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15 Dec 2003

Volume 94, Issue 12, pp. 7397-7951

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Orange-emitting frequency-doubled GaAsSb/GaAs semiconductor disk laser

Eckart Gerster, Irene Ecker, Steffen Lorch, Christian Hahn, Susanne Menzel, and Peter Unger

J. Appl. Phys. 94, 7397 (2003); http://dx.doi.org/10.1063/1.1625784 (5 pages) | Cited 22 times

Online Publication Date: 2 December 2003

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We report on an orange-emitting intracavity frequency-doubled semiconductor disk laser based on the material system GaAsSb/GaAs. The infrared fundamental wavelength of λ=1220 nm corresponds to a second-harmonic wavelength of λ=610 nm. The second-harmonic generation is done using a lithium–triborate crystal as the nonlinear material. We have achieved an orange continuous-wave frequency-doubled laser output power of 30 mW in the fundamental transverse mode at a wavelength of λ=610 nm. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Nv Optical frequency converters
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Laser propagation and energy absorption by an argon spark

C. V. Bindhu, S. S. Harilal, M. S. Tillack, F. Najmabadi, and A. C. Gaeris

J. Appl. Phys. 94, 7402 (2003); http://dx.doi.org/10.1063/1.1625413 (6 pages) | Cited 11 times

Online Publication Date: 2 December 2003

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The laser propagation and energy absorption of an argon spark induced by a laser at different pressures is investigated. 8 ns pulses from a frequency-doubled Q-switched Nd:YAG laser are used to create the spark. The pressure of the argon is varied from 1 atm to 10 Torr. Significant energy absorption by the plasma is observed at high pressures (>100 Torr) while there is negligible absorption when the pressure is lower than 50 Torr. The plasma kernel showed distinct behavior with respect to laser energy. At a laser energy well above the breakdown threshold, the spark moved only in the backward direction and the forward component was absent indicating the strong absorption of the laser by the spark front. A spiky behavior is observed in the transmitted temporal profiles of the laser at higher energies and at high pressures and can be due to the formation of a self-regulating regime. © 2003 American Institute of Physics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.38.Dx Laser light absorption in plasmas (collisional, parametric, etc.)

Dynamics of pulse phenomena in helium dielectric-barrier atmospheric-pressure glow discharges

Jichul Shin and Laxminarayan L. Raja

J. Appl. Phys. 94, 7408 (2003); http://dx.doi.org/10.1063/1.1625414 (8 pages) | Cited 21 times

Online Publication Date: 2 December 2003

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A study of pulse phenomena in conventional parallel-plate dielectric-barrier controlled atmospheric-pressure glow (DB-APG) discharges in helium is reported. Stable DB-APG discharges are found to occur at arbitrarily low frequencies as long as the gas voltage exceeds the Paschen breakdown voltage, i.e., no lower limit of ∼1 kHz exists for DB-APG operation. The interpulse preionization phenomenon is found to be an artifact of typical ∼10 kHz operation of DB-APG discharges and does not play a role in the formation of a stable pulse. Multiple pulses result from repeated temporally separated breakdown events in the discharge. A relatively simple zero-dimensional model that treats only the Paschen breakdown mechanism in the discharge and charge trapping phenomena at the dielectric surfaces can be used to simulate all important qualitative features of DB-APG phenomena. Finally, we show that control of the pulse intensity, number of pulses in a pulse train, and the time interval between pulse trains can be achieved using “ramp-plus-plateau” voltage input wave forms rather than typical sinusoidal wave forms. © 2003 American Institute of Physics.
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52.80.Hc Glow; corona

Current conduction and plasma distribution on dielectric (velvet) explosive emission cathodes

Yuri M. Saveliev, Wilson Sibbett, and David M. Parkes

J. Appl. Phys. 94, 7416 (2003); http://dx.doi.org/10.1063/1.1625411 (6 pages) | Cited 16 times

Online Publication Date: 2 December 2003

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Distributions of emission centers (ECs) on planar explosive emission dielectric (velvet) cathodes at moderate electric fields of 30–70 kV/cm and pulse durations of ∼2 μs with the use of a fast framing camera have been investigated. The experimental results suggest a link between the EC distribution and current conduction paths through which the electron current is supplied to the cathode plasma. On bare velvet, the surrounding metal electrode was shown not to be of primary importance for the current conduction, instead, the current is supplied to explosive emission plasma mainly through the base of the velvet fabric. Development of a circle of brighter and larger ECs along the perimeter of the cathode was normally observed shortly after the beginning of the high voltage pulse. These ECs were found to be a major factor in the diode perveance growth and instability. Domination of the ECs on the cathode periphery has been suppressed by adding a pattern of well defined current conduction points, e.g., perforations of the velvet fabric, to the cathode design. © 2003 American Institute of Physics.
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52.80.-s Electric discharges

