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 Aug 2006

Volume 100, Issue 4, Articles (04xxxx)

Return to All Sections
back to top
RSS Feeds

Time-domain simulation of Schrödinger equation to determine the effective potential induced by an oscillating standing wave

Y.C. Neil Na and Yoshihisa Yamamoto

J. Appl. Phys. 100, 044901 (2006); http://dx.doi.org/10.1063/1.2234803 (6 pages)

Online Publication Date: 16 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effective potential for a charged particle induced by a rapidly oscillating field is in general difficult to determine. An analytical solution for such a problem is available for the case of Paul trap, i.e., when the sinusoidally oscillating potential is a quadratic function of position. In this paper, we describe time-domain simulation of the time-dependent Schrödinger equation to determine the effective two-dimensional lattice potential induced by an oscillating standing wave. Such a scheme can be generalized to determine the effective potential induced by any rapidly oscillating field.
Show PACS
03.65.Ge Solutions of wave equations: bound states

Electromagnetic phenomena in heterogeneous media: Effective properties and local behavior

Oriano Bottauscio, Alessandra Manzin, Valeria Chiadó Piat, Marco Codegone, and Mario Chiampi

J. Appl. Phys. 100, 044902 (2006); http://dx.doi.org/10.1063/1.2234816 (8 pages) | Cited 7 times

Online Publication Date: 17 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The purpose of this paper is the use of a mathematical homogenization approach based on the multiple scale expansion theory for modeling the electromagnetic phenomena arising in heterogeneous media under an imposed magnetic flux. The attention is focused on the analysis and discussion of the merits and limits of this theoretical approach in reproducing not only the effective macroscopic properties but also the local behavior, under a wide frequency range and considering different constitutive and geometrical parameters. The results show that the proposed method is able to predict local and integral physical quantities, ranging from a substantially global behavior in the whole media to significantly localized effects determined by the microscopic structure.
Show PACS
75.60.Ch Domain walls and domain structure

Real-time, in situ spectroscopic ellipsometry for analysis of the kinetics of ultrathin oxide-film growth on MgAl alloys

M. S. Vinodh, L. P. H. Jeurgens, and E. J. Mittemeijer

J. Appl. Phys. 100, 044903 (2006); http://dx.doi.org/10.1063/1.2245197 (9 pages) | Cited 4 times

Online Publication Date: 21 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A procedure has been developed to determine the growth kinetics of thin (<3 nm) oxide films on bare binary alloys from the measured changes of the ellipsometric amplitude-ratio and phase-shift dependent parameters, ψ and Δ, versus wavelength, as function of oxidation time, as recorded by real-time, in situ spectroscopic ellipsometry. The approach has been applied to the dry, thermal oxidation of Mg-based MgAl substrates of low (2.63 at. %) and high (7.31 at. %) bulk Al content at 304 K within the partial pressure of oxygen range of 10−6–10−4 Pa. Various models have been developed to describe the time dependences of the spectra of ψ(λ) and/or Δ(λ) for the initial and subsequent stages of oxidation. It followed that the initial oxide-film growth kinetics can be accurately described by adopting a three-node graded oxide layer using the Maxwell-Garnet effective medium approximation to assess the optical properties of the compositionally inhomogeneous, Al-doped MgO film developing on the MgAl alloy surface. The specific complications that arise in the ellipsometric analysis of the oxidation of binary alloys (as compared to that of pure metals), such as due to the concurrent processes of selective oxidation and (oxidation-induced) chemical segregation, have been discussed.
Show PACS
81.65.Mq Oxidation
68.55.A- Nucleation and growth
68.35.Dv Composition, segregation; defects and impurities
82.20.-w Chemical kinetics and dynamics
78.66.Nk Insulators

Effects of surfactants Sb and Bi on the incorporation of zinc and carbon in III/V materials grown by organometallic vapor-phase epitaxy

A. D. Howard, D. C. Chapman, and G. B. Stringfellow

J. Appl. Phys. 100, 044904 (2006); http://dx.doi.org/10.1063/1.2227707 (8 pages) | Cited 6 times

Online Publication Date: 21 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The incorporation of both dopants and background impurities during the organometallic vapor phase epitaxial (OMVPE) growth of GaAs, GaInP, and GaP has been significantly altered by the use of the surfactants Sb and Bi. Sb and Bi are isoelectronic with the group V host elements, and so produce no independent doping. This paper demonstrates that the incorporation of Zn can be increased by an order of magnitude in GaP to a value of approximately 1020 cm−3, the highest value reported to date. Additionally, these same surfactants lead to significant decreases in carbon contamination during growth. At high growth temperatures the reduction can be as large as 100× in GaP. The surfactants also result in marked decreases in autodoping due to S and Si from the substrate. A marker that may help identify the mechanism for these effects is H incorporation. Both Sb and Bi surfactants give rise to increased concentrations of H in the GaP layers. Similar effects are observed in GaInP. However, in GaAs, no H is detected in the layers. One possible explanation for these phenomena is that Sb or Bi increases the surface H concentration. The increased H would have two possible effects on the incorporation of dopants and impurities. (1) Passivation of the Zn acceptor by formation of a neutral Zn-H complex would lead to increased incorporation for thermodynamic reasons. (2) Allowing increased desorption of C, S, and Si from the surface by increased formation of volatile hydrides leads to decreased incorporation levels. These results suggest a simple and effective method of controlling the incorporation of dopant and impurity atoms by adding a minute amount of surfactant during OMVPE growth.
Show PACS
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.uj III-V and II-VI semiconductors
81.65.Rv Passivation
68.43.Mn Adsorption kinetics

