pages) | Cited 5 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Employing nanosecond and femtosecond laser pulses at 355 nm (3.49 eV) and 768 nm (1.61 eV), green single- and two-photon-excited interband emission at 2.412 and 2.381 eV of thin-film cadmium sulfide (CdS) on glass has been measured at room temperature. The spectra are fitted and analyzed by a theory based on the detailed balance principle. The results demonstrate that the interband emission is independent of the mode of excitation and that the energy shift of the spectra is solely due to self-absorption of the emission evoked by two-photon excitation. The work also addresses energy dissipation in thin-film CdS excited beyond the Mott transition. © 2003 American Institute of Physics.
Show PACS
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.30.+h Metal-insulator transitions and other electronic transitions

Effect of steady-state hydrogen coverage on the evolution of crosshatch morphology during Si1−xGex/Si(001) growth from hydride precursors

T. Spila, P. Desjardins, J. D’Arcy-Gall, R. D. Twesten, and J. E. Greene

J. Appl. Phys. 93, 1918 (2003); http://dx.doi.org/10.1063/1.1533833 (8 pages) | Cited 7 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Compressively strained Si0.7Ge0.3 layers were grown on Si(001) by gas-source molecular beam epitaxy from Ge2H6/Si2H6 mixtures at 450 °C. The combination of the relatively low growth temperature and high steady-state hydrogen surface coverage, θH=0.52 monolayer, completely suppresses strain-induced roughening and provides extremely flat surfaces with root mean square widths w<1.5 Å for fully coherent layers. These samples were used as the starting point to probe mechanisms that control misfit-dislocation-induced surface roughening (i.e., crosshatch) along 90°-rotated 〈110〉 directions. For film thicknesses t just larger than the critical value for misfit dislocation formation, tc≃1000 Å, surface roughness is dominated by single- and multiple-atomic-height steps generated by the motion of threading dislocations associated with interfacial misfits. The surface steps are preferential H desorption sites and the increase in total step length results in a decrease in θH on terraces as well as at step edges. The latter effect allows a higher adatom crossing probability at ascending steps, leading to the formation of periodic ridges in response to local strain fields associated with misfit dislocation clusters; w increases from 3.1 Å at t=1350 Å (corresponding to strain relaxation R of 1%) to 27 Å at t=4400 Å (R=78%). Simultaneously, the decrease in θH on terraces strongly affects film growth kinetics as the deposition rates increase from 10 Å min−1 with t<tc to ≃60 Å min−1 with t≃1400–4400 Å. Overall, in films with t≲1440 Å (R≲5%), crosshatch is due to surface steps that result from multiple misfit dislocations on single glide planes. At higher film thicknesses (R=22–78%), crosshatch becomes dominated by local strain-induced roughening and leads to periodic ridge formation. © 2003 American Institute of Physics.
Show PACS
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Hd Other semiconductors
68.43.Mn Adsorption kinetics
61.72.Lk Linear defects: dislocations, disclinations

Characteristics and stress-induced degradation of laser-activated low temperature polycrystalline silicon thin-film transistors

Du-Zen Peng, Ting-Chang Chang, Chun-Yen Chang, Ming-Liang Tsai, Chun-Hao Tu, and Po-Tsun Liu

J. Appl. Phys. 93, 1926 (2003); http://dx.doi.org/10.1063/1.1535732 (7 pages) | Cited 2 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The characteristics and reliability of laser-activated polycrystalline silicon thin-film transistors (poly-Si TFTs) under the stress condition of drain voltage (Vd)=12 V and gate voltage (Vg)=15 V have been investigated. In spite of reducing the source/drain resistivity by using laser activation method, the leakage current (Vg<0) is larger for laser-activated poly-Si TFTs in comparison with traditional furnace-activated counterparts. It is also found that the post-stress leakage and on/off current ratio degrade much faster for laser-activated poly-Si TFTs, while the degradation rates of threshold voltage and subthreshold swing are comparable to those of traditional furnace-activated TFTs. The laser activation modifies the grain structure between drain and channel region and causes grain discontinuity extending from the drain side to the channel region. The grain discontinuity near drain side in the polysilicon film has been investigated by transmission electron microscopy analysis. The effective trap state density calculated from typical I−V curve has been compared for laser-activated and furnace-activated TFTs. As a result, an inferior reliability with extra trap state density and larger leakage current was observed in the laser-activated poly-Si TFTs. © 2003 American Institute of Physics.
Show PACS
85.30.Tv Field effect devices
81.05.Cy Elemental semiconductors
61.72.Cc Kinetics of defect formation and annealing
42.62.-b Laser applications

