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

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

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

15 Sep 2002

Volume 92, Issue 6, pp. 2959-3416

Page 1 of 3 Pages Next Page | Jump to Page
back to top
RSS Feeds

Monomode, nonleaky planar waveguides in a Nd3+-doped silicate glass produced by silicon ion implantation at low doses

Feng Chen, Ke-Ming Wang, Xue-Lin Wang, Xi-Shan Li, Qing-Ming Lu, Ding-Yu Shen, and Rui Nie

J. Appl. Phys. 92, 2959 (2002); http://dx.doi.org/10.1063/1.1499204 (3 pages) | Cited 9 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Monomode, nonleaky planar waveguides in a Nd3+-doped silicate glass were fabricated by 3.0 MeV Si+ ion implantation at doses ranging from 5×1013 to 6×1014 ions/cm2 at room temperature. The enhancement of the refractive index confined the light propagating in the waveguide without tunneling effects in contrast to the traditional barrier-type waveguide. Annealing at moderate temperatures (about 200 °C) in air was performed, which reduced the propagation loss from 20–30 dB/cm to a minimum of 0.5 dB/cm. © 2002 American Institute of Physics.
Show PACS
42.79.Gn Optical waveguides and couplers
42.70.Ce Glasses, quartz
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Et Waveguides, couplers, and arrays

Kinetics and mechanisms of laser-induced decompositions of hydrogenated amorphous carbon films on magnetic hard disks

Li Hong Zhang, Hao Gong, and Jian Ping Wang

J. Appl. Phys. 92, 2962 (2002); http://dx.doi.org/10.1063/1.1500790 (7 pages) | Cited 4 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Laser-induced structural decompositions of hydrogenated amorphous carbon films deposited by dc-magnetron sputtering on magnetic hard disks were studied using a microbeam Ar+ laser (514.5 nm). The laser had varying powers between 3.0 and 0.3 mW at a focused circular spot of 2.5 μm diameter, corresponding to approximate fluence rates between 6×104 to 6×103 J cm−2 s−1. The effect of laser power on decomposition rate could be expressed by an exponential equation. Based on the relationship between laser power and temperature, relative apparent activation energies for film decompositions were obtained and found to decrease with the increase of film hydrogen content and the elapse time of laser irradiation. All the films irradiated with laser powers between 0.75 and 0.3 mW followed the apparent first-order reaction. The reaction order tended to increase at higher laser powers and hydrogen content in the films. © 2002 American Institute of Physics.
Show PACS
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
64.75.-g Phase equilibria
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering

Second harmonic generation in two-dimensional metal photonic band gap materials

Yan-bin Chen, Xiang-bao Cai, Yong-yuan Zhu, Shi-ning Zhu, and Nai-ben Ming

J. Appl. Phys. 92, 2969 (2002); http://dx.doi.org/10.1063/1.1481779 (5 pages)

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
With plane-wave expansion and the Green function method, the second harmonic generation in a two-dimensional metal photonic band gap (PBG) material is studied theoretically. By appropriately selecting the structural parameters of the PBG material, the wave vectors of the fundamental and the second harmonics can be set at the edges of the PBG. In this case, the second harmonic can be realized efficiently due to metal surface nonlinearity. The discussion can be generalized to three-dimensional systems. © 2002 American Institute of Physics.
Show PACS
42.70.Qs Photonic bandgap materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Optical properties of low-temperature grown GaAs on Bragg reflectors

M. Giehler, J. Herfort, W. Ulrici, L. Däweritz, and K. H. Ploog

J. Appl. Phys. 92, 2974 (2002); http://dx.doi.org/10.1063/1.1499747 (3 pages) | Cited 2 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Near-infrared reflectance spectra of 5 μm thick low-temperature (LT) GaAs films grown by molecular-beam epitaxy at different substrate temperatures TG on GaAs/AlAs Bragg reflectors (BR’s) have been studied. With decreasing TG (increasing absorption coefficient αf of the film), the reflectance of the stop band of the BR decreases monotonously, while the amplitudes of the interference fringes due to the LT-GaAs layer inside the stop band initially increase followed by a decrease for large αf values. This unusual behavior is explained by a particular optical interference effect of a thick absorbing layer on a strongly reflecting structure. This effect remarkably improves the determination of αf and enables the detection of As-antisite defects in LT-GaAs films for concentrations as low as 1×1018 cm−3, where other methods fail. © 2002 American Institute of Physics.
Show PACS
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.20.-e Optical properties of bulk materials and thin films

