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8 Jun 1998

Volume 72, Issue 23, pp. 2927-3082

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Fabrication and optical characterization of Pb(Mg1/3Nb2/3)O3-PbTiO3 planar thin film optical waveguides

Yalin Lu, G.-H. Jin, M. Cronin-Golomb, S.-W. Liu, H. Jiang, F.-L. Wang, J. Zhao, S.-Q. Wang, and A. J. Drehman

Appl. Phys. Lett. 72, 2927 (1998); http://dx.doi.org/10.1063/1.121496 (3 pages) | Cited 34 times

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Highly (110)-oriented and (100) nearly epitaxial 0.7PMN-0.3PT thin films were deposited on (1012) sapphire and (100) LaAlO3 substrates, respectively, using a dip-coating method. Optical waveguide characterization and electro-optic effect measurements of the film on sapphire substrate were demonstrated. Low propagation loss of 4.1 dB/cm and high quadratic electro-optic coefficient of 0.75×10−16 (m/V)2 were obtained at wavelength of 632.8 nm. Epitaxial PMN-PT thin films will be suitable for integrated optic devices. © 1998 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.86.+b Optical workshop techniques
42.79.Wc Optical coatings
78.20.Jq Electro-optical effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

High resolution imaging microellipsometry of soft surfaces at 3 μm lateral and 5 Å normal resolution

A. Albersdörfer, G. Elender, G. Mathe, K. R. Neumaier, P. Paduschek, and E. Sackmann

Appl. Phys. Lett. 72, 2930 (1998); http://dx.doi.org/10.1063/1.121497 (3 pages) | Cited 22 times

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We report on the design of an imaging microellipsometer enabling the generation of maps of the two ellipsometric angles Δ and Ψ. Areas of 60×200 μm2 are imaged at a rate of 1–2 images per minute. By working at angles (45°) much smaller than the Brewster angle (≈73° for Si/SiO2/air) a lateral resolution of 3 μm and a height resolution of 5 Å is achieved. The performance is demonstrated by thickness measurement of a laterally structured polymer film and a transient thickness measurement of dewetting fluid film of n-hexadecane on a Si/SiO2 wafer. © 1998 American Institute of Physics.
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07.60.Fs Polarimeters and ellipsometers
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
68.15.+e Liquid thin films
61.41.+e Polymers, elastomers, and plastics

The optical gain mechanism in solid conjugated polymers

B. Schweitzer, G. Wegmann, H. Giessen, D. Hertel, H. Bässler, R. F. Mahrt, U. Scherf, and K. Müllen

Appl. Phys. Lett. 72, 2933 (1998); http://dx.doi.org/10.1063/1.121498 (3 pages) | Cited 27 times

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We report on stimulated emission from a solid conjugated methyl-substituted ladder-type poly(paraphenylene). The threshold for stimulated emission as well as the spectral narrowing is measured. Upon exciting within the low energy tail of the S1-S0 (0–0) absorption band narrow emission lines offset from the excitation by the energies of the dominant vibrational modes are observed. From these measurements we conclude that vibronic sublevels play a major role in the optical gain mechanism. Hence, the gain mechanism can be explained in terms of molecularly excited states. © 1998 American Institute of Physics.
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78.45.+h Stimulated emission
42.70.Jk Polymers and organics
63.50.-x Vibrational states in disordered systems
42.50.-p Quantum optics

Amplified spontaneous emission spectroscopy on semiconductor optical amplifiers subject to active light injection

A. P. de Boer, P. C. M. Christianen, J. C. Maan, Th. Rasing, V. I. Tolstikhin, T. G. van de Roer, and H. M. de Vrieze

Appl. Phys. Lett. 72, 2936 (1998); http://dx.doi.org/10.1063/1.121499 (3 pages) | Cited 1 time

