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

15 Feb 2005

Volume 97, Issue 4, Articles (04xxxx)

Page 1 of 2 Pages Return to All Sections Next Page
back to top
RSS Feeds

Interaction of wide-band-gap single crystals with 248-nm excimer laser irradiation. X. Laser-induced near-surface absorption in single-crystal NaCl

K. H. Nwe, S. C. Langford, J. T. Dickinson, and W. P. Hess

J. Appl. Phys. 97, 043501 (2005); http://dx.doi.org/10.1063/1.1847696 (5 pages) | Cited 5 times

Online Publication Date: 20 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ultraviolet laser-induced desorption of neutral atoms and molecules from nominally transparent, ionic materials can yield particle velocities consistent with surface temperatures of a few thousand kelvin even in the absence of visible surface damage. The origin of the laser absorption required for this surface heating has been often overlooked. In this work, we report simultaneous neutral emission and laser transmission measurements on single-crystal NaCl exposed to 248-nm excimer laser radiation. As much as 20% of the incident radiation at 248 nm must be absorbed in the near-surface region to account for the observed particle velocities. We show that the laser absorption grows from low values over several pulses and saturates at values sufficient to account for the surface temperatures required to explain the observed particle velocity distributions. The growth of absorption in these early pulses is accompanied by a corresponding increase in the emission intensities. The diffuse reflectance spectra acquired after exposure suggest that near-surface V-type centers are responsible for most of the absorption at 248 nm in single-crystal NaCl.
Show PACS
79.20.Ds Laser-beam impact phenomena
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.43.Mn Adsorption kinetics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Interaction of wide-band-gap single crystals with 248-nm excimer laser radiation. XI. The effect of water vapor and temperature on laser desorption of neutral atoms from sodium chloride

K. H. Nwe, S. C. Langford, J. T. Dickinson, and W. P. Hess

J. Appl. Phys. 97, 043502 (2005); http://dx.doi.org/10.1063/1.1847697 (10 pages) | Cited 4 times

Online Publication Date: 20 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We show that low partial pressures of water vapor (10−5 Pa) dramatically increase the intensity of neutral Na and Cl emissions from cleaved, single-crystal NaCl during pulsed laser irradiation at 248 nm (KrF excimer). The time-of-flight distributions of these emissions are consistent with thermal desorption from laser-heated surfaces. Significantly, introducing water vapor lowers the particle velocities and thus the effective surface temperature during emission. Transmission measurements confirm that laser absorption is reduced in the presence of water vapor. The Arrhenius analysis of the emission intensities and effective temperatures show reduced activation energies in the presence of water vapor, which more than compensate for the vapor-induced reduction in laser absorption and surface temperature. Atomic force and scanning electron microscopy of the irradiated surfaces show evidence for accelerated monolayer-scale erosion in the presence of water vapor. A mechanism for the effect of water on these emission and erosion processes is proposed and discussed.
Show PACS
79.20.Ds Laser-beam impact phenomena
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.43.Mn Adsorption kinetics
79.70.+q Field emission, ionization, evaporation, and desorption
68.37.Ps Atomic force microscopy (AFM)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Impurity doping effect on thermal stability of InGaN/GaN multiple quantum-well structures

Kazuhide Kusakabe, Tomoaki Hara, and Kazuhiro Ohkawa

J. Appl. Phys. 97, 043503 (2005); http://dx.doi.org/10.1063/1.1846944 (3 pages) | Cited 3 times

Online Publication Date: 20 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Thermal stability of InGaN/GaN multiple quantum-well (MQW) structures grown by metalorganic vapor phase epitaxy on (0001) sapphire substrates was investigated. Samples were annealed under atmospheric nitrogen ambient at 1000 °C after growth. The thermal stability of MQW structures was estimated by high-resolution x-ray diffraction. It was found that thermal annealing degraded MQW periodicity in an undoped sample. This was due to the thermal diffusion of indium atoms via Ga vacancies in the GaN barrier region. It was also found that both Si doping and Mg doping improved the thermal stability of MQW structures. This mechanism was considered that Si and Mg, which were incorporated into column-III sites, prevented formation of the Ga vacancies. Thus, the thermal diffusion of indium atoms was suppressed. Room temperature photoluminescence (PL) from the Si-doped MQWs retained intense emission after annealing, while the undoped and Mg-doped MQWs showed degradation of PL intensities after annealing. It was, therefore, found that Si was a desirable dopant to promote the thermal stability of InGaN/GaN MQWs.
Show PACS
81.07.St Quantum wells
81.05.Ea III-V semiconductors
61.72.uj III-V and II-VI semiconductors
68.65.Fg Quantum wells
78.67.De Quantum wells
66.30.J- Diffusion of impurities
61.72.Cc Kinetics of defect formation and annealing
78.55.Cr III-V semiconductors
61.72.J- Point defects and defect clusters

