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9 Sep 2002

Volume 81, Issue 11, pp. 1937-2132

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Fabrication and characterization of nanoscale, Er3+-doped, ultratransparent oxy-fluoride glass ceramics

V. K. Tikhomirov, D. Furniss, A. B. Seddon, I. M. Reaney, M. Beggiora, M. Ferrari, M. Montagna, and R. Rolli

Appl. Phys. Lett. 81, 1937 (2002); http://dx.doi.org/10.1063/1.1497196 (3 pages) | Cited 89 times

Online Publication Date: 5 September 2002

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We show that oxy-fluoride glass ceramics, with typical composition, 32(SiO2):9(AlO1.5):31.5(CdF2):18.5(PbF2):5.5(ZnF2): 3.5(ErF3) mol % have potential applications in telecommunications. Upon heat treatment, Er3+ nucleates the growth of the nanocrystalline β-PbF2, which acts as its host. Heat treatment at 440 °C for 5 h and at 390 °C for 3 h gave rise to ∼ 12 and ∼ 2.5 nm diameter crystals, respectively. The emission band of Er3+ in the 1.54 μm telecommunications window (4I13/2→4I15/2 transition, at the half-height width) was 75 nm in the former and 90 nm in the latter case, while 4I13/2↔4I15/2 absorption and emission bands became wavelength divergent in both cases. Also in the latter case, the spectrum was flat from 1.53 to 1.56 μm. The evolution of spectral behavior is explained by changes in average site geometry of the Er3+ dopant, related to the α→β phase transition of PbF2, which is stimulated by heat treatment. © 2002 American Institute of Physics.
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81.05.Pj Glass-based composites, vitroceramics
78.35.+c Brillouin and Rayleigh scattering; other light scattering
42.55.Wd Fiber lasers
61.43.Fs Glasses
42.70.Ce Glasses, quartz

Improved brightness of 380 nm GaN light emitting diodes through intentional delay of the nucleation island coalescence

D. D. Koleske, A. J. Fischer, A. A. Allerman, C. C. Mitchell, K. C. Cross, S. R. Kurtz, J. J. Figiel, K. W. Fullmer, and W. G. Breiland

Appl. Phys. Lett. 81, 1940 (2002); http://dx.doi.org/10.1063/1.1506793 (3 pages) | Cited 58 times

Online Publication Date: 5 September 2002

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Ultraviolet light emitting diodes (LEDs) have been grown using metalorganic vapor phase epitaxy, while monitoring the 550 nm reflected light intensity. During nucleation of GaN on sapphire, the transition from three-dimensional (3D) grain growth to two-dimensional (2D) coalesced growth was intentionally delayed in time by lowering the NH3 flow during the initial high temperature growth. Initially, when the reflectance signal is near zero, the GaN film is rough and composed of partly coalesced 3D grains. Eventually, the reflected light intensity recovers as the 2D morphology evolves. For 380 nm LEDs grown on 3D nucleation layers, we observe increased light output. For LEDs fabricated on GaN films with a longer recovery time an output power of 1.3 mW at 20 mA current was achieved.
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85.60.Jb Light-emitting devices
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology

Effect of 3 MeV electron irradiation on the photoluminescence properties of Eu-doped GaN

Y. Nakanishi, A. Wakahara, H. Okada, A. Yoshida, T. Ohshima, and H. Itoh

Appl. Phys. Lett. 81, 1943 (2002); http://dx.doi.org/10.1063/1.1504873 (3 pages) | Cited 9 times

Online Publication Date: 5 September 2002

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The effect of 3 MeV electron irradiation on the photoluminescence (PL) properties of Eu-doped GaN was investigated. Eu was introduced into GaN epitaxial layers grown on sapphire substrates by ion implantation. The peak concentration of implanted Eu was found to be a few atomic percent. The electron dose was in the range of 1016–3×1017 cm−2. PL was measured in the temperature range of 13–295 K by using a He–Cd laser as the excitation source. PL intensity corresponding to the transition of 5D0−7F2 in Eu3+ was hardly dependent on the electron fluence. In contrast, the PL intensity of the near-band-edge emission from undoped GaN decreased when increasing the electron fluence. © 2002 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors

Design and fabrication of impurity band-based photonic crystal waveguides for optical delay lines

Y. Sugimoto, S. Lan, S. Nishikawa, N. Ikeda, H. Ishikawa, and K. Asakawa

Appl. Phys. Lett. 81, 1946 (2002); http://dx.doi.org/10.1063/1.1506411 (3 pages) | Cited 17 times

Online Publication Date: 5 September 2002

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We have designed, fabricated, and characterized efficient optical delay lines for ultrashort pulses based on photonic crystal waveguides formed by coupled defects. The basic structure consists of one-dimensional cylindrical air holes formed in silicon on silicon dioxide ridge waveguides. The defects are created by intentionally increasing the separation of two neighboring air holes. Through proper design, quasiflat impurity bands located at ∼ 1.55 μm can be successfully obtained. In addition, the wavelength tunability of the impurity bands was clearly demonstrated. Good agreement was found between the experimental observations and numerical simulations. © 2002 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.50.-p Quantum optics
71.55.-i Impurity and defect levels
42.65.Wi Nonlinear waveguides
42.82.Et Waveguides, couplers, and arrays
84.40.Az Waveguides, transmission lines, striplines

Truly random number generator based on turbulent electroconvection

J. T. Gleeson

Appl. Phys. Lett. 81, 1949 (2002); http://dx.doi.org/10.1063/1.1507362 (3 pages) | Cited 11 times

Online Publication Date: 5 September 2002

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We report an approach for generating truly random digital numbers. This approach is based on probing the chaotic and unpredictable fluctuations that take place in a nematic liquid crystal when it is undergoing turbulent, electrically induced, convective flow. This technique generates a stream of numbers that passes standard benchmark tests for randomness. A device utilizing this technique is not only inexpensive to construct, but also tamper proof. We discuss various strategies for improving the operating characteristics, primarily the bit generation rate, of a device constructed on this principle. © 2002 American Institute of Physics.
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47.65.-d Magnetohydrodynamics and electrohydrodynamics
47.27.T- Turbulent transport processes
61.30.-v Liquid crystals
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion

Holographic data storage on nonphotosensitive glass with a single femtosecond laser pulse

Yan Li, Wataru Watanabe, Kazuyoshi Itoh, and Xiudong Sun

Appl. Phys. Lett. 81, 1952 (2002); http://dx.doi.org/10.1063/1.1506410 (3 pages) | Cited 6 times

Online Publication Date: 5 September 2002

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Holographic data storage on fused silica, soda-lime, and lead glasses with a single 130 fs laser pulse at a wavelength of 800 nm is presented. After the sample is exposed to the interference fringe pattern of the object beam and the reference beam, a relief microhologram is recorded through surface ablation. The recorded information can be reconstructed without destruction of the hologram when the power of the reference beam is reduced below the ablation threshold. The preliminary experimental results demonstrate the possibility of holographic data storage on nonphotosensitive glasses. © 2002 American Institute of Physics.
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42.40.Ht Hologram recording and readout methods
42.70.Ln Holographic recording materials; optical storage media
81.05.Kf Glasses (including metallic glasses)
42.79.Vb Optical storage systems, optical disks
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
52.38.Mf Laser ablation
81.65.Cf Surface cleaning, etching, patterning

Optical properties of a light-emitting polymer directly patterned by soft lithography

J. R. Lawrence, P. Andrew, W. L. Barnes, M. Buck, G. A. Turnbull, and I. D. W. Samuel

Appl. Phys. Lett. 81, 1955 (2002); http://dx.doi.org/10.1063/1.1502187 (3 pages) | Cited 19 times

Online Publication Date: 5 September 2002

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We present the optical properties of a directly patterned light-emitting polymer. The patterned poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-paraphenylenevinylene film is fabricated using hot embossing lithography. The effect of the embossed microstructure on the light emitted from the polymer is examined by measuring the angle-dependent photoluminescence and its photonic band structure. The imposed grating modifies the emitted light by Bragg scattering into free space light that would otherwise be trapped as waveguide modes. This simple patterning technique may find application in improving the performance of light-emitting polymer devices. © 2002 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
78.55.Kz Solid organic materials
81.65.Cf Surface cleaning, etching, patterning
42.70.Qs Photonic bandgap materials
42.82.Cr Fabrication techniques; lithography, pattern transfer

