bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of 1.78-μm wavelength Al0.2Ga0.8Sb/GaSb double-heterostructure lasers by molecular beam epitaxy
Authors: Tsang W. T. , Olsson N. A.
Published: February 2003

As the losses due to Rayleigh scattering decrease at a rate of λ4 with increasing wavelength λ, the future generation of optical fibers, light sources, and detectors may well be operating at still longer wavelength beyond 1.55 μm. The present letter reports the first preparation of Al0.2Ga0.8Sb/GaSb double-heterostructure (DH) lasers by molecular beam epitaxy (MBE) operating at 1.78 μm. For AlxGa1−xSb with x≲0.1, room-temperature photoluminescent intensity and linewidth similar to those of bulk GaSb substrate of similar carrier concentration were obtained. The Al0.2Ga0.8Sb/GaSb DH laser wafers grown by MBE have smooth, featureless, mirror-reflecting surfaces. Reflection high-energy electron diffraction study shows that the abrupt Al0.2Ga0.8Sb/GaSb interfaces were atomically smooth. Initial threshold current measurements gave a pulsed threshold current density of 3.4 kA/cm2 for a diode of 380×200 μm and an active GaSb layer of 0.33 μm.
Evaluation of diffusion lengths and surface recombination velocities from electron beam induced current scans
Authors: Donolato C.
Published: February 2003

A new procedure is described for the determination of the minority-carrier diffusion length and surface recombination velocity from electron beam induced current (EBIC) scans on a semiconductor containing a barrier perpendicular to the surface. The analysis relies on the evaluation of the first moment of two EBIC profiles at different beam energies. An application of the method to literature data is reported.
Two components of tunneling current in metal-oxide-semiconductor structures
Authors: Eitan B. , Kolodny A.
Published: February 2003

Two distinct components of tunneling current in silicon metal-oxide-semiconductor structures are identified. In addition to the electron tunneling from the conduction band of the semiconductor, there is a second component interpreted as electron tunneling from the valence band. This is manifested as hole current in the silicon substrate. The ratio of valence-band to conduction-band tunneling currents is about 10−3, and increases slightly with the oxide field. This ratio is independent of oxide thickness, temperature, and gate-electrode material.
Electro-optic analog-to-digital converter using channel waveguide Fabry–Perot modulator array
Authors: Chang C. L. , Tsai C. S.
Published: February 2003

A new electro-optic analog-to-digital converter that makes use of an array of channel waveguide Fabry–Perot modulators is reported. Since this converter utilizes only straight channel waveguides, it should possess the inherent advantages of small substrate size, simple geometrical layout, and low optical insertion loss. Experimental results obtained with a four-bit converter in a X-cut LiNbO3 substrate have demonstrated some of these desirable features.
Electrical and optical properties of ion-irradiated organic polymer Kapton H
Authors: Hioki Tatsumi , Noda Shoji , Sugiura Masahiro , Kakeno Mitsutaka , Yamada Kenichi , Kawamoto Junichi
Published: February 2003

An organic polymer Kapton H film was irradiated with high-energy (∼MeV) N+2 ions. The specific resistivity of the film irradiated to a dose ∼1017 N/cm2 was estimated to be ∼10−2 Ω cm, which is about 20 orders of magnitude smaller than that of the unirradiated film. With increase of dose, the irradiated region of the film became grayish silver with a remarkable metallic luster. It is suggested that the alterations of the electrical and optical properties of the film result from the decomposition and the subsequent carbonization of the polymer induced by ion irradiation. The properties of the irradiated film are compared with those of the pyrolyzed one.
Energy leakage from Rayleigh waves on a fluid-loaded, layered half-space
Authors: Chimenti D. E.
Published: February 2003

The dispersive energy leakage rate of the zeroth-order leaky Rayleigh mode on a fluid-loaded, layered half-space has been determined experimentally for the first time. Data are presented for a layer of copper on stainless steel and are compared to the prediction of a recent theoretical model. Good agreement with the model calculation is seen in the magnitude of the energy leakage rate, which is related to the lateral displacement of a finite beam, and its dependence on the layer thickness over acoustic wavelength. The rapid variation observed in this rate may be relevant to the design of layer thickness measurements in the acoustic microscope.
Wafer-scale laser pantography: Fabrication of n-metal-oxide-semiconductor transistors and small-scale integrated circuits by direct-write laser-induced pyrolytic reactions
Authors: McWilliams Bruce M. , Herman Irving P. , Mitlitsky Fred , Hyde Roderick A. , Wood Lowell L.
Published: February 2003

A complete set of processes sufficient for manufacture of n-metal-oxide-semiconductor (n-MOS) transistors by a laser-induced direct-write process has been demonstrated separately, and integrated to yield functional transistors. Gates and interconnects were fabricated of various combinations of n-doped and intrinsic polysilicon, tungsten, and tungsten silicide compounds. Both 0.1-μm and 1-μm-thick gate oxides were micromachined with and without etchant gas, and the exposed p-Si [100] substrate was cleaned and, at times, etched. Diffusion regions were doped by laser-induced pyrolytic decomposition of phosphine followed by laser annealing. Along with the successful manufacture of working n-MOS transistors and a set of elementary digital logic gates, this letter reports the successful use of several laser-induced surface reactions that have not been reported previously.
Strong sensitivity to the presence of gaseous hydrogen of the resistivity of yttrium iron garnet
Authors: Milani E. , Paroli P. , Antonini B. , Maturi B.
Published: February 2003