High-efficiency optical emission, detection, and coupling using silicon diodes

J. Zhao, M. A. Green, and A. Wang

J. Appl. Phys. 92, 2977 (2002); http://dx.doi.org/10.1063/1.1503168 (3 pages) | Cited 10 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This article reports band-edge light emission and detection using silicon diodes. A bulk crystalline silicon light-emitting diode (LED) demonstrating close to 1% power efficiency at room temperature is combined with a similar diode used as a detector, that collects the light emitted with a high quantum collection efficiency of 33%, to produce a silicon-to-silicon optically coupled system that demonstrates 0.18% coupling quantum efficiency. The silicon LED demonstrates similarly high performance at very low power levels, where it has higher power efficiency than a high efficiency GaAlAs LED. © 2002 American Institute of Physics.
Show PACS
85.60.Jb Light-emitting devices
42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
back to top
RSS Feeds

Insulator surface charging and dissipation during plasma immersion ion implantation using a thin conductive surface film

T. W. H. Oates and M. M. M. Bilek

J. Appl. Phys. 92, 2980 (2002); http://dx.doi.org/10.1063/1.1503149 (4 pages) | Cited 9 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Plasma immersion ion implantation of insulating materials is inherently problematic due to charge accumulation on the insulator surface. Surface charge can be removed by the application of an ultrathin conductive film, which is essentially transparent to the incident ions. The minimum thickness of the film is determined by its capability to effectively conduct away the implanted charge. We present a model for charge accumulation on insulators during plasma immersion ion implantation and use this to study the plasma sheath width and voltage, with and without an ultrathin metal film. Charge accumulation occurs more quickly when the plasma has a directed velocity greater than the Bohm velocity, which is the case for a cathodic arc plasma. We show that for both cases the effectiveness of plasma immersion ion implantation is improved with the application of an ultrathin conductive film. © 2002 American Institute of Physics.
Show PACS
52.77.Dq Plasma-based ion implantation and deposition
52.40.Kh Plasma sheaths

Measured energy distributions of ions driven by an asymmetrically pulsed bias during magnetron sputtering

E. V. Barnat and T. -M. Lu

J. Appl. Phys. 92, 2984 (2002); http://dx.doi.org/10.1063/1.1501739 (6 pages) | Cited 11 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A retarding field analyzer is used to obtain a measure of the energy of the ions extracted from a direct current discharge driven by a low-frequency (100–100 kHz) asymmetrically pulsed bias. Measurements are made to illustrate the effects of the pulse’s shape (frequency and duty) on the distribution in the energies of the ions extracted from the plasma. Ion energy distributions are computed by a quasistatic treatment of the ion’s response to the measured wave form of the pulsed electrode. Comparisons are made between the measured and calculated ion energy distributions to demonstrate the effectiveness of the technique used to calculate the ion energy distribution. Expressions are then produced for the time scales in which the quasistatic treatment of the sheath remains a valid approximation to predict the energy distribution of the ions. © 2002 American Institute of Physics.
Show PACS
52.70.Ds Electric and magnetic measurements
81.15.Cd Deposition by sputtering
52.77.Dq Plasma-based ion implantation and deposition
52.40.Kh Plasma sheaths
52.40.Hf Plasma-material interactions; boundary layer effects

Estimation of dissociation degree of N2 in an inductively coupled plasma by vacuum ultraviolet emission spectroscopy

