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Journal of Applied Physics

Issue 8 • Date Apr 2010

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Displaying Results 1 - 25 of 124
  • Physics of ice friction

    Page(s): 081101 - 081101-15
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    Although the study of friction has a long history, ice friction has only been investigated during the last century. The basic physical concepts underlying the different friction regimes, such as boundary, mixed, and hydrodynamic friction are also relevant to ice friction. However, these friction regimes must be described with respect to the thickness of the lubricating liquidlike layer on ice. In this review the state of knowledge on the physics of ice friction is discussed. Surface melting theories are introduced. These theories attempt to explain the existence and nature of the liquidlike surface layer on ice at any temperature and without any load applied. Pressure melting, as the long-time explanation for the ease of ice friction, is discussed, together with the prevailing theory of frictional heating. The various laboratory setups for ice friction measurements are presented as well as their advantages and disadvantages. The individual influence of the different parameters on the coefficient of ice friction is discussed; these include the effects of temperature, sliding velocity, normal force exerted by the sliding object, the contact area between ice and slider, relative humidity, and also properties of the slider material such as surface roughness, surface structure, wettability, and thermal conductivity. Finally, the most important ice friction models based on the frictional heating theory are briefly introduced and research directions on the subject of ice friction are discussed. View full abstract»

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  • Violet and blue upconversion luminescence in Tm3+/Yb3+ codoped Y2O3 transparent ceramic

    Page(s): 083101 - 083101-4
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    Tm3+/Yb3+ codoped Y2O3 transparent ceramics were fabricated and characterized from the point of upconversion luminescence. All the samples exhibited high transparency not only in near-infrared band but also in visible region. Under 980 nm excitation, the ceramics gave upconversion luminescence with very intense blue (485 nm) and considerably intense violet (360 nm) emissions. It was worthy to point out that the upconversion luminescence contained six emission bands, which dispersed in the region from 294 to 809 nm. The strongest blue emission (485 nm) was obtained with (Tm0.002Yb0.03Y0.958Zr0.01)2O3 ceramic (Yb/Tm=15). The mechanism of all upconversion emission bands were investigated in detail. The absorption, emission, and gain cross-section of blue emission (485 nm) were calculated, which indicated that Tm3+/Yb3+ codoped Y2O3 transparent ceramic has tremendous potential in short wavelength laser. View full abstract»

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  • Interference effects on bound-to-continuum quantum dot absorption

    Page(s): 083102 - 083102-5
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    We have investigated the bound-to-continuum absorption of InGaAs quantum dots as a function of n-doping. We show that the combination of multipass waveguide geometry, large number of quantum dot layers, and spectrally broad absorption leads to significant spectral oscillations on the absorption spectra. The oscillations result from the standing wave pattern caused by the interference of optical beams incident and totally reflected at the sample/air interface. The spectral modulations on the absorption spectra should not be attributed to resonant intersublevel transitions. View full abstract»

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  • Time-resolved study of polyimide absorption layers for blister-actuated laser-induced forward transfer

    Page(s): 083103 - 083103-8
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    Blister-actuated laser-induced forward transfer (BA-LIFT) is a versatile, direct-write process capable of printing high-resolution patterns from a variety of sensitive donor materials without damage to their functionality. In this work, we use time-resolved imaging to study the laser-induced formation of blisters on polyimide films in order to understand and optimize their role in BA-LIFT. We find that the initial blister expansion occurs very rapidly (<100 ns), followed by a brief oscillation (100–500 ns), and then a longer time contraction to steady-state dimensions (0.5–50 μs). This behavior is explained by kinetic and thermal effects that occur during the process. We further probe the influence of polyimide thickness, laser beam diameter, and laser fluence on blister formation characteristics. Results indicate that the presence of a thin layer of donor material on the polyimide surface does not have a significant effect on the size and shape of the blisters which form. View full abstract»

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  • Collinear phase matching for second harmonic generation using conoscopic interferometry

    Page(s): 083104 - 083104-5
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    The problem of finding phase-matching directions in noncentrosymmetric biaxial crystals is simplified here by the use of Conoscopic interferometry. Based on vector relations for wave propagation in birefringent media and solutions to phase-matching equations, we show that phase matching directions can be located on the conoscopic interferograms and that fringe numbers for dark-isochromes can be used as a guide to find phase-matching directions for a biaxial crystal. This technique can be generalized and extended to any anisotropic crystal. We have demonstrated this method for the particular case of a biaxial KTiOPO4 crystal, where it is found to be particularly suitable for finding the optimum-phase-matching directions. View full abstract»

