By Topic

Journal of Applied Physics

Issue 1 • Date Jan 2011

Filter Results

Displaying Results 1 - 25 of 176
  • Bleaching versus poling: Comparison of electric field induced phenomena in glasses and glass-metal nanocomposites

    Page(s): 011101 - 011101-11
    Save to Project icon | PDF file iconPDF (538 KB)  

    By examining the electric field induced processes in glasses and glass-metal nanocomposites (GMN) we propose mechanism of the electric field assisted dissolution (EFAD) of metal nanoparticles in glass. We show that in both glass poling and EFAD processes, the strong (up to 1 V/nm) local electric field in the subanodic region is due to the presence of “slow” hydrogen ions bonded to nonbridging oxygen atoms in glass matrix. However, the origin of these hydrogen ions in glass and GMN is different. Specifically, when we apply the electric field to a virgin glass, the enrichment of the glass with hydrogen species takes place in the course of the poling. In GMN, the hydrogen ions have been incorporated into the glass matrix during metal nanoparticles formation via reduction in a metal by hydrogen, i.e., before the electric field was applied. The EFAD of metal nanoparticles resembles the electric field stimulated diffusion of metal film in glass (the important difference however is that in GMN, there is no direct contact of dissolving metal entity with anodic electrode). This similarity makes it possible to estimate the energy of thermal activated transition of silver atoms from a nanoparticle to glass matrix as ∼1.3 eV. Electroneutrality of the GMN requires emission of electrons from nanoparticles. Photoconductivity spectra of soda-lime glasses and the results of numerical calculations of band structure of fused silica, sodium disilicate and sodium-calcium-silicate glass enable us to evaluate the bandgap and the position of electron mobility edge in soda-lime glass. The evaluated values are ∼6 eV and ∼1.2 eV below vacuum level, respectively. The bent of the glass band structure in strong electric field permits a direct tunneling of Fermi electrons from silver nanoparticle (4.6 eV below the vacuum level) to th- - e glass conductivity band. Evaluated in accordance with the Fowler–Nordheim equation the magnitude of electric field necessary to establish comparable electron emission and ion ejection rates is ∼0.27 V/nm, although other phenomena including polarization of the nanoparticles and tunneling of electrons thermally distributed above Fermi level, decreases this magnitude. We believe that the different mechanisms of ejection for electrons and ions should result in charging nanoparticles in EFAD process. The electron tunneling to localized OH- states and glass matrix relaxation process are also discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhanced femtosecond optical nonlinearity of Mn doped Ba0.6Sr0.4TiO3 films

    Page(s): 013101 - 013101-3
    Save to Project icon | PDF file iconPDF (288 KB)  

    We report the third-order optical nonlinearity of ferroelectric thin films of Mn doped Ba0.6Sr0.4TiO3 using Z-scan measurement with femtosecond laser pulses at 800 nm. The nonlinear refraction index and two-photon absorption coefficient are measured to be 3.0×10-4 cm2/GW and 1.7 cm/GW, respectively, which are about one order of magnitude larger than those of the undoped Ba0.6Sr0.4TiO3 thin films. The enhancement is attributed to the acceptor behavior of Mn ions dopant. The figure of merit, T, defined by T=βλ/n2, was calculated to be 0.44, less than 1. The results indicate that the thin films have great potential applications in nonlinear photonic devices. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultrafast relaxation and absorption saturation at near exciton resonance in a thin ZnO epilayer

    Page(s): 013102 - 013102-5
    Save to Project icon | PDF file iconPDF (275 KB)  

    We observed ultrafast free exciton thermalization time of 700–900 fs and obtained the magnitude of maximal differential absorption to be 1.8×104 cm-1 with the pumping fluence of 10 μJ/cm2 by measuring transient differential transmission in a thin ZnO epitaxial layer at room temperature. The largest induced transparency occurs near exciton resonance associated with absorption saturation by comparing the excitation from the above band-gap to band-tail states. The pumping dependent transient absorption reveals transition of excitonic relaxation from exciton-phonon scattering to exciton-exciton scattering or to an electron-hole plasma. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Laser-induced Mg production from magnesium oxide using Si-based agents and Si-based agents recycling