Toshiki Nakano, Shinya Kumagai, and Seiji Samukawa

J. Appl. Phys. 92, 2990 (2002); http://dx.doi.org/10.1063/1.1501741 (6 pages) | Cited 19 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A simple procedure for estimation of the N2 dissociation degrees in low-pressure, high-density plasmas is proposed. This procedure is applied to the estimation of the N2 dissociation in an N2 inductively coupled plasma and confirmed to give N2 dissociation degrees similar to those reported previously. The rf power and N2 pressure dependence of the N2 dissociation degree is also presented. The contribution of stepwise excitation out of N2 A3Σu+ [N2(A)] metastables to the N2 second positive emission is found to be negligible from the net excitation rate computed using an assumed cross section of the electron-impact excitation from N2(A) to the N2C3Πu state and the N2(A) number density deduced from a simple kinetic model. The recombination of N atoms on the inner surfaces of the plasma reactor used in this study is discussed briefly. Finally, the advantages of the N2 dissociation estimation by vacuum ultraviolet optical emission spectroscopy are mentioned. © 2002 American Institute of Physics.
Show PACS
34.80.Ht Dissociation and dissociative attachment
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
34.80.Gs Molecular excitation and ionization
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
34.50.-s Scattering of atoms and molecules
52.25.Dg Plasma kinetic equations
33.50.-j Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion)
back to top
RSS Feeds

Nanocrystalline order of zinc oxide thin films grown on optical fibers

E. Y. M. Lee, N. Tran, J. Russell, and R. N. Lamb

J. Appl. Phys. 92, 2996 (2002); http://dx.doi.org/10.1063/1.1495064 (4 pages) | Cited 14 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The crystallographic orientation of polycrystalline zinc oxide films grown on optical fibers using single-source chemical vapor deposition (SS CVD) of basic zinc acetate have been studied. The films have been characterized using near-edge x-ray absorption fine structure. For the SS CVD ZnO growth on planar substrates, the film orientation can be varied from randomly oriented to highly c-axis oriented. In contrast, the films grown on optical fibers were either randomly oriented or a,b-axis oriented, depending on growth conditions. The correlations between growth conditions and the crystallographic properties of the films on fibers were discussed. The results suggest that factors such as curvature may have an effect on the crystallinity of film growth. © 2002 American Institute of Physics.
Show PACS
68.55.-a Thin film structure and morphology
61.46.-w Structure of nanoscale materials
78.70.Dm X-ray absorption spectra

Structure and electronic properties of SiO2/Si multilayer superlattices: Si K edge and L3,2 edge x-ray absorption fine structure study

R. Sammynaiken, S. J. Naftel, T. K. Sham, K. W. Cheah, B. Averboukh, R. Huber, Y. R. Shen, G. G. Qin, Z. C. Ma, and W. H. Zong

J. Appl. Phys. 92, 3000 (2002); http://dx.doi.org/10.1063/1.1501742 (7 pages) | Cited 12 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report an x-ray absorption fine structure study at the Si K and L3,2 edges of a series of Si/SiO2 superlattices (SL). The SL system comprises four periods of elemental silicon with a spacing of 1, 1.4, 2.2, and 2.6 nm sandwiched by a 1.5 nm silicon oxide and capped by a 3 nm silicon oxide layer. These systems exhibit electroluminescence and photoluminescence. X-ray absorption near edge structure (XANES) at both the Si K and L3,2 edge confirms that the Si layers are amorphous. Polarization dependent measurement at the Si K edge reveals that a distinct Si/SiO2 interface exists with strong Si–O bonding oriented preferentially closer to the surface normal. High resolution XANES at the Si L3,2 edge shows a noticeable blueshift of the edge threshold as the lattice spacing decreases, in good accord with quantum confinement. The results and their implications for the origin (quantum confinement and interface/oxide defects) of luminescence in these superlattice systems are discussed. © 2002 American Institute of Physics.
Show PACS
68.65.Cd Superlattices
73.21.Cd Superlattices
78.60.Fi Electroluminescence
78.70.Dm X-ray absorption spectra
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
78.55.Hx Other solid inorganic materials
78.66.Nk Insulators

Effects of surface treatments on the adhesion of Cu and Cr/Cu metallizations to a multifunctional photoresist