Multiple-wavelength operation of electroabsorption intensity modulator array fabricated using the one-step quantum well intermixing process

S. L. Ng, H. S. Lim, Y. L. Lam, Y. C. Chan, B. S. Ooi, V. Aimez, J. Beauvais, and J. Beerens

Appl. Phys. Lett. 81, 1958 (2002); http://dx.doi.org/10.1063/1.1508159 (3 pages) | Cited 3 times

Online Publication Date: 5 September 2002

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Multiple-wavelength selective channel electroabsorption intensity modulators have been fabricated on a single InGaAs/InGaAsP chip using a one-step quantum well intermixing process. This technique was demonstrated for tailoring the intensity modulator operating wavelength by incorporating low-energy (360 keV) phosphorus ions implantation induced disordering process with gray-mask lithography technology. A modulation depth of −15 dB has been measured from these devices with a voltage swing of −4.5 V. © 2002 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
42.70.Qs Photonic bandgap materials
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.82.Cr Fabrication techniques; lithography, pattern transfer
78.20.Jq Electro-optical effects
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Effect of charge exchange ions upon Langmuir probe current

Zoltan Sternovsky and Scott Robertson

Appl. Phys. Lett. 81, 1961 (2002); http://dx.doi.org/10.1063/1.1506946 (3 pages) | Cited 18 times

Online Publication Date: 5 September 2002

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The ion current to a Langmuir probe in low-density partially ionized plasma is enhanced by the collection of ions originating from charge–exchange collisions in the probe sheath. This enhancement is modeled by finding the volume integral of the charge–exchange rate in the sheath weighted by the probability that the slower charge–exchange ions are collected. Experiments in a hot-filament argon discharge show that the current enhancement and its dependence upon neutral pressure, plasma density, and probe bias voltage agree well with the model. © 2002 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
52.25.-b Plasma properties
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions

Subcritical microwave streamer discharge at the surface of a polymer foil

S. Popović, L. Vušković, I. I. Esakov, L. P. Gratchev, and K. V. Khodataev

Appl. Phys. Lett. 81, 1964 (2002); http://dx.doi.org/10.1063/1.1506787 (2 pages) | Cited 4 times

Online Publication Date: 5 September 2002

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An innovative type of subcritical streamer discharge, generated by bursts of focused microwave (MW) radiation in transverse electromagnetic mode with wavelength of 10 cm, pulse duration of 40 μs, and intensity of 5.6×104 W/cm2, was initiated at the surface of a polymer foil at 420 Torr in air. The MW field of a quasioptical beam was three times lower than the critical breakdown field. Exposure of a polymer foil to the discharge caused a transition from hydrophobicity to hydrophilicity. © 2002 American Institute of Physics.
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61.82.Pv Polymers, organic compounds
81.65.-b Surface treatments
52.80.-s Electric discharges
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

High-energy electrons near the dielectric-plasma boundary in a large-area surface-wave plasma excited at 915 MHz

Masaaki Nagatsu, Takahiko Niwa, and Hideo Sugai

Appl. Phys. Lett. 81, 1966 (2002); http://dx.doi.org/10.1063/1.1506186 (3 pages) | Cited 8 times

Online Publication Date: 5 September 2002

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High-energy electrons produced in a planar ultrahigh frequency surface-wave plasma excited at 915 MHz have been studied using the Druyvesteyn technique of Langmuir probe measurements. Near the dielectric-plasma boundary, the hump of energetic electrons was clearly observed in the electron energy probability functions. The hump steeply shifted its center energy from about 20 eV at z = 0.2 cm to almost zero at z ∼ 1.4 cm apart from the quartz window, while the bulk electrons were strongly heated there. Peak energy and width of the hump seemed to have a strong spatial correlation with the electric field intensities. © 2002 American Institute of Physics.
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52.50.Sw Plasma heating by microwaves; ECR, LH, collisional heating
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.80.Pi High-frequency and RF discharges
52.70.Ds Electric and magnetic measurements

