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15 Dec 2004

Volume 96, Issue 12, pp. 6959-7777

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Two-dimensional distributed feedback lasers using a broadband, red polyfluorene gain medium

G. Heliotis, R. Xia, D. D. C. Bradley, G. A. Turnbull, I. D. W. Samuel, P. Andrew, and W. L. Barnes

J. Appl. Phys. 96, 6959 (2004); http://dx.doi.org/10.1063/1.1811374 (7 pages) | Cited 37 times

Online Publication Date: 2 December 2004

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We report the fabrication of widely tuneable (627–702 nm) optically pumped two-dimensional distributed feedback polymer lasers that utilize a red-emission fluorene copolymer as the active gain medium. The lasers exhibit efficient, low threshold operation and emit highly directional output beams as a result of the enhanced two-dimensional photonic confinement provided by the employed resonator. Their emission and operating characteristics are described in detail. We demonstrate that the very wide spectral range (Δλ⩾75 nm) over which these lasers can be systematically tuned is in very good agreement with theoretical predictions based on a simple waveguide model. In addition, we show that the lasers have long operating lifetimes τ1∕2⩾2×107 pulses and we discuss the impact that degradation has on the laser output characteristics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
78.55.Kz Solid organic materials
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Px Semiconductor lasers; laser diodes

Characterization of photonic crystal waveguides based on Fabry-Pérot interference

Iwan Märki, Martin Salt, Ross Stanley, Urs Staufer, and Hans-Peter Herzig

J. Appl. Phys. 96, 6966 (2004); http://dx.doi.org/10.1063/1.1810204 (4 pages) | Cited 3 times

Online Publication Date: 2 December 2004

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We present two methods based on the analysis of Fabry-Pérot interference for a detailed characterization of a 90° corner in a two-dimensional photonic crystal waveguide fabricated in a thin Si membrane. These methods are a means of identifying the critical waveguide elements in the process of improving photonic crystal devices. The effects of the elements forming the photonic crystal waveguide are identified and quantified by means of a stage-by-stage analysis. By Fourier transforming the transmission spectra we observe the amount of light that is back reflected inside the waveguide and based on the fringe contrast of the Fabry-Pérot modulation we calculate the loss contribution of each waveguide element, such as the tapers and the 90° corner.
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42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

A charge-coupled-device-based heterodyne technique for parallel photodisplacement imaging

Toshihiko Nakata and Takanori Ninomiya

J. Appl. Phys. 96, 6970 (2004); http://dx.doi.org/10.1063/1.1806534 (11 pages) | Cited 4 times

Online Publication Date: 2 December 2004

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A heterodyne interferometry technique for parallel photodisplacement imaging is presented. In the parallel photodisplacement technique, a linear region of photothermal displacement is excited using a line-focusing intensity-modulated laser beam and is detected with a parallel heterodyne interferometer in which a charge-coupled device linear image sensor is used as a detector. The integration and sampling effects of the sensor provide spatiotemporally multiplexing of the interference light. To extract the spatially resolved photodisplacement component from the multiplexed sensor signal for heterodyne interferometry, a scheme of phase-shifting light integration under an undersampling condition is developed. The frequency relation for the heterodyne beat signal, modulation signal, and sensor gate signal is optimized so as to eliminate undesirable components, allowing only the displacement component to be extracted. Preliminary experimental results using a point-focused laser beam demonstrate that the technique is effective, making it possible to accurately extract photodisplacement components from the multiplexed interferogram. Subsurface structures and defects in silicon wafers are clearly imaged with a detection time of 5.3 μs∕pixel. In combination with a line-focusing laser beam, this technique is very promising for high-throughput subsurface imaging with detection speeds more than 10 000 times faster than conventional photoacoustic microscopy.
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07.60.Ly Interferometers
42.79.Pw Imaging detectors and sensors
42.87.Bg Phase shifting interferometry
42.30.Va Image forming and processing
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Wormhole liquid crystal display modes