J. Ge and J. K. Kivilahti

J. Appl. Phys. 92, 3007 (2002); http://dx.doi.org/10.1063/1.1495528 (9 pages) | Cited 12 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effects of chemical, plasma, and reactive ion etching (RIE) treatments on the adhesion of Cu and Cr/Cu to the multifunctional polymer were investigated. The adhesion was measured with the newly developed pull test. The polymer surfaces were characterized by the x-ray photoelectron spectroscopy, atomic force microscopy, and surface free energy measurement. The failure modes were examined with the scanning electron microscopy and energy-dispersive spectroscopy. It was found that the adhesion of Cu and Cr/Cu to the highly functional photoresist was poor, regardless of the chemical, plasma, and reactive ion etching treatment with either O2 or CF4 used. However, the RIE pretreatment with the gas mixture (O2+CF4) of the photoresist surface increased the adhesion of sputtered Cr/Cu to the photoresist remarkably, and the failure mode was cohesive within the photoresist. Furthermore, the RIE pretreatment with pure oxygen gave rise to the needle-like surface together with virtually no introduced reactive functional groups, whereas the RIE with O2-rich gas mixture of O2+CF4 resulted in the relative smooth polymer surfaces and the newly formed C�O/O–C–O and O–C�O functionalities were incorporated on the treated surface with the increased polar surface free energy. The adhesion mechanism based on the experimental adhesion results and the surface characterizations of the polymer is proposed and discussed. © 2002 American Institute of Physics.
Show PACS
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
85.40.Ls Metallization, contacts, interconnects; device isolation
85.40.Hp Lithography, masks and pattern transfer
68.35.Np Adhesion
81.65.Ps Polishing, grinding, surface finishing
82.35.Gh Polymers on surfaces; adhesion
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
68.37.Xy Scanning Auger microscopy, photoelectron microscopy
68.37.Ps Atomic force microscopy (AFM)
65.40.G- Other thermodynamical quantities
68.35.Md Surface thermodynamics, surface energies

Direct measurement of Urbach tail and gap state absorption in CuGaSe2 thin films by photothermal deflection spectroscopy and the constant photocurrent method

A. Meeder, D. Fuertes Marrón, A. Rumberg, M. Ch. Lux-Steiner, V. Chu, and J. P. Conde

J. Appl. Phys. 92, 3016 (2002); http://dx.doi.org/10.1063/1.1501745 (5 pages) | Cited 11 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The applicability of photothermal deflection spectroscopy (PDS) and the constant photocurrent method (CPM) to chemical vapor deposited and physical vapor deposited CuGaSe2 (CGSe) thin films is investigated. Process dependent variations in direct band-gap energies, Urbach tail widths, bulk and surface defect densities of the films are given as a function of composition. Differences in the PDS and CPM absorption spectra of more than one order of magnitude are found. Using the standard a-Si theory of PDS and CPM analysis, a two-layer system consisting of a defect-rich near-surface layer and a less defective bulk layer is found in device-quality films. Optical improvements due to the Ga+Se annealing step as a second stage of the growth process result in a reduced bulk defect density while the near-surface defect density remains unchanged. © 2002 American Institute of Physics.
Show PACS
73.20.At Surface states, band structure, electron density of states
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.50.Pz Photoconduction and photovoltaic effects
84.60.Jt Photoelectric conversion
73.61.Le Other inorganic semiconductors
78.40.Fy Semiconductors
78.66.Li Other semiconductors

Modulation of the beam intensity for high-dynamic-range low energy electron diffraction

F. Pesty, P. Garoche, and S. Dorel

J. Appl. Phys. 92, 3021 (2002); http://dx.doi.org/10.1063/1.1494111 (6 pages) | Cited 2 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We describe a low-energy electron diffraction process with a periodical modulation of the electron beam intensity. The conditions to get a coherent modulated beam are investigated, first, by simulating the electron trajectories and second, by analyzing the diffraction pattern oscillation. The large increase in the dynamic range is exemplified by diffraction of the electrons by mica surface nanostructures. © 2002 American Institute of Physics.
Show PACS
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.46.-w Structure of nanoscale materials

