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12 Dec 1994

Volume 65, Issue 24, pp. 3039-3153

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Spectral modulation of luminescence of strained Si1−xGex/Si quantum wells in a vertical cavity with air/Si and Si/SiO2 interface mirrors

S. Fukatsu, D. K. Nayak, and Y. Shiraki

Appl. Phys. Lett. 65, 3039 (1994); http://dx.doi.org/10.1063/1.112497 (3 pages) | Cited 7 times

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Integration of strained Si1−xGex/Si quantum wells (QWs) in a vertical cavity is demonstrated on a Si substrate with a buried‐oxide using gas source Si molecular beam epitaxy. Spontaneous emission from the SiGe QW is found to be spectrally coupled to the longitudinal modes of a vertical cavity with buried oxide/Si and top Si/air interface mirrors, which is in excellent agreement with separate reflectance measurements. In addition, clear oscillations were observed in photoluminescence excitation spectra for photon energies even above the Si band gap, demonstrating cavity modulation of the incident light absorption. © 1994 American Institute of Physics.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.66.Li Other semiconductors
78.55.Hx Other solid inorganic materials

Experimental observation of transverse effects in microchip solid‐state lasers

S. Longhi, G. Cerullo, S. Taccheo, V. Magni, and P. Laporta

Appl. Phys. Lett. 65, 3042 (1994); http://dx.doi.org/10.1063/1.112498 (3 pages) | Cited 8 times

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We report on the observation of transverse effects in a microchip solid‐state laser due to gain‐guiding, demonstrating that the transverse modulation of the gain profile and detuning play a fundamental role in the control of the longitudinal lasing mode. The observed behavior is interpreted in the framework of the Maxwell–Bloch equations as a symmetry breaking between the two sides of the atomic resonance. © 1994 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.-v Laser optical systems: design and operation

Low jitter single‐mode pulse generation by a self‐seeded, gain‐switched Fabry–Pérot semiconductor laser

M. Schell, W. Utz, D. Huhse, J. Kässner, and D. Bimberg

Appl. Phys. Lett. 65, 3045 (1994); http://dx.doi.org/10.1063/1.112499 (3 pages) | Cited 29 times

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While the time jitter of gain‐switched multimode Fabry–Pérot lasers is relatively low, single‐mode distributed feedback (DFB) lasers suffer from an inherently larger time jitter, due to the different photon statistics. Here, we determine the time jitter of a mulitmode Fabry–Pérot (FP) laser (425 fs), a single‐mode DFB laser (2.2 ps), and the FP laser switched to single‐mode pulsing by self‐seeding (210 fs). Thus self‐seeding is superior by one order of magnitude to gain switching of DFB lasers, which is presently used for generation of single‐mode pulses in the low ps range. A numerical model based on multimode rate equations including Langevin terms for the spontaneous emission shows good agreement with the experimental results. © 1994 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Short cavity distributed Bragg reflection lasers with a narrow band Bragg mirror: Dynamic characteristics

N. Tessler, M. Margalit, G. Eisenstein, U. Koren, and C. A. Burrus

Appl. Phys. Lett. 65, 3048 (1994); http://dx.doi.org/10.1063/1.112990 (3 pages)

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The dynamical characteristics of distributed Bragg reflection lasers with a Bragg reflection bandwidth narrower than the cavity mode spacing are reported. The operation of this Bragg reflector as an amplitude modulator (unlike the usual frequency modulator) is demonstrated in the small and large signal modulation regimes. In the conventional mode of gain modulation, this narrow Bragg reflector exhibits detuned loading effects. The laser is capable of efficient digital modulation as well as Q‐switching, both with a very small drive current. © 1994 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Dynamics of a polymer shock optical microgauge studied by picosecond coherent Raman spectroscopy

David E. Hare, Jens Franken, Dana D. Dlott, Eric L. Chronister, and James J. Flores

Appl. Phys. Lett. 65, 3051 (1994); http://dx.doi.org/10.1063/1.112500 (3 pages) | Cited 13 times