The electrical resistivity of pure bulk yttrium iron garnet has been found to decrease considerably in presence of gaseus hydrogen, in the temperature range 50≤T≤600 °C. A relative resistivity decrease of about 45%, almost temperature independent, is observed when yttrium iron garnet is exposed to pure hydrogen. Exposing the sample to H2-N2 gas mixtures, hydrogen relative concentrations as small as 100 ppm are detectable. This phenomenon is interpreted in terms of hydrogen diffusion into the garnet, with simultaneous formation of OH− and Fe2+ centers, the latter causing the resistivity drop. Pure yttrium iron garnet thus appears promising as the basic material for chemical sensors of hydrogen, working at temperatures much higher than conventional semiconductor devices.
GaSb/AlSb multiquantum well structures: Molecular beam epitaxial growth and narrow-well photoluminescence
Authors: Griffiths Grant , Mohammed Khalid , Subbana Seshadri , Kroemer Herbert , Merz James L.
Published: February 2003

Multiquantum well structures of GaSb wells down to 12-Å width, separated by 120-Å AlSb barriers, were grown by molecular beam epitaxy, and their low-temperature photoluminescence was studied. Even though GaSb should become an indirect-gap semiconductor for well widths below about 90 Å, the direct-gap luminescence persists to the narrowest wells. The shift of photon energy with well width indicates strong nonparabolicity effects; it is in good agreement with Bastard’s simple model of quantum wells in nonparabolic semiconductors. For wells less than 45 Å wide, the direct-gap luminescence is accompanied by a strong and very broad lower-energy luminescence peak, which appears to be related to electron accumulation in the X valleys, but the exact mechanism for which is not clear. A two-electron transition model is proposed.
Single flux-quantum Josephson memory cell using a new threshold characteristic
Authors: Kurosawa Itaru , Yagi Akihiko , Nakagawa Hiroshi , Hayakawa Hisao
Published: February 2003

A new single flux-quantum Josephson memory cell in which nondestructive readout (NDRO) operations can be realized with a simple circuit configuration is proposed. The memory cell utilizes a new type of threshold characteristics in an equivalent asymmetric dc superconducting quantum interference device (SQUID) consisting of a three-junction SQUID gate and a single junction. NDRO operation has been successfully demonstrated in an experimental memory circuit.
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9Si hyperfine structure of unpaired spins at the Si/SiO2 interface
Authors: Brower K. L.
Published: February 2003

The hyperfine spectrum associated with unpaired electrons at the (111) Si/SiO2 interface (Pb centers) is reported for the first time. Electron paramagnetic resonance measurements indicate that the hyperfine interaction S↘⋅Ā⋅I↘ arises from the 29Si isotope and is characterized by A∥=146.(±5.)×10−4 cm−1 and A⊥=85.(±8.)×10−4 cm−1. An analysis of this hyperfine interaction firmly establishes many of the details in the structure of this interface defect.
High near-infrared reflectivity modulation with polycrystalline electrochromic WO3 films
Authors: Goldner R. B. , Mendelsohn D. H. , Alexander J. , Henderson W. R. , Fitzpatrick D. , Haas T. E. , Sample H. H. , Rauh R. D. , Parker M. A. , Rose T. L.
Published: February 2003

A near-infrared reflectivity exceeding 60% at 2.5-μm wavelength has been observed for a polycrystalline, rf sputter-deposited electrochromic (EC) WO3 film in a deeply colored state. This reflectivity is considerably higher than that previously reported for a thermally evaporated EC-WO3 film that was crystallized by a post-deposition thermal anneal. The shapes of the x-ray spectra of the two films are also different. The results of ellipsometry measurements of the optical constants provide convincing evidence for the validity of a free-electron Drude model to explain the reflectivity modulation observed in polycrystalline EC-WO3.
Advantages of the HgTe-CdTe superlattice as an infrared detector material
Authors: Smith D. L. , McGill T. C. , Schulman J. N.
Published: February 2003

The HgTe-CdTe superlattice is found to exhibit properties superior to those of the (Hg, Cd)Te alloy as an infrared detector material. A calculation shows that the superlattice tunneling length is shorter than that of the alloy with the same band gap. For a given cutoff wavelength tolerance, we find that less fractional precision is needed in the superlattice control parameter (layer thicknesses) than in the alloy control parameter (composition). Also, p-side diffusion currents are expected to be reduced due to the larger superlattice electron effective mass.
On the optical evaluation of the EL2 deep level concentration in semi-insulating GaAs
Authors: Walukiewicz W. , Lagowski J. , Gatos H. C.
Published: February 2003

We present a practical procedure for the evaluation of the Fermi energy in semi-insulating (SI)GaAs from electrical measurements. This procedure makes it possible to reliably extend the determination of the major deep level (EL2) concentration, by near-infrared absorption measurements, to SI GaAs. Employing this procedure, we showed that the EL2 concentration in Czochralski-grown GaAs increases monotonically with increasing As/Ga ratio (throughout the conversion from SI n type to semiconducting p-type crystals) rather than abruptly as previously proposed.
Impact ionization in (100), (110), and (111) oriented InP avalanche photodiodes
Authors: Armiento C. A. , Groves S. H.
Published: February 2003