Growth and microstructural characterizations of GaN films grown by laser induced reactive epitaxy

H. Zhou, T. Rupp, F. Phillipp, G. Henn, M. Gross, A. Rühm, and H. Schröder

J. Appl. Phys. 93, 1933 (2003); http://dx.doi.org/10.1063/1.1535257 (8 pages) | Cited 3 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Hexagonal GaN thin films have been grown by laser induced reactive epitaxy (LIRE) and characterized by various techniques. The films were deposited on sapphire (0001) and SiC (0001) without and with a buffer layer. Dislocations with predominant edge type and inversion domains were observed in the films. Dislocation density measured by x-ray diffraction is in fair agreement with that measured by transmission electron microscopy. Studies on the polarity of films indicate that Ga polarity was obtained for the films grown on SiC, while the films grown directly on sapphire were of N polarity. The atomic structure with a displacement of c/8 across the inversion domain boundary was deduced from the fringe contrast analyses and high resolution transmission electron microscopy studies. For the films grown on sapphire, the Ga polarity was achieved by using an AlGaN prelayer coupled with the introduction of low-temperature GaN buffer layer, which led to a clear improvement of the film quality. The typical cathodoluminescence spectra of such GaN films are comparable to those reported in the literature. The present work provides insight into the crystal growth and microstructure of GaN films and indicates that LIRE is a promising method to grow high quality GaN films. © 2003 American Institute of Physics.
Show PACS
81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth
81.05.Ea III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
78.66.Fd III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.60.Hk Cathodoluminescence, ionoluminescence

In situ observations of phase transitions in Ti–6Al–4V alloy welds using spatially resolved x-ray diffraction

J. W. Elmer, T. A. Palmer, and Joe Wong

J. Appl. Phys. 93, 1941 (2003); http://dx.doi.org/10.1063/1.1537464 (7 pages) | Cited 11 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In situ spatially resolved x-ray diffraction (SRXRD) experiments were used to directly observe the heat-affected zone phases present during gas tungsten arc welding of a Ti–6Al–4V alloy. The experiments were performed at the Stanford Synchrotron Radiation Laboratory using a 250 μm diam x-ray beam to gather real-time experimental information about the α−Ti→β−Ti phase transition during weld heating. Six different welding conditions were investigated using SRXRD to experimentally determine the extent of the single phase β-Ti region surrounding the liquid weld pool. These data were compared to predicted locations of the β-Ti phase boundary determined by calculated weld thermal profiles and equilibrium thermodynamic relationships. The comparison shows differences between the experimentally measured and the calculated locations of the β-Ti boundary. The differences are attributed to kinetics of the α−Ti→β−Ti phase transition, which requires superheating above the β-Ti transus temperature to take place during nonisothermal weld heating. Analysis of the results reveal that the transition to β-Ti requires an additional 3.96 s (±0.29 s) of time and 169 °C (±25.7 °C) of superheat above the β-Ti transus temperature to go to completion under an average weld heating rate of 42.7 °C/s. © 2003 American Institute of Physics.
Show PACS
81.30.Bx Phase diagrams of metals, alloys, and oxides
81.05.Bx Metals, semimetals, and alloys
81.20.Vj Joining; welding
61.05.cp X-ray diffraction
61.50.Ks Crystallographic aspects of phase transformations; pressure effects
64.70.K- Solid-solid transitions
81.40.Gh Other heat and thermomechanical treatments
64.70.D- Solid-liquid transitions

X-ray photoelectron spectroscopic study of rare-earth-doped amorphous silicon–nitrogen films

A. R. Zanatta, C. T. M. Ribeiro, and F. Alvarez

J. Appl. Phys. 93, 1948 (2003); http://dx.doi.org/10.1063/1.1536015 (6 pages) | Cited 6 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Amorphous silicon–nitrogen (a-SiN) films independently doped with different rare-earth (RE) elements (Y, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) have been prepared by cosputtering. The films were investigated in detail by x-ray photoelectron spectroscopy employing 1486.6 eV photons. Additional information was also achieved by optical techniques and ion beam analyses. As a result of the deposition method and conditions, the films present similar contents of Si and N, and rare-earth concentrations below 1.0 at. %. In spite of this relatively low concentration, and taking advantage of the high photoionization cross section of the rare-earth elements at 1486.6 eV, the signal of several different core-levels and Auger transitions could be detected and analyzed. The electronic states at the top of the valence band of the RE-doped a-SiN films were also investigated with 1486.6 eV photons. Compared to the spectroscopic data of pure metals, the RE-related core levels of the present a-SiN films exhibit an energy shift typically in the 0.8–2.5 eV range, which is attributed to the presence of nitrogen atoms. According to the experimental data, most of the RE ions remain in the 3+ state. The only clear exception occurs in the Yb-doped a-SiN film, where a large fraction of Yb2+ coexisting with Yb3+ ions is evident. © 2003 American Institute of Physics.
Show PACS
79.60.Ht Disordered structures
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Jv Disordered structures; amorphous and glassy solids
71.23.Cq Amorphous semiconductors, metallic glasses, glasses