Photoluminescence of mechanically polished ZnO

D. W. Hamby, D. A. Lucca, and M. J. Klopfstein

J. Appl. Phys. 97, 043504 (2005); http://dx.doi.org/10.1063/1.1840102 (8 pages) | Cited 14 times

Online Publication Date: 20 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effects of mechanical polishing on the photoluminescence (PL) from each polar face of wurtzite-structure ZnO are presented. Differences observed for the 4.2 K PL of a mechanically polished surface when compared to that of a chemomechanically polished surface include broadened bound-exciton peaks, hot-exciton luminescence, and a donor-acceptor pair peak at 3.2108 eV. Analysis of this donor-acceptor pair peak results in estimated donor and acceptor ionization energies of 52±10 and 230±10 meV, respectively, with a mean separation distance between pairs of approximately 3–4 nm. The donors and acceptors are attributed to point defects introduced by dislocation motion during the polishing process and identified as octahedral Zn interstitials and Zn vacancies, respectively.
Show PACS
81.05.Dz II-VI semiconductors
78.55.Et II-VI semiconductors
81.65.Ps Polishing, grinding, surface finishing
61.72.J- Point defects and defect clusters
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
71.55.Gs II-VI semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect
71.35.Ee Electron-hole drops and electron-hole plasma

Optical properties of Er3+ and Tm3+ ions in a tellurite glass

Hiroki Yamauchi, Ganapathy Senthil Murugan, and Yasutake Ohishi

J. Appl. Phys. 97, 043505 (2005); http://dx.doi.org/10.1063/1.1830088 (8 pages) | Cited 22 times

Online Publication Date: 20 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Optical spectroscopic properties of Er3+ and Tm3+ ions in a tellurite glass, TeO2-BaO-SrO-Nb2O5 (TBSN), were investigated for C- and S-band optical amplifications. On the basis of consideration for cross relaxation among Tm3+ ions and multiphonon relaxation, it was shown that the presence of Nb2O5, which was a source of the highest energy phonon, contributed to the relaxation processes in TBSN glasses.
Show PACS
78.40.Pg Disordered solids
78.35.+c Brillouin and Rayleigh scattering; other light scattering
63.50.-x Vibrational states in disordered systems
61.43.Fs Glasses
71.23.Cq Amorphous semiconductors, metallic glasses, glasses

Interface structures and periodic film distortions induced by substrate-surface steps in Gd-doped ceria thin-film growth

D. X. Huang, C. L. Chen, and A. J. Jacobson

J. Appl. Phys. 97, 043506 (2005); http://dx.doi.org/10.1063/1.1845576 (5 pages) | Cited 4 times

Online Publication Date: 21 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Gadolinium-doped ceria (Ce0.8Gd0.2O2−δ) thin films were grown on single-crystal (001) LaAlO3 (LAO) substrates by a pulsed laser ablation. The transmission electron microscope observation reveals a unique type of periodic film distortion along the film∕substrate interface. Each distorted film area is associated with a few substrate-surface steps and the spacing between these distorted areas is about 50 μm. The distortion starts at the substrate-surface steps and extends into the film along one of the {111} planes at the step-forward direction. The {111} planar defects induced by the nearby steps can interact with each other to form a planar defect network. The structure of the (001) LAO surface, the structure of the film∕substrate interface, and the mechanism of the formation of these {111} planar defects have been analyzed using a high-resolution electron microscopy. Structural models for these planar defects and their interaction are suggested.
Show PACS
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
61.72.Mm Grain and twin boundaries
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.35.Ct Interface structure and roughness
68.37.Lp Transmission electron microscopy (TEM)

Optical absorption and emission in the defect-chalcopyrite semiconductor CdGa2Te4