Mode transition for power dissipation induced by driving frequency in capacitively coupled plasma

S. J. You, H. C. Kim, C. W. Chung, H. Y. Chang, and J. K. Lee

J. Appl. Phys. 94, 7422 (2003); http://dx.doi.org/10.1063/1.1621085 (5 pages) | Cited 16 times

Online Publication Date: 2 December 2003

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We measured electrical characteristics of capacitively coupled plasma at low pressure (2.67 Pa) with different driving frequencies. From these measurements, we observed a significant change in discharge power characteristics during the frequency increase. While increasing the frequency, a square dependence of power characteristics (P∼I2) changes to a linear dependence (P∼I). This observed result reflects that a power dissipation mode transition from an ion-dominated dissipation mode to an electron-dominated dissipation mode takes place during the driving frequency increase. Both the results calculated from a simple sheath model and a particle-in-cell simulation are in a good agreement with the experimental data. © 2003 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.40.Kh Plasma sheaths
52.65.Rr Particle-in-cell method

Ion concentrations in plasmas produced from 193 nm excimer laser irradiation of LiNbO3 in vacuum and gas atmospheres

F. J. Gordillo-Vázquez and J. Gonzalo

J. Appl. Phys. 94, 7427 (2003); http://dx.doi.org/10.1063/1.1628383 (6 pages) | Cited 9 times

Online Publication Date: 2 December 2003

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We have calculated the concentration of ions in the plasma produced upon ablation of LiNbO3 with a low fluence ArF excimer laser in vacuum and different gas environments (Ar and O2). The model shows that Li and Nb ions (with the amount of Li ions being greater than that of Nb ions) are the most abundant in the plasma with their concentrations being always above their corresponding neutral densities. In addition, we show that the concentration of excited Nb ions is relatively important while no excited Li ions are predicted. We found that the concentration of both Li and Nb ions in O2 is slightly higher than in Ar and vacuum. Moreover, the calculated spatial evolution of the ionic species suggests that a significant fraction of the predicted ion concentration is not produced by electron–atom ionization events within the plasma; on the contrary, they might have been produced in the LiNbO3 crystal through a nonthermal mechanism and then ejected from the target after the laser pulse. © 2003 American Institute of Physics.
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52.38.Mf Laser ablation
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.-b Plasma properties
79.20.Ds Laser-beam impact phenomena
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Diffusion of 18 elements implanted into thermally grown SiO2

H. G. Francois-Saint-Cyr, F. A. Stevie, J. M. McKinley, K. Elshot, L. Chow, and K. A. Richardson

J. Appl. Phys. 94, 7433 (2003); http://dx.doi.org/10.1063/1.1624487 (7 pages) | Cited 3 times

Online Publication Date: 2 December 2003

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Diffusion data are presented for 18 elements implanted in SiO2 layers thermally grown on silicon and annealed at temperatures ranging from 300 to 1000 °C. Most species studied, (e.g., Be, B, Al, Sc, Ti, V, Zn, Ga, and Mo), showed negligible diffusion over the examined temperature range. In general, this study has shown that the diffusivity of dopants or impurities in SiO2 is significantly smaller than that in silicon. However we also observed that several elements (e.g., Rb and In) have a higher diffusivity in SiO2 than in Si. Because Ga and In are both used as sources for focused ion beam analyses, the lack of Ga diffusion and the movement of In in SiO2 is of interest. © 2003 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.up Other materials
61.72.S- Impurities in crystals
85.40.Ry Impurity doping, diffusion and ion implantation technology

Polarized Raman-scattering study of Ge and Sn-filled CoSb3

G. S. Nolas, C. A. Kendziora, and Hirotsugu Takizawa

J. Appl. Phys. 94, 7440 (2003); http://dx.doi.org/10.1063/1.1628377 (5 pages) | Cited 19 times

Online Publication Date: 2 December 2003

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Raman-scattering spectra of Ge-filled and Sn-filled CoSb3 were studied as a function of polarization. Polarized Raman-scattering spectra of CoSb3 were used to help distinguish the symmetry of each vibrational mode observed in the filled skutterudite specimens. Seven out of the eight Raman-active Sb vibrational modes of CoSb3 and the Ge-filled skutterudites were identified for each specimen. We also compare our experimental assignments with theoretical calculations for CoSb3. The Sn atoms “rattle” inside the voids of the crystal structure and interact strongly with the lattice vibrations to shift and broaden the Sb-vibrational modes as compared to the spectra of CoSb3. The smaller and lighter Ge atoms however do not have such an effect on the lattice vibrations, indicating that the interaction of Ge with the lattice is relatively weak in comparison. © 2003 American Institute of Physics.
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78.30.Hv Other nonmetallic inorganics
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Effect of process parameters on the structural characteristics of laterally grown, laser-annealed polycrystalline silicon films

