By Topic

Journal of Applied Physics

Issue 1 • Date Jul 2014

Filter Results

Displaying Results 1 - 25 of 65
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of the band structure of InGaN/GaN quantum well on the surface plasmon enhanced light-emitting diodes

    Page(s): 013101 - 013101-5
    Save to Project icon | PDF file iconPDF (1146 KB)  

    The spontaneous emission (SE) of InGaN/GaN quantum well (QW) structure with silver(Ag) coated on the n-GaN layer has been investigated by using six-by-six K-P method taking into account the electron-hole band structures, the photon density of states of surface plasmon polariton (SPP), and the evanescent fields of SPP. The SE into SPP mode can be remarkably enhanced due to the increase of electron-hole pairs near the Ag by modulating the InGaN/GaN QW structure or increasing the carrier injection. However, the ratio between the total SE rates into SPP mode and free space will approach to saturation or slightly decrease for the optimized structures with various distances between Ag film and QW layer at a high injection carrier density. Furthermore, the Ga-face QW structure has a higher SE rate than the N-face QW structure due to the overlap region of electron-hole pairs nearer to the Ag film. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Shockley-Read-Hall lifetimes in CdTe

    Page(s): 013102 - 013102-4
    Save to Project icon | PDF file iconPDF (133 KB)  

    A combination of first principles electronic structure calculations, Green's function method, and empirical tight-binding Hamiltonian method is used to evaluate the minority carrier lifetimes of CdTe due to recombination via native point defects in CdTe. For defect energy levels near mid-gap, our calculated value of the Shockley-Read-Hall capture cross section for both electrons and holes is ∼10−13 cm2, which is considerably different from the most commonly employed values. We further find that minority carrier lifetimes in doped CdTe are affected more by defect levels closer to the Fermi level than those in the mid-gap. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sidewall passivation for InGaN/GaN nanopillar light emitting diodes

    Page(s): 013103 - 013103-6
    Save to Project icon | PDF file iconPDF (3323 KB)  

    We studied the effect of sidewall passivation on InGaN/GaN multiquantum well-based nanopillar light emitting diode (LED) performance. In this research, the effects of varying etch rate, KOH treatment, and sulfur passivation were studied for reducing nanopillar sidewall damage and improving device efficiency. Nanopillars prepared under optimal etching conditions showed higher photoluminescence intensity compared with starting planar epilayers. Furthermore, nanopillar LEDs with and without sulfur passivation were compared through electrical and optical characterization. Suppressed leakage current under reverse bias and four times higher electroluminescence (EL) intensity were observed for passivated nanopillar LEDs compared with unpassivated nanopillar LEDs. The suppressed leakage current and EL intensity enhancement reflect the reduction of non-radiative recombination at the nanopillar sidewalls. In addition, the effect of sulfur passivation was found to be very stable, and further insight into its mechanism was gained through transmission electron microscopy. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The ejection threshold of molten aluminum induced by millisecond pulsed laser

    Page(s): 013104 - 013104-9
    Save to Project icon | PDF file iconPDF (816 KB)  

    The laser pulse energy density threshold of melt ejection induced by millisecond pulsed laser can vary widely due to the variation of focused laser spot area. An axisymmetric model of the flow of liquid Aluminum under the effect of recoil force from evaporation is built up to analyze the threshold of ejection through the temporal evolution of the temperature of melted pool. Temperature of the central point of focused laser spot, drag force induced by surface tension in melted pool, and recoil force of evaporation on molten liquid surface could be obtained through resolving heat conduction equation analytically and numerically with assumed Gaussian temperature distribution function. The relationship of laser pulse energy density threshold of the ejection and area of the focused laser spot is obtained through the theoretical calculation. The shape of the melted pool will be different when the relative magnitude of recoil force and drag force is varied. The validity of the obtained threshold is verified through comparison of melted pool shape with the experimental result reported in literature. The criterion proposed in this paper provides a reliable fast-diagnostic method for laser processing. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Structural influences on charge carrier dynamics for small-molecule organic photovoltaics

    Page(s): 013105 - 013105-7
    Save to Project icon | PDF file iconPDF (4429 KB)  