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Picosecond coherent Raman scattering (ps CARS) is used to measure dynamic frequency shifts of a thin layer of polymer compressed by a laser driven shock wave. The shock response of this optical microgauge is calibrated by static measurements of frequency shift versus pressure and temperature. A peak shock pressure of 1.9 (±0.3) GPa is observed in a microgauge with a response time of about 2 ns. The use of ps CARS optical gauges to measure ultrafast shock‐induced chemical reactivity of energetic materials is discussed briefly. © 1994 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
82.40.Fp Shock wave initiated reactions, high-pressure chemistry

Optical transmission systems employing vertical cavity surface emitting lasers and monolithically integrated photoreceivers

D. T. Nichols, W. S. Hobson, D. Vakhshoori, J. D. Wynn, G. J. Zydzik, R. A. Morgan, N. K. Dutta, D. L. Sivco, A. Y. Cho, and R. E. Leibenguth

Appl. Phys. Lett. 65, 3054 (1994); http://dx.doi.org/10.1063/1.112501 (3 pages)

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We report on an optical fiber transmission system employing a vertical cavity surface emitting laser and an integrated p‐i‐n/metal–semiconductor field effect transistor (MESFET) photoreceiver. The surface emitting laser utilizes proton implantation for current confinement and has a small signal bandwidth of 10 GHz. The p‐i‐n/MESFET photoreceiver has a bandwidth of 4.5 GHz. A transmission experiment using the vertical cavity surface emitting lasers source and the p‐i‐n/MESFET photoreceiver was carried out and error‐free operation was demonstrated. © 1994 American Institute of Physics.  
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42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.82.Bq Design and performance testing of integrated-optical systems
42.81.Wg Other fiber-optical devices

Nearly transform limited pulses from a gain‐switched InGaAsP distributed‐feedback laser using polarization dispersion effect

B. Thedrez, H. Takeshita, and T. Kamiya

Appl. Phys. Lett. 65, 3057 (1994); http://dx.doi.org/10.1063/1.112505 (3 pages)

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Due to the large change of carrier density during the pulse emission, gain‐switched distributed feedback semiconductor lasers suffer from a large frequency chirp that can extend over several nanometers. As the chirp is generally nonlinear, it is difficult to achieve transform limited pulses after a linear compression stage. We demonstrate here that polarization dispersion can be used to filter the residual nonlinear chirp after linear compression. Pulses as short as 5.5 ps with a time bandwidth of 0.38 were obtained, a value less than half that observed without polarization dispersion filtering. © 1994 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers

Ho:YLiF4 saturable absorber Q‐switch for the 2‐μm Tm,Cr:Y3Al5O12 laser

Yen‐Kuang Kuo, Milton Birnbaum, and Wei Chen

Appl. Phys. Lett. 65, 3060 (1994); http://dx.doi.org/10.1063/1.112506 (3 pages) | Cited 13 times

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Passive Q‐switching of the flashlamp pumped Tm,Cr:Y3Al5O12 2‐μm laser with a Ho:YLiF4 saturable absorber has been demonstrated at room temperature. A single Q‐switched laser pulse of 11 mJ in energy and ∼45 ns in duration at 80 J flashlamp input energy was obtained. The wavelength of the Q‐switched laser output pulse and the Tm,Cr:Y3Al5O12 free‐running output was 2.017 μm. © 1994 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes

Seeded epitaxy of metals by sputter deposition

G. R. Harp and S. S. P. Parkin

Appl. Phys. Lett. 65, 3063 (1994); http://dx.doi.org/10.1063/1.112507 (3 pages) | Cited 17 times

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It is not generally appreciated that crystalline metallic thin film structures can be prepared using sputter deposition techniques by growth onto single crystalline substrates. Three systems, fcc Co/Cu(100), bcc Co/Cr(100), and hcp Co/Ru(1013) multilayers are described in detail from a comprehensive study of more than 40 different systems. It is shown that the use of thin ‘‘seed’’ layers readily allows the preparation of different crystal structures and/or crystal orientations for the same substrate. © 1994 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering

Reflection high‐energy electron diffraction intensity oscillations of germanium growth on Si(100) using gas source molecular beam epitaxy

M. H. Xie, J. Zhang, S. M. Mokler, J. M. Fernández, and B. A. Joyce

Appl. Phys. Lett. 65, 3066 (1994); http://dx.doi.org/10.1063/1.112508 (3 pages) | Cited 2 times

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Reflection high‐energy electron diffraction intensity oscillations during Ge heteroepitaxy on Si(100) have been observed using a gas source molecular beam epitaxy system. Intensity oscillations can be observed over 6 ML (monolayers) of growth in the temperature range 400–650 °C. The oscillation frequency, however, varies from the first to subsequent layers and this variation is interpreted primarily as a change in the limiting growth kinetics as the surface composition changes from Si to Ge. Growth temperature and GeH4 flux dependence data indicate that the surface Ge concentration increases gradually, not abruptly, over the first several layers of deposition. Surface roughening effects which are attributed to Stranski–Krastanov type growth, are also found to contribute to the nonuniform oscillation frequency. © 1994 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Controlled high‐rate localized shear in porous reactive media

V. F. Nesterenko, M. A. Meyers, H. C. Chen, and J. C. LaSalvia

Appl. Phys. Lett. 65, 3069 (1994); http://dx.doi.org/10.1063/1.112509 (3 pages) | Cited 28 times

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It is demonstrated that controlled high‐strain‐rate plastic deformation of heterogeneous reactive porous materials (Nb+Si, Mo+Si+MoSi2) produces shear localization. Within the shear bands, having thicknesses 5–20 μm, the overall strains (γ≤100) and strain rates (γ≤107 s−1) result in changes in particle morphology, melting, and regions of partial reaction. The shear band thickness is smaller than the initial characteristic particle size of the porous mixture (≤44 μm). This ensures quenching of the deformed material structure in the same time scale as the deformation time (10−5 s). In the shear localization region, two types of patterning are observed: (a) a characteristic shear fracture which subdivides the Nb particles into thin parallel layers and (b) the formation of vortices. © 1994 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
62.20.-x Mechanical properties of solids
82.40.Fp Shock wave initiated reactions, high-pressure chemistry

Fabrication of single‐crystal diamond microcomponents

John D. Hunn, S. P. Withrow, C. W. White, R. E. Clausing, L. Heatherly, and C. Paul Christensen

Appl. Phys. Lett. 65, 3072 (1994); http://dx.doi.org/10.1063/1.112959 (3 pages) | Cited 16 times

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We have combined a technique for the lift‐off of thin diamond films from a bulk diamond with a technique for engraving diamond with a focused excimer laser to produce free‐standing single‐crystal diamond microstructures. One microcomponent that has been produced is a 12 tooth gear ∼400 μm in diameter and ∼13 μm thick. Other microstructures have also been demonstrated, showing the versatility of this method. This process should be applicable to producing diamond microcomponents down to spatial dimensions (width and thickness) of a few micrometers. © 1994 American Institute of Physics.
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81.65.-b Surface treatments
42.62.-b Laser applications
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Residual stresses and microstructure of Ag‐Ni multilayers

K.‐F. Badawi, N. Durand, Ph. Goudeau, and V. Pelosin

Appl. Phys. Lett. 65, 3075 (1994); http://dx.doi.org/10.1063/1.112510 (3 pages) | Cited 5 times

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A direct determination of residual stresses in very‐low‐period Ag‐Ni multilayers has been performed by x‐ray diffraction using the sin2ψ method. Stresses in silver layers as thin as three atomic planes and in nickel layers as thin as four atomic planes could be determined. They range from −3.07 to 0.522 GPa, and their genesis excludes any interfacial coherency relationship. The variation of the multilayer microstructure with respect to the period has been studied by measurement of the stress free lattice parameter and microdistortions. Important deviations with respect to the bulk microstructure have been observed and discussed. © 1994 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.Gy Mechanical properties; surface strains

