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27 Nov 2000

Volume 77, Issue 22, pp. 3487-3665

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Time-to-space conversion of Tbits/s optical pulses using a self-organized quantum-well material

Junko Ishi, Hideyuki Kunugita, Kazuhiro Ema, Takuma Ban, and Takashi Kondo

Appl. Phys. Lett. 77, 3487 (2000); http://dx.doi.org/10.1063/1.1328365 (3 pages) | Cited 11 times

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We report a time-to-space conversion technique using a material which has a large χ(3)( ≃ 10−6 esu) and a fast response time (<7 ps) at room temperature. The material is a self-organized quantum-well system consisting of inorganic well layers and organic barrier layers. We achieve a high conversion sensitivity even for nJ-order optical pulses. We demonstrate serial-to-parallel conversion of nJ-order Tbits/s signals at room temperature with conversion rates of 140 GHz. © 2000 American Institute of Physics.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.65.An Optical susceptibility, hyperpolarizability

Three-dimensionally periodic dielectric layered structure with omnidirectional photonic band gap

Steven G. Johnson and J. D. Joannopoulos

Appl. Phys. Lett. 77, 3490 (2000); http://dx.doi.org/10.1063/1.1328369 (3 pages) | Cited 69 times

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A three-dimensionally periodic dielectric structure with a large complete photonic band gap (PBG) is presented. The structure is distinguished by a sequence of planar layers, identical except for a horizontal offset, and repeating every three layers to form an fcc lattice. The layers can be thought of as an alternating stack of the two basic two-dimensional (2D) PBG slab geometries: rods in air and air cylinders in dielectric. These high-symmetry planar cross-sections should simplify the integration of optical devices and components by allowing modification of only a single layer, using simple defects of the same form as in the corresponding 2D systems. A process for fabricating the structure with conventional planar microfabrication technology is described. Gaps of over 21% are obtained for Si/air substrates. Reasonable gaps, over 8%, can be achieved even for the moderate index ratio of 2.45 (Si/SiO2). © 2000 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.82.Cr Fabrication techniques; lithography, pattern transfer

Is noise a crucial factor in rate equation modeling of nonlinear dynamics in laser diodes?

C. G. Lim, S. Iezekiel, and C. M. Snowden

Appl. Phys. Lett. 77, 3493 (2000); http://dx.doi.org/10.1063/1.1328368 (3 pages) | Cited 2 times

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The effect of noise on the accuracy of single-mode rate equations in predicting laser diode (LD) behavior is evaluated. Inclusion of noise increases the relaxation oscillation damping. Nonlinear dynamics analysis reveals that noise has disguised an important factor that governs the agreement between calculated and measured results. Instead, simulations show that the LD active layer temperature has a major impact on the accuracy of modeling LD behavior. © 2000 American Institute of Physics.
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42.60.Mi Dynamical laser instabilities; noisy laser behavior
42.55.Px Semiconductor lasers; laser diodes
85.30.De Semiconductor-device characterization, design, and modeling
05.45.-a Nonlinear dynamics and chaos

Terahertz near-field microscopy based on a collection mode detector

O. Mitrofanov, I. Brener, R. Harel, J. D. Wynn, L. N. Pfeiffer, K. W. West, and J. Federici

Appl. Phys. Lett. 77, 3496 (2000); http://dx.doi.org/10.1063/1.1328772 (3 pages) | Cited 33 times

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We report on the development of a collection mode near-field probe for the terahertz spectral range. The near-field detector is based on an aperture type probe with dimensions of 30×30 μm2. The collection mode technique provides higher sensitivity and higher resolution than the similar illumination mode approach. Spatial resolution better than 40 μm is demonstrated for a broad spectrum of 300–600 μm, which equals to λ/15 for the longest wavelength. The observed resolution is determined by the size of the probe aperture. © 2000 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.79.Pw Imaging detectors and sensors
07.05.Pj Image processing

Visible photoluminescence in amorphous SiNx thin films prepared by reactive evaporation

M. Molinari, H. Rinnert, and M. Vergnat

Appl. Phys. Lett. 77, 3499 (2000); http://dx.doi.org/10.1063/1.1329163 (3 pages) | Cited 22 times