    Page(s): 013103 - 013103-9
    Save to Project icon | PDF file iconPDF (1070 KB)  

    We succeeded in laser-induced magnesium (Mg) production from magnesium oxide (MgO) using Si-based agents, silicon (Si) and silicon monoxide (SiO). In these experiments, a cw CO2 laser irradiated a mixture of Mg and Si-based agents. Both experimental studies and theoretical analysis help not only understand the function of reducing agents but also optimize Mg extraction in laser-induced Mg production. The optimal energy efficiencies 12.1 mg/kJ and 4.5 mg/kJ of Mg production were achieved using Si and SiO, respectively. Besides, the possibility of recycling Si and SiO was preliminarily investigated without reducing agents but only with laser-irradiation. As for the Si-based agents recycling, we succeed in removing 36 mol% of oxygen fraction from SiO2, obtaining 0.7 mg/kJ of Si production efficiency as well as 15.6 mg/kJ of SiO one at the same time. In addition, the laser irradiation to MgO-SiO mixture produced 24 mg/kJ of Si with more than 99% purity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Metamaterial tunnel barrier gives broadband microwave transmission

    Page(s): 013104 - 013104-4
    Save to Project icon | PDF file iconPDF (346 KB)  

    A simple structure comprising a metal mesh, symmetrically surrounded by subwavelength thickness dielectric layers, is shown to give near total microwave transmission over a broad frequency range. The mesh may be considered to be a tunnel barrier since it behaves as an ideal plasmonic metamaterial with a negative effective permittivity and no loss. The introduction of the mesh into the dielectric cavity imposes a finite gradient on the electromagnetic fields at the two mesh-dielectric interfaces. This defines a finite wavelength of the zeroth order Fabry-Pérot-type mode, which would otherwise be infinite. Suitable choice of the mesh parameters yields a broad band of near total transmission associated with the overlap of this zeroth order mode with that of the first order half-wavelength Fabry-Pérot-type resonance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Cathodoluminescent properties and surface characterization of bluish-white LiAl5O8:Tb phosphor

    Page(s): 013105 - 013105-8
    Save to Project icon | PDF file iconPDF (2236 KB)  

    Cathodoluminescence (CL) characteristics and electron-beam induced surface chemical changes in nanocrystalline Tb3+ doped LiAl5O8 powder phosphors are presented. Bluish-white CL with a maximum at ∼543 nm was observed when the powders were irradiated with a 2 keV electron beam. The emissions in the green and the blue regions arise from the magnetic dipole 5D4-7FJ (J=6–0) and 5D3-7FJ transitions of the Tb3+ ion. The appearance of the line emissions in the blue region are discussed in terms of Tb oxidation states and their corresponding interconversion. Auger electron spectroscopy and x-ray photoelectron spectroscopy (XPS) were used to probe the chemical changes on the surface of the LiAl5O8 phosphor under electron bombardment. The XPS data suggest that the Tb ions exist both in trivalent and tetravalent oxidation states which could be the reason for the observed green as well as blue CL emissions. A thermodynamically stable Al2O3 layer formed on the surface as a result of the electron stimulated surface chemical reactions is possibly contributing to the CL stability of the LiAl5O8:Tb phosphor. The time stability of the phosphor under prolonged electron beam exposure suggests that it can be used in information displays. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The detection of terahertz waves by semimetallic and by semiconducting materials

    Page(s): 013106 - 013106-5
    Save to Project icon | PDF file iconPDF (484 KB)  