    We investigated the structural influences on the charge carrier dynamics in zinc phthalocyanine/fullerene (ZnPc/C60) photovoltaic cells by introducing poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and 2,5-bis(4-biphenylyl)-bithiophene (BP2T) between indium tin oxide and ZnPc layers. ZnPc films can be tuned to be round, long fiber-like, and short fiber-like structure, respectively. Time-resolved microwave conductivity measurements reveal that charge carrier lifetime in ZnPc/C60 bilayer films is considerably affected by the intra-grain properties. Transient photocurrent of ZnPc single films indicated that the charge carriers can transport for a longer distance in the long fiber-like grains than that in the round grains, due to the greatly lessened grain boundaries. By carefully controlling the structure of ZnPc films, the short-circuit current and fill factor of a ZnPc/C60 heterojunction solar cell with BP2T are significantly improved and the power conversion efficiency is increased to 2.6%, which is 120% larger than the conventional cell without BP2T. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time of flight emission spectroscopy of laser produced nickel plasma: Short-pulse and ultrafast excitations

    Page(s): 013301 - 013301-7
    Save to Project icon | PDF file iconPDF (1290 KB)  

    We report the experimental investigation and comparison of the temporal features of short-pulse (7 ns) and ultrafast (100 fs) laser produced plasmas generated from a solid nickel target, expanding into a nitrogen background. When the ambient pressure is varied in a large range of 10−6 Torr to 102 Torr, the plume intensity is found to increase rapidly as the pressure crosses 1 Torr. Time of flight (TOF) spectroscopy of emission from neutral nickel (Ni I) at 361.9 nm (3d9(2D) 4p → 3d9(2D) 4s transition) reveals two peaks (fast and slow species) in short-pulse excitation and a single peak in ultrafast excitation. The fast and slow peaks represent recombined neutrals and un-ionized neutrals, respectively. TOF emission from singly ionized nickel (Ni II) studied using the 428.5 nm (3p63d8(3P) 4s→ 3p63d9 4s) transition shows only a single peak for either excitation. Velocities of the neutral and ionic species are determined from TOF measurements carried out at different positions (i.e., at distances of 2 mm and 4 mm, respectively, from the target surface) on the plume axis. Measured velocities indicate acceleration of neutrals and ions, which is caused by the Coulomb pull of the electrons enveloping the plume front in the case of ultrafast excitation. Both Coulomb pull and laser-plasma interaction contribute to the acceleration in the case of short-pulse excitation. These investigations provide new information on the pressure dependent temporal behavior of nickel plasmas produced by short-pulse and ultrafast laser pulses, which have potential uses in applications such as pulsed laser deposition and laser-induced nanoparticle generation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Surface loss probability of atomic hydrogen for different electrode cover materials investigated in H2-Ar low-pressure plasmas

    Page(s): 013302 - 013302-10
    Save to Project icon | PDF file iconPDF (458 KB)  

    In an inductively coupled H2-Ar plasma at a total pressure of 1.5 Pa, the influence of the electrode cover material on selected line intensities of H, H2, and Ar are determined by optical emission spectroscopy and actinometry for the electrode cover materials stainless steel, copper, tungsten, Macor®, and aluminum. Hydrogen dissociation degrees for the considered conditions are determined experimentally from the measured emission intensity ratios. The surface loss probability βH of atomic hydrogen is correlated with the measured line intensities, and βH values are determined for the considered materials. Without the knowledge of the atomic hydrogen temperature, βH cannot be determined exactly. However, ratios of βH values for different surface materials are in first order approximation independent of the atomic hydrogen temperature. Our results show that βH of copper is equal to the value of stainless steel, βH of Macor® and tungsten is about 2 times smaller and βH of aluminum about 5 times smaller compared with stainless steel. The latter ratio is in reasonable agreement with literature. The influence of the atomic hydrogen temperature TH on the absolute value is thoroughly discussed. For our assumption of TH = 600 K, we determine a βH for stainless steel of 0.39 ± 0.13. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Large scale Tesla coil guided discharges initiated by femtosecond laser filamentation in air

    Page(s): 013303 - 013303-7
    Save to Project icon | PDF file iconPDF (1796 KB)  