Stabilization of face‐centered‐cubic Mn films via epitaxial growth on GaAs(001)

X. Jin, M. Zhang, G. S. Dong, M. Xu, Y. Chen, Xun Wang, X. G. Zhu, and X. L. Shen

Appl. Phys. Lett. 65, 3078 (1994); http://dx.doi.org/10.1063/1.112466 (3 pages) | Cited 15 times

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The epitaxial growth of fcc Mn films on the GaAs(001) surface has been achieved. The films are studied by in situ reflection high energy electron diffraction (RHEED) and ex situ x‐ray diffraction (XRD). The lattice parameters of the metastable Mn films are determined to be 0.362 nm. A transition region composed of a Mn‐Ga‐As alloy is formed at the Mn/GaAs interfaces and is clearly verified by XRD measurements. © 1994 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology

Electrical characteristics of epitaxial CeO2 on Si(111)

L. Tye, N. A. El‐Masry, T. Chikyow, P. McLarty, and S. M. Bedair

Appl. Phys. Lett. 65, 3081 (1994); http://dx.doi.org/10.1063/1.112467 (3 pages) | Cited 60 times

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Electrical properties of epitaxial CeO2 thin films on silicon (111) substrates grown in ultrahigh vacuum were studied, varying growth conditions and ex situ thermal treatments. Characterization using reflection high‐energy electron diffraction and high resolution transmission electron microscopy reveal that while the ceramic layers have a good single‐crystal structure, a dual amorphous layer of CeOx and SiO2 forms at the CeO2/Si interface. This structure has undesirable electrical properties, however, utilizing a post‐anneal in dry oxygen, the α‐CeOx layer was removed and the SiO2 amorphous layer was made thicker. This newly developed structure benefits from the SiO2/Si interface, having Dit=6×1011 cm−2, and Qf=5×1011 cm−2. The structure exhibits a high capacitance due to the large dielectric constant of CeO2, has electrical properties comparable with those of other reported gate insulators on Si, and has an epitaxial oxide lattice matched to Si. © 1994 American Institute of Physics.
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73.61.Ng Insulators
68.55.-a Thin film structure and morphology
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Influence of Coulombic broadened DX center energy levels on free electron concentration in δ‐doped AlxGa1−xAs/GaAs quantum wells

G. Brunthaler, M. Seto, G. Stöger, and K. Köhler

Appl. Phys. Lett. 65, 3084 (1994); http://dx.doi.org/10.1063/1.112989 (3 pages) | Cited 4 times

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The achievable two‐dimensional (2D) electron concentration in a δ‐doped quantum well depends on the Al content in the doping layer and is considerably lower than the nominal doping concentration. This behavior has been so far attributed to different incorporation probabilities of Si atoms depending upon the Al content. In this work, we show instead that the energy levels of the DX center together with the Coulomb interaction account for this behavior. We present calculations of the DX center density of states which are broadened by the Coulomb interaction and show that the estimated 2D carrier concentrations agree well with experiment. © 1994 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Eq III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Coupling between one‐dimensional states in a quantum point contact and an electron waveguide

M. Saito, T. Usuki, M. Okada, T. Futatsugi, R. A. Kiehl, and N. Yokoyama

Appl. Phys. Lett. 65, 3087 (1994); http://dx.doi.org/10.1063/1.112468 (3 pages) | Cited 1 time

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A study of electron‐wave interference effects in a structure which is comprised of a split‐gate point contact with a parallel reflector gate is reported. The structure constricts the injected electrons to a waveguide. The variation of point contact conductance with reflector voltage has novel oscillations directly related to the one‐dimensional (1D) states in the waveguide. The oscillations are caused by the change in matching between a mode for the 1D waveguide state and an electron wave injected into the states. The oscillations are also found to be quenched with weak magnetic fields due to electron wave deflection. © 1994 American Institute of Physics.
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73.40.-c Electronic transport in interface structures
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Optical photodetector for near‐field optics

