By Topic

Journal of Applied Physics

Issue 7 • Date Apr 1998

Filter Results

Displaying Results 1 - 25 of 87
  • Issue Cover

    Page(s): c1
    Save to Project icon | PDF file iconPDF (43 KB)  
    Freely Available from IEEE
  • Issue Table of Contents

    Page(s): toc1
    Save to Project icon | PDF file iconPDF (61 KB)  
    Freely Available from IEEE
  • Thermal expansion of scanning tunneling microscopy tips under laser illumination

    Page(s): 3453 - 3460
    Save to Project icon | PDF file iconPDF (173 KB)  

    The periodic thermal expansion of scanning tunneling microscopy (STM) tips arising under irradiation with power-modulated laser light has been investigated. The expansion was determined by comparison with a calibrated piezomotion measured in an STM, which was operated in the constant-current mode, and instrumental effects were corrected for. The experimental data concerning the frequency response of the thermal expansion for various geometries of the tip and for different positions of the laser focus are compared with theoretical results which were derived from a numerical solution of the equation of heat conduction. A very good agreement is found. The results are also interpreted in terms of simplified analytical expressions. Furthermore, the theoretical data are used to derive the response of the tip to fast transients of the light power as in the case of pulsed irradiation. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The probe dynamics under shear force in near-field scanning optical microscopy

    Page(s): 3461 - 3468
    Save to Project icon | PDF file iconPDF (162 KB)  

    We present here the results of theoretical as well as experimental studies of shear force interactions in near-field scanning optical microscopy. A continuum mechanical model that considers the realistic tapered fiber shape was used to calculate the shear force during the interactions. The frequency spectra at different probe/sample separations show that the shear force is a combination of elastic and frictional force. The relative strengths of these two forces depend on the tilt angle between the probe and the sample surface. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The directionality of quantum confinement on strain-induced quantum-wire lasers

    Page(s): 3469 - 3472
    Save to Project icon | PDF file iconPDF (74 KB)  

    Optical properties of Ga0.47-xIn0.53+xAs (x∼0.14) multiple-quantum-wire (MQWR) lasers prepared by the strain-induced lateral-layer ordering process were studied. A typical ratio of threshold current density, ∼10, was observed from the GaInAs MQWR lasers with contact stripes aligned to the [110] ([110] MQWR laser) and the [1¯10] ([1¯10] MQWR laser) directions. The threshold current density of the [110] MQWR laser is ∼30% lower than that of a Ga0.47In0.53As multiple-quantum-well (MQW) reference laser. The 77 K lasing wavelengths were 1.46, 1.57, and 1.69 μm for the MQW laser, the [1¯10] and [110] MQWR lasers, respectively. This strong anisotropy of threshold current densities and lasing wavelengths is the first direct evidence of the directionality of two-dimensional quantum confinement in the MQWR structure. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Photorefractive effect in doped Pb5Ge3O11 and in (Pb1-xBax)5Ge3O11

    Page(s): 3473 - 3479
    Save to Project icon | PDF file iconPDF (155 KB)  

    The photorefractive effect is studied in ferroelectric lead germanate crystals Pb5Ge3O11, including undoped, Fe- and Rh-doped crystals, as well as (Pb1-xBax)5Ge3O11 solid solutions. Two kinds of processes are involved in photorefractive interactions: a fast response with a time constant generally less than 1 s and the formation of slow gratings with time constants of several hours for intensities in the range of 1–30 kW/m2. Basic photorefractive parameters corresponding to the fast response, such as dark- and photoconductivities, the sign of the main charges involved in the transport process, effective trap densities, and activation energies are determined. Compared to theoretical predictions the measured effects are too small which is attributed mainly to electron-hole competition. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Silicon-based interminiband infrared laser

    Page(s): 3480 - 3485
    Save to Project icon | PDF file iconPDF (137 KB)  