Effects of implantation temperature and ion flux on damage accumulation in Al-implanted 4H-SiC

Y. Zhang, W. J. Weber, W. Jiang, C. M. Wang, A. Hallén, and G. Possnert

J. Appl. Phys. 93, 1954 (2003); http://dx.doi.org/10.1063/1.1537451 (7 pages) | Cited 19 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effects of implantation temperature and ion flux on damage accumulation on both the Si and C sublattices in 4H-SiC have been investigated under 1.1-MeV Al22+ irradiation at temperatures from 150 to 450 K. The rate of damage accumulation decreases dramatically, and the damage profile sharpens due to significant dynamic recovery at temperatures close to the critical temperature for amorphization. At 450 K, the relative disorder and the density of planar defects increase rapidly with the increasing ion flux, exhibiting saturation at high ion fluxes. Planar defects are generated through the agglomeration of excess Si and C interstitials during irradiation and post-irradiation annealing at 450 K. A volume expansion of ∼8% is estimated for the peak damage region. © 2003 American Institute of Physics.
Show PACS
61.72.up Other materials
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.J- Point defects and defect clusters
85.40.Ry Impurity doping, diffusion and ion implantation technology

Growth condition dependence of morphology and electric properties of ZnO films on sapphire substrates prepared by molecular beam epitaxy

Takeshi Ohgaki, Naoki Ohashi, Hirofumi Kakemoto, Satoshi Wada, Yutaka Adachi, Hajime Haneda, and Takaaki Tsurumi

J. Appl. Phys. 93, 1961 (2003); http://dx.doi.org/10.1063/1.1535256 (5 pages) | Cited 18 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Zinc oxide (ZnO) films were grown on sapphire (112̄0) substrates by molecular beam epitaxy under oxygen radical irradiation. The effect of the growth conditions, including the Zn/O ratio supplied to the film surface, on the electrical properties of ZnO films was studied in relation to the film morphology. We found that the growth rate strongly depended on the Zn flux from the Knudsen cell and the optimum condition for high growth rate was very narrow. The grain size in the lateral direction increased with increasing growth rate in the thickness direction. The increase in growth rate, especially in the lateral direction, resulted in the carrier mobility increasing up to 42 cm2 V−1 s−1. The carrier concentration N was sensitive to the substrate temperature, while the value of N was not sensitive to the source supplying ratio Zn/O. We discuss the decrease of the carrier concentration with increasing substrate temperature in regard to the formation of nonequilibrium defects. © 2003 American Institute of Physics.
Show PACS
73.61.Ga II-VI semiconductors
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.50.Dn Low-field transport and mobility; piezoresistance
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.My Galvanomagnetic and other magnetotransport effects

Influence of radiative transfer on optical cooling in the condensed phase

Bauke Heeg and Garry Rumbles

J. Appl. Phys. 93, 1966 (2003); http://dx.doi.org/10.1063/1.1529076 (8 pages) | Cited 2 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of fluorescence reabsorption on the optical cooling in the condensed phase was calculated using a stochastic model, based on spectral data of Rhodamine 101 in ethanol. The redshift in measured fluorescence for increasing Rhodamine 101 concentrations is reproduced for concentrations up to 10−4 M, suggesting that radiative transfer can be simulated accurately using a relatively simple random walk model. This also ensures a degree of accuracy in calculating the effect of radiative transfer processes on the optical cooling of a sample of given geometry. The stochastic method, using only the absorbance and molecular fluorescence (i.e., fluorescence unaffected by reabsorption) spectra as the input values, allows one to estimate the chromophore concentration for which maximum cooling efficiency occurs, given a cell geometry and quantum yield and vice versa. The method predicts a cooling efficiency that is an order of magnitude lower than has been reported previously [J. L. Clark and G. Rumbles, Phys. Rev. Lett. 76, 2037 (1996); J. L. Clark, P. F. Miller, and G. Rumbles, J. Phys. Chem. A 102, 4428 (1998)]. The difference is attributed to an overestimate of the experimental data that is in part due to the measurement of a local cooling effect rather than a macroscopic, bulk cooling. © 2003 American Institute of Physics.
Show PACS
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
78.55.Bq Liquids
37.10.Mn Slowing and cooling of molecules
37.10.Pq Trapping of molecules

