jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

1 Dec 2005

Volume 98, Issue 11, Articles (11xxxx)

Return to All Sections
back to top
RSS Feeds

Improved vibroacoustography imaging for nondestructive inspection of materials

F. G. Mitri and M. Fatemi

J. Appl. Phys. 98, 114901 (2005); http://dx.doi.org/10.1063/1.2130515 (8 pages) | Cited 5 times

Online Publication Date: 1 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report a method to improve image quality in the nondestructive investigation and visualization of defects using vibroacoustography (VA). Vibroacoustography is an ultrasound-based imaging technique that uses the dynamic (oscillatory) radiation force of low-frequency excitation (within kilohertz range) to remotely vibrate objects and detect the ensuing acoustic emission. This technique is nondestructive and noncontact and has shown numerous capabilities to produce high-resolution images of different types of materials. However, for reflective materials, ultrasound reflects back and forth between the object and transducer, thus establishing standing waves. This phenomenon produces an artifact in the shape of false contours in the VA images. The goal of this study is to investigate the formation of the standing wave artifacts and develop a process called chirp imaging to improve defect visibility and flaw detection capability. Chirp VA experiments are performed on a flawed fiber-reinforced ceramic composite plate and on an electronic chip. To assess the efficacy of the chirp imaging process in removing the standing-wave artifact, the resulting chirp images are compared to “fixed frequency” VA images. Results show that the false contour can be significantly reduced in the image, thus remarkably improving image quality and flaw detection.
Show PACS
43.35.Yb
43.35.Zc
43.60.Lq
43.35.Cg
81.70.Cv Nondestructive testing: ultrasonic testing, photoacoustic testing
43.40.Le
43.20.El
62.65.+k Acoustical properties of solids
43.58.-e

Diamond synthesis under atmospheric pressure from ethanol-water solution using hot-filament chemical vapor deposition method assisted by electrospray

Yuta Matsushima, Miya Naganuma, Tsutomu Yamazaki, Kazuyuki Maeda, and Takeyuki Suzuki

J. Appl. Phys. 98, 114902 (2005); http://dx.doi.org/10.1063/1.2135894 (5 pages) | Cited 2 times

Online Publication Date: 2 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of water on diamond synthesis was investigated in the hot-filament chemical vapor deposition process under atmospheric pressure. We adopted an ethanol-water-hydrogen system; an ethanol-water mixture was supplied by an electrospraying technique. With increasing the water content, the morphology of deposited diamond varied from mirror-ball-like to small-crystalline particles. Dense diamond films with distinct facets were obtained at 5.58 mol % ethanol with 1.39 mol % water and 5.27 mol % ethanol with 2.26 mol % water. In Raman spectroscopy, the full width at half maximum (FWHM) of the diamond peak at 1333 cm−1 decreased with the water content and a broad peak of nondiamond carbon around 1550 cm−1 was markedly reduced. The FWHM also decreased by lowering the ethanol concentration in an ethanol-hydrogen system. Only the ethanol-water-hydrogen system yielded the high-quality diamond with a relatively high deposition rate. The major roles of water were cleaning the filament and removing nondiamond carbon in the deposit with the water-gas reaction, H2O+C→H2+CO.
Show PACS
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Rs Spray coating techniques
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
78.30.Hv Other nonmetallic inorganics
78.66.-w Optical properties of specific thin films
82.45.Mp Thin layers, films, monolayers, membranes
82.80.-d Chemical analysis and related physical methods of analysis

Modeling and experimental studies of magnetron injection locking

P. Pengvanich, V. B. Neculaes, Y. Y. Lau, R. M. Gilgenbach, M. C. Jones, W. M. White, and R. D. Kowalczyk

J. Appl. Phys. 98, 114903 (2005); http://dx.doi.org/10.1063/1.2132513 (6 pages) | Cited 7 times

Online Publication Date: 5 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A phase-locking model has been developed from circuit theory to qualitatively explain the various regimes observed in magnetron injection-locking experiments. The experiments utilize two continuous-wave oven magnetrons: one functions as an oscillator and the other as a driver. The model includes both magnetron-specific electronic conductance and frequency-pulling parameter. Both time and frequency domain solutions are developed from the model, allowing investigations into the growth and saturation as well as the frequency response of the output signal. This simplified model recovers qualitatively many of the phase-locking frequency characteristics observed in the experiments.
Show PACS
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
84.40.Dc Microwave circuits
84.30.Ng Oscillators, pulse generators, and function generators
84.30.Bv Circuit theory

Estimating the transfer function of the cantilever in atomic force microscopy: A system identification approach