A. T. Voutsas, A. Limanov, and J. S. Im

J. Appl. Phys. 94, 7445 (2003); http://dx.doi.org/10.1063/1.1627462 (8 pages) | Cited 19 times

Online Publication Date: 2 December 2003

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In this work, we have conducted a systematic study aiming at assessing the effects of process parameters on the microstructural characteristics of laterally grown polycrystalline silicon (poly-Si) films. Poly-Si films were formed by the sequential lateral solidification (SLS) method. The Si film thickness was found to affect significantly the quality of the poly-Si microstructure, manifested by a decreased crystal-growth defect density and increased subboundary spacing in thicker films. A weak (100) texture was observed in the lateral growth direction, except for very thin films (<30 nm) where (110) texture was observed. No specific texture was identified in the normal and transverse directions. Lateral crystallization proceeds by seeded, lateral epitaxial growth at an advancing pitch. We investigated the quality of lateral growth as a function of the advancing, substrate pitch. We found that an optimum pitch range exists, bound on the low end by the detailed shape of the beam-edge profile and on the high end by the quality of crystal formed under deep, interfacial undercooling. In that sense, only a fraction of the laser beamlet can be effectively used for lateral growth and the process should be tuned towards maximizing this fraction. Thin film transistor data were used to further refine the considerations driving the selection of optimum process parameters for SLS lateral crystallization providing the least sensitivity to process-induced variations. © 2003 American Institute of Physics.
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81.05.Cy Elemental semiconductors
61.72.Cc Kinetics of defect formation and annealing
81.15.Np Solid phase epitaxy; growth from solid phases
68.55.A- Nucleation and growth
61.82.Fk Semiconductors

Fluorine atom subsurface diffusion and reaction in photoresist

Frank Greer, D. Fraser, J. W. Coburn, and David B. Graves

J. Appl. Phys. 94, 7453 (2003); http://dx.doi.org/10.1063/1.1625782 (9 pages) | Cited 5 times

Online Publication Date: 2 December 2003

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Kinetic studies of fluorine and deuterium atoms interacting with an OiR 897 10i i-line photoresist (PR) are reported. All experiments were conducted at room temperature. Films of this PR were coated on quartz-crystal microbalance (QCM) substrates and exposed to alternating fluxes of these atoms in a high vacuum apparatus. Mass changes of the PR were observed in situ and in real time during the atom beam exposures using the QCM. A molecular-beam sampled differentially pumped quadrupole mass spectrometer (QMS) was used to measure the species desorbing from the PR surface during the F and D atom exposures. During the D atom exposures, hydrogen abstraction and etching of the PR was observed, but no DF formation was detected. However, during the F atom exposures, the major species observed to desorb from the surface was DF, formed from fluorine abstraction of deuterium from the photoresist. No evidence of film etching or fluorine self-abstraction was observed. The film mass increased during F atom exposure, evidently due to the replacement of D by F in the film. The rate of DF formation and mass uptake were both characterized by the same kinetics: An initially rapid step declining exponentially with time (e−t/τ), followed by a much slower step following inverse square root of time (t−1/2) kinetics. The initially rapid step was interpreted as surface abstraction of D by F to form DF, which desorbs, with subsequent F impacting the surface inserted into surface C dangling bonds. The slower step was interpreted as F atoms diffusing into the fluorinated photoresist, forming DF at the boundary of the fluorinated carbon layer. The t−1/2 kinetics of this step are interpreted to indicate that F diffusion through the fluorinated carbon layer is much slower than the rate of F abstraction of D to form DF, or the rate of F insertion into the carbon dangling bonds left behind after DF formation. A diffusion-limited growth model was formulated, and the model parameters are consistent with values reported in related systems. The implications of these results for plasma etch applications with respect to radical diffusion through surface-passivating films is discussed. © 2003 American Institute of Physics.
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85.40.Hp Lithography, masks and pattern transfer
68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation
81.65.Cf Surface cleaning, etching, patterning
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
52.77.Bn Etching and cleaning
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Bonding configuration and density of defects of SiOxHy thin films deposited by the electron cyclotron resonance plasma method