The impact ionization process in the 〈100〉, 〈110〉, and 〈111〉 crystallographic directions in InP has been investigated by analysis of photomultiplication and multiplication noise data from InP avalanche photodiodes. This is the first report of such measurements for (110)-oriented InP and the first consistent investigation of impact ionization in the three principal crystallographic directions. Our measurements indicate that, unlike the reports for GaAs, no significant orientation dependence of the impact ionization coefficients exists in InP. Momentum-randomizing collisions with phonons, which result in intervalley transfer of energetic electrons, are believed to be the reason for the lack of anisotropy in the electron impact ionization coefficients.
Comparison of guided-wave interferometric modulators fabricated on LiNbO3 via Ti indiffusion and proton exchange
Authors: Becker R. A.
Published: February 2003

Guided-wave electro-optic Mach–Zehnder interferometric modulators have been fabricated on LiNbO3. The channel waveguides were formed by titanium indiffusion in some devices and proton exchange in benzoic acid in others. The modulators were tested at 0.85-μm and/or 1.3-μm wavelengths for insertion loss, electro-optic activity, and susceptibility to optical damage. A substantial reduction in the electro-optic activity accompanied by a reduced susceptibility to optical damage is measured for the proton-exchanged modulators.
Supersonic-nitrogen flow-field measurements with the resonant Doppler velocimeter
Authors: Cheng S. , Zimmermann M. , Miles R. B.
Published: February 2003

Laser-induced fluorescence of sodium atoms seeded into a supersonic nitrogen jet is used to determine the velocity, temperature, and pressure of the flow. The visible signal is sufficiently intense for spatially resolved flow visualization purposes.
Laser-controlled chemical etching of aluminum
Authors: Tsao Jeffrey Y. , Ehrlich Daniel J.
Published: February 2003

A new technique is described for high-spatial-resolution (<2-μm linewidth) etching of Al thin films. The process is based upon moderate local heating by a tightly focused Ar+ laser beam to activate an etching reaction in mixtures of phosphoric acid, nitric acid, and potassium dichromate. By chemically biasing the reaction near its passive/active transition, the laser can enhance the reaction rate by more than six orders of magnitude. The etching mechanism has been studied by etch-rate measurements, ellipsometry, and Auger spectroscopy, and is ascribed to a competition between the formation of soluble aluminum phosphates and insoluble aluminum oxides.
Vibrational absorption bands for implanted nitrogen in crystalline silicon
Authors: Stein H. J.
Published: February 2003

Infrared absorption bands for 15N in crystalline silicon have been observed for the first time. Isotopic substitution experiments were performed by N+ ion implantation into crystalline silicon to confirm the role of nitrogen in absorption bands at 764 and 962 cm−1 for 14N and at 748 and 937 cm−1 for 15N. Laser annealing increases the intensity of the higher frequency band. The 962-cm−1 band frequency is close to Si-N stretch frequencies for planar bonded N in crystalline Si3N4. It is suggested that the lower frequency band is associated with a mode that is made IR active by local distortion, consistent with a distorted substitutional N center identified by Brower in electron paramagnetic resonance studies on laser-annealed nitrogen-implanted Si.
Intracenter transitions in the dominant deep level (EL2) in GaAs
Authors: Kaminska M. , Skowronski M. , Lagowski J. , Parsey J. M. , Gatos H. C.
Published: February 2003

Intracenter transitions in the major deep level EL2 in GaAs were identified for the first time by superimposing photocurrent measurements on those of optical absorption. These transitions were found to be responsible for the characteristic EL2 absorption band between 1.0 and 1.3 eV. At low temperatures (<60 K) intracenter absorption exhibits a fine structure involving the zero phonon line and replicas at energies close to those of transverse acoustic phonons (TA). This coupling with TA phonons is a strong indication that EL2 is an extrinsic self-trapping center.
Method to detect a temperature rise in superconducting coils with piezoelectric sensors
Authors: Ishigohka T. , Tsukamoto O. , Iwasa Y.
Published: February 2003

A shift in the frequency spectrum of a structure induced by a local temperature rise is measured. This technique of detecting shifts in the frequency spectrum of a structure may be used to detect slight temperature-induced changes in stress distribution, which are in turn caused by local perturbation in the temperature distribution in the structure. Results from a small superconducting coil are presented.
Pulsed neodymium: yttrium aluminum garnet laser (532 nm) melting of crystalline silicon: Experiment and theory
Authors: Lowndes D. H. , Wood R. F. , Westbrook R. D.
Published: February 2003

Time-resolved reflectivity measurements have been used to determine both the time of onset-of-melting and the duration of melting resulting from frequency-doubled neodymium: yttrium aluminum garnet (532 nm) pulsed-laser irradiation of crystalline silicon. Substantially shorter surface melt durations were obtained with increasing energy density El than were reported earlier by others. Thermal melting model calculations, which take into account the temperature-dependent optical and thermal properties of silicon, are in substantial agreement with the observed El dependence of the onset of melting and surface melt duration. Inclusion of intensity-dependent absorption in the modeling further improves this agreement.
Picosecond air breakdown studies at 0.53 μm
Authors: Williams William E. , Soileau M. J. , Van Stryland Eric W.
Published: February 2003

The laser induced breakdown thresholds of laboratory air at 0.53 μm were measured for pulses varying from 30 to 140 ps for a variety of focal spot sizes. The breakdown threshold fields were found to be proportional to 1/(tp)1/2, where tp is the laser pulse width. Comparison with an earlier work at 1.06 μm under similar conditions indicates that the breakdown thresholds are higher at 0.53 than at 1.06 μm. However, this increase falls short of the λ−2 dependence exhibited by cascade ionization.
The amorphous phase and surface mechanical properties of 304 stainless steel implanted with Ti and C
Authors: Follstaedt D. M. , Yost F. G. , Pope L. E. , Picraux S. T. , Knapp J. A.
Published: February 2003