Martin Stark, Reinhard Guckenberger, Andreas Stemmer, and Robert W. Stark

J. Appl. Phys. 98, 114904 (2005); http://dx.doi.org/10.1063/1.2137887 (7 pages) | Cited 12 times

Online Publication Date: 7 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Dynamic atomic force microscopy (AFM) offers many opportunities for the characterization and manipulation of matter on the nanometer scale with a high temporal resolution. The analysis of time-dependent forces is basic for a deeper understanding of phenomena such as friction, plastic deformation, and surface wetting. However, the dynamic characteristics of the force sensor used for such investigations are determined by various factors such as material and geometry of the cantilever, detection alignment, and the transfer characteristics of the detector. Thus, for a quantitative investigation of surface properties by dynamic AFM an appropriate system identification procedure is required, characterizing the force sensor beyond the usual parameters spring constant, quality factor, and detection sensitivity. Measurement of the transfer function provides such a characterization that fully accounts for the dynamic properties of the force sensor. Here, we demonstrate the estimation of the transfer function in a bandwidth of 1 MHz from experimental data. To this end, we analyze the signal of the vibrations induced by snap-to-contact and snap-off-contact events. For the free cantilever, we determine both a parameter-free estimate [empirical transfer function estimate (ETFE)] and a parametric estimate of the transfer function. For the surface-coupled cantilever the ETFE is obtained. These identification procedures provide an intrinsic calibration as they dispense largely with a priori knowledge about the force sensor.
Show PACS
07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Pz Instruments for strain, force, and torque

The ruby pressure standard to 150 GPa

Akobuije D. Chijioke, W. J. Nellis, A. Soldatov, and Isaac F. Silvera

J. Appl. Phys. 98, 114905 (2005); http://dx.doi.org/10.1063/1.2135877 (9 pages) | Cited 18 times

Online Publication Date: 8 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A determination of the ruby high-pressure scale is presented using all available appropriate measurements including our own. Calibration data extend to 150 GPa. A careful consideration of shock-wave-reduced isotherms is given, including corrections for material strength. The data are fitted to the calibration equation P = (A/B)[(λ/λ0)B−1] (GPa), with A = 1876±6.7, B = 10.71±0.14, and λ is the peak wavelength of the ruby R1 line.
Show PACS
06.20.F- Units and standards
62.50.-p High-pressure effects in solids and liquids

Water mist flow in a vertical bore of a superconducting magnet

ShuShen Lu, Xian Wang, Hiroyuki Hirano, Toshio Tagawa, and Hiroyuki Ozoe

J. Appl. Phys. 98, 114906 (2005); http://dx.doi.org/10.1063/1.2137459 (9 pages) | Cited 1 time

Online Publication Date: 12 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of magnetic field on water mist (diamagnetic) was investigated by both experimental and numerical methods. Water mist was produced by an ultrasonic atomizer and fed from the top of a cylinder that was located in a vertical bore of a superconducting magnet of 10 T or less. Water mist descends due to gravity at 0 T, but at 10 T it mostly levitates above the magnetic coil. In the numerical computation, water mist was simulated by 1000 water droplets 0.1−5 μm in diameter d. Due to the small sizes of the water droplets, Brownian motion was considered and the Langevin equation was solved. At d<1 μm, the particles are driven by the Brownian motion extensively and the magnetic and gravitational forces have almost no effect on them. At d ≥ 1 μm, the trajectories of particles are greatly deformed by the magnetic field when they go through the magnetic coil. At γf = 1000 (10.8 T for 9 cm cylinder diameter), the bulk of the water mist took an hourglass shape above the coil just as observed experimentally. At γf = 2000 (15.2 T), the water droplets were computed to be levitated against the gravitational acceleration.
Show PACS
05.40.Jc Brownian motion

Growth and characterization of 4H-SiC epilayers on substrates with different off-cut angles

W. Chen and M. A. Capano

J. Appl. Phys. 98, 114907 (2005); http://dx.doi.org/10.1063/1.2137442 (6 pages) | Cited 16 times

Online Publication Date: 12 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this paper, epitaxial growth on 4H-SiC (0001) substrates with 4° and 8° off-cut angles is investigated. Both growth rate and nitrogen doping show a dependence on the C/Si ratio and off-cut angle. Good surface morphologies are obtained on the 8° off-angle substrates over a wide range of C/Si ratios, while macrostep bunching is observed on the 4° off-angle substrates depending on C/Si ratios. Step bunching behaviors on both substrate orientations are investigated by Nomarski microscopy and atomic force microscopy, and possible step bunching mechanisms are proposed to explain the results. Basal plane dislocation (BPD) densities are examined by means of molten KOH etching. Low off-cut angle is found to enhance the conversion of BPDs into threading edge dislocations. A BPD density of 2.6 cm−2 is achieved on the 4° off-angle substrate under optimized growth conditions. The effects of changing the C/Si ratio on BPD densities are also investigated.
Show PACS
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.up Other materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.47.Fg Semiconductor surfaces
68.37.Ps Atomic force microscopy (AFM)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.65.Cf Surface cleaning, etching, patterning