E. San Andrés, A. del Prado, I. Mártil, G. González-Díaz, D. Bravo, F. J. López, M. Fernández, W. Bohne, J. Röhrich, B. Selle, and I. Sieber

J. Appl. Phys. 94, 7462 (2003); http://dx.doi.org/10.1063/1.1626798 (8 pages) | Cited 6 times

Online Publication Date: 2 December 2003

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The composition, bonding configuration, hydrogen content, and paramagnetic defects of SiOxHy thin films were studied. Films were deposited by the electron cyclotron resonance plasma method at room temperature using SiH4 and O2 as precursor gases. The film composition was measured by heavy ion elastic recoil detection analysis and energy dispersive x-ray spectroscopy. Suboxide films with compositions ranging from SiO2 to SiH0.38 were obtained. Infrared spectroscopy showed the presence of different Si–O and Si–H vibration modes. The usual estimation of the oxygen to silicon ratio by the wave number of the Si–O–Si stretching band was not accurate for films far from stoichiometry. These off-stoichiometric films also showed a broader Si–O–Si stretching peak than the stoichiometric ones, indicating a higher bonding disorder. The position of the Si–O–Si bending and rocking modes did not depend on the film composition. On the other hand, the peak position of the Si–H modes were found strongly dependent on the Si environment. By single-wavelength ellipsometry at λ=632.8 nm the refractive index n was found to range between 1.45 (SiO2) and 2.04 (SiO0.06H0.36). Electron spin resonance measurements showed that stoichiometric films presented the well known E′ center (⋅Si≡O3) with concentrations in the 1016–1017 cm−3 range, while for Si-rich films (x≪1) the Si dangling bond center (SiDB, ⋅Si≡Si3) was the only detectable defect, with concentrations in the 1018–1019 cm−3 range. In near-stoichiometric films both E′ and SiDB centers were found. © 2003 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.Nq Composition and phase identification
61.66.Bi Elemental solids
61.66.Dk Alloys
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films
52.77.Dq Plasma-based ion implantation and deposition
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
78.30.Hv Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
76.30.Mi Color centers and other defects
82.80.-d Chemical analysis and related physical methods of analysis
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.66.Nk Insulators

Defect assessment of Mg-doped GaN by beam injection techniques

C. Díaz-Guerra, J. Piqueras, A. Castaldini, A. Cavallini, and L. Polenta

J. Appl. Phys. 94, 7470 (2003); http://dx.doi.org/10.1063/1.1628832 (6 pages) | Cited 3 times

Online Publication Date: 2 December 2003

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The electronic recombination properties of Mg-doped GaN have been investigated by steady state and time-resolved cathodoluminescence (TRCL) in the scanning electron microscope, photocurrent (PC) spectroscopy, and optical beam induced current (OBIC). CL and OBIC maps reveal an inhomogeneous recombination activity in the investigated material. Deep levels giving rise to level-to-band transitions were detected by PC spectroscopy. A large PC quenching observed upon illumination with light of (2.65–2.85) eV is tentatively attributed to metastable traps within the band gap. CL spectra reveal the existence of emission bands centered at 85 K at 3.29, 3.20, 3.15, and 3.01 eV, respectively. Both time-resolved and steady-state CL measurements carried out under different excitation conditions indicate that the 3.15 and 3.01 eV emissions are likely related to donor-acceptor pair transitions. TRCL measurements also reveal different recombination kinetics for these bands and suggest that deep donors are involved in the mechanism responsible for the 3.01 eV emission. © 2003 American Institute of Physics.
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71.55.Eq III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
73.50.Pz Photoconduction and photovoltaic effects
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics

Effect of high pressure isostatic annealing on oxygen segregation in Czochralski silicon

Simona Binetti, Alessia Le Donne, Vadim V. Emtsev, and Sergio Pizzini

J. Appl. Phys. 94, 7476 (2003); http://dx.doi.org/10.1063/1.1626801 (7 pages) | Cited 4 times

Online Publication Date: 2 December 2003

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The effect of single-step annealing at 450, 650, and 1000 °C under gigapascal hydrostatic pressures on oxygen segregation from Czochralski silicon samples was investigated. It was shown that the effect of applied pressure on the oxygen segregation processes begins to be detectable at 650 °C and significant at 1000 °C. Not only was the effect of the applied pressure clearly evidenced, but also that of the dopants. In the first case the presence of a gap level associated to self-interstitial clusters could be argued, whereas in the second case both the oxide particles segregation and the dislocation formation were demonstrated to be enhanced by the pressure and by the type of doping. Furthermore, visible and ultraviolet photoluminescence emission at cryogenic temperatures were observed from silicon dioxide particles or from oxide nuclei contained in the silicon matrix.© 2003 American Institute of Physics.
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64.75.-g Phase equilibria
61.72.Cc Kinetics of defect formation and annealing
81.10.Fq Growth from melts; zone melting and refining
78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
61.72.J- Point defects and defect clusters
61.72.uf Ge and Si
62.50.-p High-pressure effects in solids and liquids