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  • A dimensionless joint density of states formalism for the quantitative characterization of the optical response of hydrogenated amorphous silicon

    Page(s): 083105 - 083105-6
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    We simplify the empirical model of O’Leary and Malik [J. Appl. Phys. 92, 4276 (2002)] for the density of state functions associated with hydrogenated amorphous silicon, reducing the number of independent modeling parameters from six to five as a result. As a consequence of this simplification, we find that we are able to cast our joint density of states (JDOS) evaluations into a dimensionless formalism, this formalism providing an elementary and effective platform for the determination of the underlying modeling parameters from experiment. We then justify our simplification by showing, for reasonable hydrogenated amorphous silicon modeling parameter selections, that our JDOS results are very similar to those determined using the more general approach of O’Leary and Malik. We also show that this simplified model is as effective as its predecessor in capturing the results of experiment. Finally, we demonstrate the utility of our dimensionless JDOS formalism, using it for the purposes of performing a critical comparative analysis of three different hydrogenated amorphous silicon optical absorption data sets. View full abstract»

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  • An effect of “scattering by absorption” observed in near-infrared properties of nanoporous silica

    Page(s): 083106 - 083106-8
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    The obtained spectroscopic data for absorption and scattering characteristics of nanoporous silica in the wavelength range from 0.25 to 7 μm are analyzed on the basis of the Mie theory. It is shown that aggregates of primary nanoparticles are responsible for relatively high scattering in the short-wave range from 0.25 to 1.4 μm. But the presence of the aggregates and micron-size cracks in the samples cannot explain unusual behavior of scattering in the long-wave part of the spectral range. The attention of the authors is focused on understanding of strong scattering peaks observed at exactly the same wavelengths as the infrared absorption peaks of bulk silica: at λ=2.9, 5.3, and 6.1 μm. The known physical effect of “scattering by absorption” is considered as a source of these scattering peaks. It means that absorption centers are assumed to be not uniformly distributed in the nanoporous matrix but collected in some micron-size regions. The estimates based on this hypothesis are supported by the fact that near-infrared absorption peaks are produced by silanol groups which may be nonuniformly distributed in the hydroxylated nanoporous silica. View full abstract»

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  • Mode pattern dependence on the eccentricity of microstadium resonators

    Page(s): 083107 - 083107-6
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    Microdisk and microstadium resonators based on InGaAsP multiquantum-well laser structures were fabricated by focused ion beam employing Ga+ ion milling and polishing followed by selective chemical etching. Stadia with very good morphology and with different eccentricities were fabricated for the study of optical mode selection. Light emission was investigated by infrared microscopy and spectroscopy. The measured emission pattern and the spectra agree well with a simple model based on the summation over periodic orbits or scar modes. The dependence of the scar mode emission with the resonator eccentricity was modeled based on the difference between photon lifetime and orbital round-trip time. The mode selection dependence with the surrounding index of refraction is suggested for chemical sensing applications. View full abstract»

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  • Stark shifts in mid-infrared type II quantum well transitions

    Page(s): 083108 - 083108-4
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    We have studied electric field induced (Stark) shifts in mid-infrared (IR) transitions that occur in type II AlSb/InAs/GaSb quantum wells. Because of the spatial separation of the electron and hole wave functions in the type II system, the potential drop between the layers dominates the shift in the real-space-indirect transition energies when an external electric field is applied. This can result in either a redshift or a blueshift, depending on the ordering of the quantum well layers within the intrinsic region of a p-i-n diode. The case in which a reverse bias on the diode yields a blueshift in the transition energy is of particular interest for IR electro-optic device applications. The modulator section of an integrated source/waveguide modulator would strongly absorb at zero bias and could be biased into transparency, and bistable optical switches could be made more efficient than with redshifting devices. We have used low temperature current-voltage, capacitance-voltage, and photocurrent measurements to characterize a type II quantum well structure that exhibits a blueshift in the lowest energy transitions that is roughly linear with applied bias and is comparable to the potential drop across the structure. View full abstract»

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  • Dependence of facet stress on reliability of AlGaInAs edge-emitting lasers