M. Inaba, H. Okada, and H. Onnagawa

J. Appl. Phys. 96, 6981 (2004); http://dx.doi.org/10.1063/1.1814807 (6 pages)

Online Publication Date: 2 December 2004

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Wormhole liquid crystal display modes are proposed. Micron-sized and randomly arranged holes on upper and lower electrodes are formed in order to deform a liquid crystal alignment. By optimizing cell thickness, the calculation of director profiles and transmittance based on Frank’s continuum theory and Jones matrix are carried out and the maximum transmittance is compared with experimental results. Good transmittance versus voltage characteristics was obtained regardless of the sign of the dielectric anisotropy. From optical microscopy, radial and spherical domains were found at the electrode holes. The position of these domains was randomly arranged and its shape was that of a half-cut droplet. Electro-optical response and viewing angle characteristics have also been evaluated.
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42.79.Kr Display devices, liquid-crystal devices
78.20.Jq Electro-optical effects

Angular and wavelength selectivity of parasitic holograms in cerium doped strontium barium niobate

Mostafa A. Ellabban, Martin Fally, Mirco Imlau, Theo Woike, Romano A. Rupp, and Torsten Granzow

J. Appl. Phys. 96, 6987 (2004); http://dx.doi.org/10.1063/1.1815383 (7 pages) | Cited 5 times

Online Publication Date: 2 December 2004

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The angular and wavelength selectivity of noise gratings in doped strontium barium niobate crystals for samples with two different thicknesses are investigated. We found that an offset in the optimum reconstruction angle with respect to the recording geometry occurs as a function of the thickness. This is a consequence of the unidirectional amplification. Thus the scattering intensity for the thinner sample is considerably lowered at the very recording conditions. We analyze the experimental results in terms of the kinematic theory of diffraction.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Ln Holographic recording materials; optical storage media
42.40.Eq Holographic optical elements; holographic gratings
42.65.-k Nonlinear optics
42.79.Vb Optical storage systems, optical disks
42.25.Fx Diffraction and scattering
61.72.S- Impurities in crystals
78.20.-e Optical properties of bulk materials and thin films
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A time-resolved Langmuir double-probe method for the investigation of pulsed magnetron discharges

Th. Welzel, Th. Dunger, H. Kupfer, and F. Richter

J. Appl. Phys. 96, 6994 (2004); http://dx.doi.org/10.1063/1.1808481 (8 pages) | Cited 11 times

Online Publication Date: 2 December 2004

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Langmuir probes are important means for the characterization of plasma discharges. For measurements in plasmas used for the deposition of thin films, the Langmuir double probe is especially suited. With the increasing popularity of pulsed deposition discharges, there is also an increasing need for time-resolved characterization methods. For Langmuir probes, several single-probe approaches to time-resolved measurements are reported but very few for the double probe. We present a time-resolved Langmuir double-probe technique, which is applied to a pulsed magnetron discharge at several 100 kHz used for MgO deposition. The investigations show that a proper treatment of the current measurement is necessary to obtain reliable results. In doing so, a characteristic time dependence of the charge-carrier density during the “pulse on” time containing maximum values of almost 2⋅1011 cm−3 was found. This characteristic time dependence varies with the pulse frequency and the duty cycle. A similar time dependence of the electron temperature is only observed when the probe is placed near the magnesium target.
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52.70.Ds Electric and magnetic measurements
52.80.Sm Magnetoactive discharges (e.g., Penning discharges)
52.77.Dq Plasma-based ion implantation and deposition
52.25.Fi Transport properties

Coupling effects of the flow and electric fields in electrostatic precipitators

Parsa Zamankhan, Goodarz Ahmadi, and Fa-Gung Fan

J. Appl. Phys. 96, 7002 (2004); http://dx.doi.org/10.1063/1.1810201 (9 pages) | Cited 5 times

Online Publication Date: 2 December 2004

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In this study the variations of the velocity and electric fields in electrohydrodynamic (EHD) flows in a positive single-wire electrostatic precipitator are studied. The fully coupled systems of electrical and hydrodynamical governing equations are solved for both laminar and turbulent flow conditions. Particular attention is given to the flow-electric field coupling effects and the variation of the electrical potential and charge distribution induced by the gas flow field. The presented results show that the effects of airflow on electrical potential and charge density become noticeable at high cross-flow velocities. The electrical conditions in an electrostatic precipitator that was used in an earlier experimental study are also simulated. It is shown that the computational model predictions are in good agreement with the experimental data. A series of parametric studies for a range of parameters for the EHD flows in the single-wire precipitator are performed and the corresponding flow and electric fields are presented. An example of extension of the model to multiwire precipitator is also presented.
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47.65.-d Magnetohydrodynamics and electrohydrodynamics
07.68.+m Photography, photographic instruments; xerography
52.80.Hc Glow; corona
47.11.-j Computational methods in fluid dynamics