Structural evolution in Ar+ implanted Si-rich silicon oxide

R. S. Brusa, G. P. Karwasz, G. Mariotto, A. Zecca, R. Ferragut, P. Folegati, A. Dupasquier, G. Ottaviani, and R. Tonini

J. Appl. Phys. 94, 7483 (2003); http://dx.doi.org/10.1063/1.1627956 (10 pages) | Cited 8 times

Online Publication Date: 2 December 2003

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Silicon-rich silicon oxide films were deposited by plasma-enhanced chemical vapor deposition. Energy was released into the film by ion bombardment, with the aim of promoting formation of Si nanoclusters and reordering the oxide matrix. The effect of the initial stoichiometry, as well as the evolution of the oxide films due to the ion bombardment and to subsequent thermal treatments, has been studied by depth-resolved positron annihilation Doppler spectroscopy, Raman scattering and Fourier transform infrared spectroscopy. As-deposited films were found to contain an open volume fraction in the form of subnanometric cavities that are positively correlated with oxygen deficiency. No Si aggregates were observed. The ion bombardment was found to promote the formation of amorphous Si nanoclusters, together with a reduction of the open volume in the matrix and a substantial release of hydrogen. It also leaves electrically active sites in the oxide and produces gas-filled vacancy defects in the substrate, with the concentrations depending on the implantation temperature. Thermal treatment at 500 °C removes charge defects in the oxide, but vacancy defects are not completely annealed even at 1100 °C. In one case, heating at 1100 °C produced cavities of about 0.6 nm in the oxide. Transformation of Si nanoclusters into nanocrystals is observed to occur from 800 °C. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films
61.43.Er Other amorphous solids
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials

Photoemission investigation of the electronic structure of lanthanum–calcium oxoborate

A. J. Nelson, J. J. Adams, and K. I. Schaffers

J. Appl. Phys. 94, 7493 (2003); http://dx.doi.org/10.1063/1.1627955 (3 pages) | Cited 4 times

Online Publication Date: 2 December 2003

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Lanthanum calcium oxoborate is a nonlinear optical material that belongs to the calcium-rare-earth (R) oxoborate family, with general composition of Ca4RO(BO3)3 (R3+=La,Sm,Gd,Lu,Y). X-ray photoemission was used to study the valence band electronic structure and surface chemistry of this material. High resolution photoemission measurements of the valence band electronic structure and La 3d and 4d, Ca 2p, B 1s, and O 1s core lines were used to evaluate the surface and near surface chemistry. The results provide measurements of the valence band electronic structure and surface chemistry of this rare-earth oxoborate. © 2003 American Institute of Physics.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
42.70.Mp Nonlinear optical crystals
71.20.Ps Other inorganic compounds
73.20.At Surface states, band structure, electron density of states

Formation of misfit dislocations in strained-layer GaAs/InxGa1−xAs/GaAs heterostructures during postfabrication thermal processing

X. W. Liu, A. A. Hopgood, B. F. Usher, H. Wang, and N. St. J. Braithwaite

J. Appl. Phys. 94, 7496 (2003); http://dx.doi.org/10.1063/1.1627463 (6 pages) | Cited 4 times

Online Publication Date: 2 December 2003

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It is demonstrated that relaxation of GaAs/InxGa1−xAs/GaAs strained-layer heterostructures can be brought about by postfabrication thermal processing. Misfit dislocations are introduced into the structure during thermal processing, even though the thickness of the strained layer is well below the critical value predicted by the Matthews–Blakeslee model. The misfit dislocations are observed to be of both 60° mixed type and 90° pure edge type. As no relaxation occurs at the lower temperatures encountered during fabrication by molecular-beam epitaxy, it can be inferred that the critical condition for the formation of misfit dislocations is not only a function of strained-layer thickness and composition, but also of temperature. This observation cannot be accounted for by differential thermal expansion or diffusion across the strained-layer interfaces, but the temperature-dependent Peierls force may offer an explanation. The high temperature required to produce relaxation of these structures suggests that they are sufficiently thermally stable for most practical applications. © 2003 American Institute of Physics.
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68.35.Ct Interface structure and roughness
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
68.60.Dv Thermal stability; thermal effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Lk Linear defects: dislocations, disclinations