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It is shown that measurements of the effect of optical injection with an external laser on the spectral response of a semiconductor optical amplifier can probe intrinsic properties of a working device. The data demonstrate that under saturated gain conditions the carrier energy distribution within the active layer of a AlGaAs/GaAs amplifier neither shows spectral hole burning nor carrier heating, but only a decreased density. © 1998 American Institute of Physics.
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42.50.Nn Quantum optical phenomena in absorbing, amplifying, dispersive and conducting media; cooperative phenomena in quantum optical systems
42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission
78.66.Fd III-V semiconductors

Electrostrictive behavior observed in a low glass-transition temperature photorefractive polymeric composite during a two-beam coupling experiment

Feng Wang, Zhijian Chen, Shufeng Wang, Zhiwen Huang, Qihuang Gong, Zhijie Zhang, Yiwang Chen, and Huiying Chen

Appl. Phys. Lett. 72, 2939 (1998); http://dx.doi.org/10.1063/1.121500 (3 pages)

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A movement of refractive index grating was observed in two-beam coupling behavior with a low glass-transition temperature photorefractive polymeric film as the poling electric field was discharged. The photorefractive polymeric composite is poly(N-vinylcarbazole) doped with 2,5-dimethyl-4-(p-nitrophenylazo)anisole, N-ethylcarbazole and 2,4,7-trinitro-9-fluorenone in a weight ratio of 25:40:34:1. A theoretical explanation based on electrostrictive effect was given, and some evidential experiments, including degenerate four-wave mixing and Michelson interference measurement were also presented. © 1998 American Institute of Physics.
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77.65.Bn Piezoelectric and electrostrictive constants
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.22.Ej Polarization and depolarization
77.84.Jd Polymers; organic compounds
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.20.-e Optical properties of bulk materials and thin films

Second-harmonic generation at λ = 1.6 μm in AlGaAs/Al2O3 waveguides using birefringence phase matching

A. Fiore, S. Janz, L. Delobel, P. van der Meer, P. Bravetti, V. Berger, E. Rosencher, and J. Nagle

Appl. Phys. Lett. 72, 2942 (1998); http://dx.doi.org/10.1063/1.121501 (3 pages) | Cited 37 times

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We demonstrate phase-matched second-harmonic generation from a λ = 1.6 μm pump in a GaAs-based waveguide. Phase matching is obtained by using the form birefringence in an AlGaAs/Al2O3 multilayer obtained by selective wet oxidation. © 1998 American Institute of Physics.
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42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.25.Lc Birefringence
42.81.Gs Birefringence, polarization
78.20.Fm Birefringence

Single-mode optical waveguide fabricated by oxidization of selectively doped titanium porous silicon

Seiichi Nagata, Chiaki Domoto, Takehiro Nishimura, and Kazuaki Iwameji

Appl. Phys. Lett. 72, 2945 (1998); http://dx.doi.org/10.1063/1.121502 (3 pages) | Cited 12 times

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Metal-organic compound molecules were selectively doped into the larger pores of a two-layered porous silicon (PS) which had different pore sizes. PS with a graded pore-size distribution was area-selectively formed by utilizing a thin film mask. Titanium-organic compound molecules were doped into the larger pores and the PS was oxidized to form an optical waveguide. Single-mode transmission of 1.55 μm wavelength laser light was successfully observed. © 1998 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.86.+b Optical workshop techniques
81.65.Mq Oxidation
61.72.uf Ge and Si
81.05.Cy Elemental semiconductors

Homogeneous photorefractive polymer/nematogen composite

J. Zhang and K. D. Singer

Appl. Phys. Lett. 72, 2948 (1998); http://dx.doi.org/10.1063/1.121503 (3 pages) | Cited 16 times