The wear tracks resulting from unlubricated pin-on-disc tests of 304 stainless steel which was ion implanted with Ti and C have been examined with transmission electron microscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy. At light pin loads, where the maximum wear depths were reduced by the implantation from ∼1.5 to ∼0.15 μm, nearly continuous amorphous layers containing Ti were found to exist across the wear tracks. However, the amorphous phase was not observed in deeper wear tracks (≳1 μm) produced by higher loads. This correlation of the presence of the amorphous layer with reduced wear demonstrates that this layer is responsible for the reduction in wear produced by implantation of Ti and C.
Whisker growth and cone formation on metal surfaces under ion bombardment
Authors: Wehner G. K.
Published: February 2003

We were able to show experimentally that the seed metals which can cause cone development on ion bombarded metal targets need not to have a lower sputtering yield as widely believed but a higher melting point. By lowering the bombarding ion energy to near sputtering threshold values (<100 eV) one observes the growth of genuine single crystal whiskers which point in all directions not related to the direction of ion incidence. We are now convinced that (intentional or unintentional) seed cones are the result of an interplay among whisker growth, surface movement of atoms, and the effects of sputtering.
Effect of boron compensation on the photovoltaic properties of amorphous silicon solar cells
Authors: Moustakas T. D. , Maruska H. P. , Friedman R. , Hicks M.
Published: February 2003

Intrinsic amorphous silicon films are normally slightly n type. As a result, in n+-i-metal and n+-i-p+ solar cell structures the major potential barrier is at the i-m or i-p+ interfaces. Low levels of boron compensation of the i layer move the Fermi level down to midgap. Further increases in boron render the i layer slightly p type, and move the major barrier to the i-n+ interface. Therefore, it becomes possible to tailor the level of boron doping throughout the i layer so as to achieve high electric fields in all regions of the layer, and thus maximize the short circuit current.
Remote sensing applications of pulsed photothermal radiometry
Authors: Tam A. C. , Sullivan B.
Published: February 2003

The technique of pulsed photothermal radiometry (PPTR) (i.e., detection of the transient infrared thermal radiation from a condensed matter sample heated by a short-pulsed radiation) is useful for single-ended remote sensing applications. We demonstrate for the first time such applications for spectroscopic detection, measurement of absolute absorption coefficients in opaque materials, and sensing of dimensions or thermal properties in inhomogeneous materials. Theory of the PPTR technique in the simple case of a semi-infinite homogeneous material is described.
High-quality ZnSe thin films grown by molecular beam epitaxy
Authors: Yao Takafumi , Ogura Mutsuo , Matsuoka Seiji , Morishita Toshihide
Published: February 2003

High-quality, nominally undoped, low-resistivity ZnSe thin films are grown by molecular beam epitaxy (MBE). The MBE ZnSe shows the largest peak intensity ratio of the near-band-edge emission to the deep center luminescence even at room temperature compared with other epitaxial techniques, which indicates the smallest concentration of complex defects in the MBE ZnSe. From the temperature dependence of electron mobility for MBE ZnSe, we obtained the mobility value as high as 6.9×103 cm2/Vs. This is the highest value ever obtained in epitaxial ZnSe films and indicates the concentration of isolated charged defects as low as 1×1016 cm−3.
Simulation of the noise rise in three-photon Josephson parametric amplifiers
Authors: Miracky Robert F. , Clarke John
Published: February 2003

Analog simulations of the three-photon Josephson parametric amplifier indicate that the noise rise observed in experimental devices arises from occasional hopping between a mode at the pump frequency ωP and a mode at the half-harmonic ωP/2 . The hopping is induced by thermal noise associated with the shunt resistance.
Liquid phase growth of epitaxial Ni and Co silicides
Authors: Tung R. T. , Gibson J. M. , Jacobson D. C. , Poate J. M.
Published: February 2003

Epitaxial Ni and Co silicides have been fabricated using pulsed laser melting and ultrarapid solidification techniques. Interfacial instabilities and cell formation are suppressed during the liquid phase epitaxy by melting mono or disilicide layers. Single crystal NiSi2 and CoSi2 films have been grown on (100) and (111) Si. This method does not require ultrahigh vacuum deposition or reaction techniques.
Fabrication of germanium-coated nickel hollow waveguides for infrared transmission
Authors: Miyagi Mitsunobu , Hongo Akihito , Aizawa Yoshizo , Kawakami Shojiro
Published: February 2003

Circular hollow nickel waveguides with an inner germanium layer are fabricated by using a method based on rf sputtering, plating, and etching techniques. Transmission losses less than 0.5 dB are achieved including launching losses for straight waveguides with 1.5 mmφ×1 m at 10.6-μm wavelength. Bending losses of the waveguides are also examined.
Si-SiO2 interface structures on Si(100), (111), and (110) surfaces
Authors: Hattori Takeo , Suzuki Toshihisa
Published: February 2003

The distributions of intermediate oxides (SiOx, 0<x<2) in ultrathin oxide films formed on (100), (111), and (110) surfaces were investigated by using the nondestructive measurements of Si 2p photoelectron spectra. The experimental observations can be understood as follows: (1) the abrupt interfaces are formed for three crystal orientations; (2) the interface formed at 1000 °C on (100), (111), and (110) surface consists mainly of SiO, Si2O, and the mixture of SiO and Si2O, respectively; (3) Si2O3 is distributed in the oxide films for three crystal orientations.
Quantitative ion beam process for the deposition of compound thin films
Authors: Harper J. M. E. , Cuomo J. J. , Hentzell H. T. G.
Published: February 2003