Contamination due to memory effects in filtered vacuum arc plasma deposition systems

D. R. Martins, M. C. Salvadori, P. Verdonck, and I. G. Brown

Appl. Phys. Lett. 81, 1969 (2002); http://dx.doi.org/10.1063/1.1506019 (3 pages) | Cited 13 times

Online Publication Date: 5 September 2002

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Thin film synthesis by filtered vacuum arc plasma deposition is a widely used technique with a number of important emerging technological applications. A characteristic feature of the method is that during the deposition process not only is the substrate coated by the plasma, but the plasma gun itself and the magnetic field coil and/or vacuum vessel section constituting the macroparticle filter are also coated to some extent. If then the plasma gun cathode is changed to a new element, there can be a contamination of the subsequent film deposition by sputtering from various parts of the system of the previous coating species. We have experimentally explored this effect and compared our results with theoretical estimates of sputtering from the stopping and range of ions in matter code. We find film contamination of the order of 10−4–10−3, and the memory of the prior history of the deposition hardware can be relatively long lasting. © 2002 American Institute of Physics.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.80.Vp Discharge in vacuum

Electron temperature in a sodium–iodide lighting plasma

D. Karabourniotis and E. Drakakis

Appl. Phys. Lett. 81, 1972 (2002); http://dx.doi.org/10.1063/1.1506415 (3 pages) | Cited 8 times

Online Publication Date: 5 September 2002

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The time-dependent electron temperature at the axis of an ac mercury–sodium–iodide arc discharge is determined experimentally. It modulates in phase with the discharge voltage and differs in modulation and magnitude from the temperature obtained assuming thermodynamic equilibrium. The method used is independent of plasma equilibrium assumptions as well as of line-transition probabilities, and since it is based on relative emission measurements, it can, in principle, be applied to discharges contained within translucent envelopes. © 2002 American Institute of Physics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Kn Thermodynamics of plasmas
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Spherulitic growth kinetics of protein crystals

P. S. Chow, X. Y. Liu, J. Zhang, and R. B. H. Tan

Appl. Phys. Lett. 81, 1975 (2002); http://dx.doi.org/10.1063/1.1506208 (3 pages) | Cited 9 times

Online Publication Date: 5 September 2002

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The spherulitic growth mechanism of lysozyme crystals from aqueous solutions was examined quantitatively by taking advantage of a “buffer zone” of liquid–liquid phase separation occurring in lysozyme aqueous solution. This buffer zone technique allows us to obtain constant concentrations in both liquid phases during the whole process of crystallization from solution. Under such a constant concentration (or supersaturation) condition, a constant growth rate along the radial direction of lysozyme spherulites was obtained for the spherulitic growth from solution. This evidently indicates that the growth of lysozyme spherulites is controlled by surface kinetics rather than by volume diffusion. In addition, it was found that microscopic droplets resulted from phase separation, and heterogeneous impurities normally serve as cores causing the formation of the radial pattern of spherulites. © 2002 American Institute of Physics.
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87.15.N- Properties of solutions of macromolecules
87.14.E- Proteins
64.70.D- Solid-liquid transitions
64.75.-g Phase equilibria
81.10.Dn Growth from solutions

Increased nucleation temperature of NiSi2 in the reaction of Ni thin films with Si1−xGex

J. Seger, S.-L. Zhang, D. Mangelinck, and H. H. Radamson

Appl. Phys. Lett. 81, 1978 (2002); http://dx.doi.org/10.1063/1.1498868 (3 pages) | Cited 35 times