Shunji Ozaki, Kei-Ichi Muto, Hisatoshi Nagata, and Sadao Adachi

J. Appl. Phys. 97, 043507 (2005); http://dx.doi.org/10.1063/1.1845582 (7 pages) | Cited 5 times

Online Publication Date: 21 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Optical-absorption and photoluminescence (PL) spectra have been measured on the defect-chalcopyrite-type semiconductor CdGa2Te4 in the 0.9–1.5‐eV photon-energy range at temperatures between 11 and 300 K. The temperature dependence of the direct-gap energy of CdGa2Te4 has been determined from the optical-absorption spectra and fit using the Varshni equation and an analytical four-parameter expression developed for the explanation of the band-gap shrinkage effect in semiconductors. The PL spectra show an asymmetric emission band peaking at ∼ 1.326 eV and a symmetric emission band at ∼ 1.175 eV at T = 11 K, which are attributed to donor-acceptor-pair recombination between exponentially tailed or Gaussian-like donor states and acceptor levels, respectively. A multiple-exponential fit analysis of the PL emission suggests acceptor levels of 50 and 86 meV and a deep donor level of 190 meV, together with an unidentified shallow level of 9 meV. An energy-band scheme has been proposed for the explanation of PL emission observed in CdGa2Te4.
Show PACS
78.55.Hx Other solid inorganic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.55.-i Impurity and defect levels
71.20.Nr Semiconductor compounds
72.80.Jc Other crystalline inorganic semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
63.20.K- Phonon interactions

Dopant penetration studies through Hf silicate

M. A. Quevedo-Lopez, M. R. Visokay, J. J. Chambers, M. J. Bevan, A. LiFatou, L. Colombo, M. J. Kim, B. E. Gnade, and R. M. Wallace

J. Appl. Phys. 97, 043508 (2005); http://dx.doi.org/10.1063/1.1846138 (15 pages) | Cited 10 times

Online Publication Date: 21 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a study of the penetration of B, P, and As through Hf silicate (HfSixOy) and the effect of N incorporation in Hf silicate (HfSixOyNz) on dopant penetration from doped polycrystalline silicon capping layers. The extent of penetration through Hf silicate was found to be dependent upon the thermal annealing budget for each dopant investigated as follows: B(T ≥ 950 °C/60 s), P(T ≥ 1000 °C/20 s), and As (T ≥ 1050 °C/60 s). We propose that the enhanced diffusion observed for these dopants in HfSixOy, compared with that of SiO2 films, is related to grain boundary formation resulting from HfSixOy film crystallization. We also find that, as in the case of SiO2, N incorporation inhibits dopant (B, P, and As) diffusion through the Hf silicate and thus penetration into the underlying Si substrate. Only B penetration is clearly observed through HfSiON films for anneals at 1050 °C for durations of 10 s or longer. The calculated B diffusivity through the HfSixOyNz layer is D0 = 5.2×10−15 cm2/s.
Show PACS
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
66.30.J- Diffusion of impurities
66.30.Dn Theory of diffusion and ionic conduction in solids
61.72.up Other materials
61.72.Cc Kinetics of defect formation and annealing
61.72.S- Impurities in crystals
61.72.Mm Grain and twin boundaries
81.65.Cf Surface cleaning, etching, patterning
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films

Correlation of structural, chemical, and magnetic properties in annealed Ti/Ni multilayers

Pramod Bhatt, Anupam Sharma, and S. M. Chaudhari

J. Appl. Phys. 97, 043509 (2005); http://dx.doi.org/10.1063/1.1835561 (8 pages) | Cited 4 times

Online Publication Date: 21 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ti/Ni multilayer samples have been synthesized on float glass substrates using an electron-beam evaporation technique under ultrahigh vacuum conditions at room temperature. Grazing incidence x-ray diffraction (GIXRD) and grazing incidence x-ray reflectivity (GIXRR) techniques were used, respectively, to study structural modifications and to determine corresponding changes in microstructural parameters, such as individual layer thickness, interface roughness, and electron density due to annealing treatment. In addition to this, the chemical nature of the surface and interfaces of these samples were also studied using a depth profile x-ray photoelectron spectroscopy (XPS) technique. The GIXRD measurement show clear amorphization of the as-deposited multilayer sample annealed in the temperature range of 300–400 °C. The corresponding GIXRR measurement indicates the formation of a sufficiently thick layer of Ti–Ni at interfaces converting the Ti/Ni bilayer into a Ti/Ti–Ni/Ni trilayer multilayer structure. The precipitation of the Ti–Ni alloy phase at the interface in the case of samples annealed at 400 °C has been confirmed by XPS measurements. The magnetization behavior investigated using the magneto-optical Kerr effect technique clearly shows well the saturation magnetization behavior for all samples annealed up to 300 °C, while the sample annealed at 400 °C does not show saturation magnetization. The corresponding coercivity value (Hc) is also found to be changed drastically from 15.5 to 0.6 Oe. This observed magnetization behavior is discussed and correlated with structural and chemical changes in the multilayer structure.
Show PACS
81.05.Bx Metals, semimetals, and alloys
68.65.Ac Multilayers
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Ct Interface structure and roughness
81.40.Gh Other heat and thermomechanical treatments
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
61.43.Dq Amorphous semiconductors, metals, and alloys
68.37.Xy Scanning Auger microscopy, photoelectron microscopy
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.60.Jv Interfaces; heterostructures; nanostructures