Improved Fourier method of thickness determination by x-ray reflectivity

L. Grave de Peralta and H. Temkin

J. Appl. Phys. 93, 1974 (2003); http://dx.doi.org/10.1063/1.1536722 (4 pages) | Cited 5 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Layer thickness can be reliably determined from x-ray reflectivity data using an improved Fourier method presented here. Before performing the Fourier transform the logarithm of the intensity corresponding to the incoherent superposition of x rays reflected from sample’s interfaces is subtracted from the experimental reflectivity curve. The subtracted curve is found by simple local average of the data. The connection between the Fourier methods and the dynamic and kinematic approaches is discussed. © 2003 American Institute of Physics.
Show PACS
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
61.05.cm X-ray reflectometry (surfaces, interfaces, films)

Incoherent neutron scattering and the dynamics of thin film photoresist polymers

Christopher L. Soles, Jack F. Douglas, Eric K. Lin, Joseph L. Lenhart, Ronald L. Jones, Wen-Li Wu, Darío L. Goldfarb, and Marie Angelopoulos

J. Appl. Phys. 93, 1978 (2003); http://dx.doi.org/10.1063/1.1539538 (9 pages) | Cited 5 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Elastic incoherent neutron scattering is employed to parameterize changes in the atomic/molecular mobility in lithographic polymers as a function of film thickness. Changes in the 200 MHz and faster dynamics are estimated in terms of a harmonic oscillator model and the corresponding Debye–Waller factor mean-square atomic displacement 〈u2〉. We generally observe that relatively large 〈u2〉 values in the glassy state lead to a strong suppression of 〈u2〉 when the polymer is confined to exceedingly thin films. In contrast, this thin film suppression is diminished or even absent if 〈u2〉 in the glass is relatively small. We further demonstrate that highly localized side group or segmental dynamics of hydrogen-rich moieties, such as methyl groups, dominate 〈u2〉 and that thin film confinement apparently retards these motions. With respect to photolithography, we demonstrate that a reduced 〈u2〉 in exceedingly thin model resist films corresponds to a decrease in the reaction front propagation kinetics. © 2003 American Institute of Physics.
Show PACS
63.50.-x Vibrational states in disordered systems
61.05.fg Neutron scattering (including small-angle scattering)
85.40.Hp Lithography, masks and pattern transfer
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
61.41.+e Polymers, elastomers, and plastics
68.55.-a Thin film structure and morphology
66.30.H- Self-diffusion and ionic conduction in nonmetals
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions

Ellipsometric characterization of damage profiles using an advanced optical model

P. Petrik, O. Polgár, M. Fried, T. Lohner, N. Q. Khánh, and J. Gyulai

J. Appl. Phys. 93, 1987 (2003); http://dx.doi.org/10.1063/1.1539306 (4 pages) | Cited 6 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Damage created by ion implantation into single crystalline silicon was characterized with an optical model based on the coupled half-Gaussian model developed by Fried et al [J. Appl. Phys. 71, 2835 (1992)]. In the improved optical model the damage profile was described by sublayers with thicknesses inversely proportional to the slope of the profile. This method allows a better resolution at the quickly changing parts of the profile, and a better approximation of the Gaussian profile with the same number of sublayers. A fitting procedure, which we call “multipoint random search,” was applied to minimize the probability of getting in a local minimum. The capabilities of our method were demonstrated for amorphizing doses using different ions and energies. The improved fit quality and the correlation with results of backscattering spectrometry basically supported the optical model. © 2003 American Institute of Physics.
Show PACS
61.82.Fk Semiconductors
68.47.Fg Semiconductor surfaces
61.72.uf Ge and Si
78.68.+m Optical properties of surfaces
78.40.Fy Semiconductors
07.60.Fs Polarimeters and ellipsometers
61.80.Jh Ion radiation effects
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.43.Dq Amorphous semiconductors, metals, and alloys