    We present a survey of photoresponse (PR) measurements of various devices containing quantum wells (QWs) of HgTe of various widths dQW and of InSb. By varying dQW for HgTe, the material properties of the QW material change from semiconducting to semimetallic as dQW is increased above a value of about 6nm. We have studied the PR of devices made from CdxHg1-xTe/HgTe/CdxHg1-xTe wafers with values of the QW width in the range of 6 nm≤dQW≤21 nm. Only for samples with semimetallic HgTe QWs, a measurable PR could be detected. However, our investigations of samples made from AlxIn1-xSb/InSb/AlxIn1-xSb wafers gave evidence that a measurable PR also can appear from devices with a semiconducting QW. Both cyclotron-resonant (CR) and nonresonant (bolometric, BO) interaction mechanisms can contribute to the PR signal. Whereas the CR contribution is dominant in AlxIn1-xSb/InSb/AlxIn1-xSb samples, in CdxHg1-xTe/HgTe/CdxHg1-xTe samples the behavior is more complex. In a sample with dQW=8 nm, the PR is clearly dominated - - by the BO contribution. In the PR of another sample of dQW=12 nm, both contributions (BO and CR) are present. The sample of dQW=21 nm shows a PR with not clearly separable BO and CR contributions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Distorted wurtzite unit cells: Determination of lattice parameters of nonpolar a-plane AlGaN and estimation of solid phase Al content

    Page(s): 013107 - 013107-8
    Save to Project icon | PDF file iconPDF (954 KB)  

    Unlike c-plane nitrides, “nonpolar” nitrides, e.g., those grown in the a-plane or m-plane orientation encounter anisotropic in-plane strain due to the anisotropy in the lattice and thermal mismatch with the substrate or buffer layer. Such anisotropic strain results in a distortion of the wurtzite unit cell and creates difficulty in accurate determination of lattice parameters and solid phase group-III content (xsolid) in ternary alloys. In this paper we show that the lattice distortion is orthorhombic, and outline a relatively simple procedure for measurement of lattice parameters of nonpolar group III-nitrides epilayers from high resolution x-ray diffraction measurements. We derive an approximate expression for xsolid taking into account the anisotropic strain. We illustrate this using data for a-plane AlGaN, where we measure the lattice parameters and estimate the solid phase Al content, and also show that this method is applicable for m-plane structures as well. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Structural, optical, and photoluminescence characterization of electron beam evaporated ZnS/CdSe nanoparticles thin films

    Page(s): 013108 - 013108-5
    Save to Project icon | PDF file iconPDF (490 KB)  

    Structural, optical, and photoluminescence investigations of ZnS capped with CdSe films prepared by electron beam evaporation are presented. X-ray diffraction analysis revealed that the ZnS/CdSe nanoparticles films contain cubic cadmium selenide and hexagonal zinc sulfide crystals and the ZnS grain sizes increased with increasing ZnS thickness. The refractive index was evaluated in terms of envelope method, which has been suggested by Swanepoel in the transparent region. The refractive index values were found to increase with increasing ZnS thickness. However, the optical band gap and the extinction coefficient were decreased with increasing ZnS thickness. Photoluminescence (PL) investigations revealed the presence of two broad emission bands. The ZnS thickness significantly influenced the PL intensities. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A quantitative model for doping contrast in the scanning electron microscope using calculated potential distributions and Monte Carlo simulations

    Page(s): 013109 - 013109-9
    Save to Project icon | PDF file iconPDF (3565 KB)  

    This paper describes the use of a Monte Carlo model incorporating a finite-element method computing the electrostatic fields inside and outside a semiconductor, plus a ray-tracing algorithm for determining the doping contrast observed in a scanning electron microscope (SEM). This combined numerical method also enables the effects on the doping contrast of surface band-bending to be distinguished from those of external patch fields outside the specimen, as well as any applied macroscopic external fields from the detection system in the SEM. Good agreement of our new theory with experiment is obtained. The contrast characteristics in energy-filtered secondary electron images are also explained. The results of this work lead to a more advanced understanding of the doping contrast mechanisms, thereby enabling quantitative dopant profiling using the SEM. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nanometer-resolution optical probe using a metallic-nanoparticle-intercalated carbon nanotube

    Page(s): 013110 - 013110-5
    Save to Project icon | PDF file iconPDF (8690 KB)  