Effective elastic stiffnesses of InAs under uniform strain

S. W. Ellaway and D. A. Faux

J. Appl. Phys. 92, 3027 (2002); http://dx.doi.org/10.1063/1.1500421 (7 pages) | Cited 25 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effective elastic stiffnesses C11, C12 and C44 of InAs and derived elastic constants are determined for states of uniform volumetric strain by atomistic simulation. The effective elastic stiffnesses C11 and C12 are found to increase significantly with strain whereas C44 is found to be nearly independent of strain. Results for the bulk modulus are consistent with high-pressure experiments and nonlinear elasticity theories. The effective Young’s modulus is found to be nearly independent of strain whereas the effective Poisson’s ratio increases by about 40% over the range 0%–20% volumetric strain. The use of effective elastic stiffnesses within the isotropic approximation leads to a hydrostatic strain for an InAs quantum dot which is 16% smaller than the uncorrected value. It is concluded that continuum techniques for calculating quantum-dot-induced strain in the InAs/GaAs system should include strain-dependent InAs elastic stiffnesses for maximum accuracy. © 2002 American Institute of Physics.
Show PACS
62.20.D- Elasticity
81.05.Ea III-V semiconductors
81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
68.35.Gy Mechanical properties; surface strains
46.25.Cc Theoretical studies

Ultraviolet excitation fine tuning of luminescence bands of oxygen-deficient centers in silica

A. Anedda, C. M. Carbonaro, F. Clemente, and R. Corpino

J. Appl. Phys. 92, 3034 (2002); http://dx.doi.org/10.1063/1.1499984 (5 pages) | Cited 9 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The photoluminescence (PL) activity of oxygen deficient centers in commercial silica samples has been reconstructed by exciting in the spectral range of their optical absorption band around 5 eV. The fine tuning of the excitation was provided by a tunable pulsed optical parametric oscillator seeded by a Nd:yttrium–aluminum–garnet laser. The experimental results, analyzed in the spectral moment framework, indicate the presence of different centers whose spectral features are modulated by structural disorder typical of the glassy matrix. The photoluminescence excitation spectra at different emission energies evidence the composite structure of the luminescence bands around 3.1 and 4.2 eV, usually ascribed to triplet and singlet transitions of the same oxygen deficient center. Besides the well-known emission bands centered at 3.15 and 4.20 eV, the contribution of a new PL band below 3 eV is reported. Time resolved photoluminescence measurements of the low energy band give an estimate of its spectral characteristics, with peak position around 2.8 eV, full width at half maximum of about 1 eV and exponential lifetime of 840 ns. © 2002 American Institute of Physics.
Show PACS
78.55.Hx Other solid inorganic materials
71.55.Ht Other nonmetals
78.47.-p Spectroscopy of solid state dynamics
71.35.-y Excitons and related phenomena

Structural and morphological modifications in double layer heterostructures containing H2Pc, perylene-3, 4, 9, 10-tetracarboxylic dianhydride and Alq3

S. Heutz and T. S. Jones

J. Appl. Phys. 92, 3039 (2002); http://dx.doi.org/10.1063/1.1499743 (8 pages) | Cited 15 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The morphological, structural and spectroscopic properties of molecular double layers grown by organic molecular beam deposition have been investigated using atomic force microscopy, Nomarski microscopy, powder x-ray diffraction and electronic absorption spectroscopy. The structures, based on metal-free phthalocyanine (H2Pc), perylene-3, 4, 9, 10-tetracarboxylic dianhydride (PTCDA) and aluminum-tris-quinolate (Alq3), were deposited on glass substrates, with individual layer thicknesses ranging from 7 to 380 nm. Alq3 has no influence on the subsequent growth of either H2Pc or PTCDA, and its properties are not affected by a first molecular layer. By contrast, significant structural modifications are observed in double layers based on the two crystalline materials H2Pc and PTCDA. H2Pc deposited onto a PTCDA first layer departs from its herringbone structure, and adopts a layered structure with an interplanar spacing of 3.33 Å and an intermolecular shift of 1.7 Å. The structure of a PTCDA film deposited onto a α-H2Pc layer is completely disrupted. When PTCDA is deposited onto a β-H2Pc first layer, a morphological templating is observed and this annihilates any structural disruption. This is consistent with the growth of a microcrystalline PTCDA film on top of a α-H2Pc first layer. © 2002 American Institute of Physics.
Show PACS
68.65.Ac Multilayers
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.37.Ps Atomic force microscopy (AFM)
78.66.Qn Polymers; organic compounds