We describe a quantitative ion beam technique for the deposition of compound thin films. The metal atom flux is supplied by inert ion beam sputtering, and the reactive flux is supplied by a low-energy ion beam directed at the growing film, allowing the fundamental deposition parameters of arrival rates, ion energy, and direction to be measured and controlled. Analysis gives the sputtering yields and incorporation probabilities as a function of film composition, arrival rate ratios, and ion energy. Results are presented for Al films deposited under a range of N2+ ion bombardment (100–500 eV) up to arrival rate ratios exceeding the value needed to form AlN. Nitrogen ions are almost fully incorporated into Al films, and excess N is rejected above the composition N/Al=1. The microstructure is shown to depend on the N/Al arrival rate ratio and the nitrogen ion energy used during deposition.
Dissipation-theory treatment of the transition from diffusion-controlled to diffusionless solidification
Authors: Aziz Michael J.
Published: February 2003

The steady-state velocity of a planar liquid-solid interface is predicted by calculating the free energy dissipated by irreversible processes at the interface and equating it to the available driving free energy. A solute drag term and an intrinsic interfacial mobility term are included in the dissipation calculations for a binary alloy. The solute drag calculation employs a solute trapping model, which has been extended to concentrated alloys. The result is presented in terms of a single unknown parameter, the interfacial diffusivity Di. A transition from diffusion controlled to diffusionless solidification occurs over approximately an order of magnitude in growth velocity, as the interface speed surpasses the maximum speed with which solute atoms can diffuse across the interface to remain ahead of the growing crystal.
Double zinc diffusion fronts in InP—Theory and experiment
Authors: Yamada M. , Tien P. K. , Martin R. J. , Nahory R. E. , Ballman A. A.
Published: February 2003

Diffusion of Zn or Cd in n-type III-V material has been extensively used for forming p-n junctions in lasers and detectors. However, if the substrate material used for diffusion has an electron concentration less than 5×1016 cm−3, two separate diffusion fronts will appear which alter completely the electrical property of the junction. We have investigated this phenomenon by electron beam induced current (EBIC) and secondary ion mass spectroscopy (SIMS). A theory is proposed, for the first time, in good agreement with experiment.
Radio-frequency amplifier based on a dc superconducting quantum interference device
Authors: Hilbert Claude , Clarke John
Published: February 2003

A dc superconducting quantum interference device used as a radio-frequency amplifier has achieved a power gain of 19.5±0.5 dB and a noise temperature of 1.0±0.4 K at a frequency of 100 MHz and an operating temperature of 1.5 K.
Subpicosecond electro-optic shock waves
Authors: Auston D. H.
Published: February 2003

When an extremely short optical pulse is focused into an electro-optic material, a moving polarization is produced which radiates in a Cerenkov-like cone. At the boundary of this shock wave, the electric field consists of an extremely fast electrical transient with a correspondingly wide spectral distribution extending well into the far infrared. When appropriately coupled out of the material, this shock wave can be used as a fast electronic impulse generator or far-infrared source without requiring subminiature transmission structures to guide the signal.
Direct etching of polymeric materials using a XeCl laser
Authors: Andrew J. E. , Dyer P. E. , Forster D. , Key P. H.
Published: February 2003

The direct etching of polyethylene terephthalate film using a XeCl laser has been investigated and is shown to be consistent with a thermal model for degradation. Microstructure revealed by deep etching suggests the UV laser may prove useful for studying polymeric materials. Polyimide and photoresist film has also been directly etched.
Phase formation by ion beam mixing in Ni/Al, Pd/Al, and Pt/Al bilayers
Authors: Nastasi M. , Hung L. S. , Mayer J. W.
Published: February 2003

Ion beam and thermal reactions in thin-film bilayers of Ni/Al, Pd/Al, and Pt/Al have been investigated using electron diffraction and Rutherford backscattering (RBS). Ion mixing was performed with 600-keV Xe ions at room temperature with doses ranging between 0.25 to 12×1015 ions/cm2. The compositions of the ion induced crystalline phases, NiAl and PdAl, differ both from the overall atomic compositions of the ion mixed layers (as determined by RBS) and from the compositions of the layers obtained by thermal annealing. In Pt/Al bilayers ion mixing forms an amorphous region with atomic composition Pt40Al60 while thermal annealing shows the formation of crystalline Pt2Al3. We believe that actual crystal compound formation during mixing is dependent on the high quench rate in the collision cascade region.
Ferroelectric properties of poly(vinylidenefluoride-trifluoroethylene) copolymer thin films
Authors: Kimura Kuniko , Ohigashi Hiroji
Published: February 2003

The ferroelectric, piezoelectric, and pyroelectric characteristics in thin films (0.5–2.5 μm thick) of a copolymer composed of 74 mol % vinylidenefluoride and 26 mol % trifluoroethylene have been studied. They maintain remarkable ferroelectricity similar to that found in the thicker films of this copolymer. Both the temperature dependence of the reciprocal dielectric constant 1/ε and the biasing field dependence of the phase transition temperature Tc indicate the phase transition to be of a first order. A large pyroelectric coefficient (35–50 μC/m2 K) and the significant piezoelectricity related to e33 have been found in thin films of this copolymer.
Synthesis of metastable, semiconducting Ge-Sn alloys by pulsed UV laser crystallization
Authors: Oguz S. , Paul William , Deutsch T. F. , Tsaur B-Y. , Murphy D. V.
Published: February 2003