Online Publication Date: 5 September 2002

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The formation of a ternary solid solution NiSi1−xGex, instead of a mixture of NiSi and NiGe, is found during solid-state interactions between Ni and various Si1−xGex films ranging from pure Si to pure Ge. The lattice parameters of the solid solution of orthorhombic structure increase linearly with Ge content (x) as: a = 5.24+0.19x Å, b = 3.25+0.16x Å, and c = 5.68+0.15x Å. The specific resistivity increases from 17 μΩ cm for NiSi to 21 μΩ cm for NiSi0.71Ge0.29 and NiSi0.42Ge0.58. Although the Ge content rapidly drops from 30–60 to about 10 at. % in the solid solutions formed above 600 °C, the crystallographic structure remains unchanged and no NiSi2 [or Ni(Si,Ge)2] is found in the Si1−xGex samples even after annealing at 850 °C. Without Ge, the NiSi completely disappears at 750 °C. These results indicate a strong effect of the entropy of mixing in NiSi–NiGe on the nucleation of NiSi2. © 2002 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
73.40.Ns Metal-nonmetal contacts
61.72.Cc Kinetics of defect formation and annealing
64.75.-g Phase equilibria

Characterization of surface layers in Zn-diffused LiNbO3 waveguides by heavy ion elastic recoil detection

O. Espeso-Gil, G. García, F. Agulló-López, A. Climent-Font, T. Sajavaara, M. Domenech, E. Cantelar, and G. Lifante

Appl. Phys. Lett. 81, 1981 (2002); http://dx.doi.org/10.1063/1.1506405 (3 pages) | Cited 6 times

Online Publication Date: 5 September 2002

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The surface layers formed in LiNbO3 waveguides, fabricated by Zn diffusion from the vapor phase, have been investigated by time of flight elastic recoil detection analysis using 127I ions. The key features of this technique, simultaneous profiling of all ions and a depth of analysis <1 μm, have allowed a detailed and quantitative characterization of the surface layers. The Zn diffusion into LiNbO3 can be understood as a 2Li↔Zn exchange process. As a consequence, an outermost layer of several hundreds of nanometers is formed, consisting of LiNbO3 and ZnNb2O6 phases showing complementary profiles. A good correlation has been found between the composition profiles and the optical waveguiding behavior. After thermal annealing of the waveguides, a thinner layer containing a uniform mixture of ZnO and LiNbO3 is generated followed by a transition to a graded solid solution of Zn into LiNbO3. © 2002 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
68.35.Fx Diffusion; interface formation
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
68.35.Dv Composition, segregation; defects and impurities
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.Cc Kinetics of defect formation and annealing

Cross-sectional imaging of pendeo-epitaxial GaN using continuous-wave two-photon microphotoluminescence

P. J. Schuck, R. D. Grober, A. M. Roskowski, S. Einfeldt, and R. F. Davis

Appl. Phys. Lett. 81, 1984 (2002); http://dx.doi.org/10.1063/1.1506948 (3 pages) | Cited 4 times

Online Publication Date: 5 September 2002

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A technique utilizing continuous-wave two-photon absorption has been developed for optically sectioning and imaging deep into GaN structures. Imaging at depths greater than 20 μm below the surface of a coalesced pendeo-epitaxial GaN sample is demonstrated. Free and donor-bound excitonic emission in this sample appears to originate at the surface, acceptor-bound exciton transitions are strongest in the top bulk portion of the sample, and subgap luminescence is most intense deep in the sample. The depth resolution of the imaging system is measured to be 1.75 μm near the GaN surface. © 2002 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.55.-a Thin film structure and morphology
71.35.-y Excitons and related phenomena

Characterization of a diamond p-n junction using electron-beam-induced current and cathodoluminescence

Takashi Sekiguchi and Satoshi Koizumi

Appl. Phys. Lett. 81, 1987 (2002); http://dx.doi.org/10.1063/1.1506409 (3 pages) | Cited 14 times

Online Publication Date: 5 September 2002

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We have characterized a diamond p-n junction by means of electron-beam-induced current (EBIC) and cathodoluminescence (CL). The diamond p-n junction was fabricated by growing a B-doped p-type layer and a P-doped n-type layer on the {111} diamond substrate by microwave plasma enhanced chemical vapor deposition. The cross section of p-n junction was revealed by the mesa etching. The substrate, B- and P-doped layers were distinguished by CL spectra. The EBIC profiles across the p-n junction were recorded under various reverse bias conditions. These data confirmed that the p-n junction was actually formed at the interface between B- and P-doped layers. The energy-band profile suggests that the carrier concentration of P-doped layer is more than ten times higher than that of B-doped layer. The observed results strongly support the fact that the UV luminescence is emitted from the p-n junction region in diamond light-emitting diode. © 2002 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.05.U- Carbon/carbon-based materials
81.05.Cy Elemental semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
73.20.At Surface states, band structure, electron density of states
78.66.Db Elemental semiconductors and insulators
73.61.Cw Elemental semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Polarity determination for GaN thin films by electron energy-loss spectroscopy