Step-wise Fréedericksz transition in a nematic liquid crystal

Tatsutoshi Shioda, Bing Wen, and Charles Rosenblatt

J. Appl. Phys. 94, 7502 (2003); http://dx.doi.org/10.1063/1.1629389 (3 pages) | Cited 5 times

Online Publication Date: 2 December 2003

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The stylus of an atomic force microscope is used to rub a polyimide-coated substrate with a spatial period of 10 μm. A spatial periodicity is thereby introduced into the anchoring strength coefficient, resulting in a shoulder in the intensity–voltage curve above the Fréedericksz transition threshold of a nematic liquid crystal. © 2003 American Institute of Physics.
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64.70.M- Transitions in liquid crystals
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Photoluminescence excitonic linewidth in GaAsN alloys

R. T. Senger and K. K. Bajaj

J. Appl. Phys. 94, 7505 (2003); http://dx.doi.org/10.1063/1.1628405 (4 pages) | Cited 4 times

Online Publication Date: 2 December 2003

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We have calculated the variation of the photoluminescence excitonic linewidth, defined as the full width at half maximum, due to composition fluctuations as a function of nitrogen composition in completely random GaAs1−xNx alloys. We have considered the effects of a constant and of the composition dependent bowing parameter (and, thus, the energy band gap) on the excitonic linewidth. We have used two different recently proposed variations of the conduction electron mass with nitrogen composition. We have considered both the free and localized excitons. We find that the behavior of excitonic linewidth as a function of nitrogen composition, using two different bowing parameters, is qualitatively and quantitatively quite different. © 2003 American Institute of Physics.
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71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds

Influence of low energy–high flux nitrogen implantation on the oxidation behavior of AISI 304L austenitic stainless steel

F. Pedraza, J. L. Grosseau-Poussard, G. Abrasonis, J. P. Rivière, and J. F. Dinhut

J. Appl. Phys. 94, 7509 (2003); http://dx.doi.org/10.1063/1.1629151 (11 pages) | Cited 5 times

Online Publication Date: 2 December 2003

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Low energy–high flux (1.2 keV, 1 mA/cm2) nitriding of an austenitic AISI 304L stainless steel has been carried out by implanting a dose of 3.5×1019 ions cm−2 at 400 °C for 1 h. An important increase in surface hardness has been found to occur as a result of the formation of the so-called expanded austenite γN phase. Transmission electron microscopy studies have also shown the existence of hexagonal Cr2N precipitates at the nitrided layer/matrix interfacial region. The oxidation behavior has been then studied in the temperature range between 400 and 550 °C for 24 h under synthetic air. It is shown that nitridation slightly modifies the oxidation kinetics as a result of the progressive transformation of the γN phase towards CrN precipitation and α-FeNi matrix formation. More chromium enriched scales are, anyhow, developed on the nitrided steel than in the untreated one. These results are discussed on the basis of the chromium diffusion in the nitrided layer and its preferential chemical bonding with nitrogen atoms. © 2003 American Institute of Physics.
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61.82.Bg Metals and alloys
61.80.Jh Ion radiation effects
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
81.65.Mq Oxidation
61.72.up Other materials
68.37.Lp Transmission electron microscopy (TEM)
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
66.30.Fq Self-diffusion in metals, semimetals, and alloys

Prediction of boron transient enhanced diffusion through the atom-by-atom modeling of extended defects

E. Lampin, F. Cristiano, Y. Lamrani, A. Claverie, B. Colombeau, and N. E. B. Cowern

J. Appl. Phys. 94, 7520 (2003); http://dx.doi.org/10.1063/1.1627461 (6 pages) | Cited 8 times

Online Publication Date: 2 December 2003

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The modeling of the atom-by-atom growth of extended defects is coupled to the diffusion equations of boron by transferring the free interstitial supersaturation calculated with a defect model into a process simulator. Two methods to achieve this coupling (equilibrium method and fully coupled method, respectively) are presented and tested against a variety of experimental conditions. They are first applied to a transient enhanced diffusion experiment carried out on a structure containing several B delta-doped layers, in which the amount of diffusion of the different layers is accurately predicted. The fully coupled method is then used to simulate the diffusion of ultrashallow B-implanted profiles. This work definitely demonstrates the relevance of accurate physical defect models for the successful design of ultrashallow junctions in future generations of integrated circuits. © 2003 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.Nn Stacking faults and other planar or extended defects
61.72.uf Ge and Si
61.72.S- Impurities in crystals
61.72.J- Point defects and defect clusters