Thin microcrystalline films of the metastable semiconducting alloy Ge1−xSnx (x≊0.22) have been formed using excimer laser radiation to crystallize amorphous sputtered films on glass and semiconducting crystalline substrates. X-ray diffraction, electroreflectance, and Raman spectroscopy have been used to characterize the semiconducting material which is stable to at least 200 °C. The study demonstrates the possibility of extending earlier studies of amorphous Ge1−xSnx alloys into a crystalline regime with a direct band-gap variable with x from 0 up to about 0.5 eV. The crystallization technique is potentially applicable to the formation of other metastable semiconducting compounds of device potential.
Field dependence of two large hole capture cross sections in thermal oxide on silicon
Authors: Tzou Joseph Jengtao , Sun Jack Yuan-Chen , Sah Chih-Tang
Published: February 2003

The oxide field dependence of the hole capture cross sections of two oxide hole traps is reported. The capture cross section varies with the average oxide field as E−nox with n≂0.6 for the 10−13 cm2 hole trap and n≂0.4 for the 10−14 cm2 hole trap. The observed field dependences can be explained by the potential lowering of a highly localized neutral potential, V(r)=A/rm, with m=4 for the 10−13 cm2 hole trap and m=6.5 for the 10−14 cm2 hole trap.
Holographic lithography with thick photoresist
Authors: Anderson Erik H. , Horwitz C. M. , Smith Henry I.
Published: February 2003

Gratings with periods as fine as 199 nm and height-to-width ratios ∼5:1 have been produced directly in photoresist by holographic lithography using a technique that reduces ‘‘orthogonal standing wave’’ problems. The technique uses a single layer of photoresist to attenuate the ‘‘orthogonal standing wave,’’ as well as record the grating pattern. The technique is tolerant of process variations and produces structures suitable for further processing steps such as liftoff and etching.
Surface segregation and diffusion kinetics study of a Pt-Ir alloy using the time-of-flight atom-probe field ion microscope
Authors: Ahmad M. , Tsong T. T.
Published: February 2003

Two absolute composition depth profiles of single atomic layer depth resolution have been obtained for the (001) surface of a Pt-20% Ir alloy. Pt segregates only to the top two surface layers. A feature of a diffusion kinetic effect has also been observed from which diffusion parameters of alloy species in the near surface layers are estimated.
Scaling relations in the equation of state, thermal expansion, and melting of metals
Authors: Guinea Francisco , Rose James H. , Smith John R. , Ferrante John
Published: February 2003

A simple and yet quite accurate prediction of volume as a function of pressure for metals and alloys is presented. Thermal expansion coefficients and melting temperatures are predicted by simple, analytic expressions and results compare favorably with experiment for a broad range of metals. All of these predictions are made possible by the discovery of universality in binding energy relations for metals.
Hysteresis in a low-pressure argon discharge
Authors: Merlino Robert L. , Cartier Steven L.
Published: February 2003

Hysteresis in the discharge characteristics of a low pressure (p≂10−4 Torr), magnetized argon plasma column is reported. The hysteresis is associated with sudden jumps in plasma density and discharge current as either the discharge voltage or magnetic field strength is varied. A substantial change in the plasma density profile and the appearance of coherent plasma oscillations are also observed.
Neutralization of a propagating intense ion beam in vacuum
Authors: Sudan R. N.
Published: February 2003

A simple analysis of the neutralization of an intense ion beam propagating in vacuum is presented which predicts the principal results of previous numerical simulation and experiments.
Schottky-barrier height of ideal metal contacts to GaAs
Authors: Waldrop J. R.
Published: February 2003

The Schottky-barrier height φB of ideal (no interfacial oxide) contacts to GaAs has been measured for a diverse group of eleven metals, Cu, Pd, Ag, Au, Al, Ti, Pb, Bi, Ni, Cr, and Fe, by using current-voltage and capacitance-voltage techniques. The contacts were formed by metal evaporation in ultrahigh vacuum onto clean (100) surfaces of both n-type and p-type GaAs. For n-type contacts φB ranged from 0.96 to 0.72 eV, in the metal order listed above; for p-type contacts φB ranged from 0.45 to 0.62 eV. No simple correlation was found between φB and metal work function nor between φB and the chemical reactivity at the metal-GaAs interface.
Four-wave mixing in semi-insulating InP and GaAs using the photorefractive effect
Authors: Glass A. M. , Johnson A. M. , Olson D. H. , Simpson W. , Ballman A. A.
Published: February 2003

The photorefractive effect has been observed for the first time in semi-insulating InPe:Fe and GaAsCr. These materials are sensitive and versatile recording media for high bit rate parallel optical processing in the 0.8–1.8-μm spectral region using injection lasers of milliwatt power levels.
Excimer laser induced deposition of InP and indium-oxide films
Authors: Donnelly V. M. , Geva M. , Long J. , Karlicek R. F.
Published: February 2003

InP and In-oxide films have been deposited on quartz, GaAs, and InP substrates by excimer laser induced photodecomposition of (CH3)3InP(CH3)3 and P(CH3)3 vapors at 193 nm. The oxide film refractive index and stoichiometry are close to In2O3. Phosphorus incorporation in the films was greatly enhanced by focusing the laser beam to promote multiple-photon dissociation processes. These conditions also lead to enhanced carbon inclusion in the films, due to formation of species such as CH and CH2 in the gas phase. However, this carbon inclusion could be suppressed by focusing the beam onto the surface at normal incidence. In the irradiated zone InP could be deposited with P(CH3)3-to-(CH3)3InP(CH3)3 ratios of only ∼1:1. The technique offers several potential advantages over conventional metalorganic chemical vapor deposition, including lower temperature, enhanced rates, safer gases, and three-dimensional film composition control. Strong atomic In emission is observed in the gas phase above the depositing film, due to a multiple photon dissociation process. Gas phase fluorescence from P, CH, and C was also observed. These emissions give insight into the photodecomposition mechanism and also serve as a monitor of metalorganic precursor concentrations.
Single crystalline Si islands on an amorphous insulating layer recrystallized by an indirect laser heating technique for three-dimensional integrated circuits
Authors: Mukai R. , Sasaki N. , Iwai T. , Kawamura S. , Nakano M.
Published: February 2003