    Simulations of a room-temperature p-i-p coherently strained Si0.5Ge0.5/Si superlattice quantum-parallel laser diode have been made. Calculations have been made of the local-in-k-space population inversion between the nonparabolic heavy-hole valence minibands, HH2 and HH1. Lasing is at 5.4 μm and the optical dipole matrix element is 3.7 A. Analysis of radiative-and-phonon scattering between the “mixed” bands indicates a lifetime difference between the upper and lower states of 2.4 ps. At an injected current density of 5000 A/cm2, a laser gain of 134 cm-1 is calculated. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Parametric interactions in the organic salt 4-N,N-dimethylamino-4-N- methyl-stilbazolium tosylate at telecommunication wavelengths

    Page(s): 3486 - 3489
    Save to Project icon | PDF file iconPDF (104 KB)  

    We show that the organic salt 4-N,N-dimethylamino-4-N-methyl-stilbazolium tosylate, originally developed for electro-optic applications, is also a very interesting material for phase-matched parametric interactions such as frequency-doubling and optic parametric oscillation in the near infrared. These favorable properties are due to the large off-diagonal element d26 which gives measured effective phase-matchable nonlinear optical coefficients of deff=31±5 and 15±3 pm/V at the telecommunication wavelengths of λ=1313 and 1535 nm, respectively. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fabrication of a polymer composite with periodic structure by the use of ultrasonic waves

    Page(s): 3490 - 3494
    Save to Project icon | PDF file iconPDF (376 KB)  

    A polymer composite was fabricated by solidification of a particle suspension in ultrasonic standing waves. Particles of various materials and shapes can be arranged periodically at the nodes of standing waves. A polysiloxane resin is suitable as a host material of the composite, since it is synthesized easily from a solution and it yields a small periodic structure even at a low ultrasonic frequency due to the low sound velocity. This method is useful for fabrication of bulk materials with periodic microstructures. Optical diffraction of a laser beam was observed in a polymer composite made of a polysiloxane resin and acrylic particles. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Application of a generalized methodology for quantitative thermal diffusivity depth profile reconstruction in manufactured inhomogeneous steel-based materials

    Page(s): 3495 - 3498
    Save to Project icon | PDF file iconPDF (87 KB)  

    Several applications will be presented using an inversion methodology based on the generalized theoretical formulation [J. Appl. Phys. 80, 5570 (1996)] of the Hamilton-Jacobi formulation of thermal-wave physics to the problem of photothermal radiometric depth profilometry of the thermal diffusivity of inhomogeneous solids. In the depth profile reconstruction algorithm three channels of information, namely, the amplitude, the phase, and the derivative of phase, of the photothermal signal are utilized to reduce multiple solutions to a single consistent and continuous solution. Wherever possible, diffusivity profiles are compared with those resulting from destructive microhardness testing. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermal composition of DyF-, HoF-, and TmF-based gases

    Page(s): 3499 - 3508
    Save to Project icon | PDF file iconPDF (195 KB)  

    The partition functions are calculated for gases consisting of Ln and F atoms, Ln+ ions, LnF and F2 molecules, and LnF+ molecular ions (Ln≡Dy, Ho, Tm) and are subsequently used in determining the local thermal equilibrium compositions of such gases. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Transport of plasmas produced by pulsed laser ablation of HgCdTe

    Page(s): 3509 - 3513
    Save to Project icon | PDF file iconPDF (109 KB)  

    A time- and space-resolved diagnostic technique was used to investigate the emission spectra from the plasmas produced by pulsed laser-ablated HgCdTe targets at different pressures. According to the time-of-flight curves of the excited atoms, the propagation distances and velocities of species in the plasma were measured. To investigate the propagation of the plasma, a shock wave model considering ejected HgCdTe mass was established. The propagation distances and velocities of the plasmas were calculated by using the model. The calculated results were consistent with the experimental results. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Microwave generation in a high voltage triggered pseudospark discharge experiment