Physics of high-pressure helium and argon radio-frequency plasmas

M. Moravej, X. Yang, G. R. Nowling, J. P. Chang, R. F. Hicks, and S. E. Babayan

J. Appl. Phys. 96, 7011 (2004); http://dx.doi.org/10.1063/1.1815047 (7 pages) | Cited 39 times

Online Publication Date: 2 December 2004

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The physics of helium and argon rf discharges have been investigated in the pressure range from 50 to 760 Torr. The plasma source consists of metal electrodes that are perforated to allow the gas to flow through them. Current and voltage plots were obtained at different purity levels and it was found that trace impurities do not affect the shape of the curves. The electron temperature was calculated using an energy balance on the unbound electrons. It increased with decreasing pressure from 1.1 to 2.4 eV for helium and from 1.1 to 2.0 for argon. The plasma density calculated at a constant current density of 138 mA∕cm2 ranged from 1.7×1011 to 9.3×1011 cm−3 for helium and from 2.5×1011 to 2.4×1012 cm−3 for argon, increasing with the pressure. At atmospheric pressure, the electron density of the argon plasma is 2.5 times that of the helium plasma.
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52.80.Pi High-frequency and RF discharges
52.50.Dg Plasma sources
52.25.Vy Impurities in plasmas
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Optical properties of correlation-induced paramagnetic FeAl alloy

Joo Yull Rhee

J. Appl. Phys. 96, 7018 (2004); http://dx.doi.org/10.1063/1.1810639 (4 pages) | Cited 2 times

Online Publication Date: 2 December 2004

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The first-principles electronic-structure calculations of FeAl alloy using the density-functional theory within the local-(spin)-density approximation (LDA) cannot correctly predict the paramagnetic ground state even when using the generalized-gradient approximation (GGA), while the application of the LDA+U method can correctly predict the paramagnetic ground state. Therefore, the FeAl alloy is believed to have a correlation-induced paramagnetic ground state. The electronic structures and optical-conductivity (OC) spectrum of the equiatomic FeAl alloy were calculated using a full-potential linearized-augmented-plane-wave method within the GGA with and without the inclusion of the LDA+U method. The calculated OC spectrum without the LDA+U method does not agree well with the experimental one, while the application of the LDA+U method markedly improves the agreement between the experimental and calculated spectra. The application of the LDA+U method redistributes the Fe eg and t2g bands near the Fermi level and this redistribution causes the difference between the OC spectra calculated with a simple GGA and the LDA+U method.
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75.20.En Metals and alloys
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Gj Other metals and alloys
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

Optical and magnetic properties of Mn+-implanted GaAs

Yoon Shon, Y. S. Park, K. J. Chung, D. J. Fu, D. Y. Kim, H. S. Kim, H. J. Kim, T. W. Kang, Yongmin Kim, X. J. Fan, and Y. J. Park

J. Appl. Phys. 96, 7022 (2004); http://dx.doi.org/10.1063/1.1804227 (7 pages) | Cited 8 times

Online Publication Date: 2 December 2004

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Neutron-transmutation-doped GaAs samples were prepared by irradiating the middle-level neutrons into the semi-insulating GaAs grown by a liquid encapsulated Czochralski method and subsequently implanted with Mn+. The characteristics of the Mn+-implanted neutron-transmutation-doped GaAs (namely, the implantation of Mn+ subsequent to neutron-transmutation-doping) were investigated by various measurements. The result of the energy dispersive x-ray peak displayed an injected Mn concentration of 9.65%. The photoluminescence peaks related to carbon and germanium acceptors were resolved, and the peaks related to Mn due to a neutral Mn acceptor were evidently observed. It is found that the proper activation for the neutral Mn acceptor starts from a relatively low annealing temperature of 600 °C for 15 min. The atomic force microscopy and magnetic forcemicroscopy images showed that magnetic clusters were well formed. The ferromagnetic hysteresis loop measured at 10 K was observed, and the temperature-dependent magnetization revealed that the two different phases exist at 135 and 360 K. The Curie temperature (Tc∼360 K) is caused by MnAs, which agrees with the clusters of the magnetic force microscopy image.
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75.50.Pp Magnetic semiconductors
81.05.Ea III-V semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
81.10.Fq Growth from melts; zone melting and refining
61.72.uj III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.80.Hg Neutron radiation effects
61.82.Fk Semiconductors
81.40.Gh Other heat and thermomechanical treatments