Force-displacement relationships for spherical inclusions in finite elastic media

David C. Lin, Noshir A. Langrana, and Bernard Yurke

J. Appl. Phys. 97, 043510 (2005); http://dx.doi.org/10.1063/1.1847698 (4 pages) | Cited 5 times

Online Publication Date: 21 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Here we present derivations of the force-displacement relationship for a rigid spherical inclusion embedded in homogeneous, isotropic, linear solids. Formulas are given for both the case of perfect interfacial bonding (no slip) and the case of a sliding contact (slip) between the medium and the inclusion. The formulas are applicable to both compressible and incompressible solids and are applicable for elastic media of finite extent. The results allow the determination of the elastic modulus of the medium from force-displacement measurements on the inclusion provided Poisson’s ratio is known. We find that, when the size of the medium is much larger than that of the inclusion, the inclusion displacement in response to an applied force is 50% larger when slip is present.
Show PACS
46.25.Cc Theoretical studies
46.80.+j Measurement methods and techniques in continuum mechanics of solids
46.35.+z Viscoelasticity, plasticity, viscoplasticity

Stark effect in the optical absorption in quantum wires

Johnson Lee and Harold N. Spector

J. Appl. Phys. 97, 043511 (2005); http://dx.doi.org/10.1063/1.1849430 (6 pages) | Cited 9 times

Online Publication Date: 21 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have calculated the effect of a transverse electric field on the ground and the first few excited states of the electrons confined in a quantum wire and used these results to examine the effect of the electric field on the intersubband optical absorption in such quantum wires. The electric field removes the degeneracies between several of the excited states in the wire, which leads to peaks in the intersubband optical absorption of the wire. The application of the electric field leads to a Stark shift of the electron energies, which is quadratic in the field at low fields but becomes almost linear in the field at high fields. The electric field shifts the peaks in a manner which depends upon the polarization of the optical field with respect to the applied electric field. We have also investigated the range of wire radii and electric fields at which the infinite well model is valid in a material where the height of the confining potential barrier is finite. We have found that for small wire radii and strong electric fields, the infinite well model breaks down.
Show PACS
73.21.Hb Quantum wires
78.67.Lt Quantum wires
78.20.Jq Electro-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Optimization techniques for the estimation of the thickness and the optical parameters of thin films using reflectance data

S. D. Ventura, E. G. Birgin, J. M. Martínez, and I. Chambouleyron

J. Appl. Phys. 97, 043512 (2005); http://dx.doi.org/10.1063/1.1849431 (12 pages) | Cited 10 times

Online Publication Date: 21 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The present work considers the problem of estimating the thickness and the optical constants (extinction coefficient and refractive index) of thin films from the spectrum of normal reflectance R. This is an ill-conditioned highly underdetermined inverse problem. The estimation is done in the spectral range where the film is not opaque. The idea behind the choice of this particular spectral range is to compare the film characteristics retrieved from transmittance T and from reflectance data. In the first part of the paper a compact formula for R is deduced. The approach to deconvolute the R data is to use well-known information on the dependence of the optical constants on photon energy of semiconductors and dielectrics and to formulate the estimation as a nonlinear optimization problem. Previous publications of the group on the subject provide the guidelines for designing the new procedures. The consistency of the approach is tested with computer-generated thin films and also with measured R and T spectral data of an a-Si:H film deposited onto glass. The algorithms can handle satisfactorily the problem of a poor photometric accuracy in reflectance data, as well as a partial linearity of the detector response. The results on gedanken films and on a-Si:H indicate a very good agreement between expected and retrieved values.
Show PACS
78.66.Db Elemental semiconductors and insulators
78.66.Jg Amorphous semiconductors; glasses
68.55.-a Thin film structure and morphology
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Bh Theory, models, and numerical simulation
78.30.Am Elemental semiconductors and insulators
78.40.Fy Semiconductors