Thermal oxidation of tantalum films at various oxidation states from 300 to 700 °C

Ramesh Chandrasekharan, Inkyu Park, R. I. Masel, and Mark A. Shannon

J. Appl. Phys. 98, 114908 (2005); http://dx.doi.org/10.1063/1.2139834 (10 pages) | Cited 6 times

Online Publication Date: 12 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This paper presents the combined use of mathematical modeling and Auger depth profiling to study and quantify the oxidation of Ta films over a wide range of temperatures. The thermal oxidation of tantalum films ( ∼ 700 nm) is studied using direct measurements of species concentration by means of Auger depth profiling. The oxidation temperature range of this study extends from 300 to 700 °C and the oxidation period varies from 5 s to 12.5 h. The Auger depth profiles revealed that the metallic film oxidizes to first form low valence oxides of Ta that progressively convert to tantalum pentoxide with increasing temperature and time. A first-order reaction diffusion model is used to quantify the diffusion of oxygen through a film that is evolving in composition. The Auger depth profiling and reaction-diffusion model are used to estimate the actual diffusivity values for oxygen in the evolving Ta/Ta-oxide thin-film matrix, rather than more conventional techniques that estimate either the initial diffusion of oxygen through a semi-infinite metal or give a depth- and time-integrated value for the diffusivity. A comparison between the actual diffusivity values estimated in this work and the depth- and time-integrated version using the same model revealed that the integrated values are higher than the actual diffusion values by greater than 300% for the temperature range tested. Moreover, these depth- and time-integrated values for diffusivity values match over the applicable temperature ranges the diffusivity values given in the literature, which are essentially integrated average values for Ta/Ta oxide matrix. Furthermore, using the Auger depth profiles, the oxide growth rates are quantified as a function of temperature and compared with available literature. The growth rate of the oxide that is observed to be logarithmic at 300 °C is seen to have a parabolic growth at 500 °C and then a multistep growth behavior (a combination of parabolic and linear growth) at 700 °C. These growth rates and the transition from one growth type to another strongly correlate to the change in surface and film morphology and also the transition from amorphous to crystalline Ta2O5.
Show PACS
81.65.Mq Oxidation
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
79.20.Fv Electron impact: Auger emission
66.30.-h Diffusion in solids
68.47.De Metallic surfaces

Growth and characterization of dual-beam pulsed-laser-deposited Zn1−xCoxO thin films

Y. Z. Peng, T. Liew, T. C. Chong, W. D. Song, H. L. Li, and W. Liu

J. Appl. Phys. 98, 114909 (2005); http://dx.doi.org/10.1063/1.2060938 (7 pages) | Cited 11 times

Online Publication Date: 14 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Dual beam pulsed laser deposition was used to synthesize Zn1−xCoxO thin films with a large range of Co concentrations. In this paper, the influence of growth temperature on the crystal structures, magnetic properties, and semiconductor properties of these films was studied. It was found that the growth temperature has a significant effect on dopant concentration, as well as the structure and properties of the films. The optimum growth temperature is around 650 °C. The thin films were of single crystal especially at low Co concentrations. Epitaxial growth of the thin films was observed. No precipitates were observed at low Co concentrations. Magnetic hysteresis loops were observed at room temperature, indicating that magnetism can be realized with Co doped into ZnO. However, the improvement was limited. The Hall resistivity tended to increase, while carrier density tended to decrease with Co concentration until a certain Co concentration (10%) is achieved. When the growth temperature was greater than 650 °C, the Hall resistivity decreased, while carrier density increased. The Hall mobility increased with growth temperature. The possible reasons of the observed magnetism and semiconductor properties were also discussed.
Show PACS
81.05.Hd Other semiconductors
75.50.Pp Magnetic semiconductors
68.55.A- Nucleation and growth
81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.61.Le Other inorganic semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
61.72.uj III-V and II-VI semiconductors
61.66.Fn Inorganic compounds

Generating random and nonoverlapping dot patterns for liquid-crystal display backlight light guides using molecular-dynamics method

Jee-Gong Chang, Ming-Horng Su, Cheng-Tai Lee, and Chi-Chuan Hwang

J. Appl. Phys. 98, 114910 (2005); http://dx.doi.org/10.1063/1.2138802 (8 pages) | Cited 11 times

Online Publication Date: 14 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This paper employs the molecular-dynamics method to generate random-dot patterns for light guides designed for backlight systems. The proposed approach combines various numerical techniques and is designed to optimize the dot-density distribution in order to satisfy the uniform luminance requirements demanded by liquid-crystal displays. In the proposed algorithm, the total domain is divided into a prescribed number of cells whose dot densities can be individually adjusted in order to fine tune the luminance conditions in accordance with the light source position and type. In addition, a variable truncation distance is implemented in each cell according to the dot density of that cell. This variable r-cut technique localizes the repulsive force effects acting within each cell in order that a high-dot-density gradient can be achieved in the overall dot distribution. Finally, an average force control technique is developed to ensure the uniformity of the dot distribution as it passes across the cell boundaries. Several illustrative examples are provided to demonstrate the robustness of the proposed molecular-dynamics dot-generation algorithm.
Show PACS
42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems

Transmission electron microscopy observations of Cu-induced directional crystallization of amorphous silicon

Sung Bo Lee, Duck-Kyun Choi, and Dong Nyung Lee

J. Appl. Phys. 98, 114911 (2005); http://dx.doi.org/10.1063/1.2139835 (7 pages) | Cited 7 times

Online Publication Date: 14 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
By annealing at 500 °C for 1 h with an electric field of 180 V/cm, a Cu-deposited a-Si/glass sample undergoes a partial crystallization of amorphous Si, whose microstructure is characterized by conventional and high-resolution transmission electron microscopy. The Si crystallites grow in the ⟨111⟩ and ⟨211⟩ directions with their {011} planes parallel to the amorphous Si film surface, assuming a needlelike shape. Copper silicides are not observed at the leading edges of the crystalline Si needles. The growth directions of ⟨111⟩ and the {011} surface plane orientations are accepted to arise from elastic anisotropy of c-Si and can be explained by considering the strain energy under the uniaxial stress state and the plane stress, equibiaxial strain state. Crystallization behavior of a-Si in the Ni/a-Si layer is also briefly discussed.
Show PACS
61.43.Dq Amorphous semiconductors, metals, and alloys
62.20.D- Elasticity
64.70.D- Solid-liquid transitions
68.37.Lp Transmission electron microscopy (TEM)

Crystalline silicon surface passivation with amorphous SiCx:H films deposited by plasma-enhanced chemical-vapor deposition

I. Martín, M. Vetter, M. Garín, A. Orpella, C. Voz, J. Puigdollers, and R. Alcubilla

J. Appl. Phys. 98, 114912 (2005); http://dx.doi.org/10.1063/1.2140867 (10 pages) | Cited 7 times

Online Publication Date: 15 December 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Surface-passivating properties of hydrogenated amorphous silicon carbide films (a-SiCx:H) deposited by plasma-enhanced chemical-vapor deposition on both p- and n-type crystalline silicon (c-Si) have been extensively studied by our research group in previous publications. We characterized surface recombination by measuring the dependence of the effective lifetime (τeff) on excess carrier density (Δn) through quasi-steady-state photoconductance technique. Additionally, we fitted the measured τeff(Δn) curves applying an insulator/semiconductor model which allows us to determine the surface recombination parameters. In this paper, this model is analyzed in detail focusing on the accuracy in the determination of the fitting parameters and revealing uncertainties not detected up to now. Taking advantage of this analysis, the dependence of surface passivation on film deposition conditions is revised including intrinsic a-SiCx:H films on both p- and n-type c-Si and phosphorus-doped a-SiCx:H films on p-type c-Si. As a consequence, a broad view of this passivation scheme is obtained.
Show PACS
81.65.Rv Passivation
68.47.Fg Semiconductor surfaces
52.77.Dq Plasma-based ion implantation and deposition
81.05.Cy Elemental semiconductors
72.80.Cw Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.25.+i Surface conductivity and carrier phenomena
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Pz Photoconduction and photovoltaic effects

Frequency response of cantilever beams immersed in viscous fluids near a solid surface with applications to the atomic force microscope

Christopher P. Green and John E. Sader

J. Appl. Phys. 98, 114913 (2005); http://dx.doi.org/10.1063/1.2136418 (12 pages) | Cited 32 times

Online Publication Date: 15 December 2005

Full Text: Read Online (HTML) | Download PDF


See Also: Erratum

Show Abstract
Theoretical models for the frequency response of a cantilever beam immersed in a viscous fluid commonly assume that the fluid is unbounded. Experimental measurements show, however, that proximity to a surface can significantly affect the frequency response of a cantilever beam. In this article, we rigorously calculate the effect of a nearby surface on the frequency response of a cantilever beam immersed in a viscous fluid, and present a general theoretical model. Due to its practical relevance to applications of the atomic force microscope and microelectromechanical systems, detailed results are presented for cantilever beams with rectangular geometries executing flexural and torsional oscillations. It is found that dissipative loading in the fluid is primarily responsible for the observed variation in the frequency response, whereas inertial loading exerts a relatively weak influence.
Show PACS
46.70.De Beams, plates, and shells
07.10.Cm Micromechanical devices and systems
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close