Polarization filtering by nonpolar M-plane GaN films on LiAlO2

Pranob Misra, Yue Jun Sun,, Oliver Brandt, and Holger T. Grahn

J. Appl. Phys. 96, 7029 (2004); http://dx.doi.org/10.1063/1.1808483 (7 pages) | Cited 18 times

Online Publication Date: 2 December 2004

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The anisotropic optical properties and polarization filtering are investigated for strained M-plane GaN films as a function of the angle of the in-plane polarization vector. Since the c axis of the underlying wurtzite crystal structure lies in the film plane, its symmetry is reduced in comparison to conventional C-plane films, giving rise to an in-plane polarization anisotropy. This anisotropy is further enhanced by the anisotropic compressive in-plane strain, which occurs due to the lattice mismatch between the GaN film and the substrate LiAlO2. In addition to linear birefringence, the film also exhibits linear dichroism, resulting in a polarization filtering of an incident, linearly polarized light beam after transmission. This filtering manifests itself as a rotation of the polarization vector towards the c axis and can be as large as 80°. We compare the measured polarization rotation with calculated values taking into account the birefringence of the GaN film. In the energy range where the filtering is most effective, the birefringence almost disappears and can therefore be neglected for the determination of the rotation angle. Finally, the rotation, which is determined by the transmittance for the two orthogonal polarization directions, can be very well approximated by the product of the film thickness and the difference of the absorption coefficients for the two polarization directions.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
68.60.Bs Mechanical and acoustical properties
78.20.Fm Birefringence
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

A comparison of plasma-activated N2∕O2 and N2O∕O2 mixtures for use in ZnO:N synthesis by chemical vapor deposition

T. M. Barnes, J. Leaf, S. Hand, C. Fry, and C. A. Wolden

J. Appl. Phys. 96, 7036 (2004); http://dx.doi.org/10.1063/1.1804614 (9 pages) | Cited 27 times

Online Publication Date: 2 December 2004

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A high-vacuum plasma-assisted chemical-vapor deposition system was used to systematically study ZnO:N thin film synthesis. Nitrogen doping was achieved by mixing either N2O or N2 with O2 in a high-density inductively coupled plasma (ICP) source. In situ diagnostics showed that the ICP composition was predominantly a function of the elemental oxygen to nitrogen ratio, and relatively insensitive to the choice of N2 or N2O as the molecular precursor. Nitrogen incorporation was measured by both x-ray photoelectron spectroscopy and secondary ion mass spectrometry and was found to increase monotonically with both N2O and N2 addition. Nitrogen doping was correlated with systematic shifts in the lattice spacing, electrical conductivity, and optical absorption. Quantitative comparisons between film properties and gas composition suggest that atomic nitrogen is the primary precursor for doping in this system.
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68.55.A- Nucleation and growth
81.05.Dz II-VI semiconductors
78.66.Hf II-VI semiconductors
73.61.Ga II-VI semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.60.Dp Adsorbed layers and thin films
78.40.Fy Semiconductors
78.30.Fs III-V and II-VI semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Boron-enhanced blistering and exfoliation in hydrogen-implanted SrTiO3

Jung-Kun Lee, Richard D. Averitt, and Michael Nastasi

J. Appl. Phys. 96, 7045 (2004); http://dx.doi.org/10.1063/1.1804623 (7 pages) | Cited 1 time

Online Publication Date: 2 December 2004

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The blistering behavior and the exfoliation of SrTiO3 single crystals were investigated using co-implantation with boron and hydrogen. In contrast to H-only-implantation, co-implantation of B+ with 1×1015 ions∕cm2 at 80 kV and H+ with 5×1016 ions∕cm2 at 40 kV caused a vigorous blistering and a complete exfoliation during the annealing process. A comparison of the blistering depth and the hydrogen distribution in the co-implanted samples revealed that the exfoliation did not occur in the regions of maximum hydrogen concentration or maximum hydrogen-related radiation damage. It occurred at the crossover of the boron distribution profile and hydrogen distribution profile. With the aid of an elastic recoil detection and the Rutherford backscattering spectroscopy in the channeling mode, the preimplanted boron was found to facilitate the long-range H movement into the B-implanted region, resulting in the chemical interaction between B and H. A bond analysis obtained from the Fourier transform infrared-attenuated total reflection spectroscopy showed that B–H interactions resulted in the formation of boron hydride. It is proposed that the boron hydride formation and decomposition upon annealing provided the needed gas pressure for the complete exfoliation of B+H co-implanted SrTiO3 crystals.
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61.72.up Other materials
61.72.S- Impurities in crystals
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
78.30.Hv Other nonmetallic inorganics
81.40.Gh Other heat and thermomechanical treatments