Normalized photoacoustic techniques for thermal diffusivity measurements of buried layers in multilayered systems

J. A. Balderas-López, A. Mandelis, and J. A. García

J. Appl. Phys. 92, 3047 (2002); http://dx.doi.org/10.1063/1.1500784 (9 pages) | Cited 13 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The one-dimensional heat diffusion problem for a three-layer system is solved assuming the surface absorption model. The analytical solution is shown to be suitable for the implementation of normalized depth-profilometric photoacoustic methodologies involving the open photoacoustic-cell configuration for thermal diffusivity measurements in buried underlayers within a three-layer stack. Our normalization procedures eliminate the frequency-dependent instrumental electronic contribution (transfer function) and some thermophysically nonrelevant proportionality factors in the theoretical equations, thus making the depth-profilometric analysis feasible. The measurement methodology is achieved by normalizing the theoretical photoacoustic signal from the three layers with the corresponding signal from the uppermost two layers, involving linear fits to measure the thermal diffusivity of the third underlayer. Three different multilayered materials were examined using the proposed methodologies. High reproducibility of the thermal diffusivity measurements and good agreement with values reported in literature were found. Besides the foregoing procedures, a lumped photoacoustic model was developed, which yields the effective thermal-diffusivity value of the multilayer stack. © 2002 American Institute of Physics.
Show PACS
68.60.Dv Thermal stability; thermal effects
68.65.Ac Multilayers
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Subsurface segregation of yttria in yttria stabilized zirconia

M. de Ridder, R. G. van Welzenis, A. W. Denier van der Gon, H. H. Brongersma, S. Wulff, W.-F. Chu, and W. Weppner

J. Appl. Phys. 92, 3056 (2002); http://dx.doi.org/10.1063/1.1499748 (9 pages) | Cited 20 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The segregation behavior in 3 and 10 mol % polycrystalline yttria stabilized zirconia (YSZ), calcined at temperatures ranging from 300 to 1600 °C, is characterized using low-energy ion scattering (LEIS). In order to be able to separate the Y and Zr LEIS signals, YSZ samples have been prepared using isotopically enriched 94ZrO2 instead of natural zirconia. The samples are made via a special precipitation method at a low temperature. The segregation to the outermost surface layer is dominated by impurities. The increased impurity levels are restricted to this first layer, which underlines the importance of the use of LEIS for this study. For temperatures of 1000 °C and higher, the oxides of the impurities Na, Si, and Ca even cover the surface completely. The performance of a device like the solid oxide fuel cell which has an YSZ electrolyte and a working temperature around 1000 °C, will, therefore, be strongly hampered by these impurities. The reduction of impurities, to prevent accumulation at the surface, will only be effective if the total impurity bulk concentration can be reduced below the 10 ppm level. Due to the presence of the impurities, yttria cannot accumulate in the outermost layer. It does so, in contrast to the general belief, in the subsurface layer and to much higher concentrations than the values reported previously. The difference in the interfacial free energies of Y2O3 and ZrO2 is determined to be −21±3 kJ/mol.© 2002 American Institute of Physics.
Show PACS
68.35.Dv Composition, segregation; defects and impurities
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
68.35.Md Surface thermodynamics, surface energies
61.72.S- Impurities in crystals
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Frequency upconversion involving triads and quartets of ions in a Pr3+/Nd3+ codoped fluoroindate glass

Edilson L. Falcão-Filho, Cid B. de Araújo, and Y. Messaddeq

J. Appl. Phys. 92, 3065 (2002); http://dx.doi.org/10.1063/1.1501757 (6 pages) | Cited 20 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Frequency upconversion (UC) processes involving energy transfer (ET) among Nd3+ and Pr3+ ions in a fluoroindate glass are reported. In a first experiment, the excitation of Pr3+ [transition 3H4→1D2] and of Nd3+ [transition 4I9/2→(2G7/2+4G5/2)] was achieved with a dye laser operating in the 575–590 nm range. In a second experiment, the Nd3+ ions were excited with the second harmonic of a Nd: YAG laser at 532 nm. The ET processes leading to UC in both experiments were studied by monitoring the blue fluorescence decay at 480 nm due to the transition 3P0→3H4 in Pr3+. In the more relevant UC process, quartets of ions (Nd–Nd–Pr–Pr) are excited due to absorption of three laser photons by two Nd3+ ions which transfer their energy to two Pr3+ ions. Each Pr3+ ion promoted to the 3P0 level decays to the ground state emitting one photon in the blue region. This conclusion was achieved investigating the dependence of the UC fluorescence intensity as a function of laser intensity, samples concentrations, and temporal behavior of the UC signal. Other UC processes involving nonisoionic groups of three ions are also reported. © 2002 American Institute of Physics.
Show PACS
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Ce Glasses, quartz