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Photoluminescence in the visible domain can be observed in amorphous silicon nitride (a-SiNx) alloys prepared by evaporation of silicon under a flow of nitrogen ions. A strong improvement of the photoluminescence intensity was obtained with annealing treatments in the range 500–1150 °C. Structural investigations were performed by infrared and Raman spectrometry experiments. The optical gap was obtained from transmission measurements in the ultraviolet, visible, and near infrared range. The evolutions of the structure and the optical properties with annealing treatments are correlated to the evolution of the photoluminescence. © 2000 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.66.Jg Amorphous semiconductors; glasses
81.05.Gc Amorphous semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
81.40.Tv Optical and dielectric properties related to treatment conditions
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.40.Pg Disordered solids

Low optical loss planar waveguides prepared in an organic–inorganic hybrid system

S. J. L. Ribeiro, Y. Messaddeq, R. R. Gonçalves, M. Ferrari, M. Montagna, and M. A. Aegerter

Appl. Phys. Lett. 77, 3502 (2000); http://dx.doi.org/10.1063/1.1329159 (3 pages) | Cited 34 times

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HfO2-(3-glycidoxipropil)trimethoxisilane (GPTS) planar waveguides were prepared by a sol–gel route. A stable sol of Hafnia nanocrystals was prepared and characterized by photon correlation spectroscopy and high resolution transmission electron microscopy. The suspension was incorporated in GPTS host and the resulting sol was deposited on borosilicate substrates by the spin coating technique. Optical properties such as refractive index, thickness, number of propagating modes, and attenuation coefficient were measured at 632.8, 543.5, and 1550 nm by the prism coupling technique as a function of the HfO2 content. © 2000 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
81.05.Pj Glass-based composites, vitroceramics
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
42.79.Wc Optical coatings
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Laser with guided pump and free-propagating resonator mode using diffusion-bonded rectangular channel waveguides

U. Griebner, R. Grunwald, H. Schönnagel, J. Huschke, and G. Erbert

Appl. Phys. Lett. 77, 3505 (2000); http://dx.doi.org/10.1063/1.1329331 (3 pages) | Cited 4 times

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We report the laser performance of a short diffusion-bonded diode-pumped Yb:YAG rectangular channel waveguide of 100 μm cross section. Using an end-pumped configuration guiding only the slow axis, a high overlap of the pump mode and the nonguided resonator mode is achieved. With 4 W of pump power from two 60 μm high-power broad-stripe diodes, 0.7 W of output power with nearly diffraction-limited performance is obtained. © 2000 American Institute of Physics.
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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.Fc Modulation, tuning, and mode locking

Nonvolatile two-color holography in indium-doped lithium niobate

Guoquan Zhang, Yasuo Tomita, Wusheng Xu, and Chunhui Yang

Appl. Phys. Lett. 77, 3508 (2000); http://dx.doi.org/10.1063/1.1329166 (3 pages) | Cited 7 times

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We demonstrate nonvolatile two-color holography in an as-grown congruent LiNbO3:In crystal of 2.2 mm thickness. We show that the nonvolatile two-color holographic performance of the crystal is significantly improved as compared with that of other congruent LiNbO3 crystals reported so far. The figure of merit M/# and the two-color recording sensitivity S are measured to be ∼ 0.04 and ∼ 3.5×10−4 cm/J, respectively, with a writing intensity of 4 W/cm2 at 780 nm and a gating intensity of 1.15 W/cm2 at 488 nm. These values are comparable to those of unreduced near-stoichiometric LiNbO3 crystals under similar recording conditions. © 2000 American Institute of Physics.
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42.70.Ln Holographic recording materials; optical storage media
42.40.Ht Hologram recording and readout methods
42.79.Vb Optical storage systems, optical disks

Influence of output waveguide on mode quality factor in semiconductor microlasers with an equilateral triangle resonator

Yong-Zhen Huang, Wei-Hua Guo, and Qi-Ming Wang

Appl. Phys. Lett. 77, 3511 (2000); http://dx.doi.org/10.1063/1.1329861 (3 pages) | Cited 17 times

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Semiconductor microlasers with an equilateral triangle resonator (ETR) and an output waveguide are proposed and analyzed by the finite-difference time-domain technique and the Padé approximation. The numerical results show that microlasers with an output waveguide still have a high-quality factor (Q factor) and are suitable to realize directional emission. For the ETR with a 0.46-μm-width opening in one of the vertices connected to the output waveguide, we have the Q factor of 1.5×103 and 2.5×102 for the TM fundamental mode at the wavelength of 1.55 μm, as the side length of the ETR is 5 and 3 μm. The simulated intensity distributions are presented for the fundamental mode in the ETR with a side length of 3 μm and an opening of 0.23 μm. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.55.Sa Microcavity and microdisk lasers
42.79.Gn Optical waveguides and couplers
02.70.Bf Finite-difference methods