    We propose a nanometer-resolution optical probe tip for near-field scanning optical microscopy that utilizes a carbon nanotube (CNT) with a conical bottom end, in which gold nanoparticles are intercalated. The near-field component of the input source was coupled with a nanoparticle at the top end of the CNT and was plasmonically transferred through both the CNT and nanoparticles to reproduce a nanometer-order near-field spot at the bottom end of the CNT. The field distribution at the output plane of the CNT probe tip was calculated using the finite-difference time-domain algorithm; a 5 nm near-field optical spot was obtained at a wavelength of 886 nm for a 20 nm diameter and 200 nm long CNT probe tip filled with 4 nm diameter gold nanoparticles. The spectral response of the CNT probe tip was also presented. These results indicate that a metallic-nanostructure-intercalated CNT probe tip has significant potential for nanometer-resolution optical imaging. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Coherent transport description of the dual-wavelength ambipolar terahertz quantum cascade laser

    Page(s): 013111 - 013111-5
    Save to Project icon | PDF file iconPDF (259 KB)  

    A transport and gain model is developed for the recently realized ambipolar dual-wavelength terahertz quantum cascade laser. The model is based on the simplified density matrix formalism, describing the population and coherence terms of five relevant states per period, which includes the laser optical field and single-temperature thermal balance. Using the measured current densities under forward and reverse bias for calibration, a good theoretical/experimental agreement is found for the current-optical power characteristics and the laser dynamic range. This shows that the model is a reliable analyzer, if not yet a fully predictive tool, for quantum cascade laser simulation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design of selective emitting media within a cylindrical tube for conversion of wasted heat energy to electrical energy

    Page(s): 013112 - 013112-10
    Save to Project icon | PDF file iconPDF (379 KB)  

    Thermophotovoltaic (TPV) energy conversion is the conversion of heat energy to electrical energy via light. This manuscript focuses on the geometric design of emitting material within an exhaust tube to convert wasted heat energy to light, and achieve an optimal amount of irradiance at the PV diode cells. Due to the large value of the absorption coefficient for the selectively emitting erbia-doped nanofibers under discussion, the diffusion approximation to the equation of radiation transfer is used. This approximate equation is solved for emission from hot-spot sources within the emitting material. Several geometric distributions of the emitting material are considered. Within an axisymmetric geometry all erbia-doped nanofibers, all quartz wool, and mixtures of disk-shaped or cylindrical shell shaped distributions of nanofibers and wool are investigated. Within a polar geometry all erbia-doped nanofibers, all quartz wool, and mixtures of spoke-shaped or cylindrical shell shaped distributions are investigated. In both geometries the mixture distributions consist of alternating thin layers of emitting and non-emitting material. Homogenization techniques are applied to these distributions to define expressions for the effective absorption and scattering coefficients for these spatially distributed emitting structures. The effective expressions are input into the diffusion approximation that is solved for the spectral irradiance. The net radiation obtained from these emitting structures is examined to optimize the geometry of the TPV material to maximize emission with use of minimal TPV material. Results show that disk-shaped bands or spokes allow for maximum irradiation in the radial direction toward the diode collectors. A large volume fraction of erbia-doped nanofibers is optimal when hot spots are close to the diodes. Smaller volume fractions work better when hot spots are away from the diodes due to reabsorption of emitted light by the emitting material. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Microdischarge extreme ultraviolet source with alkali metal vapor for surface morphology application

    Page(s): 013301 - 013301-6
    Save to Project icon | PDF file iconPDF (274 KB)  

