Showing papers by "Alcatel-Lucent published in 1984"

GexSi1−x/Si strained‐layer superlattice grown by molecular beam epitaxy

Abstract: GexSi1−x films are grown on Si by molecular beam epitaxy and analyzed by Nomarski optical interference microscopy, Rutherford ion backscattering and channeling, x‐ray diffraction, and transmission electron microscopy. The full range of alloy compositions will grow smoothly on silicon. GexSi1−x films with x≤0.5 can be grown free of dislocations by means of strained‐layer epitaxy where lattice mismatch is accommodated by tetragonal strain. Critical thickness and composition values are tabulated for strained‐layer growth. Multiple strained layers are combined to form a GexSi1−x/Si strained‐layer superlattice.

Scaling and related techniques for geometry problems

Abstract: Three techniques in computational geometry are explored: Scaling solves a problem by viewing it at increasing levels of numerical precision; activation is a restricted type of update operation, useful in sweep algorithms; the Cartesian tree is a data structure for problems involving maximums and minimums. These techniques solve the minimum spanning tree problem in Rk1 and Rk

Surface infrared study of Si(100)-(2×1)H

Abstract: Combinaison de la spectrometrie IR et de calculs ab initio sur des agregats pour la determination complete de la geometrie et des parametres vibrationnels de cette structure

Amplified femtosecond optical pulses and continuum generation at 5-kHz repetition rate.

Abstract: Pulses of 90-fsec duration from a cavity-dumped colliding-pulse mode-locked laser have been amplified to microjoule energies at 5-kHz repetition rate using a copper-vapor-laser pump source. Near-diffraction-limited focusing and efficient femtosecond continuum generation are demonstrated.

Pseudomorphic growth of GexSi1−x on silicon by molecular beam epitaxy

Abstract: GexSi1−x layers are grown on Si substrates over the full range of alloy compositions at temperatures from 400–750 °C by means of molecular beam epitaxy. At a given growth temperature films grow in a smooth, two‐dimensional manner up to a critical germanium fraction xc. Beyond xc growth is rough. xc increases from 0.1 at 750 °C to 1.0 at ∼550 °C. Rutherford ion backscattering measurements indicate good crystallinity over a wide range of growth conditions. Transmission electron microscopy reveals that in thin films, the lattice mismatch between the GexSi1−x and Si layers can be accommodated by lattice distortion rather than by misfit dislocation formation. This pseudomorphic growth condition can persist to alloy thicknesses as large as l/4 μm.

Organic‐on‐inorganic semiconductor contact barrier diodes. I. Theory with applications to organic thin films and prototype devices

Abstract: We discuss the properties of organic‐on‐inorganic (OI) semiconductor contact barrier diodes. A model for charge transport is developed which suggests that thermionic emission over the organic/inorganic contact barrier dominates at low current densities, whereas space‐charge effects dominate transport through the organic layer at high current densities. The effects of charge trapping in the organic layer are also considered. This model is applied to OI diodes using thin films of the prototypical aromatic compound; 3,4,9,10‐perylenetetracarboxylic dianhydride, (PTCDA) vapor‐deposited onto n‐ and p‐Si substrates. Several electrical and optical properties of PTCDA are investigated to provide a basis for analyzing the OI diodes. Both ohmic and space‐charge‐limited transport are observed in the PTCDA. We discuss mobility, transient response, and photoresponse of the thin‐film organic material. Also described are the general properties of organic‐on‐inorganic contact barrier diodes which employ PTCDA and related...

Confidence Bands for Survival Functions With Censored Data: A Comparative Study

Abstract: Consider the problem of obtaining simultaneous confidence bands for the survival function S(x) when the data are arbitrarily right censored. The usual pointwise confidence intervals based on Greenwood's variance formula can be adapted to yield a large-sample confidence band. This band has, in a certain sense, equal precision at each point of S(x). It is compared with the censored versions of the Kolmogorov band and the Renyi band. The comparisons are made in terms of the widths and the adequacy of large-sample approximations and are carried out under various censoring models and degrees of censoring. The bands are illustrated by applying them to data from a mechanical-switch life test.

A radix 4 delay commutator for fast Fourier transform processor implementation

Abstract: The development is described of a semicustom delay commutator circuit to support the implementation of high-speed fast Fourier transform processors based on the radix 4 pipeline FFT algorithm of J.H. McClellan and R.J. Purdy (1978). The delay commutator is a 108000-transistor circuit comprising 12288 shift register stages and approximately 2000 gates of random logic realized with 2.5-micrometer design rule CMOS standard cell technology. It operates at a 10-MHz clock rate, which processes data at a 40-MHz rate. The delay commutator is suitable for implementing processors that compute transforms of 16, 64, 256, 1024, and 4096 (complex) points. It is implemented as a 4-bit-wide data slice to facilitate cocatenation to accommodate common data word sizes and to use a standard 48-pin dual-in-line package.

Commensurate and incommensurate structures in molecular beam epitaxially grown GexSi1−xfilms on Si(100)

Abstract: The transition between commensurate and incommensurate growth of GexSi1−x alloys on Si is observed directly by means of ion channeling and x‐ray diffraction measurements. Molecular beam epitaxial films of thickness h up to 2500 A thick show commensurate epitaxy for x≲50% and h≲hc, a critical thickness dependent upon x. The observed values of hc are discussed in terms of a model invoking the maximum theoretical interfacial shear strength and a barrier to misfit dislocation formation.