    The guiding of meter scale electric discharges produced in air by a Tesla coil is realized in laboratory using a focused terawatt laser pulse undergoing filamentation. The influence of the focus position, the laser arrival time, or the gap length is studied to determine the best conditions for efficient laser guiding. Discharge parameters such as delay, jitter, and resistance are characterized. An increase of the discharge length by a factor 5 has been achieved with the laser filaments, corresponding to a mean breakdown field of 2 kV/cm for a 1.8 m gap length. Consecutive guided discharges at a repetition rate of 10 Hz are also reported. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Shaping gas jet plasma density profile by laser generated shock waves

    Page(s): 013304 - 013304-5
    Save to Project icon | PDF file iconPDF (2034 KB)  

    The Gaussian plasma density profile from a simple cylindrical nozzle jet was modified using laser generated shock wave. This modification provided great variety of density profiles suitable for different applications. The Gaussian plasma density distribution was modified into fast-rise slow-fall profile with adjustable gradients, almost flat-top profiles, and profiles with variable lengths. Position of the shock wave center and time delay were the major parameters used for shaping the density profiles. Other easily adjustable parameters such as shock wave energy and backing pressure provided linear scaling of the modified plasma densities. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multi-channel composite spoof surface plasmon polaritons propagating along periodically corrugated metallic thin films

    Page(s): 013501 - 013501-5
    Save to Project icon | PDF file iconPDF (2081 KB)  

    In this work, we demonstrate that composite spoof surface plasmon polaritons can be excited by coplanar waveguide, which are composed of two different spoof surface plasmon polaritons (SSPPs) modes propagating along a periodically corrugated metallic thin film simultaneously. These two SSPPs correspond to the dominant modes of one-dimensional (1D) periodical hole and groove arrays separately. We have designed and simulated a planar composite plasmonic waveguide in the microwave frequencies, and the simulation results show that the composite plasmonic waveguide can achieve multi-channel signal transmission with good propagation performance. The proposed planar composite plasmonic metamaterial can find potential applications in developing surface wave devices in integrated plasmonic circuits and multi-channel signal transmission systems in the microwave and terahertz frequencies. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An active metallic nanomatryushka with two similar super-resonances

    Page(s): 013502 - 013502-5
    Save to Project icon | PDF file iconPDF (1479 KB)  

    The optical properties of a simple metallic nanomatryushka (nanosphere-in-a-nanoshell) with gain have been investigated theoretically. The spaser (surface plasmon amplification by stimulated emission of radiation) phenomena can be observed at two critical wavelengths in the active metallic nanomatryushkas. With increasing the gain coefficient of the middle layer, a similar super surface plasmon (SP) resonance is first found at the ω+|1 mode of the active nanoparticles and then breaks down. With further increasing the gain coefficient, another similar super-resonance occurs at the ω|1 mode. The near-field enhancements in the active nanomatryushkas also have been greatly amplified at the critical wavelengths for ω+|1 and ω|1 modes. It is further found that the amplifications of SPs in the active Ag–SiO2–Au nanoshell are strongest in four kinds of nanoshells and hence the largest near fields. The giant near-field enhancement can greatly enhance the Raman excitation and emission. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • In-situ neutron diffraction of LaCoO3 perovskite under uniaxial compression. I. Crystal structure analysis and texture development

    Page(s): 013503 - 013503-10
    Save to Project icon | PDF file iconPDF (2606 KB)  

    The dynamics of texture formation, changes in crystal structure, and stress accommodation mechanisms have been studied in perovskite-type R3¯c rhombohedral LaCoO3 during uniaxial compression using in-situ neutron diffraction. The in-situ neutron diffraction revealed the complex crystallographic changes causing the texture formation and significant straining along certain crystallographic directions during compression, which are responsible for the appearance of hysteresis and non-linear ferroelastic deformation in the LaCoO3 perovskite. The irreversible strain after the first loading was connected with the appearance of non-recoverable changes in the intensity ratio of certain crystallographic peaks, causing non-reversible texture formation. However, in the second loading/unloading cycle, the hysteresis loop was closed and no further irrecoverable strain appeared after deformation. The significant texture formation is responsible for an increase in the Young's modulus of LaCoO3 at high compressive stresses, ranging from 76 GPa at the very beginning of the loading to 194 GPa at 900 MPa at the beginning of the unloading curve. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • In-situ neutron diffraction of LaCoO3 perovskite under uniaxial compression. II. Elastic properties