    We have characterized a discharge-produced potassium plasma extreme ultraviolet (XUV) source. Potassium ions produced strong broadband emission around 40 nm with a bandwidth of 8 nm (full width at half-maximum). By comparison with atomic structure calculations, the broadband emission is found to be primarily due to 3d–3p transitions in potassium ions ranging from K2+ to K4+. The current-voltage characteristics of the microdischarge suggest that the source operates in a hollow cathode mode and consequently the emitting ions may be localized on the potassium electrode surface at the hole into the capillary. To understand the spectral behavior from the potassium plasmas we compared the spectra from the discharge-produced plasma with that from a laser-produced plasma. The spectra from the different (electric and laser) plasmas at the same electron temperature (12 eV) were almost the same. This compact capillary XUV source with a photon energy of 30 eV is a useful XUV emission source for surface morphology applications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical investigation of closed-loop control for Hall accelerators

    Page(s): 013302 - 013302-10
    Save to Project icon | PDF file iconPDF (277 KB)  

    Low frequency discharge current oscillations in Hall accelerators are conventionally damped with external inductor-capacitor (LC) or resistor-inductor-capacitor (RLC) networks. The role of such network in the stabilization of the plasma discharge is investigated with a numerical model and the potential advantages of proportional-integral-derivative (PID) closed-loop control over RLC networks are subsequently assessed using either discharge voltage or magnetic field modulation. Simulations confirm the reduction of current oscillations in the presence of a RLC network, but suggest that PID control could ensure nearly oscillation-free operation with little sensitivity toward the PID settings. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Kinetics of illuminated complex plasmas considering Mie scattering by spherical dust particles with a size distribution

    Page(s): 013303 - 013303-5
    Save to Project icon | PDF file iconPDF (211 KB)  

    In this paper Mie scattering of light by dust particles having Mathis, Rumpl, and Nordsieek power law distribution of size has been incorporated in the formulation of the kinetics of an illuminated complex plasma which takes into account the ionization of neutral atoms by an external agency, ion-electron recombination, photoemission of electrons by the dust particles, and accretion of electrons and ions on the surface of the particles; the number and energy balance of the constituent species has also been taken into account. An interesting conclusion is that unlike the usual case (when Mie scattering is neglected) the charge on a particle is not proportional to the radius and that for certain sets of parameters the smaller particles are negatively charged while the larger particles, carry positive charge. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spatially resolved argon microplasma diagnostics by diode laser absorption

    Page(s): 013304 - 013304-6
    Save to Project icon | PDF file iconPDF (2702 KB)  

    Microplasmas were diagnosed by spatially resolved diode laser absorption using the Ar 801.4 nm transition (1s5-2p8). A 900 MHz microstrip split ring resonator was used to excite the microplasma which was operated between 100–760 Torr (13–101 kPa). The gas temperatures and the Ar 1s5 line-integrated densities were obtained from the atomic absorption lineshape. Spatially resolved data were obtained by focusing the laser to a 30 μm spot and translating the laser path through the plasma with an xyz microdrive. At 1 atm, the microplasma has a warm core (850 K) that spans 0.2 mm and a steep gradient to room temperature at the edge of the discharge. At lower pressure, the gas temperature decreases and the spatial profiles become more diffuse. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical analysis of electronegative plasma in the extraction region of negative hydrogen ion sources

    Page(s): 013305 - 013305-12
    Save to Project icon | PDF file iconPDF (1526 KB)  

    This numerical study focuses on the physical mechanisms involved in the extraction of volume-produced H- ions from a steady state laboratory negative hydrogen ion source with one opening in the plasma electrode (PE) on which a dc-bias voltage is applied. A weak magnetic field is applied in the source plasma transversely to the extracted beam. The goal is to highlight the combined effects of the weak magnetic field and the PE bias voltage (upon the extraction process of H- ions and electrons). To do so, we focus on the behavior of electrons and volume-produced negative ions within a two-dimensional model using the particle-in-cell method. No collision processes are taken into account, except for electron diffusion across the magnetic field using a simple random-walk model at each time step of the simulation. The results show first that applying the magnetic field (without PE bias) enhances H- ion extraction, while it drastically decreases the extracted electron current. Secondly, the extracted H- ion current has a maximum when the PE bias is equal to the plasma potential, while the extracted electron current is significantly reduced by applying the PE bias. The underlying mechanism leading to the above results is the gradual opening by the PE bias of the equipotential lines towards the parts of the extraction region facing the PE. The shape of these lines is due originally to the electron trapping by the magnetic field. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ionization in inductively coupled argon plasmas studied by optical emission spectroscopy