High pressure effect on structural and electrical properties of glassy carbon

X. Wang, Z. X. Bao, Y. L. Zhang, F. Y. Li, R. C. Yu, and C. Q. Jin

J. Appl. Phys. 93, 1991 (2003); http://dx.doi.org/10.1063/1.1539914 (4 pages) | Cited 4 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The structural evolutions of glassy carbon (GC) and graphitized glassy carbon (GGC) treated under high temperatures and high pressures have been studied by energy-dispersive x-ray diffraction in a diamond anvil cell. The equations of state of GC and GGC are determined from x-ray density data. GC has a higher bulk modulus than that of GGC. It is found that the two-dimensional order of stacked layers in GC decreases with increasing the stresses, and the orientated layers merge with the disorientated layers at higher pressures, in which it can also be attributed to the appearance of a bump in the electrical resistance measurements under high pressures. © 2003 American Institute of Physics.
Show PACS
61.43.Fs Glasses
72.80.Ng Disordered solids
62.50.-p High-pressure effects in solids and liquids
64.30.-t Equations of state of specific substances
62.20.D- Elasticity
81.05.U- Carbon/carbon-based materials

Blue, green, red, and white electroluminescence from multichromophore polymer blends

Bin Hu and Frank E. Karasz

J. Appl. Phys. 93, 1995 (2003); http://dx.doi.org/10.1063/1.1536018 (7 pages) | Cited 38 times

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We extend our previous investigations of electro-optically active polymer blends to report enhanced blue, green, red, or white electroluminescence (EL) from a multicomponent multiphase polymer blend containing blue, green, and red light emitting chromophores in different proportions as required together with both hole and electron transport materials. The general architecture of the EL devices employed was indium–tin–oxide (ITO)/poly p-phenylene vinylene (PPV)/blend/Ca or Al, in which a PPV layer was interspersed between the ITO and the blend layers to provide more efficient hole injection, enhance overall emission, and increase device longevity. The relevant EL mechanisms are discussed in terms of color related and efficiency related processes. The color related EL processes involve blueshifted emissions controlled by chromophore dilution, Förster energy transfer controlled mainly by spectral overlap between absorption and emission in chromophores, and an interfacial emission from the PPV layer. The efficiency related processes involve double charge injection controlled by the nature and concentration of the hole and electron transport materials present, the confinement of injected charge carriers controlled by the blend morphology, and potential barriers within the polymer blend layer. The design of devices which emit the desired color, efficiently balance the double charge injection, and optimize the confinement of injected charge carriers to provide high quantum yields by using polymer blends, is discussed. © 2003 American Institute of Physics.
Show PACS
78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
78.66.Qn Polymers; organic compounds
61.41.+e Polymers, elastomers, and plastics
78.20.Jq Electro-optical effects
73.61.Ph Polymers; organic compounds

Model study of soft x-ray spectroscopy techniques for observing magnetic circular dichroism in buried SmCo magnetic films

S. Itza-Ortiz, D. L. Ederer, T. M. Schuler, N. Ruzycki, J. Samuel Jiang, and S. D. Bader

J. Appl. Phys. 93, 2002 (2003); http://dx.doi.org/10.1063/1.1538339 (7 pages)

Online Publication Date: 30 January 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
X-ray emission and absorption spectroscopy (XES and XAS, respectively) are important and powerful techniques for determining the electronic properties of materials. Both are used to study magnetic circular dichroism (MCD) which is especially useful for analyzing the magnetic properties of materials. We present XAS and XES measurements and a MCD model study of two thin film layered samples containing SmCo layers in order to report on the applicability of soft x-ray spectroscopic techniques to determine the composition, layer thickness, and electronic structure of such materials. Using a transmission by fluorescence attenuation (TFA) technique we determined the composition and thickness of the SmCo layer to be consistent with the intended composition and thickness. We also confirmed the thickness of the other layers by comparing the XES from the thin film with that of a bulk sample. We showed by a model study that TFA could be used to obtain MCD, and thus the anisotropy of the sample, for film thicknesses between about 400 and 800 Å. © 2003 American Institute of Physics.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.20.Ls Magneto-optical effects
78.70.En X-ray emission spectra and fluorescence
78.70.Dm X-ray absorption spectra
75.50.Cc Other ferromagnetic metals and alloys
Page 1 of 4 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Your Recent History Recent History Help

Recently Viewed

  1. High open-circuit voltage photovoltaic devices from carbon-nanotube-polymer composites
  2. Nanoscale thermal transport
  3. Improved light-output and electrical performance of InGaN-based light-emitting diode by microroughening of the p-GaN surface
  4. Current-induced switching in low resistance magnetic tunnel junctions
  5. Chopping techniques for low-frequency nanotesla spin-dependent tunneling field sensors
Go to AIP Home
Copyright © American Institute of Physics
close