    Page(s): 083109 - 083109-4
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    The relationship between facet stress and reliability of AlGaInAs edge-emitting lasers is unclear despite it being an important issue. We prepared two 1.3 μm AlGaInAs Fabry–Pérot buried-heterostructure (BH) lasers that were identical except that they had tensile and compressive stress at the facet. The magnitude of the facet stress was controlled to be approximately 200 MPa in both lasers. We performed three reliability tests. In forward-biased electrostatic discharge tests, which can evaluate the resistance to optical damage, the cumulative degradation ratio of the compressive stressed laser was 33% lower than that of the tensile stressed laser. This result indicates a reduction in the optical absorption due to enlargement of the energy band gap at the facet. In the long-term aging of the light output power of 8 mW at 85 °C over 5 000 h, no dependence of the facet stress on the lifetime was observed. Since a major limitation of InP-based BH lasers is the BH interface, the aging results are reasonable. In the accelerated aging of a large current of 200 mA at 85 °C over 800 h, degradation (defined as an increase in the threshold current of over 10%) was observed only in the tensile stressed laser. This degradation differed completely from that caused by optical absorption; dislocation loops covered the entire active layer at the facet. To the best of our knowledge, this is the first time such degradation has been reported. We found the degradation depends on the facet stress and that compressive stress can suppress the degradation. View full abstract»

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  • Realization of submicrometer structures by a confocal system on azopolymer films containing photoluminescent chromophores

    Page(s): 083110 - 083110-5
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    The mass migration phenomenon occurring on the free surface of azobenzene-containing polymers illuminated by light of appropriate wavelength is employed to pattern polymeric films constituted by an azopolymer doped with photoluminescent chromophore. Different topographical features are obtained by adjusting the laser scanning parameters, in particular the laser polarization direction. A detailed microscopic analysis of the patterned samples, based on atomic force microscopy and spectral confocal imaging, evidences the photobleaching of the emitting chromophore in the exposed regions, whereas the emitting features of the chromophore are preserved by the mass migration process. Our results are important for the design of nanostructured light emitting photonic devices based on azopolymers. View full abstract»

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  • Measurement of the air gap width between double-deck metal layers based on surface plasmon resonance

    Page(s): 083111 - 083111-8
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    In this article, we verify that the traditional Kretschmann–Raether configuration of surface plasmon resonance (SPR) could be used to measure the air gap width between a gold-plated prism and another gold-plated glass slide. Due to the presence of double-deck metal layers, the Fabry–Perot resonance and surface plasmon tunnel-coupled effects could occur, which would cause the SPR angle to begin to shift at a larger air gap width of about 700 nm as compared to the case of single metal layer with an air gap width of about 350 nm. The simulated results reveal that the SPR angle begins monotonically to shift initially from 44.5° to 46° when the air gap width between double-deck metal layers decreases from 700 to 500 nm. The smallest air gap width is measured to be 539 nm, in which the SPR angle is 45.5°, by fitting the simulated curves to the experimental results. View full abstract»

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  • Magneto-optics of InAs/GaSb superlattices

    Page(s): 083112 - 083112-5
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    We investigate the optical and electrical properties of a series of InAs/GaSb superlattices (SLs) as a function of InAs layer width d, from 21 to 55 Å, with a fixed GaSb layer width of 24 Å, corresponding to SLs with the cutoff wavelengths between 4 and 19 μm. Since the higher electron mass in InAs/GaSb SLs than in mercury cadmium telluride should lead to lower photodiode tunneling currents, we also measured the cyclotron effective mass for a very long wavelength infrared design SLs. For d<40 Å, the SLs were p-type, with hole mobilities of approximately 8 000 cm2/Vs. For a high mobility p-type sample no hole cyclotron resonance signal was detected. However, the SLs with d≥40 Å were n-type, with electron mobilities increasing from 865 to 6126 cm2/Vs. Cyclotron resonance data on an n-type SL sample yielded an electron cyclotron mass of 0.068 m0, which is three times the InAs bulk value of 0.023 m0. The mass enhancement was only partially accounted for by conduction band nonparabolicity, based on our 8×8 envelope function calculation. View full abstract»

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  • A small radius hydrogen discharge: An effective source of volume produced negative ions