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A photorefractive composite consisting of the polymer poly(N-vinylcarbazole) (PVK) doped with 4,4′-n-pentylcyanobiphenyl (5CB) and C60 is reported. The material shows no sign of phase separation, is stable, and does not require a plasticizer agent. Gain coefficients over 100 cm−1 are observed. Measurements of orientational and electro-optic responses indicate that the orientational response is large, but markedly inhibited. © 1998 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Gi Light-sensitive materials
42.70.Jk Polymers and organics
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
81.05.Qk Reinforced polymers and polymer-based composites
61.30.-v Liquid crystals
78.20.Jq Electro-optical effects
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Optically induced rotation of a trapped micro-object about an axis perpendicular to the laser beam axis

E. Higurashi, R. Sawada, and T. Ito

Appl. Phys. Lett. 72, 2951 (1998); http://dx.doi.org/10.1063/1.121504 (3 pages) | Cited 22 times

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A strongly focused Nd:YAG laser beam has been used experimentally to achieve optical trapping and simultaneous rotation of a micro-object about an axis perpendicular to the trapping laser beam axis. The micro-object (12 μm in diameter), which has shape anisotropy in its interior, can be produced by oxygen reactive ion etching of a fluorinated polyimide film (refractive index n = 1.53). This optically induced rotation of the micro-object in ethanol (n = 1.36) is accomplished by utilizing the net radiation pressure force arising from the momentum change of light scattered at the micro-object’s inner walls. © 1998 American Institute of Physics.
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37.10.Mn Slowing and cooling of molecules
37.10.Pq Trapping of molecules
78.20.Ek Optical activity
33.55.+b Optical activity and dichroism
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Single molecule detection and underwater fluorescence imaging with cantilevered near-field fiber optic probes

Chad E. Talley, M. Annie Lee, and Robert C. Dunn

Appl. Phys. Lett. 72, 2954 (1998); http://dx.doi.org/10.1063/1.121505 (3 pages) | Cited 14 times

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Tapping-mode near-field scanning optical microscopy (NSOM) employing a cantilevered fiber optic probe is utilized to image the fluorescence from single molecules and samples in aqueous environments. The single molecule fluorescence images demonstrate both the subdiffraction limit spatial resolution and low detection limit capabilities of the cantilevered probe design. Images taken as a function of tip oscillation drive amplitude reveal a degradation in the resolution as the amplitude is increased. With all cantilevered probes studied, however, a minimum plateau region in the resolution is reached as the drive amplitude is decreased, indicating that the tapping mode of operation does not reduce the optical resolution. Images of fluorescently doped lipid films illustrate the ability of the probe to track small height changes (<1.5 nm) in ambient and aqueous environments, while maintaining high resolution in the fluorescence image. When the tip is immersed in water (1.3 mm), the cantilevered NSOM tip resonance, 25–50 kHz, shifts approximately 100–150 Hz, the amplitude dampens less than 40% and the Q factor is reduced from 300–500 to 100–200. © 1998 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
78.55.Kz Solid organic materials
78.66.Qn Polymers; organic compounds
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A sensitive detection method for capacitive ultrasonic transducers

A. S. Ergun, A. Atalar, B. Temelkuran, and E. Özbay

Appl. Phys. Lett. 72, 2957 (1998); http://dx.doi.org/10.1063/1.121506 (3 pages) | Cited 5 times

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We report a sensitive detection method for capacitive ultrasonic transducers. Detection experiments at 1.6 MHz reveal a minimum detectable displacement around 2.5×10−4 Å/math. The devices are fabricated on silicon using surface micromachining techniques. We made use of microwave circuit considerations to obtain a good displacement sensitivity. Our method also eliminates the dependence of the sensitivity on the ultrasound frequency, allowing the method to be used at low audio frequency and static displacement sensing applications. © 1998 American Institute of Physics.
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43.38.Ar Transducing principles, materials, and structures: general
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Laser-induced breakdown spectroscopy for sizing and elemental analysis of discrete aerosol particles

D. W. Hahn

Appl. Phys. Lett. 72, 2960 (1998); http://dx.doi.org/10.1063/1.121507 (3 pages) | Cited 21 times