G. Kolb, K. Karraï, and G. Abstreiter

Appl. Phys. Lett. 65, 3090 (1994); http://dx.doi.org/10.1063/1.112469 (3 pages) | Cited 8 times

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A p‐n homojunction GaAs‐based photodetector is developed in order to operate in the near field of a subwavelength sized light source. It has a spatial resolution of about 270 nm, limited by diffusion of minority carriers. A detector with a built‐in AlGaAs diffusion barrier is also studied, demonstrating an improved resolution of better than 100 nm. © 1994 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.60.Pb Conventional optical microscopes

Study of the two‐dimensional–three‐dimensional growth mode transition in metalorganic vapor phase epitaxy of GaInP/InP quantum‐sized structures

N. Carlsson, W. Seifert, A. Petersson, P. Castrillo, M. E. Pistol, and L. Samuelson

Appl. Phys. Lett. 65, 3093 (1994); http://dx.doi.org/10.1063/1.112447 (3 pages) | Cited 112 times

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Ga0.5In0.5P/InP quantum‐sized structures, grown by metalorganic vapor phase epitaxy, have been optically characterized by photoluminescence, cathodoluminescence, and photoluminescence excitation spectroscopy. Additional structural information has been obtained by atomic force microscopy. We find that the two‐dimensional layer‐by‐layer growth mode is limited to the growth of 1‐ML‐thick and, in part, 2‐ML‐thick quantum wells. The transition towards three‐dimensional Stranski–Krastanow island growth occurs before the second monolayer of InP is completed. To further study the dynamics of the island formation, growth interruptions were introduced between the InP deposition and the subsequent growth of the upper GaInP barrier. The two types of coherent islands show a quantum confinement in vertical direction, corresponding to about 2‐ and 3‐ML‐thick and about 9‐ and 10‐ML‐thick InP strained quantum wells. © 1994 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

One‐dimensional quantum electron states in n‐AlxGa1−xAs/u‐GaAs modulation‐doped corrugated heterojunctions

Karel Vacek, Akemi Sawada, and Toshiyuki Usagawa

Appl. Phys. Lett. 65, 3096 (1994); http://dx.doi.org/10.1063/1.112448 (3 pages) | Cited 6 times

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New quasi‐one‐dimensional quantum electron states are proposed in modulation‐doped n‐AlxGa1−xAs/u‐GaAs heterostructures with periodic interface bending. Unlike usual flat heterointerfaces, the investigated system is sawtooth corrugated by bendings with a period of about 850 Å and a bending angle 90°. Quantum‐mechanical simulations yield energy spectrum with a single level below the Fermi energy. The probability distribution of electrons shows formation of a densely packed quasi‐one‐dimensional electron gas in the convex corner of the GaAs region. The ground level is as high as 100 meV above the deepest bottom of the conduction band potential and the excited state is separated by a significant energy gap of 16 meV. © 1994 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Influence of hydrogen and oxygen plasma treatments on grain‐boundary defects in polycrystalline silicon

N. H. Nickel, A. Yin, and S. J. Fonash

Appl. Phys. Lett. 65, 3099 (1994); http://dx.doi.org/10.1063/1.112449 (3 pages) | Cited 20 times

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The effects of hydrogen, oxygen, and helium plasma exposures on the grain‐boundary defects of polycrystalline silicon (poly‐Si) were examined. While a remote hydrogen plasma passivates Si dangling‐bonds efficiently no change in the defect density is observed after exposing poly‐Si to a remote oxygen plasma. On the other hand, an electron cyclotron resonance oxygen and helium plasma results in a decrease of the spin density. Secondary ion mass spectrometry measurements reveal that both plasma exposures vastly increase the hydrogen content of the samples while the O concentration remains unchanged. The increase of the H concentration is proportional to the number of passivated grain‐boundary defects. © 1994 American Institute of Physics.
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61.72.Mm Grain and twin boundaries
61.72.uf Ge and Si
66.30.J- Diffusion of impurities

Nucleation of Co silicide on H passivated Si(111)