Morphology evolution and luminescence properties of porous GaN generated via Pt-assisted electroless etching of hydride vapor phase epitaxy GaN on sapphire

Diego J. Díaz, Todd L. Williamson, Ilesanmi Adesida, Paul W. Bohn, and Richard J. Molnar

J. Appl. Phys. 94, 7526 (2003); http://dx.doi.org/10.1063/1.1628833 (9 pages) | Cited 12 times

Online Publication Date: 2 December 2003

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Porous gallium nitride (PGaN) is produced by Pt-assisted electroless etching of hydride vapor phase epitaxy (HVPE)–GaN. Ultrathin Pt films are sputtered onto the GaN surface, and etching is carried out in a 1:2:1 solution of CH3OH:HF:H2O2. The evolution of the morphology proceeds by first forming a network of small pores, after which a ridge-trench morphology evolves, with ridges separated by a porous network in trenches between the ridges. As the etch progresses further the ridges evolve to a maximum size and then start to disappear. The formation and evolution of the ridge-trench morphology is explained by the presence of two different etch rates, an enhanced etch rate which generates the porous network and a slower etch rate that leads to the terraces of the ridge morphology. The rate at which the morphology evolves depends on the carrier concentration, with more heavily doped samples etching faster. In all cases, the final depth of the trenches between ridges is independent on the thickness of the starting GaN film. Cathodoluminescence (CL) spectroscopy of the unintentionally doped and the Si doped HVPE materials produce PGaN which shows only band gap emission at 368 nm before and after etching with only small shifts in the wavelength of maximum emission. The intensity of CL emission decreases with etch time as the GaN is consumed. CL spectroscopy and imaging show the ridges to be optically inactive, suggesting that the ridges might arise from grain boundaries or dislocations present in the starting GaN material. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
68.47.Fg Semiconductor surfaces
81.65.Cf Surface cleaning, etching, patterning

Directional nickel-induced fielded aided lateral crystallization of amorphous silicon

M. A. T. Izmajlowicz, A. J. Flewitt, W. I. Milne, and N. A. Morrison

J. Appl. Phys. 94, 7535 (2003); http://dx.doi.org/10.1063/1.1627455 (7 pages) | Cited 7 times

Online Publication Date: 2 December 2003

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For application to active matrix liquid crystal displays (AMLCDs), a low temperature (<900 K) process for the production of polycrystalline silicon is required to permit the use of inexpensive glass substrates. This would allow the integration of drive electronics onto the display panel. Current low temperature processes include excimer laser annealing and solid phase crystallization, both of which are currently unsuitable for the fabrication of low cost, large area devices. The addition of small amounts of metal (e.g., Ni) to the amorphous silicon has been shown to significantly reduce the solid phase crystallization temperature. The rate of this solid phase metal induced crystallization can also be increased as a result of the presence of an electric field. The work presented here reports directional crystallization of amorphous silicon thin films during heat treatment in the presence of an electric field. Models are proposed for metal induced crystallization with and without an applied electric field in which a reaction between Ni and Si to produce NiSi is the rate-limiting step. The crystallization rate is increased through the application of an electric field that leads to the drift of Ni ions to the growth front. The model and experimental data reveal that the crystallization rate increases exponentially with temperature and linearly with electric field strength. © 2003 American Institute of Physics.
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61.43.Dq Amorphous semiconductors, metals, and alloys
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Gc Amorphous semiconductors
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Effect of low-temperature annealing on the luminescent lifetime and negative differential resistance of silicon-implanted borosilicate glass

Gong-Ru Lin

J. Appl. Phys. 94, 7542 (2003); http://dx.doi.org/10.1063/1.1630366 (5 pages) | Cited 1 time

Online Publication Date: 2 December 2003

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The silicon-implanted borosilicate glass (BSO:Si+) low-temperature (500 °C) annealed at a different time are structurally, electrically, and optically characterized. The weak and broadened x-ray diffraction reveal insignificant Si nano-crystallization even after long-term annealing, whereas the redshifted photoluminescence (PL) interprets the change in category and the decrease in density of irradiative defects in BSO:Si+. Time-resolved PL analysis reveals a lengthening luminescent lifetime of BSO:Si+ from 1.7 to 2.8 ns, which indicates that the density ratio of nonradiative defects in as-implanted BSO:Si+ are reduced by one-tenth after annealing for 60 min. Transmission line mode analysis shows that both the leakage current and the contact resistance of a metal–BSO:Si+–metal diode has dramatically changed by three orders of magnitude. A strong negative differential resistance (NDR) and associated double-barrier electron tunneling phenomenon are observed with a threshold electric field of 290–350 kV/cm. The decreasing barrier height of the metal–BSO:Si+ junction from 3.0 to 1.9 eV is mainly contributed by deep-level defects with activation energy of ∼1 eV. After annealing, the NDR effect significantly diminishes, the barrier height raises to >2.4 eV, and most electrical characteristics of the metal–BSO:Si+ junction have recovered back to be comparable with those of the metal–BSO junction due to the elimination of these defects. © 2003 American Institute of Physics.
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61.72.Cc Kinetics of defect formation and annealing
78.55.Qr Amorphous materials; glasses and other disordered solids
72.20.Ht High-field and nonlinear effects
71.55.Jv Disordered structures; amorphous and glassy solids