Self-pulsations in vertical-cavity semiconductor lasers

M. B. Willemsen, A. S. van de Nes, M. P. van Exter, J. P. Woerdman, M. Brunner, and R. Hövel

Appl. Phys. Lett. 77, 3514 (2000); http://dx.doi.org/10.1063/1.1330217 (3 pages) | Cited 4 times

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We report the observation of strong self-pulsations in oxide-confined vertical-cavity surface-emitting lasers. From optical spectra and intensity noise spectra, we deduce that the pulses are strongly chirped. © 2000 American Institute of Physics.
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42.60.Rn Relaxation oscillations and long pulse operation
42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Optical properties of a photonic crystal of hollow spherical shells

Rajesh Rengarajan, Peng Jiang, Vicki Colvin, and Daniel Mittleman

Appl. Phys. Lett. 77, 3517 (2000); http://dx.doi.org/10.1063/1.1320863 (3 pages) | Cited 33 times

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We report on optical transmission studies of three-dimensionally ordered photonic crystals of close-packed spherical shells. These samples are fabricated using a double-template method, which allows for extensive control over shell thickness. The transmission spectra exhibit an optical stop band, whose spectral position and width depend on the thickness of the shell and on the overlap between adjacent spheres, in a manner consistent with numerical simulations. These parameters can be controlled over a wide range, thus permitting systematic studies of the optical properties, and providing a valuable method for engineering the characteristics of the optical stop band in colloidal photonic media. © 2000 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
78.40.-q Absorption and reflection spectra: visible and ultraviolet

Alternating current thin-film electroluminescence of GaN:Er

J. Heikenfeld and A. J. Steckl

Appl. Phys. Lett. 77, 3520 (2000); http://dx.doi.org/10.1063/1.1330564 (3 pages) | Cited 7 times

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Thin-film electroluminescence has been obtained from GaN:Er deposited directly on amorphous dielectric layers. Electroluminescent device (ELD) structures consisting of metal/dielectric/GaN:Er/dielectric were fabricated on p+-Si substrates. In contrast to previous GaN:Er ELDs which used epitaxial growth conditions on crystalline substrates and were operated under direct current bias, these ELDs were operated under alternating current bias. Under bias conditions of 170 peak voltage (Vp) and frequencies of 10 and 100 kHz, the ELDs exhibit a luminance of 50 and 300 cd/m2, respectively. The emission spectra, which originate from Er3+ 4f–4f transitions, consist of dominant green emission at ∼537/558 nm accompanied by violet (415 nm) and infrared (1.5 μm) peaks. The violet emission peak indicates that hot carriers can gain up to ∼3 eV energy for a Vp corresponding to 1.5 MV/cm applied field. The emitted intensity initially increases linearly with frequency, followed by a trend towards saturation. The frequency for 3 dB reduction from the linear relation is at ∼65 kHz for the visible emission and ∼8 kHz for the infrared emission. © 2000 American Institute of Physics.
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78.60.Fi Electroluminescence
78.66.Fd III-V semiconductors
42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems
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Transition of electron heating mode in a planar microwave discharge at low pressures

H. Sugai, I. Ghanashev, and K. Mizuno

Appl. Phys. Lett. 77, 3523 (2000); http://dx.doi.org/10.1063/1.1329322 (3 pages) | Cited 22 times

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Spatial distributions of electron density ne, electron temperature Te, and wave field intensity in a planar microwave discharge at low pressures (10–100 mTorr) are measured with the discharge power as a parameter. Two different modes of electron heating are found: a bulk heating mode characterized with high Te( ∼ 10 eV) in underdense plasma, and a surface heating mode with low Te( ∼ 3 eV) in overdense plasma with a hot layer near the plasma-dielectric boundary. Abrupt transition between the two modes takes place near the cutoff density nc where the electron plasma frequency coincides with the discharge frequency (2.45 GHz). In the underdense case (ne<nc), the microwave penetrates the bulk plasma and heats the majority of electrons confined in the dc ambipolar potential well, leading to high Te. In the overdense case (ne>nc), the evanescent wave (surface wave) near the microwave window strongly heats the electrons in the boundary layer, which are transported to the bulk region and ionize the neutral particles to therein produce relatively cold electrons. © 2000 American Institute of Physics.
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52.50.Gj Plasma heating by particle beams
52.80.Pi High-frequency and RF discharges
52.25.-b Plasma properties