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The laser-induced breakdown spectroscopy technique has been extended to provide quantitative analysis of the mass and elemental composition of individual, submicrometer to micrometer-sized aerosol particles. A two-part approach was used for calibration of the overall mass concentration response, and of the characteristic plasma volume, equal to 2.5×10−4 cm3. Laboratory results are presented for submicrometer-sized particles containing a known concentration of magnetite. Additional data are presented for fine particulate matter measured in ambient air, including magnesium-containing particles with an average size of 313 nm. © 1998 American Institute of Physics.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
07.88.+y Instruments for environmental pollution measurements
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
42.62.Fi Laser spectroscopy
52.80.-s Electric discharges
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Domain structure of epitaxial SrRuO3 thin films on miscut (001) SrTiO3 substrates

J. C. Jiang, W. Tian, X. Q. Pan, Q. Gan, and C. B. Eom

Appl. Phys. Lett. 72, 2963 (1998); http://dx.doi.org/10.1063/1.121508 (3 pages) | Cited 46 times

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The microstructure of epitaxial SrRuO3 thin films grown on vicinal (001) SrTiO3 substrates with miscut angle of 1.9° and miscut direction of 12° away from [100] direction was studied using transmission electron microscopy (TEM). Cross-section as well as plan-view TEM studies revealed that these films are single domain with the in-plane epitaxial orientation relationship of SrRuO3[001]//SrTiO3[010] and SrRuO3[math10]//SrTiO3[100]. This result is in contrast to the previous studies of the SrRuO3 thin films grown on exactly (001) SrTiO3, which are composed of two types of [110] domains with nearly the same volume fraction. The occurrence of these different domain structures is attributed to the step-flow growth of the film on the substrate surface due to the miscut. © 1998 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.80.Dj Domain structure; hysteresis
77.55.-g Dielectric thin films
61.72.-y Defects and impurities in crystals; microstructure
68.55.-a Thin film structure and morphology

Observation of small interfacial strains in YBa2Cu3Ox sub-micron-thick films grown on SrTiO3 substrates

W. J. Lin, P. D. Hatton, F. Baudenbacher, and J. Santiso

Appl. Phys. Lett. 72, 2966 (1998); http://dx.doi.org/10.1063/1.121509 (3 pages) | Cited 7 times

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We have observed x-ray intensity oscillation fringes around low index Bragg reflections in a YBa2Cu3Ox (YBCO) thin film. By employing a combination of crystal truncation rod interference fringe measurements and x-ray reflectivity using synchrotron radiation, we have been able to probe the structures of highly oriented [001] YBCO grown on [001] SrTiO3 substrates. The results demonstrate the presence of a thin disordered surface layer, the excellent coherence between the YBCO surface and the film-substrate interface, the presence of a small (3.2×10−4) interfacial strain existing in the YBCO film. This strain exists close to the film-substrate interface and extends approximately 300 Å into the micron-thick film. Our results demonstrate that high quality detailed information can be obtained, nondestructively, from thin film superconductors of thicknesses typically used for microwave and other applications. © 1998 American Institute of Physics.
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74.72.-h Cuprate superconductors
61.05.cm X-ray reflectometry (surfaces, interfaces, films)
68.60.Bs Mechanical and acoustical properties
74.78.-w Superconducting films and low-dimensional structures
68.35.Ct Interface structure and roughness
81.70.Ex Nondestructive testing: electromagnetic testing, eddy-current testing

Kinetics of lossy grazing impact oscillators

Jeffery P. Hunt and Dror Sarid

Appl. Phys. Lett. 72, 2969 (1998); http://dx.doi.org/10.1063/1.121510 (3 pages) | Cited 21 times

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The equation of motion of a grazing impact oscillator is generalized to include compliant boundaries and impact energy dissipation, yielding the phase diagram, indentation and force. Good agreement with experimental results using tapping-mode atomic force microscopy is demonstrated. The relationship between phase and set-point amplitude is discussed in terms of the dissipation, showing that for a parameter space for which the system is highly nonlinear a chaotic response is possible. © 1998 American Institute of Physics.
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07.79.Lh Atomic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
46.55.+d Tribology and mechanical contacts