    Page(s): 013306 - 013306-7
    Save to Project icon | PDF file iconPDF (285 KB)  

    Contribution of stepwise ionization to total ionization was experimentally investigated in low-pressure inductively coupled argon plasmas. In the pressure range 3–50 mTorr, optical emission spectroscopy was employed to determine metastable fractions (metastable density relative to ground state density) by measuring the emission intensity of selected lines. The measured metastable fractions were in good agreement with the calculation, showing a dependence on the discharge pressure. The rate of stepwise ionization was estimated from the excited level densities (measurements and model predictions) and their ionization rate coefficients. It is observed that at relatively low discharge pressures (<10 mTorr) the ionization is mainly provided by the direct ionization, whereas at higher pressure the stepwise ionization is predominant with increasing absorbed power. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Polaritonic pulse and coherent X- and gamma rays from Compton (Thomson) backscattering

    Page(s): 013307 - 013307-6
    Save to Project icon | PDF file iconPDF (149 KB)  

    The formation of polariton wave-packets created by high-intensity laser beams focused in plasmas is analyzed, and the velocity, energy, size, structure, stability, and electron content of such polaritonic pulses are characterized. It is shown that polaritonic pulses may transport trapped electrons with appreciable energies, provided the medium behaves as a rarefied classical plasma. The relativistic electron energy is related to the polariton group velocity, which is close to the velocity of light in this case. The plasma pulse is polarized, and the electron number in the pulse is estimated as being proportional to the square root of the laser intensity and the 3/2-power of the pulse size. It is shown that Compton (Thomson) backscattering by such polaritonic pulses of electrons may produce coherent X- and gamma rays, as a consequence of the quasirigidity of the electrons inside the polaritonic pulses and their relatively large number. The classical results of the Compton scattering are re-examined in this context, the energy of the scattered photons and their cross-section are analyzed, especially for backscattering, the great enhancement of the scattered flux of X- or gamma rays due to the coherence effect is highlighted and numerical estimates are given for some typical situations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical simulations of electrical asymmetry effect on electronegative plasmas in capacitively coupled rf discharge

    Page(s): 013308 - 013308-8
    Save to Project icon | PDF file iconPDF (588 KB)  

    Recently a so-called electrical asymmetry effect (EAE), which could achieve high-degree separate control of ion flux and energy in dual-frequency capacitively coupled radio-frequency (CCRF) discharges, was discovered theoretically by Heil etal [J. Phys. D: Appl. Phys. 41, 165202 (2008)] and was confirmed by experiments and theory/numerical simulations later on for electropositive argon discharges. In this work simulations based on particle-in-cell/Monte Carlo collision are performed to study the EAE on electronegative oxygen plasmas in geometrically symmetric CCRF discharges. Dual frequency discharges operating at 13.56 and 27.12 MHz are simulated for different pressures and the results are compared with those of electropositive argon discharges at the same conditions. It is found that in general the EAE on oxygen discharges has similar behavior as on argon discharge: The self-bias voltage η increases monotonically and almost linearly with the increase in the phase angle θ between the two driving voltages in the range 0<θ<90°, and the maximum ion energy varies by a factor of 3 by adjusting θ. However, the ion flux varies with θ by ±12% for low pressure and by ±15% for higher pressure, due primarily to an enhanced plasma series resonance, which then leads to dramatic changes in plasma density, power absorption and consequently the electronegativity. This may place a limitation for achieving separate control of ion energy and flux for electronegative plasma via the EAE. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Deuterium retention in tungsten exposed to low-energy pure and helium-seeded deuterium plasmas

    Page(s): 013309 - 013309-10
    Save to Project icon | PDF file iconPDF (1468 KB)  