A new laser recrystallizing technique for producing single crystalline Si islands on an amorphous insulating layer has been developed. Si islands are recrystallized by indirect Ar ion laser heating utilizing a Si cap. This technique is an effective recrystallizing method for fabricating three-dimensional integrated circuits. During recrystallization, this technique easily and stably produces a desired temperature profile to eliminate grain boundaries in recrystallized Si islands; the interior of the Si islands is kept cooler than the periphery and crystal growth begins from the interior. This desired temperature profile is realized because an Ar ion laser power is absorbed in the Si cap and heat flow takes place to the Si islands laterally as well as vertically from the heated Si cap through a separation cap. Damage to the underlying layer is not observed, which suggests that the laser beam power is cut in the Si cap. No grain boundaries are observed in more than 90% of the Si islands recrystallized with such an arrangement that laser beam traces include Si islands; the size of the islands is 20×60 μm. Field effect mobility of 460 cm2/Vs is obtained for Si on insulator/metal-oxide-semiconductor field-effect transistors fabricated in the recrystallized Si islands with this technique.
Optical studies of cerium doped yttrium aluminum garnet single crystals
Authors: Wong C. M. , Rotman S. R. , Warde C.
Published: February 2003

Single crystals of undoped and cerium-doped yttrium aluminum garnet have been pumped with laser radiation of 220- and 266-nm wavelength. A broadband defect emission at approximately 300 nm was observed, similar to that obtained with cathodoluminescence, although decreased in magnitude. Evidence of a transfer of energy from these defect states to the Ce+3 states was inferred from the photoluminescence decay time measurements. We have associated the absorption spectra from 200–300 nm with the defect excitation spectrum, including the peaks at 225 and 270 nm.
Increased radiation resistance in lithium-counterdoped silicon solar cells
Authors: Weinberg I. , Mehta S. , Swartz C. K.
Published: February 2003

Lithium-counterdoped n+p silicon solar cells are found to exhibit significantly increased radiation resistance to 1-MeV electron irradiation when compared to boron-doped n+p silicon solar cells. In addition to improved radiation resistance, considerable damage recovery by annealing is observed in the counterdoped cells at T≤100 °C. Deep level transient spectroscopy measurements are used to identify the defect whose removal results in the low-temperature anneal. It is suggested that the increased radiation resistance of the counterdoped cells is primarily due to interaction of the lithium with interstitial oxygen.
Theory of excitonic photoluminescence linewidth in semiconductor alloys
Authors: Singh J. , Bajaj K. K.
Published: February 2003

An expression for the excitonic photoluminescence linewidth in intentionally undoped semiconductor alloys is derived. The dominant mechanism for the line broadening is due to the statistical potential fluctuations caused by the components of the alloy. These fluctuations are accounted for by using statistical arguments developed by Lifshitz and then related to the linewidth. Compositional dependence of the linewidth is derived. It is shown that the linewidth is strongly dependent on the short range disorder present in the alloy. The theoretical results are compared with the available low-temperature photoluminescence data in GaAlAs.
Sintering of new oxide ceramics using a high power cw CO2 laser
Authors: Okutomi M. , Kasamatsu M. , Tsukamoto K. , Shiratori S. , Uchiyama F.
Published: February 2003

The sintering of ceramic oxide powders has been investigated using a high power CO2 laser as the heat source. The laser sintering method is very useful for the densification of oxides such as ZrO2, HfO2, and Y2O3 which have high melting points above 2000 °C. The new ceramic in the ternary system of (ZrO2-Y2O3-HfO2) processed by the laser method has a high melting point (2850 °C) and a hardness of about 1800 kg/mm2. The new oxide ceramic is composed of the crystalline phase of tetragonal ZrO2 and ZrO2 HfO2 Y2O3 solid solution, and does not show any phase transitions at high temperatures.
Detection of SiH2 in silane and disilane glow discharges by frequency modulation absorption spectroscopy
Authors: Jasinski J. M. , Whittaker E. A. , Bjorklund G. C. , Dreyfus R. W. , Estes R. D. , Walkup R. E.
Published: February 2003

The reactive species SiH2 has been directly observed in dc glow discharges using the technique of frequency modulation absorption spectroscopy. The spatial distribution of SiH2 in the discharge and the relative amounts of SiH2 in silane and disilane discharges have been measured.
Doping of silicon in molecular beam epitaxy systems by solid phase epitaxy
Authors: Streit D. , Metzger R. A. , Allen F. G.
Published: February 2003