Determination of the cubic to hexagonal fraction in GaN nucleation layers using grazing incidence x-ray scattering

A. Munkholm, C. Thompson, C. M. Foster, J. A. Eastman, O. Auciello, G. B. Stephenson, P. Fini, S. P. DenBaars, and J. S. Speck

Appl. Phys. Lett. 72, 2972 (1998); http://dx.doi.org/10.1063/1.121511 (3 pages) | Cited 23 times

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Recent electron diffraction and microscopy studies of GaN nucleation layers have shown that faults in the stacking of the close-packed planes result in the coexistence of cubic and hexagonal phases within the layers. Using grazing incidence x-ray scattering, we have quantified the proportion of the cubic and hexagonal phases throughout the nucleation layer. We compare the structure of a 20 nm nucleation layer grown on sapphire by atmospheric pressure metal-organic chemical vapor deposition at 525 °C to that of an identical layer heated to 1060 °C. The fractions of cubic and hexagonal phases in the layers are determined by a comparison of the scattering data with a Hendricks–Teller model. High temperature exposure results in a decrease of the cubic fraction from 0.56 to 0.17. The good agreement with the Hendricks–Teller model indicates that the positions of the stacking faults are uncorrelated. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.70.Ck X-ray scattering
61.72.Nn Stacking faults and other planar or extended defects

Disorder effects in epitaxial thin films of (La,Ca)MnO3

J. Aarts, S. Freisem, R. Hendrikx, and H. W. Zandbergen

Appl. Phys. Lett. 72, 2975 (1998); http://dx.doi.org/10.1063/1.121512 (3 pages) | Cited 60 times

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We have investigated as-grown sputtered films of La0.7Ca0.3MnO3 in a thickness range between 5 and 200 nm on SrTiO3 substrates. The films are epitaxial, strained, and smooth. All films order magnetically around 175 K. Very thin films show full magnetization at low temperatures, but the temperature of the metal–insulator transition is appreciably lower than the magnetic ordering temperature. In thick films, the magnetization is much lower than expected. Both effects are probably related to structural disorder as found by transmission electron microscopy. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
72.60.+g Mixed conductivity and conductivity transitions
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
71.30.+h Metal-insulator transitions and other electronic transitions
75.47.De Giant magnetoresistance

Experimental evidence of photoinduced expansion in hydrogenated amorphous silicon using bending detected optical lever method

T. Gotoh, S. Nonomura, M. Nishio, S. Nitta, M. Kondo, and A. Matsuda

Appl. Phys. Lett. 72, 2978 (1998); http://dx.doi.org/10.1063/1.121513 (3 pages) | Cited 25 times

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Photoinduced structural change in hydrogenated amorphous silicon (a-Si:H) has been studied by a sensitive bending detection method using an optical lever. We observed that a-Si:H films show not only thermal expansion due to a photothermal effect but also residual and persistent expansion after light soaking. The volume change is recovered by thermal annealing at 200 °C. A dehydrogenated sample annealed at 550 °C and a microcrystalline sample, in which photoinduced defects are not created, show little photoinduced expansion. The photoinduced expansion and photoinduced defect density show identical time evolution. These results suggest that the photoinduced expansion is related to the photoinduced defect creation. A quantitative evaluation of the photoinduced expansion indicates that the photoinduced structural change is spread over several molecular volumes around a photocreated defect. © 1998 American Institute of Physics.
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81.05.Gc Amorphous semiconductors
81.05.Cy Elemental semiconductors
65.40.De Thermal expansion; thermomechanical effects
68.60.Bs Mechanical and acoustical properties
61.43.Dq Amorphous semiconductors, metals, and alloys
73.61.Jc Amorphous semiconductors; glasses
73.61.Cw Elemental semiconductors
68.55.-a Thin film structure and morphology
72.40.+w Photoconduction and photovoltaic effects
61.72.Cc Kinetics of defect formation and annealing