    Page(s): 3514 - 3520
    Save to Project icon | PDF file iconPDF (131 KB)  

    A set of five experiments to study the microwave emission accompanying the high voltage pseudospark discharge are reported. The generation of the microwaves in all cases but one is attributed to electron beam-plasma interaction. In the other case, Cherenkov radiation was also considered as a possible mechanism of generation. Initial simulation studies were carried out which predict a background peak plasma density on the order of 1–2×1013cm-3. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comparison of a consistent theory of radio frequency sheaths with step models

    Page(s): 3521 - 3528
    Save to Project icon | PDF file iconPDF (194 KB)  

    In order to find analytically tractable models for the electrode sheath of a capacitively coupled rf discharge, step models are used in the literature, describing the electron density by a step function oscillating with the radio frequency ω pi≪ω≪ωpe). Comparison of the results of these step models with the results of numerical calculations shows similar current–voltage characteristics for symmetric discharges. On the other hand, distinct deviations in the spatial behavior of field and potential for a single sheath are observed. We discuss the deviations of the step models and show that they arise from systematic errors in the boundary conditions which are due to misinterpretations of the asymptotic two scale formalism. On the basis of a systematic two scale theory, we develop an improved step model with correct boundary conditions. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • X-ray diffraction studies of the effects of N incorporation in amorphous CNx materials

    Page(s): 3529 - 3534
    Save to Project icon | PDF file iconPDF (103 KB)  

    The effects of nitrogen incorporation on the atomic-scale structure of amorphous CNx samples have been studied for 0, 5, 20, and 30 at. % N concentration, by x-ray diffraction. Significant differences in the structure are observed on the incorporation of only 5 at. % N, and the changes in structure continue as further N is added. From the experimental data, we are able to obtain directly the average bond distances and then calculate the average bond angles for each of the samples. The average first neighbor distance shows a gradual decrease from 1.55 Å for 0 at. % N, to 1.44 Å for 30 at. % N, and a similar trend is observed in the position of the second neighbor peak. This gives a corresponding increase in the average bond angle from 108° to 114°. The results show an increase in the fraction of sp2 bonded carbon atoms with increasing N concentration, and there is evidence for the presence of significant numbers of CN and CN bonds. These results are also consistent with stress, hardness, and optical gap measurements for these samples. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Two-dimensional nuclear magnetic resonance study of a hydrated porous medium: An application to white cement

    Page(s): 3535 - 3540
    Save to Project icon | PDF file iconPDF (132 KB)  

    Structure and dynamics of a hydrated white cement were investigated by the T1-weighted lineshape, two-dimensional (2D) exchange, and 2D separation of inhomogeneous and homogeneous lineshapes nuclear magnetic resonance (NMR) techniques. T1 weighting of the proton spectrum eliminates the strong bulk water signal from the pores so that the weaker spectrum of the solid cement matrix becomes observable. The proton spectrum of the solid cement fraction exhibits a characteristic Pake doublet shape and shows a close similarity to the powder spectra of pure calcium hydroxide and the crystalline water of gypsum. The 2D exchange NMR spectrum of white cement demonstrates the existence of slow chemical exchange processes of protons in the solid matrix on a sub-kHz frequency scale. This exchange is orders of magnitude slower than the exchange between the surface and bulk water. The 2D NMR separation of inhomogeneous and homogeneous lineshapes technique demonstrates that the absorption lines of a set white cement are inhomogeneously broadened due to the existence of a distribution of static local magnetic fields. The major contribution to these fields comes from the dipolar fields of the paramagnetic electrons whereas the magnetic susceptibility differences of the liquid and solid fractions add a small part at the solid-liquid boundary where the direction of the external magnetic field is changed. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermal deposition and characterization of Se-Sn mixed oxide thin films for NO gas sensing applications

    Page(s): 3541 - 3546
    Save to Project icon | PDF file iconPDF (212 KB)  