    Page(s): 013504 - 013504-9
    Save to Project icon | PDF file iconPDF (940 KB)  

    Calculations of elastic constants and development of elastic anisotropy under uniaxial compression in originally isotropic polycrystalline LaCoO3 perovskite are reported. The lattice strains in individual (hkl) planes as well as average lattice strain were determined both for planes oriented perpendicular and parallel to the loading direction using in-situ neutron diffraction. Utilizing average lattice strains as well as lattice strains along the a and c crystallographic directions, an attempt was made to determine Poisson's ratio of LaCoO3, which was then compared with that measured using an impulse excitation technique. The elastic constants were calculated and Young's moduli of LaCoO3 single crystal in different crystallographic directions were estimated. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Lattice parameters and Raman-active phonon modes of (InxGa1–x)2O3 for x < 0.4

    Page(s): 013505 - 013505-7
    Save to Project icon | PDF file iconPDF (3799 KB)  

    We present X-ray diffraction and Raman spectroscopy investigations of (InxGa1–x)2O3 thin films and bulk-like ceramics in dependence of their composition. The thin films grown by pulsed laser deposition have a continuous lateral composition spread allowing the determination of phonon mode properties and lattice parameters with high sensitivity to the composition from a single 2-in. wafer. In the regime of low indium concentration, the phonon energies depend linearly on the composition and show a good agreement between both sample types. We determined the slopes of these dependencies for eight different Raman modes. While the lattice parameters of the ceramics follow Vegard's rule, deviations are observed for the thin films. Further, we found indications of the high-pressure phase InGaO3 II in the thin films above a critical indium concentration, its value depending on the type of substrate. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Surface stoichiometry of pulsed ultraviolet laser treated polycrystalline CdTe

    Page(s): 013506 - 013506-8
    Save to Project icon | PDF file iconPDF (1536 KB)  

    The effects of nanosecond pulsed ultraviolet laser annealing on the surface stoichiometry of close-space sublimated polycrystalline thin films are investigated using angle-resolved x-ray photoemission spectroscopy (XPS). The raw data suggest the formation of a Cd-rich surface layer, but this is counter to the expectation based on Cd and Te vapor pressures above CdTe that predicts a Te-rich layer and to direct observation of elemental Te at the surface. In order to explain this apparent discrepancy, we analyze our XPS data in the context of prior reports of lateral segregation of Cd and Te at the surface after pulsed laser treatments with a simple model of angular dependent XPS in the presence of surface roughness. This analysis reveals that a uniform Te layer cannot explain our results. Instead, our analysis suggests that Te enrichment occurs near grain boundaries and that a sub-monolayer Cd layer exists elsewhere. These complex yet repeatable results underscore the challenges in measuring surface stoichiometry to high precision on films relevant for polycrystalline CdTe devices. It also suggests that the Cd and Te vapor pressures above grain boundaries may differ from those above grain interiors and that ohmic contact may be made preferentially at the grain boundaries after pulsed laser annealing. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hard wear-resistant coatings with anisotropic thermal conductivity for high thermal load applications

    Page(s): 013507 - 013507-8
    Save to Project icon | PDF file iconPDF (1902 KB)  

    High thermal load applications such as high speed dry cutting lead to high temperatures in the coated tool substrate that can soften the tool and high temperature gradients that can put stress on the coating/tool interface. In this work, theoretical considerations are presented for multilayer and graded protective coatings that can induce a significant anisotropy in their thermal conductivity. Solution of the heat equation shows that anisotropy of thermal conductivity has the potential to reduce temperatures and temperature gradients arising due to brief, localized heat at the coating surface (“hot-spots”). Experimental realization of high anisotropy is demonstrated in TiN/AlCrN multilayer coatings with variable layer thickness. In the coating with 50 nm bilayer periodicity, the highest anisotropy was obtained with a value of κ||=3.0±0.9. Time-domain thermoreflectance is used to measure in-plane and cross-plane thermal conductivity of fabricated coatings. The observed high values of anisotropy of thermal conductivity are compared with theoretical predictions and its realisation is discussed with regard to the coating microstructure. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of point and grain boundary defects on the mechanical behavior of monolayer MoS2 under tension via atomistic simulations