Electromechanical behavior of BaTiO3 from first principles

Alberto García and David Vanderbilt

Appl. Phys. Lett. 72, 2981 (1998); http://dx.doi.org/10.1063/1.121514 (3 pages) | Cited 8 times

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Using an effective Hamiltonian parametrized from first principles, Monte Carlo simulations are performed in order to study the piezoelectric response of BaTiO3 in the ferroelectric tetragonal phase as a function of temperature. The effect of an electric field on the phase behavior is also illustrated by a simulation of the transformation of a rhombohedral domain into a tetragonal one under a strong field. © 1998 American Institute of Physics.
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77.65.Bn Piezoelectric and electrostrictive constants
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Elastic energy of strained islands: Contribution of the substrate as a function of the island aspect ratio and inter-island distance

A. Ponchet, D. Lacombe, L. Durand, D. Alquier, and J.-M. Cardonna

Appl. Phys. Lett. 72, 2984 (1998); http://dx.doi.org/10.1063/1.121515 (3 pages) | Cited 15 times

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The finite element method is applied to strain-induced islands. The distribution of the elastic energy in the island and the substrate is determined as a function of the island aspect ratio and inter-island distance. When the height-over-base ratio increases, the total elastic energy density decreases and the relative contribution of the substrate increases. When the inter-island distance decreases, the elastic energy density increases and the relative contribution of the substrate decreases. The influence of the aspect ratio on the relaxation rate is amplified for short inter-island distances. © 1998 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.35.Md Surface thermodynamics, surface energies
68.35.Gy Mechanical properties; surface strains
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
02.70.Dh Finite-element and Galerkin methods
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Time-resolved imaging of gas phase nanoparticle synthesis by laser ablation

David B. Geohegan, Alex A. Puretzky, Gerd Duscher, and Stephen J. Pennycook

Appl. Phys. Lett. 72, 2987 (1998); http://dx.doi.org/10.1063/1.121516 (3 pages) | Cited 123 times

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The dynamics of nanoparticle formation, transport, and deposition by pulsed laser ablation of c-Si into 1–10 Torr He and Ar gases are revealed by imaging laser-induced photoluminescence and Rayleigh-scattered light from gas-suspended 1–10 nm SiOx particles. Two sets of dynamic phenomena are presented for times up to 15 s after KrF-laser ablation. Ablation of Si into heavier Ar results in a uniform, stationary plume of nanoparticles, while Si ablation into lighter He results in a turbulent ring of particles which propagates forward at 10 m/s. Nanoparticles unambiguously formed in the gas phase were collected on transmission electron microscope grids for Z-contrast imaging and electron energy loss spectroscopy analysis. The effects of gas flow on nanoparticle formation, photoluminescence, and collection are described. © 1998 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.-w Structure of nanoscale materials
81.15.Fg Pulsed laser ablation deposition
78.47.-p Spectroscopy of solid state dynamics
78.55.Hx Other solid inorganic materials
78.35.+c Brillouin and Rayleigh scattering; other light scattering
79.20.Kz Other electron-impact emission phenomena

Optical characterization of lateral epitaxial overgrown GaN layers

Jaime A. Freitas, Ok-Hyun Nam, Robert F. Davis, Gennady V. Saparin, and Sergey K. Obyden

Appl. Phys. Lett. 72, 2990 (1998); http://dx.doi.org/10.1063/1.121517 (3 pages) | Cited 24 times