Conditions for self-assembly of quantum fortresses and analysis of their possible use as quantum cellular automata

T. E. Vandervelde, R. M. Kalas, P. Kumar, T. Kobayashi, T. L. Pernell, and J. C. Bean

J. Appl. Phys. 97, 043513 (2005); http://dx.doi.org/10.1063/1.1844620 (9 pages) | Cited 1 time

Online Publication Date: 24 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this study, we detail the conditions that result in the generation of self-assembled quantum fortresses (QFs), in SiGe/Si. A QF consists of four quantum dots (QDs) clustered around a central square pit, one QD per side. This structure strongly resembles the proposed quantum cellular automata (QCA) unit cell—the basis for a computer architecture. We map the growth conditions (epilayer thickness and Ge concentration) under which self-assembly of strain-stabilized QFs and their precursors occur. Additionally, we characterize how QFs change in height, width, and internal size scales within this parameter space. From this information, we develop a phenomenological model for why QFs form based upon changes in lattice spacing. We then calculate how QFs of the observed shapes and sizes would function as QCAs based on a Hubbard-type Hamiltonian model. This analysis reveals that self-assembled QFs grown at 550 °C, a rate of 1 Å/s, a SiGe alloy composition of 37–40%, and a thickness of 15–35 nm could be used as QCAs.
Show PACS
81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Vacancy-type defects in Si-doped InN grown by plasma-assisted molecular-beam epitaxy probed using monoenergetic positron beams

A. Uedono, S. F. Chichibu, M. Higashiwaki, T. Matsui, T. Ohdaira, and R. Suzuki

J. Appl. Phys. 97, 043514 (2005); http://dx.doi.org/10.1063/1.1845575 (5 pages) | Cited 12 times

Online Publication Date: 24 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
High-quality InN layers grown on sapphire substrates by plasma-assisted molecular-beam epitaxy were characterized using monoenergetic positron beams. The carrier concentrations of the films were controlled by Si doping (2.1×1018 to 1.4×1019 cm−3), and the highest obtained Hall mobility was 1300 cm2 V−1 s−1. The Doppler broadening spectra of the annihilation radiation and the lifetime spectra of positrons were measured as a function of the incident positron energy for undoped and Si-doped InN films. The line-shape parameter S increased with increasing carrier concentration, suggesting the introduction of vacancy-type defects by a Fermi-level effect. The major defect species were varied with carrier concentration, and its species were identified as In vacancies (VIn) or their related defects.
Show PACS
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.J- Point defects and defect clusters
61.82.Fk Semiconductors
61.80.Fe Electron and positron radiation effects
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
78.70.Bj Positron annihilation
73.20.At Surface states, band structure, electron density of states

Fingering instability of a retracting solid film edge

Wanxi Kan and Harris Wong

J. Appl. Phys. 97, 043515 (2005); http://dx.doi.org/10.1063/1.1845579 (10 pages) | Cited 20 times

Online Publication Date: 24 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A thin gold film under annealing on a silica substrate can develop “fingers” at the perimeter of the film. The perimeter retracts to leave behind longer fingers, which eventually pinch off to reduce the surface energy of the system. New fingers then form at the film edge and the process continues until the entire film disintegrates. To maintain the structure integrity of annealed thin films, this fingering instability must be understood. The retraction of a straight film edge via capillarity-driven surface diffusion has been analyzed in two dimensions by Wong et al.[Acta Mater. 48, 1719 (2000) ]. They found that a retracting film is thickened at the edge followed by a valley before the film thickness becomes uniform. We study the three-dimensional linear stability of this two-dimensional film profile and find one unstable mode of perturbation. The growth rate of the perturbation is determined as a function of the wavelength of the perturbation and the speed of the receding edge. The results show that a straight film edge becomes wavy when perturbed. The wavelength λm of the fastest growing perturbation agrees with the distance between adjacent fingers observed in a gold-film experiment. Fingers can also form during annealing at the retracting edges of cracks in sapphire, and our predicted λm compares well with the measured finger spacing.
Show PACS
68.35.Fx Diffusion; interface formation
68.35.Md Surface thermodynamics, surface energies
68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
81.40.Gh Other heat and thermomechanical treatments
68.35.Gy Mechanical properties; surface strains
62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Composition of Ge(Si) islands in the growth of Ge on Si(111) by x-ray spectromicroscopy