    Page(s): 013508 - 013508-6
    Save to Project icon | PDF file iconPDF (1748 KB)  

    Atomistic simulation is used to study the structure and energy of defects in monolayer MoS2 and the role of defects on the mechanical properties of monolayer MoS2. First, energy minimization is used to study the structure and energy of monosulfur vacancies positioned within the bottom S layer of the MoS2 lattice, and 60° symmetric tilt grain boundaries along the zigzag and armchair directions, with comparison to experimental observations and density functional theory calculations. Second, molecular dynamics simulations are used to subject suspended defect-containing MoS2 membranes to a state of multiaxial tension. A phase transformation is observed in the defect-containing membranes, similar to prior work in the literature. For monolayer MoS2 membranes with point defects, groups of monosulfur vacancies promote stress-concentration points, allowing failure to initiate away from the center of the membrane. For monolayer MoS2 membranes with grain boundaries, failure initiates at the grain boundary and it is found that the breaking force for the membrane is independent of grain boundary energy. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Near infrared emission from molecule-like silver clusters confined in zeolite A assisted by thermal activation

    Page(s): 013509 - 013509-5
    Save to Project icon | PDF file iconPDF (2764 KB)  

    Strong and broad near infrared (NIR) emission peaked at ∼855 nm upon optimal excitation at 342 nm has been observed from molecule-like silver clusters (MLSCs) confined in zeolite A assisted by thermal activation. To the best of our knowledge, this is the first observation of NIR emission peaked at longer than 800 nm from MLSCs confined in solid matrices. The decay time of the NIR emission is over 10 μs, which indicates that it is a spin-forbidden transition. The ∼855 nm NIR emission shows strong dependence on the silver loading concentration and the thermal activation temperature. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermodynamically constrained correction to ab initio equations of state

    Page(s): 013510 - 013510-5
    Save to Project icon | PDF file iconPDF (693 KB)  

    We show how equations of state generated by density functional theory methods can be augmented to match experimental data without distorting the correct behavior in the high- and low-density limits. The technique is thermodynamically consistent and relies on knowledge of the density and bulk modulus at a reference state and an estimation of the critical density of the liquid phase. We apply the method to four materials representing different classes of solids: carbon, molybdenum, lithium, and lithium fluoride. It is demonstrated that the corrected equations of state for both the liquid and solid phases show a significantly reduced dependence of the exchange-correlation functional used. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ellipsometric characterization and density-functional theory analysis of anisotropic optical properties of single-crystal α-SnS

    Page(s): 013511 - 013511-7
    Save to Project icon | PDF file iconPDF (1236 KB)  

    We report on the anisotropic optical properties of single-crystal tin monosulfide (SnS). The components εa, εb, and εc of the pseudodielectric-function tensor ⟨ε⟩ = ⟨ε1⟩ + i⟨ε2⟩ spectra are taken from 0.73 to 6.45 eV by spectroscopic ellipsometry. The measured ⟨ε⟩ spectra are in a good agreement with the results of the calculated dielectric response from hybrid density functional theory. The ⟨ε⟩ spectra show the direct band-gap onset and a total of eight above-band-gap optical structures that are associated with the interband-transition critical points (CPs). We obtain accurate CP energies by fitting analytic CP expressions to second-energy-derivatives of the ⟨ε⟩ data. Their probable electronic origins and implications for photovoltaic applications are discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The effects of optical phonon on the binding energy of bound polaron in a wurtzite ZnO/MgxZn1−xO quantum well

    Page(s): 013512 - 013512-6
    Save to Project icon | PDF file iconPDF (627 KB)  