    Influence of helium (He) on the deuterium (D) retention in tungsten (W) under simultaneous He-D plasma exposure was investigated. Bulk polycrystalline tungsten and two W coatings on carbon substrate, namely, plasma-sprayed tungsten and combined magnetron-sputtered and ion implanted tungsten (CMSII-W) were exposed to pure and He-seeded D plasmas generated by electron-cyclotron-resonance plasma source. The D retention in each sample was subsequently analyzed by various methods such as nuclear reaction analysis for the D depth profiling up to 6 μm and thermal desorption spectroscopy for the determination of total amount of D retention. It is shown that seeding of helium into D plasma with helium ion flux fraction of 10% reduces the deuterium retention for all tungsten grades but more significant reduction was observed for polycrystalline W and less significant effect was found for W coatings. From the thermal desorption spectroscopy measurements, we conclude that the presence of He modifies the density of existing traps for D but does not modify the nature of traps. Maximum effect of a reduction in the deuterium retention due to helium seeding was observed at around 500 K for bulk polycrystalline W. Mechanisms of deuterium retention and He effect in different W materials are discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hydrophobic treatment of organics against glass employing nonequilibrium atmospheric pressure pulsed plasmas with a mixture of CF4 and N2 gases

    Page(s): 013310 - 013310-6
    Save to Project icon | PDF file iconPDF (510 KB)  

    A hydrophobic organics surface selectively against glass was realized by employing nonequilibrium atmospheric-pressure pulsed plasmas with a mixture of CF4 and N2 gases. The organic surface was drastically altered to have a high hydrophobicity, while the glass surface itself remained hydrophilic after the plasma treatment with the addition of a small amount of CF4 to the N2 gas. After 100 CF4/N2 plasma treatments, no thin film deposition was observed on the organic material. To investigate the characteristics of the CF4/N2 plasma, the exhaust gas from the plasma was measured by using ion attachment mass spectroscopy (IAMS). The IAMS spectrum indicated that the amounts of CF3 and F radicals were increased drastically with increasing addition of CF4. A mechanism of the selective surface modification was clarified on a result of surface chemical bonding with the gas phase. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influence of cathode material on generation of energetic hydrogen atoms in a glow discharge

    Page(s): 013311 - 013311-7
    Save to Project icon | PDF file iconPDF (358 KB)  

    In this paper influence of cathode material on formation of fast hydrogen atoms in an abnormal glow discharge is investigated using Balmer alpha emission spectroscopy. Energetic H atoms are generated in charge exchange reactions of hydrogen ions that are accelerated in the electric field, and also formed in the backscattering process at the cathode surface. Copper and graphite cathodes were used. Investigation was performed in two orthogonal directions of observation in pure hydrogen and argon-hydrogen mixture. The shapes of the profiles are examined together with the space intensity distribution of Balmer alpha line. Reduced atom reflection from graphite was manifested in the spectroscopic result, in accordance to the field acceleration model. The effect was evident only at high ion energies. This is explained by energy dependence of reflection coefficient for H atoms. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Correlation between nanoparticle and plasma parameters with particle growth in dusty plasmas

    Page(s): 013312 - 013312-5
    Save to Project icon | PDF file iconPDF (186 KB)  

    Since plasma parameters are altered by dust particles, studying how plasma parameters are related to dust particle growth is an important research issue in dusty plasma. In this paper, the correlation between plasma parameters (electron temperature and ion flux) and particle parameters (particle radius and density) is investigated in silane plasma both experimentally using a floating probe and theoretically by solving balance equations including an additional electron and ion loss to the dust. The results reveal that while the ion flux shows two peak values in the early discharge phase and at the end of coagulation phase, the electron temperature shows a sudden increase in the coagulation step and a gradual decrease in the molecular accretion step. Moreover, the calculated results with the secondary electron emission taken into account produce the best fit with the experimental results. Thus the study confirms that the secondary electron emission plays a crucial role in the coagulation of the dust particles. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics

Full Aims & Scope

Meet Our Editors

P. James Viccaro
Argonne National Laboratory