Dynamic photothermal and thermoelastic microscopies described by complex finite element analysis

Bruno Cavallier, Sylvain Ballandras, Bernard Cretin, and Pascal Vairac

J. Appl. Phys. 100, 044905 (2006); http://dx.doi.org/10.1063/1.2234815 (12 pages)

Online Publication Date: 21 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Photothermal and thermoelastic microscopes are nondestructive apparatus that generally work with lock-in detection. The related magnitude and phase images are obtained for one modulation frequency. These techniques, devoted to nondestructive evaluation, are suitable for inverse problems such as thermoelastic parameter reconstruction. But up to now the thermoelastic models have been limited to simple geometries or have encountered many problems with temporal sampling. In order to overcome these problems we develop a finite element analysis dynamic method, based upon complex analysis, that enables us to directly obtain both thermal and thermoelastic magnitude and phase fields. This method has been applied to thermoelastic microscopy and has shown very good agreement with experiments.
Show PACS
07.20.-n Thermal instruments and apparatus
02.70.Dh Finite-element and Galerkin methods

Real-time quantitative investigation of photochemical reaction using thermal lens measurements: Theory and experiment

P. R. B. Pedreira, L. R. Hirsch, J. R. D. Pereira, A. N. Medina, A. C. Bento, M. L. Baesso, Maria C. Rollemberg, Mladen Franko, and Jun Shen

J. Appl. Phys. 100, 044906 (2006); http://dx.doi.org/10.1063/1.2245201 (7 pages) | Cited 10 times

Online Publication Date: 22 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this work the time-resolved mode-mismatched thermal lens method is applied to investigate Cr(VI) species in water. An abnormal behavior of the thermal lens transient induced by a photochemical reaction was observed during optical excitation. With the purpose of better understanding this phenomenon, the existing theoretical model of thermal lens effect was generalized in order to take the time dependence of the absorbance of the sample into account due to the changes in concentration resulting from photochemical reaction and diffusion of absorbing species. Consequently, the photochemical reaction rate can be quantitatively evaluated by this technique with the generalized model. The adopted procedure demonstrates the usefulness of the time-resolved thermal lens method for the study of photochemical reactions under the presence of absorbing species diffusion with the advantage of monitoring the processes in a quantitative way and with a temporal resolution of a few milliseconds.
Show PACS
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
82.50.-m Photochemistry
66.30.-h Diffusion in solids

Acceleration of electrons by a circularly polarized laser pulse in the presence of an intense axial magnetic field in vacuum

K. P. Singh

J. Appl. Phys. 100, 044907 (2006); http://dx.doi.org/10.1063/1.2234549 (4 pages) | Cited 6 times

Online Publication Date: 23 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Acceleration of electrons by a circularly polarized laser pulse in the presence of a short duration intense axial magnetic field has been studied. Resonance occurs between the electrons and the laser field for an optimum magnetic field leading to effective energy transfer from laser to electrons. The value of optimum magnetic field is independent of the laser intensity and decreases with initial electron energy. The electrons rotate around the axis of the laser pulse with small angle of emittance and small energy spread. Acceleration gradient increases with laser intensity and decreases with initial electron energy.
Show PACS
52.38.Kd Laser-plasma acceleration of electrons and ions
52.38.-r Laser-plasma interactions