Influence of free carrier screening on the luminescence energy shift and carrier lifetime of InGaN quantum wells

Takamasa Kuroda and Atsushi Tackeuchi

J. Appl. Phys. 92, 3071 (2002); http://dx.doi.org/10.1063/1.1502186 (4 pages) | Cited 42 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We studied the influence of free carrier screening on the luminescence energy shift and carrier lifetime of InGaN multiple quantum wells (MQWs) mainly in relation to a quantum-confined Stark effect. We performed a systematic time-resolved photoluminescence measurement of MQWs for various carrier densities and three different well widths (2.5, 4.0, and 5.5 nm). We show that the energy shift and the change in carrier lifetime are explained well by the free carrier screening effect which compensates for the internal electric field. © 2002 American Institute of Physics.
Show PACS
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.67.De Quantum wells
73.21.Fg Quantum wells
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Structural and magnetic characteristics of monodispersed Fe and oxide-coated Fe cluster assemblies

D. L. Peng, T. Hihara, K. Sumiyama, and H. Morikawa

J. Appl. Phys. 92, 3075 (2002); http://dx.doi.org/10.1063/1.1501754 (9 pages) | Cited 29 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We systematically studied structural and magnetic characteristics of size- monodispersed Fe and oxide-coated Fe cluster assemblies with the mean cluster sizes of 7–16 nm. Transmission electron microscopy and scanning electron microscopy (SEM) observations show that the Fe clusters in the assemblies maintain their original size at room temperature. In the SEM images, a random stacking of the Fe clusters and a porous structure with a low cluster packing fraction of about 25% are observed. For the Fe cluster assemblies, magnetic coercivity (Hc) at room temperature increases from 4×101 to 4×102 Oe by increasing the mean cluster size from 7.3 to 16.3 nm. Using the experimental values of the coercivity at T⩾100 K and the fitting values of blocking temperature TB from Hc=Hc0[1−(T/TB)1/2], we estimated the values of magnetic anisotropy constant K of the order of 106 erg/cm3 from TB=KV/25kB, which is larger by an order of magnitude than the bulk Fe value (5×105 erg/cm3). Such a large effective anisotropy at T⩾100 K is ascribed to the large surface anisotropy effects of the small clusters and the low cluster-packing fraction of the Fe cluster assemblies. For the oxide-coated Fe cluster samples, the coercivity strongly depends on the oxygen gas flow rate during deposition, cluster size, and temperature. In the case of a high oxygen gas flow rate (namely high surface-oxidized clusters), the ferrimagnetic oxide shell crystallites also affect the coercivity at T>50 K: The hysteresis loop shift disappears, leading to a complex change in the coercivity and an enhancement of the effective anisotropy constant. © 2002 American Institute of Physics.
Show PACS
61.46.-w Structure of nanoscale materials
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
81.65.Mq Oxidation

Elastic analysis of an inhomogeneous quantum dot in multilayered semiconductors using a boundary element method