    Thin films made by a mixing of selenium and tin oxides have been obtained by high vacuum thermal evaporation. A detailed optical, electrical and structural characterization has been performed on all deposited films. Electron microscopy observations show that the films consist of nanosized grains of SeO2 and SnO2 homogeneously arranged. The NO gas sensing properties of this material have been tested in controlled atmosphere. In addition, the influence of oxygen in the test gas mixture was analyzed. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Microfabrication of microtip on photocantilever for near-field scanning microscopy and investigation of effect of microtip shape on spatial resolution

    Page(s): 3547 - 3551
    Save to Project icon | PDF file iconPDF (755 KB)  

    We experimentally investigated the dependence of spatial resolution on the shape of a microtip on our photocantilever, in order to improve the spatial resolution of near-field scanning optical microscopy. Two different cone angles of silicon-dioxide microtips were microfabricated by a new fabrication process. The experimental results, which indicate there is a relationship between the spatial resolution and cone angle of the microtip, were interpreted by calculations based on a simple theoretical model. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Diffraction anomalous near-edge structure in ordered GaInP

    Page(s): 3552 - 3555
    Save to Project icon | PDF file iconPDF (171 KB)  

    We report the diffraction anomalous near-edge structure (DANES) of a nominally lattice matched GaxIn1-xP/GaAs (x=0.51) heteroepitaxial layer, grown by metal organic chemical vapor deposition, which shows long range ordering in the cationic sublattice along the <111> direction. DANES spectra, originating from the 004 reflections of the substrate and of the epi-layer and that from the “forbidden” -5/2 5/2 -5/2 reflection of the superstructure, have been recorded at the Ga K edge. A full theoretical simulation, based on the kinematic formalism, largely agrees with the experimental data. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Excimer laser irradiation of Si3N4 films deposited on Si

    Page(s): 3556 - 3559
    Save to Project icon | PDF file iconPDF (60 KB)  

    We have investigated the effect of argon excimer laser irradiation of silicon nitride films deposited on silicon substrates. When the film thickness is equal to or greater than 40 nm, the irradiation induces amorphous silicon precipitation near the thin surface layer of the film, which has been clarified by means of x-ray photoelectron and Raman spectroscopy. The formation mechanism of amorphous silicon with the irradiation is discussed. The phase of silicon precipitation depends on the thermal properties of the substrate material. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Chemical etching of ion tracks in LiF crystals

    Page(s): 3560 - 3564
    Save to Project icon | PDF file iconPDF (2109 KB)  

    In LiF, the formation of defects upon electronic excitations was studied using various heavy ions with energies up to 11.4 MeV/u. The induced damage was revealed by the technique of selective chemical etching. Track etching was successful only in those cases where the linear energy transfer of the ions had surpassed a critical threshold of about 1 keV/Å. Annealing tests after ion irradiation show that track etching is possible up to a temperature of 450 °C, i.e., the thermal stability of the etchable damage in ion tracks is much higher than simple defects such as color centers. It is concluded that the etchability of tracks in LiF is strongly related to the creation of defect aggregates. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Profile broadening of high dose germanium implants into (100) silicon at elevated temperatures due to channeling

    Page(s): 3565 - 3573
    Save to Project icon | PDF file iconPDF (177 KB)  