Relationship between the optical gap and the optical-absorption tail breadth in amorphous GaAs

J. H. Dias da Silva, R. R. Campomanes, D. M. G. Leite, Farida Orapunt, and Stephen K. O’Leary

J. Appl. Phys. 96, 7052 (2004); http://dx.doi.org/10.1063/1.1797541 (8 pages) | Cited 5 times

Online Publication Date: 2 December 2004

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We study the relationship between the optical gap and the optical-absorption tail breadth for the case of amorphous gallium arsenide (a-GaAs). In particular, we analyze the optical-absorption spectra corresponding to some recently prepared a-GaAs samples. The optical gap and the optical-absorption tail breadth corresponding to each sample is determined. Plotting the optical gap as a function of the corresponding optical-absorption tail breadth, we note that a trend, similar to that found for the cases of the hydrogenated amorphous silicon and hydrogenated amorphous germanium, is also found for the case of a-GaAs. The impact of alloying on the optical-absorption spectrum associated with a-GaAs is also briefly examined.
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78.66.Jg Amorphous semiconductors; glasses
78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.05.Ea III-V semiconductors
81.05.Gc Amorphous semiconductors

Conversion of p-type to n-type diamond by exposure to a deuterium plasma

R. Kalish, C. Saguy, C. Cytermann, J. Chevallier, Z. Teukam, F. Jomard, T. Kociniewski, D. Ballutaud, J. E. Butler, C. Baron, and A. Deneuville

J. Appl. Phys. 96, 7060 (2004); http://dx.doi.org/10.1063/1.1811777 (6 pages) | Cited 15 times

Online Publication Date: 2 December 2004

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The lack of a shallow donor in diamond with reasonable room temperature conductivity has been a major obstacle, until now, for the realization of many diamond based electronic devices. Most recently it has been shown that exposure of p-type (B doped) homoepitaxial diamond layers to a deuterium plasma can result in the formation of n-type diamond with a shallow donor state (Ea=0.34 eV) and high room temperature mobility (430 cm2∕V s) [Z. Teukam et al., Nat. Mater. 2, 482 (2003); C. Saguy et al., Diamond Relat. Mater. 13, 700 (2004)]. Experimental results, based on the comparison of secondary ion mass spectrometry profiles of B and D and Hall effect measurements at different temperatures are presented. They confirm the previous speculation that some deuterium related complex is responsible for the donor activity in diamond. These donors are shown to be formed in a two-step process. First, deuterium diffuses into the entire B containing layer rather slowly, being trapped by the boron acceptors and passivating them. Once all B have formed complexes, further exposure to a D plasma results in the formation of a layer that contains about twice as many D atoms as the B content. This step is the one that gives rise to the excellent n-type features observed. The most recent theoretical attempts to explain the donor state by simulations of various boron-hydrogen complexes in diamond are reviewed.
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81.05.Cy Elemental semiconductors
71.55.Cn Elemental semiconductors
52.77.-j Plasma applications
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Cw Elemental semiconductors
66.30.J- Diffusion of impurities
81.65.Rv Passivation

The study of mass transport of acetone in polycarbonate

Hao Ouyang, Ming-Tsang Wu, and Wen Ouyang

J. Appl. Phys. 96, 7066 (2004); http://dx.doi.org/10.1063/1.1811782 (5 pages) | Cited 4 times

Online Publication Date: 2 December 2004

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The mechanism of mass transport and associated crystallization in polycarbonate (PC) were studied. Based on Harmon’s model for case I (or Fickian), case II (or swelling), and anomalous transport, the data of the initial period of mass uptake were analyzed. Due to the initially small dimensional variation of the PC and the initially small amount of crystallization, the influence of crystallinity on the mass transport can be ignored. The diffusivity in case I and the velocity in case II both followed the Arrhenius relationship. Case II dominated the transport process as the activation energy of case II is lower than that of case I. This finding was further verified by measuring the movement of diffusion fronts with a carefully selected observation coordinate. A distinct transport front was identified from the measurements of optical microscope and the microhardness. This investigation addresses more complicated microstructures of PC during mass transport.
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61.41.+e Polymers, elastomers, and plastics
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
66.30.Lw Diffusion of other defects
78.70.Ck X-ray scattering