    Page(s): 083301 - 083301-8
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    Free-fall regime maintenance of hydrogen discharges is analyzed based on numerical solutions of a set of equations involving the balance equations of the charged particles [electrons, the three types of the positive ions (H+, H2+, and H3+), and negative H- ions] and of the neutral species (hydrogen atoms H and vibrationally excited molecules), the momentum equations of the positive ions, the electron energy balance equation, and the Poisson equation, all together 25 differential equations. The obtained results for varying discharge radius show strong accumulation of the negative ions in the on-axis region of the discharge when the discharge radius is small, which leads to a concept for a design of a volume-production based source as a matrix of small radius discharges. The variation in the negative ion density with changing gas pressure and electron density at the discharge axis is also analyzed. View full abstract»

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  • Measure of precursor electron density profiles of laser launched radiative shocks

    Page(s): 083302 - 083302-9
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    We have studied the dynamics of strong radiative shocks generated with the high-energy subnanosecond iodine laser at Prague Asterix Laser System facility (Prague) over long time scales, up to 100 ns. These shock waves are characterized by a developed radiative precursor, a radiation driven ionization wave in front of the density jump of the shock. Electronic density profiles are measured at different times after the laser pulse and at different distances from the axis of the shock tube. A new feature, described as a split precursor, has been observed. Comparisons with two-dimensional computations are shown. View full abstract»

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  • Magnetohydrodynamics control of capillary Z-pinch discharge by using a triangular current pulse for lasing a H-like N recombination soft x-ray laser

    Page(s): 083303 - 083303-7
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    In expansion cooling phase of pinched nitrogen plasma generated by fast capillary discharge, it might be possible to realize lasing a Blamer α recombination SXRL, which requires a rapid cooling of nonequilibrium plasma. It is effective to decrease the discharge current rapidly in reducing the additional heating caused by the joule heating and the magnetic compression of plasma as quickly as possible. The shaping of discharge current waveform was demonstrated with a transmission line and its effect on expanding plasma dynamics were investigated through magnetohydrodynamics (MHD) calculation, and validity of the MHD calculation in the expansion phase was shown using the discharge photographs taken by using a high speed camera. As a result, strong radiation from the H-like N ion at the maximum pinch, which is in the current decay phase of the triangular current with peak amplitude of over 70 kA and pulse width of 60 ns, has been confirmed in x-ray photodiode signals at wavelength of less than 2.5 nm, to clarify the existence of the Lyman series and continuum of the H-like N ion. Without additional heating by the discharge current after the generation of the fully stripped nitrogen ions, it might be possible to generate the population inversion between the principal quantum number n=2 and 3. View full abstract»

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  • Experimental study of a helium surface-wave discharge at atmospheric pressure

    Page(s): 083304 - 083304-7
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    An experimental characterization of a helium surface-wave discharge (SWD) at atmospheric pressure using spectroscopic techniques is presented. Values of plasma parameters (densities and temperatures) were obtained from these techniques and the degree of thermodynamic equilibrium was shown to be that of an ionizing plasma. The experimental values of the plasma parameters were compared to those obtained from a theoretical model developed for the same He discharge type and to those found in the literature for other noble gases (neon and argon) SWDs also generated at atmospheric pressure. These comparisons enable to infer the main cause of departure from local thermodynamic equilibrium to processes involving He molecular ions, namely, associative ionization and dissociative recombination. View full abstract»

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  • Ultrafast electron beam imaging of femtosecond laser-induced plasma dynamics

    Page(s): 083305 - 083305-6
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    Plasma dynamics in the early stage of laser ablation of a copper target are investigated in real time by making ultrafast electron shadow images and electron deflectometry measurements. These complementary techniques provide both a global view and a local perspective of the associated transient electric field and charge expansion dynamics. The results reveal that the charge cloud above the target surface is composed predominantly of thermally ejected electrons and that it is self-expanding, with a fast front-layer speed exceeding 107 m/s. The average electric field strength of the charge cloud induced by a pump fluence of 2.2 J/cm2 is estimated to be ∼2.4×105 V/m. View full abstract»

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  • Time-resolved optical emission spectroscopy of laser-produced air plasma