    An improved Lee-Low-Pines intermediate coupling method is used to study the energies and binding energies of bound polarons in a wurtzite ZnO/MgxZn1−xO quantum well. The contributions from different branches of long-wave optical phonons, i.e., confined optical phonons, interface optical phonons, and half-space optical phonons are considered. In addition to electron-phonon interaction, the impurity-phonon interaction, and the anisotropy of material parameters, such as phonon frequency, electron effective mass, and dielectric constant, are also included in our computation. Ground-state energies, binding energies and detailed phonon contributions from various phonons as functions of well width, impurity position and composition are presented. Our result suggests that total phonon contribution to ground state and binding energies in the studied wurtzite ZnO/Mg0.3Zn0.7O quantum wells varies between 28–23 meV and 62–45 meV, respectively, which are much larger than the corresponding values (about 3.2–1.8 meV and 1.6–0.3 meV) in GaAs/Al0.3Ga0.7As quantum wells. For a narrower quantum well, the phonon contribution mainly comes from interface and half-space phonons, for a wider quantum well, most of phonon contribution originates from confined phonons. The contribution from all the phonon modes to binding energies increases slowly either when impurity moves far away from the well center in the z direction or with the increase in magnesium composition (x). It is found that different phonons have different influences on the binding energies of bound polarons. Furthermore, the phonon contributions to binding energies as functions of well width, impurity position, and composition are very different from one another. In general, the electron-optical phonon interaction and the impurity center-optical phonon interaction play an important role i- electronic states of ZnO-based quantum wells and cannot be neglected. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Digital model for X-ray diffraction with application to composition and strain determination in strained InAs/GaSb superlattices

    Page(s): 013513 - 013513-11
    Save to Project icon | PDF file iconPDF (2688 KB)  

    We propose a digital model for high quality superlattices by including fluctuations in the superlattice periods. The composition and strain profiles are assumed to be coherent and persist throughout the superlattice. Using this model, we have significantly improved the fit with experimental X-ray diffraction data recorded from the nominal InAs/GaSb superlattice. The lattice spacing of individual layers inside the superlattice and the extent of interfacial intermixing are refined by including both (002) and (004) and their satellite peaks in the fitting. For the InAs/GaSb strained layer superlattice, results show: (i) the GaSb-on-InAs interface is chemically sharper than the InAs-on-GaSb interface, (ii) the GaSb layers experience compressive strain with In incorporation, (iii) there are interfacial strain associated with InSb-like bonds in GaSb and GaAs-like bonds in InAs, (iv) Sb substitutes a significant amount of In inside InAs layer near the InAs-on-GaSb interface. For support, we show that the composition profiles determined by X-ray diffraction are in good agreement with those obtained from atom probe tomography measurement. Comparison with the kinetic growth model shows a good agreement in terms of the composition profiles of anions, while the kinetic model underestimates the intermixing of cations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Physics of band-gap formation and its evolution in the pillar-based phononic crystal structures

    Page(s): 013514 - 013514-7
    Save to Project icon | PDF file iconPDF (1743 KB)  

    In this paper, the interplay of Bragg scattering and local resonance is theoretically studied in a phononic crystal (PnC) structure composed of a silicon membrane with periodic tungsten pillars. The comparison of phononic band gaps (PnBGs) in three different lattice types (i.e., square, triangular, and honeycomb) with different pillar geometries shows that different PnBGs have varying degrees of dependency on the lattice symmetry based on the interplay of the local resonances and the Bragg effect. The details of this interplay is discussed. The significance of locally resonating pillars, specially in the case of tall pillars, on PnBGs is discussed and verified by examining the PnBG position and width in perturbed lattices via Monte Carlo simulations. It is shown that the PnBGs caused by the local resonance of the pillars are more resilient to the lattice perturbations than those caused by Bragg scattering. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-refractive-index CuI waveguide with aligned cylindrical micropores for high-resolution X-ray imaging

    Page(s): 013515 - 013515-4
    Save to Project icon | PDF file iconPDF (2580 KB)  

    We have fabricated porous CuI crystals and used them as scintillator plates for high-resolution X-ray imaging by combining the properties of high-refractive-index light waveguide and scintillation. Porous CuI crystals containing aligned cylindrical micropores with pore volumes of 6% and 30% were fabricated by leaching directionally solidified CuI/NaCl and CuI/KCl eutectic crystals. The continuous cylindrical pores, which had a smooth surface, extended inward from the front to the back surface of the CuI crystal; therefore, light is confined in the CuI matrix with high refractive index (n ≈ 2.35) and transported along the pore direction by a total reflection mode. High-resolution X-ray imaging was demonstrated by using a 30% pore volume CuI crystal for an X-ray resolution chart and the 10 lp/mm pattern was clearly resolved. 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

Editor
P. James Viccaro
Argonne National Laboratory