Real-time observation of initial stages of copper film growth on silicon oxide using reflection high-energy electron diffraction

Jason T. Drotar, T.-M. Lu, and G.-C. Wang

J. Appl. Phys. 96, 7071 (2004); http://dx.doi.org/10.1063/1.1811785 (9 pages) | Cited 9 times

Online Publication Date: 2 December 2004

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We have studied, in real time, the evolution of a thin (less than 200 math) copper film deposited onto an oxidized silicon surface using reflection high-energy electron diffraction. We show that quantitative measurements of island size and shape as functions of time are possible and the results are presented. While the film texture is initially random, texture competition leads to an absence of the low-energy (111) and (200) oriented grains for later times. It is also found that the film surface is composed of facets that increase in size with time. This behavior is explained in terms of facet coalescence.
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81.05.Bx Metals, semimetals, and alloys
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Mq Oxidation

Hydrogen diffusion at moderate temperatures in p-type Czochralski silicon

Y. L. Huang, Y. Ma, R. Job, and A. G. Ulyashin

J. Appl. Phys. 96, 7080 (2004); http://dx.doi.org/10.1063/1.1812379 (7 pages) | Cited 12 times

Online Publication Date: 2 December 2004

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In plasma-hydrogenated p-type Czochralski silicon, rapid thermal donor (TD) formation is achieved, resulting from the catalytic support of hydrogen. The n-type counter doping by TD leads to a p-n junction formation. A simple method for the indirect determination of the diffusivity of hydrogen via applying the spreading resistance probe measurements is presented. Hydrogen diffusion in silicon during both plasma hydrogenation and post-hydrogenation annealing is investigated. The impact of the hydrogenation duration, annealing temperature, and resistivity of the silicon wafers on the hydrogen diffusion is discussed. Diffusivities of hydrogen are determined in the temperature range 270–450°C. The activation energy for the hydrogen diffusion is deduced to be 1.23 eV. The diffusion of hydrogen is interpreted within the framework of a trap-limited diffusion mechanism. Oxygen and hydrogen are found to be the main traps.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
66.30.J- Diffusion of impurities
61.72.Cc Kinetics of defect formation and annealing
81.65.-b Surface treatments
52.77.-j Plasma applications

Misfit dislocation formation in the AlGaN∕GaN heterointerface

J. A. Floro, D. M. Follstaedt, P. Provencio, S. J. Hearne, and S. R. Lee

J. Appl. Phys. 96, 7087 (2004); http://dx.doi.org/10.1063/1.1812361 (8 pages) | Cited 37 times

Online Publication Date: 2 December 2004

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Heteroepitaxial growth of AlxGa1−xN alloy films on GaN results in large tensile strain due to the lattice mismatch. During growth, this strain is partially relieved both by crack formation and by the coupled introduction of dense misfit dislocation arrays. Extensive transmission electron microscopy measurements show that the misfit dislocations enter the film by pyramidal glide of half loops on the 1∕3〈1math23〉∕{11math2} slip system, which is a well-known secondary slip system in hcp metals. Unlike the hcp case, however, where shuffle-type dislocations must be invoked for this slip plane, we show that glide-type dislocations are also possible. Comparisons of measured and theoretical critical thicknesses show that fully strained films can be grown into the metastable regime, which we attribute to limitations on defect nucleation. At advanced stages of relaxation, interfacial multiplication of dislocations dominates the strain relaxation process. This work demonstrates that misfit dislocations are important mechanisms for relaxation of strained III-nitride heterostructures that can contribute significantly to the overall defect density.
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81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Lk Linear defects: dislocations, disclinations
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
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
68.35.Gy Mechanical properties; surface strains
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

“Migration energy” for impurity diffusion in crystalline solids: A closer look

Panchapakesan Ramanarayanan, Balaji Srinivasan, Kyeongjae Cho, and Bruce M. Clemens