    Page(s): 083306 - 083306-9
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    Time-resolved optical emission spectroscopy (OES) is used to analyze a mesh-initiated air breakdown plasma induced by a transverse excitation atmospheric CO2 pulsed laser (λ=10.591 μm, 64 ns (full width at half maximum), 70–160 J/cm2). Emission from excited N, O, C, H, and Ar; ionic fragment N+, O+, N2+, O2+, C+, and molecular band systems of N2+(B2Σu+-X2Σg+; D2Πg-A2Πu), N2(C3Πu-B3Πg), and OH(A2Σ+-X2Π) is observed. Plasma characteristics are examined in detail on the emission lines of N+, O+, and C by time-resolved OES technique. The results show a faster decay of continuum and ionic spectral species than of neutral atomic and molecular ones. The velocity and kinetic energy distributions for the different species were obtained from time-of-flight measurements. Excitation temperature and electron density in the laser-induced plas- - ma were estimated from the analysis of spectral data at various times from the laser pulse incidence. Temporal evolution of electron density has been used for the estimation of the three-body recombination rate constant. View full abstract»

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  • Temperature dependent properties of silicon containing diamondlike carbon films prepared by plasma source ion implantation

    Page(s): 083307 - 083307-6
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    Silicon containing diamondlike carbon (Si-DLC) films were prepared on silicon wafer substrates by a plasma source ion implantation method with negative pulses superposed on a negative dc voltage. A mixture of acetylene and tetramethylsilane gas was introduced into the discharge chamber as working gases for plasma formation. Ions produced in the plasma are accelerated toward a substrate holder because of the negative voltage applied directly to it. After deposition, the films were annealed for 0.5 h in ambient air at temperatures up to 923 K in order to evaluate the thermal stability of the Si-DLC films. The films were analyzed by x-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy, and Raman spectroscopy. The surface morphology of the films and the film thickness were observed by atomic force microscopy and scanning electron microscopy. The mechanical and tribological properties were investigated by an indentation method and a ball-on-disk test. The results show the silicon containing DLC films were amorphous and the surface roughness of the Si containing DLC films was very smooth and no special structure was observed. Integrated intensity ratios ID/IG of Raman spectroscopy of the Si containing DLC films decreased with Si content. The Raman spectra showed that the structure of the Si-free DLC film changed to a graphitelike structure with increasing annealing temperature, whereas that of the 24 at. % Si containing DLC films did not change at the maximum temperature used in this study. A very low friction coefficient was obtained for the 13 at. % Si containing DLC film. The surface roughness and the hardness of the films changed with increasing annealing temperature. The formation of Si oxide in a near su- - rface layer was confirmed by XPS and it prevents further oxidation of the inside of the film. Heat resistivity of DLC films can be improved by Si addition into the DLC films. View full abstract»

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  • Properties of inductively coupled rf Ar/H2 plasmas: Experiment and global model

    Page(s): 083308 - 083308-9
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    Experiments with a Langmuir probe and optical emission spectroscopy combined with actinometry are carried out in inductively coupled rf (13.56 MHz) Ar/H2 discharges at total pressures of 20 m, 40 m, and 60 mTorr in hydrogen fractions ranging from 0% to 50%. The measured electron energy probability functions (EEPFs), which deviate from the Maxwellian distributions owing to the depletion of high-energy electrons, can be approximated using two temperatures. The electron temperatures, which can be deduced from the slopes of low-energy and high-energy parts of the EEPFs, relatively abruptly increase with increasing the hydrogen fraction in the hydrogen fractions below 10%, whereas the measured electron density markedly decreases with increasing the hydrogen fraction in the hydrogen fractions below 20%. The effective ion mass, which can be estimated from the ion current collected into the probe, markedly decreases with increasing the hydrogen fraction. The density of hydrogen atoms estimated by actinometry markedly increases as molecular hydrogen is added to Ar discharges, and then gradually increases with increasing the hydrogen fraction at the hydrogen fractions higher than 10%–20%. A global model is used to study the effect of Ar dilution to hydrogen discharges on the plasma parameters assuming the Maxwellian electron energy distribution. The model results are compared with the experimental results, obtaining reasonably good agreement. View full abstract»

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  • Atom-by-atom simulations of chemical vapor deposition of nanoporous hydrogenated silicon nitride