Nonlinear wave interaction in a magnetron plasma

Praburam Gopalraja and John Forster

Appl. Phys. Lett. 77, 3526 (2000); http://dx.doi.org/10.1063/1.1328367 (3 pages) | Cited 1 time

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Oscillations in the frequency range 10<f<300 MHz were measured using a Langmuir probe in a magnetron plasma. Dual probes were used to obtain wave number information. Three distinct peaks were observed that obeyed the nonlinear selection rule ω = ω0−ω1, where ω0 is the pump frequency, and ω and ω1 are the decay frequencies. The phase velocity of the highest frequency wave (f = 262 MHz) was consistent with beam plasma oscillations driven by secondary electrons from the target. The nonlinearly driven lower frequency wave had a phase velocity enabling efficient Landau damping. The resulting transfer of energy from the secondary electrons to the waves to the bulk electrons may explain the enhanced ionization of sputtered material observed in some high power density magnetron discharges. © 2000 American Institute of Physics.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.70.Ds Electric and magnetic measurements
52.40.Mj Particle beam interactions in plasmas
81.15.Cd Deposition by sputtering
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Characterization of strain in Si1−xGex films using multiple angle of incidence ellipsometry

Subroto Mukerjee and V. Venkataraman

Appl. Phys. Lett. 77, 3529 (2000); http://dx.doi.org/10.1063/1.1329165 (3 pages) | Cited 1 time

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In this letter we characterize strain in Si1−xGex based heterojunction bipolar transistors and modulation doped field effect transistors grown by rapid thermal chemical vapor deposition exploiting the phenomenon of strain-induced birefringence. The technique used is multiple angle of incidence ellipsometry at a wavelength of 670 nm to measure the ordinary and extraordinary refractive indices of the Si1−xGex films. We report measurements on thin fully strained films (with thicknesses less than the critical thickness) with Ge concentration varying from 9% to 40% with an accuracy of the order of 1 part in 104 and propose an empirical relation between the difference in the ordinary and extraordinary refractive indices (δn) and the Ge concentration (x) given by δn(x) = 0.18x−0.12x2. © 2000 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
78.66.Li Other semiconductors
07.60.Fs Polarimeters and ellipsometers
78.20.Fm Birefringence
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
85.30.Pq Bipolar transistors
85.30.Tv Field effect devices

Dislocation density in GaN determined by photoelectrochemical and hot-wet etching

P. Visconti, K. M. Jones, M. A. Reshchikov, R. Cingolani, H. Morkoç, and R. J. Molnar

Appl. Phys. Lett. 77, 3532 (2000); http://dx.doi.org/10.1063/1.1329330 (3 pages) | Cited 62 times

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Defects in GaN layers grown by hydride vapor-phase epitaxy have been investigated by photoelectrochemical (PEC) etching, and by wet etching in hot H3PO4 acid and molten potassium hydroxide (KOH). Threading vertical wires (i.e., whiskers) and hexagonal-shaped etch pits are formed on the etched sample surfaces by PEC and wet etching, respectively. Using atomic-force microscopy, we find the density of “whisker-like” features to be 2×109 cm−2, the same value found for the etch-pit density on samples etched with both H3PO4 and molten KOH. This value is comparable to the dislocation density obtained in similar samples with tunneling electron microscopy, and is also consistent with the results of Youtsey and co-workers [Appl. Phys. Lett. 73, 797 (1998); 74, 3537 (1999)]. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)

Optical losses in porous silicon waveguides in the near-infrared: Effects of scattering

P. Ferrand and R. Romestain

Appl. Phys. Lett. 77, 3535 (2000); http://dx.doi.org/10.1063/1.1329161 (3 pages) | Cited 23 times

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Benefitting from the long path inside planar waveguides, we have investigated the optical losses of porous silicon, in the continuous 0.8–1.6 μm (0.77–1.55 eV) range. The obtained values, typically a few cm−1, are 1 order of magnitude larger than “pure” absorption losses measured previously. The other main sources of loss, including scattering on both interface roughness and nanocrystallites, are invoked. Calculations give the same order of magnitude as measurements. We also detected scattered light close to the direct beam. © 2000 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
81.05.Cy Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
81.05.Rm Porous materials; granular materials
68.35.Ct Interface structure and roughness
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization

Stable nonplanar surface formed on patterned GaAs (311)A substrate by molecular-beam epitaxy

Q. Gong, R. Nötzel, H.-P. Schönherr, and K. H. Ploog

Appl. Phys. Lett. 77, 3538 (2000); http://dx.doi.org/10.1063/1.1328372 (3 pages) | Cited 4 times

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The evolution of the growth front during molecular-beam epitaxy on patterned GaAs (311)A substrates is investigated by cross-sectional atomic force microscopy. The growth rate on the sidewalls is enhanced due to the preferential atom migration from the mesa top and bottom to the sidewalls. The growth front evolution is terminated by the formation of a stable, corrugated surface which is composed of (311)A terraces and steps toward the [2mathmath] and [math33] directions. Modulation of island density in strained-layer growth is demonstrated by growing 4 ML InAs on this nonplanar surface. © 2000 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors

Epitaxial growth of germanium dots on Si(001) surface covered by a very thin silicon oxide layer

A. Barski, M. Derivaz, J. L. Rouvière, and D. Buttard

Appl. Phys. Lett. 77, 3541 (2000); http://dx.doi.org/10.1063/1.1328771 (3 pages) | Cited 28 times

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We show that germanium dots can be directly grown by molecular beam epitaxy (MBE) on a silicon (001) surface covered by a thin (1.2-nm-thick) thermal silicon oxide layer. We describe the experimental procedure, which induces the growth of a high density (1011/cm2) of nanometric germanium dots on silicon oxide. Germanium dots grown by MBE exhibit an epitaxial relationship with the underlying silicon substrate. We show that despite the presence of the thin silicon oxide layer, the silicon grown to embed the germanium dots is also single crystal in epitaxy with the silicon substrate. Nanometric size high-density crystalline inclusions in silicon oxide, seen in high-resolution transmission electron microscopy observations, are tentatively proposed as nucleation seeds for germanium dots and silicon lateral overgrowth on silicon oxide. © 2000 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Nondestructive detection of stacking faults for optimization of CdSe/ZnSe quantum-dot structures

T. Passow, H. Heinke, J. Falta, K. Leonardi, and D. Hommel

Appl. Phys. Lett. 77, 3544 (2000); http://dx.doi.org/10.1063/1.1328760 (3 pages) | Cited 8 times

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CdSe/ZnSe quantum structures were systematically investigated by high-resolution x-ray diffraction. The samples were grown at different growth temperatures on GaAs(001) substrates by molecular-beam epitaxy. A model is presented enabling the simulation and quantitative analysis of x-ray diffraction profiles influenced by stacking faults. This yields a fast and nondestructive method for the determination of stacking fault densities after calibration by transmission electron microscopy. A steep increase of the stacking fault density above a critical thickness was found. The critical thickness decreases with increasing growth temperature. Above this critical thickness, the amount of incorporated CdSe remains apparently constant. © 2000 American Institute of Physics.
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61.72.Nn Stacking faults and other planar or extended defects
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Strain modification of epitaxial perovskite oxide thin films using structural transitions of ferroelectric BaTiO3 substrate

M. K. Lee, T. K. Nath, C. B. Eom, M. C. Smoak, and F. Tsui

Appl. Phys. Lett. 77, 3547 (2000); http://dx.doi.org/10.1063/1.1328762 (3 pages) | Cited 51 times

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Effects of induced biaxial strain on the electrical transport and magnetic properties of epitaxial thin films of SrRuO3 and La0.67Sr0.33MnO3 by structural transitions of ferroelectric BaTiO3 substrates have been studied. Large jumps of electrical resistivity (∼5% in SrRuO3 and ∼12% in La0.67Sr0.33MnO3) and low field magnetization (∼70% in La0.67Sr0.33MnO3) have been observed in the films at the structural transition temperatures of BaTiO3 substrate. The hysteretic jumps are reproducible through many thermal cycles, and they can be attributed to strain effects induced by the substrate. The use of phase transitions of ferroelectric substrates to manipulate lattice strain of epitaxial thin film heterostructures can be a useful way to modify the properties of perovskite oxides. © 2000 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.-a Thin film structure and morphology
73.61.Ng Insulators
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.80.-e Ferroelectricity and antiferroelectricity
61.50.Ks Crystallographic aspects of phase transformations; pressure effects
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Size effects on the luminescence spectrum in amorphous Si/SiO2 multilayer structures