M. Copel and R. M. Tromp

Appl. Phys. Lett. 65, 3102 (1994); http://dx.doi.org/10.1063/1.112957 (3 pages) | Cited 14 times

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We have investigated the effect of H passivation on the deposition of Co on Si(111). The H terminated surface has fewer nucleation sites for silicide formation than either the bare (7×7) surface or the boron (√3×√3)R30°. This leads to a growth mode dominated by the formation of sparse nonepitaxial islands, which grow laterally to merge. The H passivated (1×1) surface does not contain Si adatoms, unlike the (7×7) and boron (√3×√3)R30° surfaces, which must be the nucleation site for cobalt silicide formation on Si(111). © 1994 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Optical transition properties of β‐FeSi2 film

Lianwei Wang, Linhong Qin, Yuxiang Zheng, Wenzhong Shen, Xiangdong Chen, Xian Lin, Chenglu Lin, and Shichang Zou

Appl. Phys. Lett. 65, 3105 (1994); http://dx.doi.org/10.1063/1.112450 (3 pages) | Cited 14 times

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Optical transition of properties of β‐FeSi2 film have been investigated by optical transmittance absorption measurement, spectroscopic ellipsometry and reflectivity. Optical transmittance absorption measurement ranging from 0.5 to 1.1 eV revealed the direct transition at E0=0.84 eV, while absorption curve obtained from the spectroscopic measurement in the range of 1.5–4.5 eV implied additional transition at E′=1.05 eV, it is suggested that such additional transition originates from spin–orbit splitting at Γ (center of Brillouin’s zone). Reflectivity goes to the maximum value near Eg, indicating that the joint density of states in the transition at Eg is very high. Another peak which is related with the transition at E′ was also observed in the reflectivity spectra. © 1994 American Institute of Physics.
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78.66.Li Other semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Mode‐locked pulse operation of GaAs/AlGaAs field effect transistor self‐electro‐optic effect device smart pixels and saturation considerations

G. D. Boyd, G. Livescu, L. M. F. Chirovsky, and A. L. Lentine

Appl. Phys. Lett. 65, 3108 (1994); http://dx.doi.org/10.1063/1.112451 (3 pages) | Cited 3 times

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The input/output ports of Smart Pixels are the optical signal receivers and transmitters. We have tested the simplest, lowest power dissipating, receiver‐transmitter pair circuit with mode‐locked (ML) laser pulses and find switching times as short as 200 ps. We also observe that the product of the set optical energy and switching time is a constant. In addition we present a comparison of the saturation properties of quantum well modulators when operated with short ML pulses, versus bit‐period length pulses (quasi‐continuous wave operation). Although the read pulse energy requirements of smart pixel optical signal transmitters are near saturation conditions, we conclude that with careful design, operation with short pulses, which gives the minimum switching time, should be possible. © 1994 American Institute of Physics.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.82.-m Integrated optics

Photoluminescence of oxidized silicon nanoclusters deposited on the basal plane of graphite

L. N. Dinh, L. L. Chase, M. Balooch, L. J. Terminello, and F. Wooten

Appl. Phys. Lett. 65, 3111 (1994); http://dx.doi.org/10.1063/1.112452 (3 pages) | Cited 32 times

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Silicon (Si) nanoclusters, with an average size of 3–5 nm in diameter, have been deposited on the basal plane of highly oriented pyrolytic graphite in an ultrahigh vacuum chamber, and investigated by scanning tunneling microscopy. Clusters passivated in situ with hydrogen or oxygen showed no detectable visible photoluminescence (PL). Prolonged exposure of the clusters to ambient air, however, resulted in strong stable red to green‐blue PL spectra. Further study of these clusters by x‐ray photoelectron spectroscopy and Auger electron spectroscopy revealed the existence of only SiO2 for the prolonged air‐exposed samples, and the existence of SiOx (x ranged from 0 to 2) for the in situ oxidized samples which did not exhibit any detectable visible PL. We believe that the observed visible PL originated from defects in SiO2. © 1994 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
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