Doped Si films were deposited by controlled coevaporation or Ga( p) of Sb(n) and Si at room temperature on an atomically clean Si substrate in ultrahigh vacuum. The amorphous films were then crystallized at 230 Å/min by heating the substrate to 575 °C. Good crystal quality results, judged by Rutherford backscattering and transmission electron microscopy. Advantages over normal evaporative doping during molecular beam epitaxial growth at ∼750 °C include (1) unity sticking coefficient of the dopant, (2) no smearing or carry-over of the dopant, (3) better mobility (bulk values for n or p∼1018 cm−3), and (4) higher doping levels (>8×1018 cm−3 for Ga, 8×1019 cm−3 for Sb).
Magnetic penetration depths in superconducting NbN films prepared by reactive dc magnetron sputtering
Authors: Kubo Shugo , Asahi Masayoshi , Hikita Makoto , Igarashi Masaru
Published: February 2003

Penetration depth λ behavior in reactively sputtered NbN films has been examined. For NbN films deposited at 300 °C or higher by means of dc magnetron technique, λ values around 300 nm were obtained, very short compared with the previously reported values (500–700 nm). The measured λ dependences on deposition parameters are discussed in connection with film structure on the basis of the Ginzburg–Landau–Abrikosov–Gor’kov theory of type II superconductivity.
Coupled-mode analysis of phase-locked injection laser arrays
Authors: Butler J. K. , Ackley D. E. , Botez D.
Published: February 2003

A coupled-mode analysis has been developed to describe the output of phase-locked injection laser arrays. We show that an array of emitters with weak coupling can only operate in a set of discrete modes determined by the number and the spacing of the emitters. The interaction between emitters leads to a splitting of the common frequency of operation that can be estimated from the coupling strength. The coupled-mode analysis is compared to calculations based on simple diffraction theory. A consequence of the analysis is an explanation for the commonly observed discrepancy between experimentally observed far-field lobe(s) widths and those predicted by simple diffraction theory.
Enhanced activation of Zn-implanted GaAs
Authors: Davies D. Eirug , McNally P. J.
Published: February 2003

Limitations on high level doping have been investigated for implanted Zn in GaAs. Fast diffusive redistribution during the annealing of heavy dose Zn implants generally leads to broader doped layers of lesser concentrations. Though such a redistribution can be prevented by short duration annealing of ∼1 s, this alone is not sufficient to increase the peak concentration. Significantly better activation can be obtained if an excess of As is also provided. It is found that coimplanting As with Zn in addition to short duration annealing provides layers with peak doping concentrations increased to levels approaching 1020 cm−3. Doping enhancement related to encapsulation and the outdiffusion of Ga into SiO2 has also been observed.
Persistent photoluminescence quenching of 0.68-eV emission in undoped semi-insulating GaAs
Authors: Yu Phil Won
Published: February 2003

The persistent photoluminescence quenching effect is shown to occur on the broad 0.68-eV emission commonly present in undoped semi-insulating GaAs bulk materials. The dependence of this persistent emission on below band-gap energy excitation has been measured. The data indicate involvement of the main deep donor EL2 in the radiative mechanism of the 0.68-eV emission. The persistent photoluminescence quenching effect can be explained by the presence of both normal and metastable states of EL2.
Direct modulation of semiconductor lasers at f>10 GHz by low-temperature operation
Authors: Lau K. Y. , Harder Ch. , Yariv A.
Published: February 2003

Using a 175-μm-long buried-heterostructure laser fabricated on a semi-insulating substrate operating at −50 °C, a direct amplitude modulation bandwidth in excess of 10 GHz has been achieved.
Low-temperature silicon epitaxy using low pressure chemical vapor deposition with and without plasma enhancement
Authors: Donahue T. J. , Burger W. R. , Reif R.
Published: February 2003

Specular epitaxial silicon films have been deposited at 775 °C using a low pressure chemical vapor deposition process both with and without plasma enhancement. This is the lowest silicon epitaxial deposition temperature reported for thermally driven chemical vapor deposition. It was found that the predeposition in situ cleaning of the surface, rather than any plasma effects during the deposition, was essential for achieving epitaxial growth at this low temperature. Surface cleaning in these experiments was done by sputtering the wafer in an argon plasma at 775 °C with a dc bias applied to the susceptor. This is the lowest pre-epitaxial cleaning temperature reported for thermally driven chemical vapor deposition.
Photoinduced quenching of infrared absorption nonuniformities of large diameter GaAs crystals
Authors: Skolnick M. S. , Reed L. J. , Pitt A. D.
Published: February 2003

Low-temperature quenching of inhomogeneities in two-dimensional infrared images of large diameter liquid encapsulated Czochralski (LEC) crystals of semi-insulating GaAs is reported. The temperature and wavelength dependence of the ‘‘fatiguing’’ phenomena have the same characteristics as those reported for the deep donor EL2. These results demonstrate in a clear way that the dominant nonuniformities of the infrared (0.7–1.4 eV) transmission of LEC GaAs are due to fluctuations in the concentration of neutral EL2. In the quenched state, weak nonuniformities with reverse contrast to EL2 still remain. These may be due to a photoelastic effect in the strain fields of dislocations, or to the presence of another center whose spatial fluctuations are the reverse of those of EL2.
Interaction of a modulated intense relativistic electron beam with a cavity
Authors: Friedman M. , Serlin V.
Published: February 2003

The mutual interaction between intense relativistic electron bunches and a cavity was investigated. It was found that this interaction generated an oscilating voltage in the cavity with an amplitude and a phase that depended on (1) the frequency of the modulated electron beam, (2) the characteristic frequency of the cavity, (3) the characteristic impedance of the cavity, and (4) peak beam current. This voltage caused energy exchange between electrons within a bunch resulting in modifications of the shape and peak current of the bunches. For a ‘‘critical’’ cavity geometry the voltage increased to a high amplitude, drastically reducing beam peak and average currents.