J. Appl. Phys. 96, 7095 (2004); http://dx.doi.org/10.1063/1.1809254 (13 pages) | Cited 3 times

Online Publication Date: 2 December 2004

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Point defect mediated diffusion of impurities in crystalline materials involves a sequence of several processes, which are repeated in varying combinations a multiple number of times. The concept of “activation energy” has been borrowed from simple chemical reactions, where the reactants are postulated to form an activated complex before decomposing into products. While ideas such as the smallest rate (or the rates of a select few “important” processes) being the rate determining step and hence the overall activation energy may be applicable in the case of chemical reactions that are sequential, such ideas are shown to be too simplistic to be applicable to describe diffusion in the crystalline phase. In this paper, we present a systematic scheme to arrive at the macroscopic activation energy in terms of the energy barriers for the constituent microscopic processes. We apply this scheme to the case of vacancy mediated diffusion of impurities in a diamond lattice. We present results of numerical verification of the scheme performed by kinetic Monte Carlo simulations based on the energy barriers obtained using the density functional theory within the local density approximation. We then present observations on the dependence of the macroscopic “migration energy” on the energy barriers for the constituent microscopic processes. As an illustration of how the energy barriers for the microscopic processes can be affected, we present first principles calculation of the effect of biaxial strain on these energy barriers.
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66.30.J- Diffusion of impurities
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.S- Impurities in crystals
61.72.J- Point defects and defect clusters
82.20.Pm Rate constants, reaction cross sections, and activation energies

Controlled growth of O-polar ZnO epitaxial film by oxygen radical preconditioning of sapphire substrate

Z. X. Mei, Y. Wang, X. L. Du, M. J. Ying, Z. Q. Zeng, H. Zheng, J. F. Jia, Q. K. Xue, and Z. Zhang

J. Appl. Phys. 96, 7108 (2004); http://dx.doi.org/10.1063/1.1812362 (4 pages) | Cited 23 times

Online Publication Date: 2 December 2004

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Oxygen radicals pregrowth treatment and surface nitridation were used to eliminate Zn-polar inversion domains and control the growth of single-domain O-polar ZnO film on sapphire (0001) substrate by rf plasma-assisted molecular beam epitaxy. We found that the formation of oxygen-terminated sapphire surface prior to nitridation is crucial for achieving the anion polarity in subsequent AlN and ZnO layers, as demonstrated by formation of the 3×3 surface reconstruction during ZnO growth and ex situ polarity determination. This method, in general, can be applied to growth of other polar films, such as II-VI oxides and III-V nitrides, on sapphire (0001) substrates.©
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81.05.Dz II-VI semiconductors
81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
52.77.Dq Plasma-based ion implantation and deposition
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Influence of the photodepoling parameters on quasiphase-matched second-harmonic generation and optical parametric fluorescence in polymer channel waveguides

G. Martin, O. Alibart, R. Hierle, D. Josse, P. Baldi, and J. Zyss

J. Appl. Phys. 96, 7112 (2004); http://dx.doi.org/10.1063/1.1809770 (6 pages) | Cited 1 time

Online Publication Date: 2 December 2004

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We report on periodical modulation of the nonlinear susceptibility tensor by optical means in organic channel waveguides and its applications to second-harmonic generation and optical parametric fluorescence. The modulation is achieved by photoisomerization of a typical azo dye, Disperse Red One, through a photolithographic mask in order to transfer the desired periodicity. The choice of the illuminating beam wavelength is shown to be a tradeoff between efficient excitation and penetration depth of the photoisomerization process, the depth to be achieved being directly related to the thickness of the waveguide. For the estimated ideal wavelength, we show experimental evidence of second-harmonic generation and optical parametric flurorescence at a close to degeneracy wavelength of 1586 nm. A comparison between the experimental and theoretical expected values is also presented.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Gn Optical waveguides and couplers
78.55.Kz Solid organic materials
42.65.An Optical susceptibility, hyperpolarizability
82.30.Qt Isomerization and rearrangement
42.82.Cr Fabrication techniques; lithography, pattern transfer

Microstructural properties and atomic arrangements in GaN/sapphire and AlxGa1−xN∕AlN∕GaN∕sapphire heterostructures