    Page(s): 083501 - 083501-9
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    Amorphous hydrogenated silicon nitride (SiNH) materials prepared by plasma-enhanced chemical vapor deposition (PECVD) are of high interest because of their suitability for diverse applications including optical coatings, gas/vapor permeation barriers, corrosion resistant, and protective coatings and numerous others. In addition, they are very suitable for structurally graded systems such as those with a graded refractive index. In parallel, modeling the PECVD process of SiN(H) of an a priori given SiN(H) ratio by atomistic calculations represents a challenge due to: (1) different (and far from constant) sticking coefficients of individual elements, and (2) expected formation of N2 (and H2) gas molecules. In the present work, we report molecular-dynamics simulations of particle-by-particle deposition process of SiNH films from SiHx and N radicals. We observe formation of a mixed zone (damaged layer) in the initial stages of film growth, and (under certain conditions) formation of nanopores in the film bulk. We investigate the effect of various PECVD process parameters (ion energy, composition of the SiHx+N particle flux, ion fraction in the particle flux, composition of the SiHx radicals, angle of incidence of the particle flux) on both (1) deposition characteristics, such as sticking coefficients, and (2) material characteristics, such as dimension of the nanopores formed. The results provide detailed insight into the complex relationships between these process parameters and the characteristics of the deposited SiNH materials and exhibit an excellent agreement with the experimentally observed results. View full abstract»

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  • The equation of state and nonmetal–metal transition of benzene under shock compression

    Page(s): 083502 - 083502-5
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    We employ quantum molecular dynamic simulations to investigate the behavior of benzene under shock conditions. The principal Hugoniot derived from the equation of state is determined. We compare our first principles results with available experimental data and provide predictions of chemical reactions for shocked benzene. The decomposition of benzene is found under the pressure of 11 GPa. The nonmetal–metal transition, which is associated with the rapid C–H bond breaking and the formation of atomic and molecular hydrogen, occurs under the pressure around 50 GPa. Additionally, optical properties are also studied. View full abstract»

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  • Thermal conductivity of silicon bulk and nanowires: Effects of isotopic composition, phonon confinement, and surface roughness

    Page(s): 083503 - 083503-14
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    We present a rigorous analysis of the thermal conductivity of bulk silicon (Si) and Si nanowires (Si NWs) which takes into account the exact physical nature of the various acoustic and optical phonon mechanisms. Following the Callaway solution for the Boltzmann equation, where resistive and nonresistive phonon mechanisms are discriminated, we derived formalism for the lattice thermal conductivity that takes into account the phonon incidence angles. The phonon scattering processes are represented by frequency-dependent relaxation time. In addition to the commonly considered acoustic three-phonon processes, a detailed analysis of the role of the optical phonon decay into acoustic phonons is performed. This optical phonon decay mechanism is considered to act as acoustic phonon generation rate partially counteracting the acoustic phonon scattering rates. We have derived the analytical expression describing this physical mechanism which should be included in the general formalism as a correction to the resistive phonon-point-defects and phonon-boundary scattering expressions. The phonon-boundary scattering mechanism is taken as a function of the phonon frequency, incidence angles, and surface roughness. The importance of all the mechanisms we have involved in the model is demonstrated clearly with reference to reported data regarding the isotopic composition effect in bulk Si and Si NW samples. Namely, our model accounts for previously unexplained experimental results regarding (i) the isotope composition effect on the thermal conductivity of bulk silicon reported by Ruf etal [Solid State Commun. 115, 243 (2000)], (ii) the size effect on κ(T) of individual Si NWs reported by Li etal [Appl. Phys. Lett. 83, 2934 (2003)], and (iii) the dramatic decrease in the thermal conductivity for rough Si NWs reported by Hochbaum etal [Nature (London) 451, 163 (2008)]. View full abstract»

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  • Quantum yield excitation spectrum (UV-visible) of CdSe/ZnS core-shell quantum dots by thermal lens spectrometry

    Page(s): 083504 - 083504-6
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    A recently developed thermal lens spectrometry configuration has been used to study CdSe/ZnS core-shell quantum dots (QDs) suspended in toluene and tetrahydrofuran (THF) solvents. The special features of this configuration make it very attractive to measure fluorescence quantum yield (η) excitation spectrum since it simplifies the measurement procedure and consequently improve the accuracy. Furthermore, the precision reached is much higher than in conventional photoluminescence (PL) technique. Two methods, called reference sample and multiwavelength have been applied to determine η, varying excitation wavelength in the UV-visible region (between 335–543 nm). The η and PL spectra are practically independent of the excitation wavelength. For CdSe/ZnS QDs suspended in toluene we have obtained η=76±2%. In addition, the aging effect on η and PL has been studied over a 200 h period for QDs suspended in THF. View full abstract»

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

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P. James Viccaro
Argonne National Laboratory