Fulvio Ratto, Federico Rosei, Andrea Locatelli, Salia Cherifi, Stefano Fontana, Stefan Heun, Pierre-David Szkutnik, Anna Sgarlata, Maurizio De Crescenzi, and Nunzio Motta

J. Appl. Phys. 97, 043516 (2005); http://dx.doi.org/10.1063/1.1832747 (8 pages) | Cited 19 times

Online Publication Date: 24 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The stoichiometry of Ge/Si islands grown on Si(111) substrates at temperatures ranging from 460 to 560 °C was investigated by x-ray photoemission electron microscopy (XPEEM). By developing a specific analytical framework, quantitative information on the surface Ge/Si stoichiometry was extracted from laterally resolved XPEEM Si 2p and Ge 3d spectra, exploiting the chemical sensitivity of the technique. Our data show the existence of a correlation between the base area of the self-assembled islands and their average surface Si content: the larger the lateral dimensions of the 3D structures, the higher their relative Si concentration. The deposition temperature determines the characteristics of this relation, pointing to the thermal activation of kinetic diffusion processes.
Show PACS
68.55.Nq Composition and phase identification
79.60.Dp Adsorbed layers and thin films
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.60.Jv Interfaces; heterostructures; nanostructures
66.30.H- Self-diffusion and ionic conduction in nonmetals

Radiation resistance of GaAs–GaAlAs vertical cavity surface emitting lasers

J. Jabbour, M. Zazoui, G. C. Sun, J. C. Bourgoin, and O. Gilard

J. Appl. Phys. 97, 043517 (2005); http://dx.doi.org/10.1063/1.1850619 (5 pages) | Cited 1 time

Online Publication Date: 25 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The variations of the optical and electrical characteristics of a vertical cavity surface emitting laser based on GaAs quantum wells have been monitored versus irradiation with 1 MeV electrons. The results are understood by the introduction of nonradiative recombination centers in the wells whose characteristics, capture cross section for minority carriers times their introduction rate, can be determined. A similar study performed for proton irradiation shows that the results can be explained in the same way when the introduction rate of the defects is replaced by the proton energy loss into atomic collisions. These results allow us to deduce the equivalence between electron and proton irradiations: A flux of 1 proton cm−2 which loses an energy Enℓ (eV) into atomic collisions is equivalent to a fluence of about 9×10−2 Enℓ cm−2, 1 MeV electrons.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
61.82.Fk Semiconductors
61.80.Fe Electron and positron radiation effects
61.80.Jh Ion radiation effects

Intermediate crystalline states produced by isothermal annealing of sputter-deposited a‐Si films

Housei Akazawa

J. Appl. Phys. 97, 043518 (2005); http://dx.doi.org/10.1063/1.1850994 (9 pages)

Online Publication Date: 25 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The crystalline states produced by isothermally annealing sputter-deposited hydrogen-free amorphous-Si (a‐Si) films greatly differ from those of a‐Si:H films. Strained network and numerous vacancies in the a‐Si film are indicated by the 〈ε2〉 spectrum. Annealing the sample at temperatures between 300 and 550 °C relaxes the strained network due to local exchanges of Si–Si bond while maintaining the amorphous state. Self-assembly of hemispherical grains of microcrystalline Si on the film surface occurs during the onset of crystallization (600 °C). At a slightly elevated temperature of 690 °C, the cohesion of Si atoms in the film creates nanocrystalline Si (2‐nm diameter), which directly corresponds to the emergence of the absorption peak feature below 3 eV in the 〈ε2〉 spectrum. Dense voids at the interfacial region severely limit the range of solid phase epitaxy, thus facilitating preferential nucleation in the film.
Show PACS
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.43.Dq Amorphous semiconductors, metals, and alloys
61.72.Cc Kinetics of defect formation and annealing
64.70.K- Solid-solid transitions
78.40.Fy Semiconductors
78.66.Db Elemental semiconductors and insulators