Electrical properties of sputtered-indium tin oxide film contacts on n-type GaN

J. D. Hwang, C. C. Lin, and W. L. Chen

J. Appl. Phys. 100, 044908 (2006); http://dx.doi.org/10.1063/1.2336978 (5 pages) | Cited 4 times

Online Publication Date: 25 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A transparent indium tin oxide (ITO) Ohmic contact on n-type gallium nitride (GaN) (dopant concentration of 2×1017 cm−3) having a specific contact resistance of 4.2×10−6 Ω cm2 was obtained. In this study, ITO film deposition method was implemented by sputtering. We found that the barrier height, 0.68 eV, between ITO and n-type GaN is the same for both evaporated- and sputtered-ITO films. However, the 0.68 eV in barrier height renders the evaporated-ITO/n-GaN Schottky contact. This behavior is different from that of our sputtered-ITO/n-GaN, i.e., Ohmic contact. During sputtering, oxygen atoms on the GaN surface were significantly removed, thereby resulting in an improvement in contact resistance. Moreover, a large number of nitrogen (N) vacancies, caused by sputtering, were produced near the GaN surface. These N vacancies acted as donors for electrons, thus affecting a heavily doped n-type formed at the subsurface below the sputtered ITO/n-GaN. Both oxygen removal and heavy doping near the GaN surface, caused by N vacancies, in turn led to a reduction in contact resistivity as a result of electrons tunneling across the depletion layer from the ITO to the n-type GaN. All explanations are given by Auger analysis and x-ray photoelectron spectroscopy.
Show PACS
73.40.Cg Contact resistance, contact potential
81.15.Cd Deposition by sputtering
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Gk Tunneling
61.72.J- Point defects and defect clusters
79.60.Jv Interfaces; heterostructures; nanostructures

Detection of ferromagnetic particles using spin valve sensors

L. W. Y. Lui, Y. Y. Tan, K. B. Li, C. H. Sow, and S. J. O’Shea

J. Appl. Phys. 100, 044909 (2006); http://dx.doi.org/10.1063/1.2234537 (6 pages) | Cited 1 time

Online Publication Date: 25 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have attached single ferromagnetic particles of 8 μm diameter to the tips of microfabricated atomic force microscope cantilevers. These cantilevers were magnetized to fix the magnetization direction of the ferromagnetic particles and scanned in a controlled manner over a spin valve structure of dimension 12×8 μm2. Two dimensional image scans representing the change in resistance of the spin valve due to a scanning bead were obtained. The results are explained using a simple model where the scanning bead is treated as a pure dipole.
Show PACS
75.47.De Giant magnetoresistance
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
07.55.-w Magnetic instruments and components

Quantitative analysis of hydrogenated diamondlike carbon films by visible Raman spectroscopy

Achintya Singha, Aditi Ghosh, Anushree Roy, and Nihar Ranjan Ray

J. Appl. Phys. 100, 044910 (2006); http://dx.doi.org/10.1063/1.2219983 (8 pages) | Cited 13 times

Online Publication Date: 25 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The correlations between properties of hydrogenated diamondlike carbon films and their Raman spectra have been investigated. The films are prepared by plasma deposition technique, keeping different hydrogen to methane ratios during the growth process. The hydrogen concentration, sp3 content, hardness, and optical Tauc gap of the materials have been estimated from a detailed analysis of their Raman spectra. We have also measured the same parameters of the films by using other commonly used techniques, such as sp3 content in films by x-ray photoelectron spectroscopy, their Tauc gap by ellipsometric measurements, and hardness by microhardness testing. The reasons for the mismatch between the characteristics of the films, as obtained by Raman measurements and by the above mentioned techniques, have been discussed. We emphasize on the importance of the visible Raman spectroscopy in reliably predicting the above key properties of diamondlike carbon films.
Show PACS
78.30.Hv Other nonmetallic inorganics
78.66.Tr Fullerenes and related materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness

Band structure and reflectivity of omnidirectional Si-based mirrors with a Gaussian profile refractive index

J. Arriaga and X. I. Saldaña

J. Appl. Phys. 100, 044911 (2006); http://dx.doi.org/10.1063/1.2336078 (4 pages) | Cited 9 times

Online Publication Date: 29 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using the transfer matrix method we calculate the band structure for a one-dimensional photonic crystal consisting of alternating layers of two dielectric materials A and B with refractive indices nA and nB, respectively. The refractive index of layer A is constant and the refractive index for layer B varies according to the envelope of a Gaussian function. We find that under certain circumstances it is possible to obtain a 100% reflectivity for both polarizations (TE and TM) and any value of the incident angle of the electromagnetic waves. The interval of maximum reflectivity coincides with the photonic band gap of the structure. By an adequate selection of the parameters forming the structure, it is possible to tune the interval of frequencies with maximum reflectivity. This could be used in the fabrication of the so-called omnidirectional mirrors.
Show PACS
42.70.Qs Photonic bandgap materials
42.79.Bh Lenses, prisms and mirrors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

The electrical conductivity of microcellular metals

Russell Goodall, Ludger Weber, and Andreas Mortensen

J. Appl. Phys. 100, 044912 (2006); http://dx.doi.org/10.1063/1.2335672 (7 pages) | Cited 10 times

Online Publication Date: 30 August 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electrical conductivity of metallic foams varies strongly with porosity. Data are presented for replicated open-pore microcellular metal over a wide range of relative density. These data, together with data from the literature for different foam structures, are compared with previously suggested models for the conductivity of porous materials. We show that clear differences exist between the behavior of foams according to their different structural types and that simple models exist to capture these differences.
Show PACS
82.70.Rr Aerosols and foams
72.15.Cz Electrical and thermal conduction in amorphous and liquid metals and alloys
61.43.Gt Powders, porous materials
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close