X. Kong, G. Q. Hu, X. F. Duan, Y. Lu, and X. L. Liu

Appl. Phys. Lett. 81, 1990 (2002); http://dx.doi.org/10.1063/1.1504876 (3 pages) | Cited 12 times

Online Publication Date: 5 September 2002

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The intensity of the N K edge in electron energy-loss spectra from a GaN thin film shows a pronounced difference when the orientation of the film approaches the (0002) and (000-2) Bragg reflections, along the polar direction. This experimental result can be interpreted by the effect associated with interference between the Bloch waves of the incident electron in the GaN crystal. The theoretical calculations indicate that, at the Bragg condition of g = 0002 along the Ga–N bond direction, the thickness-averaged electron current density on the N atom plane is much higher than that at g = 000math, with a maximum as the specimen thickness is about 0.4ξ0002 (the two-beam extinction distance). The delocalization effect on the experimental spectra is also discussed. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
68.49.Jk Electron scattering from surfaces
79.20.Uv Electron energy loss spectroscopy

Microstructural properties of Eu-doped GaN luminescent powders

O. Contreras, S. Srinivasan, F. A. Ponce, G. A. Hirata, F. Ramos, and J. McKittrick

Appl. Phys. Lett. 81, 1993 (2002); http://dx.doi.org/10.1063/1.1507355 (3 pages) | Cited 18 times

Online Publication Date: 5 September 2002

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GaN powders doped with europium have been prepared using Eu and Ga nitrates and N2H4 as reactants. The resulting particles have dimensions ranging from 0.5 to 1.0 μm. The crystalline structure was studied by transmission electron microscopy, and it consisted of single crystals with a hexagonal (wurtzite) structure containing small cubic domains (zinc blende) and a high density of stacking faults, all aligned along the [0001] and 〈111〉 directions, respectively. Cathodoluminescence measurements show strong light emission in the red region. This luminescence corresponds to transitions of Eu with the strongest emission in the 611 nm line, which is associated to the Eu3+ 4f transition from 5D0 to 7F2. These results demonstrate the feasibility of GaN:RE powders for luminescent applications. © 2002 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
61.72.Nn Stacking faults and other planar or extended defects

Alternative mechanism for misfit dislocation generation during high-temperature Ge(Si)/Si (001) island growth

J. Zou, X. Z. Liao, D. J. H. Cockayne, and Z. M. Jiang

Appl. Phys. Lett. 81, 1996 (2002); http://dx.doi.org/10.1063/1.1506414 (3 pages) | Cited 11 times

Online Publication Date: 5 September 2002

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The misfit dislocations in [001] Ge(Si)/Si islands grown at 700 °C were investigated using transmission electron microscopy. 30° partial misfit dislocations are found both in the island/substrate interface and near the island surface. Since the 30° partial leads the movement of the 60° dissociated misfit dislocation in a (001) compressively strained system such as (001) GeSi/Si, a generation mechanism of misfit dislocations through partial misfit dislocations half loops is proposed. © 2002 American Institute of Physics.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Hd Other semiconductors
68.55.-a Thin film structure and morphology
61.72.Lk Linear defects: dislocations, disclinations
66.30.Lw Diffusion of other defects
68.37.Lp Transmission electron microscopy (TEM)

Visible luminescence from silicon surfaces microstructured in air

C. Wu, C. H. Crouch, L. Zhao, and E. Mazur

Appl. Phys. Lett. 81, 1999 (2002); http://dx.doi.org/10.1063/1.1504868 (3 pages) | Cited 34 times