Yoshihiko Kanemitsu and Takashi Kushida

Appl. Phys. Lett. 77, 3550 (2000); http://dx.doi.org/10.1063/1.1328376 (3 pages) | Cited 10 times

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We have studied size effects on the photoluminescence (PL) spectrum in amorphous silicon (a-Si)-based multilayer structures. At low temperatures, the PL spectrum and the PL lifetime are sensitive to the a-Si well thickness in a-Si/SiO2 multilayers. With a decrease of the a-Si well thickness, the PL peak energy and the mobility edge shift to higher energy. The temperature dependence of the PL spectrum shows that the size-dependent visible luminescence is ascribed to radiative recombination of carriers localized in the band-tail state, rather than the band-edge emission in quantum-confined states. The quantum confinement and localization of carriers in the band-tail states will be discussed. © 2000 American Institute of Physics.
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78.55.-m Photoluminescence, properties and materials
78.66.-w Optical properties of specific thin films
73.20.At Surface states, band structure, electron density of states

Crystallization in Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass under pressure

J. Z. Jiang, T. J. Zhou, H. Rasmussen, U. Kuhn, J. Eckert, and C. Lathe

Appl. Phys. Lett. 77, 3553 (2000); http://dx.doi.org/10.1063/1.1328375 (3 pages) | Cited 43 times

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The effect of pressure on the crystallization behavior of the bulk metallic glass-forming Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy with a wide supercooled liquid region has been investigated by in situ high-pressure and high-temperature x-ray powder diffraction measurements using synchrotron radiation. In the pressure range from 0 to 3 GPa, the crystallization temperature increases with pressure having a slope of 19 K/GPa, which can be explained by the suppression of atomic mobility. This observation is opposite to the results of W.H. Wang, D.W. He, D.Q. Zhao, and Y.S. Yao [Appl. Phys. Lett. 75, 2770 (1999)], reporting a decrease of the crystallization temperature under pressure in a pressure range of 0–6 GPa for the bulk glass Zr41Ti14Cu12.5Ni9Be22.5C1 alloy. Compressibility with a volume reduction of approximately 22% at room temperature does not induce crystallization in the Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk glass alloy. This indicates that the densification effect induced by pressure in the pressure range investigated plays a minor role in the crystallization behavior of this bulk glass alloy. The different crystallization behavior of the carbon-free and the carbon-containing glassy alloys has been critically assessed. © 2000 American Institute of Physics.
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61.43.Fs Glasses
81.05.Kf Glasses (including metallic glasses)
62.50.-p High-pressure effects in solids and liquids

Quantum-dot phonons in self-assembled InAs/GaAs quantum dots: Dependence on the coverage thickness

L. Artús, R. Cuscó, S. Hernández, A. Patanè, A. Polimeni, M. Henini, and L. Eaves

Appl. Phys. Lett. 77, 3556 (2000); http://dx.doi.org/10.1063/1.1329157 (3 pages) | Cited 17 times

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We study the phonons of self-assembled InAs/GaAs quantum dots for different coverage thicknesses L. The additional Raman feature detected between the GaAs transverse optical and the InAs longitudinal optical modes, which we assign to phonons of the dots, exhibits an upward frequency shift with L. This shift is attributed to compressive strain in the dots and, on the basis of its dependence on L, we show that these phonons arise from the quantum dots and not from the wetting layer. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.30.Fs III-V and II-VI semiconductors

Efficient infrared imaging upconversion via quantum coherence

Robert W. Boyd and Marlan O. Scully

Appl. Phys. Lett. 77, 3559 (2000); http://dx.doi.org/10.1063/1.1329160 (3 pages) | Cited 10 times

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We show that quantum coherence can be used to achieve marked improvement in the efficiency of the process of infrared upconversion. In one particular example which we analyze in detail, we show that it is possible to convert infrared radiation at a wavelength of 100 μm to the visible with essentially 100% efficiency while maintaining diffraction-limited imaging of the infrared field. © 2000 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Pw Imaging detectors and sensors
42.50.Ar Photon statistics and coherence theory
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