B. Yang and E. Pan

J. Appl. Phys. 92, 3084 (2002); http://dx.doi.org/10.1063/1.1502201 (5 pages) | Cited 10 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this work, we examine the elastostatic field due to a buried quantum dot (QD) in multilayered semiconductors using a boundary element method. Since the integral kernels employ a special Green’s function that satisfies the interfacial continuity and boundary conditions for a multilayered matrix, coupled with the conventional Kelvin-type Green’s function for the QD, the present method only requires discretization along the interface between the matrix and QD to solve the problem. With this method, the QD can be modeled in general as an inhomogeneity relative to the matrix. We have examined a practical semiconductor multilayer system of an InAs wetting/GaAs spacer with a buried cuboidal QD of either wetting or a spacer medium. The QD is correspondingly modeled by either the inhomogeneity or inclusion approach. Two crystallographic orientations of the spacer medium, GaAs(001) and GaAs(111), are considered. The analytical results have shown that these two approaches generally result in considerable differences in the prediction of the QD-induced elastic field. Also, different crystallographic orientation of a spacer medium can cause a characteristic change in the QD-induced field. © 2002 American Institute of Physics.
Show PACS
68.65.Hb Quantum dots (patterned in quantum wells)
68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Photoluminescence of an assembly of size-distributed self-assembled InAs quantum dots

Y. Fu, F. Ferdos, M. Sadeghi, S. M. Wang, and A. Larsson

J. Appl. Phys. 92, 3089 (2002); http://dx.doi.org/10.1063/1.1499528 (4 pages) | Cited 15 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have performed experimental and theoretical studies of the effects of inhomogeneous broadening on the luminescence properties of a self-assembled InAs quantum dot (QD) assembly. From atomic force microscopic (AFM) images the InAs QD assembly is found to have an average lateral size of 20–22 nm and a height of 10–12 nm, and the dot density is in the range of 1–2×1010 cm−2. Using the statistical distribution of the QD size from AFM measurements and the results from the theoretical analysis of the photoluminescene (PL) spectrum, it is found that the distance between QDs is larger than 30 nm (the average distance is about 100 nm), the penetration of the ground-state wave function into the GaAs barrier is negligible, and the calculated PL spectrum agrees well with that measured when the carriers in each QD are assumed to be at a local thermal equilibrium state, resulting in the conclusion that the QDs are physically independent. The width of the PL peak is determined by the inhomogeneous QD size. © 2002 American Institute of Physics.
Show PACS
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots

Optical constants and thickness determination of very thin amorphous semiconductor films

I. Chambouleyron, S. D. Ventura, E. G. Birgin, and J. M. Martínez

J. Appl. Phys. 92, 3093 (2002); http://dx.doi.org/10.1063/1.1500785 (10 pages) | Cited 15 times

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This contribution addresses the relevant question of retrieving, from transmittance data, the optical constants, and thickness of very thin semiconductor and dielectric films. The retrieval process looks for a thickness that, subject to the physical input of the problem, minimizes the difference between the measured and the theoretical spectra. This is a highly underdetermined problem but, the use of approximate—though simple—functional dependencies of the index of refraction and of the absorption coefficient on photon energy, used as an a priori information, allows surmounting the ill posedness of the problem. The method is illustrated with the analysis of transmittance data of very thin amorphous silicon films. The method enables retrieval of physically meaningful solutions for films as thin as 300 Å. The estimated parameters agree well with known data or with optical parameters measured by independent methods. The limitations of the adopted model and the shortcomings of the optimization algorithm are presented and discussed. © 2002 American Institute of Physics.
Show PACS
78.66.Jg Amorphous semiconductors; glasses
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
68.55.-a Thin film structure and morphology
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Gc Amorphous semiconductors

Polarized ultraviolet Raman spectroscopy of β-Si3N4

R. Vogelgesang, M. Grimsditch, and J. S. Wallace

J. Appl. Phys. 92, 3103 (2002); http://dx.doi.org/10.1063/1.1503164 (4 pages) | Cited 1 time

Online Publication Date: 27 August 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have studied single crystals of β-Si3N4 with polarization-resolved Raman spectroscopy in order to unambiguously obtain the symmetry character of zone center optical phonon modes. By applying ultraviolet excitation radiation, approaching resonance condition, we have overcome the usual difficulties with overwhelming fluorescence obscuring Raman spectra of β-Si3N4 in the visible. Superior extinction ratios have been achieved and the application of group theory allows us to assign ten out of eleven Raman-active modes in excellent correlation with recent theoretical results. The probable nature of the eleventh mode is discussed. © 2002 American Institute of Physics.
Show PACS
78.30.Hv Other nonmetallic inorganics
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
Page 1 of 3 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close