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The optical properties of homoepitaxial GaN layers deposited by organometallic vapor phase epitaxy on stripe-patterned GaN films on 6H-SiC substrates have been investigated. Analysis of the spatially-resolved Raman scattering spectra indicate an improvement in material quality of the overgrown region. Room-temperature color cathodoluminescence imaging and low-temperature photoluminescence measurements indicate that a donor and an acceptor, different from those detected in the underlying GaN/AlN/SiC substrate, have been incorporated in the epitaxial layer. Detailed photoluminescence studies of the near-band-edge emission strongly suggest that Si is the additional donor detected in the homoepitaxial GaN layer. Its occurrence, along with that of an acceptor-related defect which is primarily found in the laterally overgrown region, is discussed. © 1998 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Optical depth profiling of band gap engineered interfaces in amorphous silicon solar cells at monolayer resolution

H. Fujiwara, Joohyun Koh, C. R. Wronski, R. W. Collins, and J. S. Burnham

Appl. Phys. Lett. 72, 2993 (1998); http://dx.doi.org/10.1063/1.121518 (3 pages) | Cited 6 times

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Real time spectroellipsometry and a two-layer optical analysis have been applied to obtain alloy composition (x) and optical gap (Eg) depth profiles with ∼3 Å resolution and sensitivities better than ±0.01 in x and ±0.02 eV in Eg for graded amorphous semiconductor alloy thin films prepared by plasma-enhanced chemical vapor deposition. Graded amorphous silicon–carbon alloy (a-Si1−xCx:H) layers incorporated at the i–p interfaces of a-Si:H n-i-p solar cells have been studied using these methods, and the layer characteristics have been related to improvements in solar cell performance. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.43.Dq Amorphous semiconductors, metals, and alloys
78.66.Jg Amorphous semiconductors; glasses
84.60.Jt Photoelectric conversion
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Low-temperature Si epitaxy with high deposition rate using ion-assisted deposition

R. B. Bergmann, C. Zaczek, N. Jensen, S. Oelting, and J. H. Werner

Appl. Phys. Lett. 72, 2996 (1998); http://dx.doi.org/10.1063/1.121519 (3 pages) | Cited 16 times

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Ion-assisted deposition is suitable for the formation of epitaxial Si films at high deposition rate and low substrate temperature. We demonstrate epitaxial deposition of Si films on (100)-oriented Si wafers using deposition rates up to 0.3 μm/min at deposition temperatures in the range of 500–650 °C. Hall-effect measurements show a majority carrier mobility of 200 cm2/V s at a hole concentration of 1.4×1017 cm−3 in our films. A minority carrier diffusion length of 4.5 μm is determined from quantum efficiency measurements in the epitaxially grown Si films. © 1998 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.15.Jj Ion and electron beam-assisted deposition; ion plating
73.61.Cw Elemental semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Incorporation of oxygen and nitrogen in ultrathin films of SiO2 annealed in NO

I. J. R. Baumvol, J.-J. Ganem, L. G. Gosset, I. Trimaille, and S. Rigo

Appl. Phys. Lett. 72, 2999 (1998); http://dx.doi.org/10.1063/1.121520 (3 pages) | Cited 18 times

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The areal densities of oxygen and nitrogen incorporated into ultrathin films of silicon dioxide during rapid thermal processing in nitric oxide, as well as the regions where these incorporations took place, were determined by combining nuclear reaction analysis and narrow nuclear resonance depth profiling with isotopic enrichment of the processing gas. Oxygen is seen to incorporate in the near-surface and near-interface regions of the oxynitride films, whereas nitrogen is incorporated only in the near-interface regions. The growth of the oxynitride film is very moderate as compared to that of a SiO2 film in dry O2. The thermal oxynitridation of ultrathin SiO2 films takes place by two mechanisms in parallel: the major part of the NO molecules, which react with the silica, decompose in the near-surface region, the O atoms being exchanged for O atoms preexistent in this region of the SiO2 films; a minor portion of the NO molecules diffuse through the silica film in interstitial sites, without reacting with it, to react at the oxynitride/Si interface. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
68.35.Ct Interface structure and roughness
61.72.J- Point defects and defect clusters
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