    (100) Silicon wafers were implanted with 120 keV germanium ions at substrate temperatures up to 600 °C. The germanium profile was monitored together with the crystalline fraction of the implanted silicon by Rutherford backscattering spectroscopy channeling in the <100> direction. Extensive profile broadening was seen with elevated temperature implants accompanied by a peak shift of 50 nm away from the surface for the highest temperature implant at 600 °C. A germanium tail was also seen extending deeper than 300 nm for this implant together with a reduction in the peak germanium concentration of more than 60% when compared with similar implants at room temperature. Radiation enhanced diffusion and enhanced sputtering are ruled out as causes for the profile broadening. Instead we demonstrate channeling along the <100> direction to be the cause of both the observed broadening and the increase in the peak depth. This was confirmed by eliminating such profile broadening in a sample implanted at 600 °C by tilting the implant away from major axial and planar channels. Positron annihilation spectroscopy was used to monitor the profile of open volume defects in the implanted material. Data from this analysis show that a defect concentration of greater than 1016/cm3 extends to a depth of ≈1.2 μm for 1×1014Ge/cm2 at room temperature. A higher concentration of such defects appear deeper for similar implants at 450 °C. These deep open volume defects can be eliminated by using tilted implants through an amorphous 0.5 μm SiO2 mask layer. Their formation is consistent with germanium ion channeling during the initial sta- ges of room temperature implantation and extensive channeling for elevated temperature implantation. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fracture initiation at sharp notches in single crystal silicon

    Page(s): 3574 - 3582
    Save to Project icon | PDF file iconPDF (180 KB)  

    In the context of linear anisotropic elasticity, a universal singular stress field may exist in the region surrounding a sharp reentrant corner (notch). In general, both the radial and tangential variation of the stress fields differ for mode I (symmetric) and mode II (antisymmetric) deformations, and for general anisotropy the mode I and II deformations are coupled. A failure criterion based on critical values of the stress intensities may be appropriate in situations where the region around the corner dominated by the singular fields is large compared to the size of intrinsic flaws and any inelastic zones. We determined the mode I stress fields and stress intensities for two sets of notched silicon flexure specimens using a combination of an asymptotic analysis using the Stroh formalism, dimensional considerations, and continuum finite element analysis. We carried out a companion experimental study to assess the suitability of a critical stress intensity failure criterion. Specifically, assuming such a criterion is valid, we extracted critical values of the mode I stress intensities for a series of notched silicon flexure specimens with notch angles of 70.53° and 125.26°. The specimens were fabricated by anisotropic etching of silicon wafers in KOH, resulting in notch angles of 70.53° between (111) and (1¯1¯1) planes and 125.26° between (111) and (100) planes. The data show that good failure correlation is obtained through the use of a single parameter, the critical mode I stress intensity. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Microcracks, spall and fracture in glass: A study using short pulsed laser shock waves

    Page(s): 3583 - 3594
    Save to Project icon | PDF file iconPDF (1004 KB)  

    This work reports our meso mechanical study of microcrack behavior, especially the process leading from microcracking to macro failure. Using laser loading with a duration on the order of nanoseconds, spallation in a cylindrical geometry was achieved in soda-lime glass at the microcrack evolution stage. Laser induced shock waves were used to conduct crack initiation experiments for the first time. The specimens were examined after experiments and were compared with those loaded by conventional static and dynamic methods. A meso scale failure model of nucleation, growth, and percolation (NGP) is suggested based on the experiments. The NGP model is characterized by a randomly generated microcrack field and by simultaneous percolation statistics in time iteration. In most existing damage models, the statistical average of microcracks over a finite space is required in order to evaluate the damage variables. This procedure is not necessary in the NGP model. We show that the connection of microcracks can be very complicated, possibly a self-organized process. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of “bamboo” grain boundaries on the maximum electromigration-induced stress in microelectronic interconnect lines

    Page(s): 3595 - 3599
    Save to Project icon | PDF file iconPDF (3556 KB)  

    A model which describes the steady-state mechanical stresses resulting from electromigration in microelectronic interconnect lines is presented. This model is valid when sidewall and grain boundary interface diffusion are the dominant transport paths, and accounts for the two-dimensional microstructure present in such lines. By applying the model to simulated line microstructures, we find that bamboo grain boundaries may substantially increase the maximum electromigration stress. Furthermore, microstructural simulations on bounded interconnect segments show that variations in grain size may lead to a large scatter in the maximum stress, particularly as line length decreases. © 1998 American Institute of Physics. 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