Cation self-diffusion of 44Ca, 88Y, and 96Zr in single-crystalline calcia- and yttria-doped zirconia

M. Kilo, M. A. Taylor, Ch. Argirusis, G. Borchardt, B. Lesage, S. Weber, S. Scherrer, H. Scherrer, M. Schroeder, and M. Martin

J. Appl. Phys. 94, 7547 (2003); http://dx.doi.org/10.1063/1.1628379 (6 pages) | Cited 26 times

Online Publication Date: 2 December 2003

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Self-diffusion of calcium, yttrium, and zirconium in single-crystalline YSZ and CSZ (YSZ: yttria-stabilized zirconia; containing 10 to 32 mol % Y2O3; CSZ: calcia-stabilized zirconia; containing 11 and 17 mol % CaO) was measured at temperatures between 960 and 1700 °C. For zirconium and calcium diffusion, the stable isotopes 44Ca and 96Zr were used as tracers and the samples were analyzed with secondary ion mass spectrometry. In the case of yttrium diffusion, the radioactive tracer 88Y was used and an abrasive sectioning technique was applied. Zirconium bulk diffusion is slower than yttrium and calcium bulk diffusion, and there is a nearly linear correlation of diffusion coefficient with cation radius. In YSZ, zirconium and yttrium bulk diffusivity are maximum for a stabilizer content of 10–11 mol %, while in CSZ both calcium and zirconium tracer diffusion are independent of the calcium content. The activation enthalpy of yttrium stabilizer bulk diffusion (4.2 eV) is, as in CSZ, slightly smaller than for zirconium bulk diffusion (4.5 eV). The yttrium dislocation pipe diffusivity is five to six orders of magnitude faster than the bulk diffusivity, and its activation enthalpy (3.5 eV) is also smaller than that of the bulk diffusion. From the activation enthalpy and from the concentration dependence of the cation bulk diffusion, it is concluded that the cation diffusion occurs either via free vacancies (VZr4′ in YSZ) or via bound vacancies ([VZr4′−2VO2•]x in CSZ). © 2003 American Institute of Physics.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
66.30.J- Diffusion of impurities
61.72.Mm Grain and twin boundaries
61.72.J- Point defects and defect clusters

Dislocation-free relaxed SiGe-on-insulator mesa structures fabricated by high-temperature oxidation

Tsutomu Tezuka, Naoharu Sugiyama, and Shin-ichi Takagi

J. Appl. Phys. 94, 7553 (2003); http://dx.doi.org/10.1063/1.1628404 (7 pages) | Cited 10 times

Online Publication Date: 2 December 2003

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Relaxed SiGe-on-Insulator (SGOI) mesa structures were fabricated using mesa etching and successive high-temperature oxidation of SiGe layer on a Si-on-insulator (SOI) substrate for strained SOI (SSOI) metal–oxide–semiconductor field effect transistors (MOSFETs). In this procedure, the oxidation induces an increase in Ge fraction in the SiGe layer due to the rejection of Ge atoms from the oxide layer, while the mesa isolation enhances the lattice relaxation in the SiGe mesa. As a consequence, almost fully relaxed SGOI mesa structures with the Ge fraction up to 0.35 were obtained without introducing dislocations and surface undulation. Raman measurements revealed that a higher relaxation has been obtained for smaller and thicker mesas as well as at higher oxidation temperature. The experimental results were qualitatively explained by a relaxation model in which a strained SiGe island expands laterally without introducing dislocations on a plastic substrate. Based on this model, the applicability of this method to the fabrication of scaled MOSFETs was examined. In conclusion, this technique is promising for the fabrication of dislocation-free SGOI layers for scaled SSOI-MOSFETs without using any processes which are incompatible with conventional MOSFET processes. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
81.65.Cf Surface cleaning, etching, patterning
81.65.Mq Oxidation
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