Online Publication Date: 5 September 2002

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We report visible luminescence from SiOx formed by microstructuring silicon surfaces with femtosecond laser pulses in air. Incorporation of oxygen into the silicon lattice occurs only where the laser beam strikes the surface. Laser microstructuring therefore offers the possibility of writing submicrometer luminescent features without lithographic masks. The amount of oxygen incorporated into the silicon surface depends on the laser fluence; the peak wavelength of the primary luminescence band varies between 540 and 630 nm and depends on the number of laser shots. Upon annealing, the intensity of the primary luminescence band increases significantly without any change in the luminescence peak wavelength, suggesting that the luminescence comes from defects rather than quantum confinement. © 2002 American Institute of Physics.
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78.55.Ap Elemental semiconductors
81.65.-b Surface treatments
42.62.-b Laser applications
81.40.Tv Optical and dielectric properties related to treatment conditions
81.40.Gh Other heat and thermomechanical treatments

Optical loss mechanisms in GeSiON planar waveguides

A. V. Osinsky, R. A. Bellman, I. A. Akwani, P. A. Sachenik, S. L. Logunov, and J. W. McCamy

Appl. Phys. Lett. 81, 2002 (2002); http://dx.doi.org/10.1063/1.1507611 (3 pages) | Cited 21 times

Online Publication Date: 5 September 2002

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A double frequency overtone of the fundamental N�H bond related vibration was found to dominate the optical loss in the 1.5–1.6 μm range in high index GeSiON-based planar waveguides deposited by plasma-enhanced chemical vapor deposition using hydrogen-based precursors. The fundamental N�H bond-related absorption and its double frequency overtone were measured to be ∼560 cm−1 and 1.8 cm−1, respectively, resulting in their ratio of 310±10. The optical loss, extracted from analysis of the N�H-related absorption is consistent with the directly measured optical loss in the waveguide structures. It was shown that using the deuterated precursors results in incorporation of N�D bonds in the GeSiON films. The N�H bond absorption band was eliminated in the deuterated films, leading to low optical losses in the communication band. © 2002 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.50.Lt Crystal binding; cohesive energy
52.77.Dq Plasma-based ion implantation and deposition

Probing the step structure of buried metal/semiconductor interfaces using quantized electron states: The case of Pb on Si(111) 6×6-Au

Hongbin Yu, C.-S. Jiang, Ph. Ebert, and C.-K. Shih

Appl. Phys. Lett. 81, 2005 (2002); http://dx.doi.org/10.1063/1.1506404 (3 pages) | Cited 6 times

Online Publication Date: 5 September 2002

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The three-dimensional step structure at the buried Pb on Si(111) 6×6-Au interface is determined by utilizing the presence of quantum well states. We demonstrate that the spatial step positions as well as the step heights can be extracted nondestructively and with atomic layer precision by scanning tunneling microscopy and spectroscopy. © 2002 American Institute of Physics.
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68.65.Fg Quantum wells
68.35.Ct Interface structure and roughness
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
73.21.Fg Quantum wells
73.40.Ns Metal-nonmetal contacts

Chemical bonding of hydrogen in MgH2

T. Noritake, M. Aoki, S. Towata, Y. Seno, Y. Hirose, E. Nishibori, M. Takata, and M. Sakata

Appl. Phys. Lett. 81, 2008 (2002); http://dx.doi.org/10.1063/1.1506007 (3 pages) | Cited 23 times

Online Publication Date: 5 September 2002

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MgH2 is one of the promising base materials for hydrogen storage, which is a key technology of clean energy source. In this study, the bonding nature of hydrogen in MgH2 was fully uncovered by examining the charge density distribution of this substance obtained by the maximum entropy method from the synchrotron radiation powder data. MgH2 can be expressed as Mg1.91+ H0.26−, which is much weaker ionicity than the theoretical expectations. It also shows weak covalence between Mg and H. Though the bonding nature of hydrogen in MgH2 is rather complex, i.e., the mixture of ionic and covalent bonding, it is certain that hydrogen is weakly bonded to Mg, which must be a big advantage of hydrogenation–dehydrogenation of this substance. © 2002 American Institute of Physics.
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61.50.Lt Crystal binding; cohesive energy
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