Critical thickness enhancement of epitaxial SiGe films grown on small structures

Yue Liang, William D. Nix, Peter B. Griffin, and James D. Plummer

J. Appl. Phys. 97, 043519 (2005); http://dx.doi.org/10.1063/1.1854204 (7 pages) | Cited 13 times

Online Publication Date: 25 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This paper explores stress management in SiGe with two kinds of structures, namely, epitaxial SiGe films on small pillars and fins. In addition to the compliant substrate effect in the film/fin structures, the geometric effect in the film/pillar structures plays another important role in critical thickness enhancement. The stress-strain states of these two systems are calculated and the equilibrium critical thicknesses are predicted, using the work method, for different fin thicknesses, pillar radii, and Ge concentrations. Compared to conventional films grown on planar bulk substrates, the critical thicknesses for fin and pillar structures are increased significantly. SiGe films with various thicknesses and compositions were epitaxially grown around vertical fins and horizontal membranes with thicknesses as thin as 12 nm to demonstrate the concepts. Cross-sectional transmission electron microscopy analysis showed that dislocation densities are much smaller than for films grown on bulk Si substrates. The dislocation density versus fin thickness also illustrated the expected trend.
Show PACS
81.05.Hd Other semiconductors
68.55.-a Thin film structure and morphology
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.60.Bs Mechanical and acoustical properties
68.55.Nq Composition and phase identification
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.F- Deformation and plasticity

Dislocation reduction in sulfur- and germanium-doped indium phosphide single crystals grown by the vertical gradient freeze process: A transient finite-element study

X. A. Zhu and C. T. Tsai

J. Appl. Phys. 97, 043520 (2005); http://dx.doi.org/10.1063/1.1848190 (9 pages) | Cited 1 time

Online Publication Date: 25 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
During the growth of indium phosphide (InP) crystals, dislocations are mostly generated in a plastically deformed crystal due to crystallographic glide caused by excessive thermal stresses. High dislocation density presented in the InP crystal can reduce the performance, lifetime, and reliability of the InP-based microelectronic and optoelectronic devices/circuits. The generation of dislocations in InP single crystals grown from the melt can be predicted by using a transient finite-element model. This model couples microscopic dislocation motion and multiplication to macroscopic plastic deformation during the crystal growth process. The temperature fields in the crystal are determined by solving the partial differential equations of heat transfer for the vertical gradient freeze (VGF) process. These temperature fields are then employed to the transient finite-element model to study the effects of doping impurities and growth parameters (i.e., imposed temperature gradient, crystal radius, and growth rate) on dislocation reduction in InP crystals grown by different VGF processes.
Show PACS
81.05.Ea III-V semiconductors
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
81.10.Fq Growth from melts; zone melting and refining
61.72.Bb Theories and models of crystal defects
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.72.uj III-V and II-VI semiconductors
61.72.S- Impurities in crystals
64.70.D- Solid-liquid transitions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors

Measurement of the shock-heated melt curve of lead using pyrometry and reflectometry

D. Partouche-Sebban, J. L. Pélissier, F. G. Abeyta, W. W. Anderson, M. E. Byers, D. Dennis-Koller, J. S. Esparza, R. S. Hixson, D. B. Holtkamp, B. J. Jensen, J. C. King, P. A. Rigg, P. Rodriguez, D. L. Shampine, J. B. Stone, et al.

J. Appl. Phys. 97, 043521 (2005); http://dx.doi.org/10.1063/1.1849436 (11 pages) | Cited 12 times

Online Publication Date: 25 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Data on the high-pressure melting temperatures of metals is of great interest in several fields of physics including geophysics. Measuring melt curves is difficult but can be performed in static experiments (with laser-heated diamond-anvil cells, for instance) or dynamically (i.e., using shock experiments). However, at the present time, both experimental and theoretical results for the melt curve of lead are at too much variance to be considered definitive. As a result, we decided to perform a series of shock experiments designed to provide a measurement of the melt curve of lead up to about 50 GPa in pressure. At the same time, we developed and fielded a reflectivity diagnostic, and conducted measurements on tin as well. The results show that the melt curve of lead is somewhat higher than the one previously obtained with static compression and heating techniques.
Show PACS
62.50.-p High-pressure effects in solids and liquids
64.70.D- Solid-liquid transitions

Infrared detection of hydrogen-generated free carriers in polycrystalline ZnO thin films