T. W. Kim, D. U. Lee, H. S. Lee, J. Y. Lee, Jae-Hoon Lee, and Jung-Hee Lee

J. Appl. Phys. 96, 7118 (2004); http://dx.doi.org/10.1063/1.1812352 (4 pages)

Online Publication Date: 2 December 2004

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Microstructural and atomic structure studies of GaN/sapphire and AlxGa1−xN∕AlN∕GaN heterointerfaces have been performed by using bright-field transmission electron microscopy (TEM) and selected area electron diffraction pattern (SADP) measurements. TEM and SADP results from the GaN/sapphire and the Al0.4Ga0.6N∕AlN∕GaN∕sapphire heterointerfaces showed that GaN epilayers and Al0.4Ga0.6N, AlN, and GaN active layers, respectively, had been grown on the sapphire substrates. The values of the strain and the stress in the Al0.4Ga0.6N, the AlN, and the GaN layers were determined. Possible schematic diagrams of the two heterostructures, as well as diagrams of the [2mathmath0] projections of the GaN epilayer and the Al0.4Ga0.6N∕AlN∕GaN heterostructure, are presented based on the TEM and SADP results. These results can help improve the understanding of the microstructural properties of the strained AlxGa1−xN∕AlN∕GaN∕sapphire heterostructures for applications in the high-speed and high-power electronic devices.
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81.05.Ea III-V semiconductors
68.35.Ct Interface structure and roughness
68.37.Lp Transmission electron microscopy (TEM)

Mechanisms of the refractive index change in femtosecond laser-irradiated Au3+-doped silicate glasses

Quan-Zhong Zhao, Jian-Rong Qiu, Xiong-Wei Jiang, Chong-Jun Zhao, and Cong-Shan Zhu

J. Appl. Phys. 96, 7122 (2004); http://dx.doi.org/10.1063/1.1812353 (4 pages) | Cited 7 times

Online Publication Date: 2 December 2004

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We report on the refractive index change in Au3+-doped silicate glasses irradiated by a femtosecond laser and successive heat treatment. The refractive index of the irradiated area increased after the femtosecond laser irradiation and decreased with increasing annealing temperature up to 450 °C and then increased again with increasing annealing temperature. Absorption spectra of the glass samples before and after femtosecond laser irradiation and after further annealing manifested the formation of color centers after laser irradiation, disappearance of color centers after annealing at 300 °C, and precipitation of gold nanoparticles after annealing at high temperature. The mechanisms of the observed phenomena are discussed.
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81.05.Kf Glasses (including metallic glasses)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.40.Gh Other heat and thermomechanical treatments
61.43.Fs Glasses
81.30.Mh Solid-phase precipitation

The initial, thermal oxidation of zirconium at room temperature

A. Lyapin, L. P. H. Jeurgens, P. C. J. Graat, and E. J. Mittemeijer

J. Appl. Phys. 96, 7126 (2004); http://dx.doi.org/10.1063/1.1809773 (10 pages) | Cited 14 times

Online Publication Date: 2 December 2004

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Angle-resolved x-ray photoelectron spectroscopy (ARXPS) and in situ spectroscopic ellipsometry have been used to investigate the initial oxidation of polycrystalline zirconium at room temperature in the partial oxygen pressure range of 1.3×10−7–1.3×10−4 Pa. Detailed quantitative analysis of the measured Zr 3d ARXPS spectra of the oxidized metal allowed separation of the intrinsic and extrinsic metallic and oxidic contributions to the spectra. It was shown that, in addition to the metallic contribution from the substrate and the oxidic contribution from stoichiometric ZrO2, two additional suboxidic components are contained in the measured Zr 3d spectra of the oxidized Zr metal. As evidenced by angle-resolved XPS and in situ ellipsometry, both of these components can be attributed to a gradient of Zr enrichment in the region of the oxide film adjacent to the metal∕oxide interface (with the highest Zr enrichment at the metal∕oxide interface). Investigation of the oxide-film growth kinetics at various pO2, as determined independently using both techniques, showed the occurrence of an initial regime of very fast, electric-field-controlled growth, followed by a much slower oxidation stage. As a result, an, on average, nonstoichiometric oxide film develops. The observed effect of the pO2 on the low-temperature oxidation of Zr has been discussed in terms of the relationship between the fraction of coverage of the surface with physi- and chemisorbed oxygen and the applied pO2.
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68.55.A- Nucleation and growth
81.65.Mq Oxidation
68.43.Mn Adsorption kinetics
81.05.Bx Metals, semimetals, and alloys
68.55.Nq Composition and phase identification
61.66.Bi Elemental solids
61.66.Dk Alloys
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
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