Colin A. Wolden, Teresa M. Barnes, Jason B. Baxter, and Eray S. Aydil

J. Appl. Phys. 97, 043522 (2005); http://dx.doi.org/10.1063/1.1851599 (7 pages) | Cited 22 times

Online Publication Date: 26 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The changes in the free-carrier concentration in polycrystalline ZnO films during exposure to H2 and O2 plasmas were studied using in situ attenuated total reflection Fourier transform infrared spectroscopy. The carrier concentration and mobility were extracted from the free-carrier absorption in the infrared using a model for the dielectric function. The electron density in polycrystalline zinc oxide films may be significantly increased by >1019 cm−3 by brief exposures to hydrogen plasma at room temperature and decreased by exposure to O2 plasmas. Room-temperature oxygen plasma removes a fraction of the H at donor sites but both elevated temperatures ( ∼ 225 °C) and O2 plasma were required to remove the rest. We demonstrate that combinations of O2 and H2 plasma treatments can be used to manipulate the carrier density in ZnO films. However, we also show the existence of significant drifts ( ∼ 15%) in the carrier concentrations over very long time scales (hours). Possible sites for H incorporation in polycrystalline films and reasons for the observed carrier-concentration changes are proposed.
Show PACS
78.66.Hf II-VI semiconductors
78.30.Fs III-V and II-VI semiconductors
73.61.Ga II-VI semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
52.77.-j Plasma applications
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Modeling room-temperature lasing spectra of 1.3-μm self-assembled InAs/GaAs quantum-dot lasers: Homogeneous broadening of optical gain under current injection

M. Sugawara, N. Hatori, H. Ebe, M. Ishida, Y. Arakawa, T. Akiyama, K. Otsubo, and Y. Nakata

J. Appl. Phys. 97, 043523 (2005); http://dx.doi.org/10.1063/1.1849426 (8 pages) | Cited 38 times

Online Publication Date: 26 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We studied the injection current dependence of room-temperature lasing spectra of a 1.3-μm self-assembled InAs/GaAs quantum-dot laser both experimentally and theoretically. Starting from the ground-state lasing with a few longitudinal modes, the spectra showed splitting, broadening, excited-state lasing, and quenching of the ground-state lasing as the current increased. We could explain this unique current dependence by numerical simulation based on our quantum-dot laser theory, taking into account the inhomogeneous and homogeneous broadening of the optical gain as well as the carrier relaxation processes in the spatially isolated quantum dots. Through the simulation, we found that the homogeneous broadening of the ground state is kept between 5 and 10 meV under the ground-state lasing, while it increases up to 20 meV under the excited-state lasing.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.55.Ah General laser theory
78.67.Hc Quantum dots
85.30.De Semiconductor-device characterization, design, and modeling
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

The response of soda-lime glass-hydroxyterminated polybutadiene composites to shock loading

J. C. F. Millett, N. K. Bourne, J. Akhavan, and A. M. Milne

J. Appl. Phys. 97, 043524 (2005); http://dx.doi.org/10.1063/1.1850174 (7 pages) | Cited 5 times

Online Publication Date: 28 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of particle size on the shock response of three soda-lime glass-hydroxyterminated polybutadiene composites has been investigated. While the shock velocity–particle velocity relationship has been shown to be nearly identical in all three materials, thus indicating that the hydrodynamic response is particle size independent, the shock stresses have been shown to be strongly dependent upon particle size. It has been proposed that this be due to the nature of the microstructure, with the larger particles restricting flow, and thus increasing shear strength, while the finer microstructure can flow as a whole.
Show PACS
62.50.-p High-pressure effects in solids and liquids
64.30.-t Equations of state of specific substances

Friction-induced nonequilibrium phase transformation of low-temperature ice

H. Liang, J. M. Martin, and Th. Le Mogne

J. Appl. Phys. 97, 043525 (2005); http://dx.doi.org/10.1063/1.1852722 (5 pages) | Cited 2 times

Online Publication Date: 28 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We used an ultrahigh vacuum chamber to form an ice layer, then conducted friction experiments at temperatures below 123 K, a range much lower than previous experiments conducted in atmosphere environments. We found melting and vaporization induced by friction at temperatures below 145 K. At such a low temperature, the liquid and vapor phases are not in equilibrium. Simple analysis indicated that such metastable phases are possible with sufficient mechanical energy through friction stimulation.
Show PACS
68.60.Bs Mechanical and acoustical properties
81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness
64.70.F- Liquid-vapor transitions
64.70.D- Solid-liquid transitions
Page 1 of 2 Pages Return to All Sections Next Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close