Organic‐on‐inorganic semiconductor contact barrier diodes. II. Dependence on organic film and metal contact properties

Abstract: We discuss the effects of organic film thickness, film crystalline texture, contact metal, and temperature on the current‐voltage characteristics (I‐V) of organic‐on‐inorganic (OI) semiconductor contact barrier diodes, where the prototypical compound; 3, 4, 9, 10‐perylenetetracarboxylic dianhydride (PTCDA) serves as the organic thin film. The results presented can be fully understood in terms of the thermionic emission‐space‐charge‐limited (TE‐SCL) current model introduced in previous papers. Studies of the I‐V characteristics suggest the presence of a trap distribution centered at Δe=0.20 eV above the PTCDA valence band edge. Also, we have found a correlation between the hole mobility (μeff) and PTCDA crystalline texture, and obtain a mobility as high as μeff=1.4 cm2/V s for highly ordered crystalline thin films. Finally, the general criteria which must be fulfilled by an organic compound used to achieve high‐performance OI devices are outlined. The properties of several such devices using various organi...

Characterization of LPCVD Aluminum for VLSI Processing

Abstract: Aluminum and aluminum alloys are widely used for metallizing devices in VLSI processing. Such films can be deposited by a variety of techniques, which all presently suffer from inadequate step coverage. In this paper, we discuss the properties of aluminum films deposited by a low pressure chemical vapor deposition process using tri‐isobutyl aluminum as a source. Results of this work demonstrate that this process provides conformal step coverage, introduces no surface states, and promises to yield high wafer throughput. Films deposited on oxidized silicon monitors exhibit excellent properties in terms of chemical purity, adhesion, and electrical resistivity. Films deposited on device wafers prove to be compatible with current VLSI processing in terms of patterning, dry etching, and bondability and appear to have no effect on overall device performance. However, drawbacks of LPCVD aluminum appear to be in its structure‐related properties: namely, electromigration resistance and Al‐Si interdiffusion. These problems and potential solutions are addressed.

Characterization and optical properties of arrays of small gold particles.

Abstract: Square arrays of 20–35‐nm‐diam gold particles with 50‐nm spacings were formed on thick sapphire substrates by electron beam lithography. After annealing at 125 °C the particles had an approximately circular projection on the substrate with a slightly smaller dimension in the perpendicular direction as inferred from scanning electron microscopy. Optical transmission measurements were made on 15‐μm square areas of particles using an optical microscope modified for microspectroscopy. The regular geometry of the well characterized samples makes possible a detailed comparison to theory.

Physical mechanisms of dc switching in a liquid‐crystal bistable boundary layer display

Abstract: We discuss two mechanisms proposed to explain dc switching of a bistable liquid‐crystal boundary layer display. These are (1) biasing by double layer fields that arise from charge of one sign preferentially adsorbed at the walls, and (2) asymmetry in the transient depletion layer fields which result from a difference in mobility of the positive and negative ions. By a quantitative discussion, we argue that both mechanisms are plausible, but crucial parameters remain unknown. For the double layer mechanism the surface density of adsorbed charge is estimated as 8×10−10 C/cm2 from published measurements of the thickness dependence of the resistivity. For a numerical example of the differential mobility mechanism, we arbitrarily take μ−=3μ+=9×10−6 cm2/V sec. Either mechanism may be made dominant by the choice of material and surface properties. For fast switching, it may prove advantageous to choose interfaces to exploit the double layer mechanism because it begins to act immediately upon application of the v...

Preparation and characterization of functionalized polyethylene surfaces

Abstract: Preparation en combinant des techniques chimique et de decharge gazeuse. Les reactions apparaissent etre limitees a une couche superficielle tres fine du polymere

High pressure phase transitions and hydrogen‐bond symmetry in ice polymorphs

Abstract: A recently developed ground state variational wave function theory of hydrogen‐bonded crystals is employed to investigate the high pressure behavior of several ice polymorphs. The theory accurately accounts for short and long range proton correlations and quantum mechanical tunneling, all of which are important in the high pressure regime. Attention is focused on pressure induced order–disorder phase transitions and hydrogen‐bond symmetrization for the ices VII, VIII, and Ic. We find a strongly first order transition (driven by proton tunneling) at approximately 330 kbar from the antiferroelectrically ordered ice VIII phase to a highly ionized form of proton disordered ice VII. Despite the large degree of ionization, significant short range proton order remains at the transition as indicated by the bimodality of the proton charge density along the bond. The crossover to a unimodal situation, i.e., hydrogen‐bond symmetrization, is predicted to occur at 450 kbar. The effects of deuterium isotope substitutio...

Multi-function communication board for expanding the versatility of a computer

Abstract: A single board multiple option card for expanding the versatility of a host computer includes an onboard microprocessor, a digital signal processor and a switched memory device. The switched memory is accessible by the onboard microprocessor and the digital signal processor under the control of the onboard microprocessor. The card further includes an analog signal interface having a plurality of switches, the positions of which are controlled by the onboard microprocessor. As a result, multiple options are provided by varying the positions of the switches. Typically, such options may include: "Invisible Keyboard"; "Voice Command Over Telephone Lines"; "Voice Store and Forward Over the Telephone"; "Voice Record and Playback"; and "Hands-free Telephone".

Characterization of high purity Si-doped molecular beam epitaxial GaAs

Abstract: High‐purity, lightly Si‐doped (μ77∼70 000–126 000 cm2/V s and n77∼2–8×1014 cm−3) molecular beam epitaxy (MBE) GaAs layers have been characterized using variable‐temperature Hall effect and C‐V measurements, photothermal ionization spectroscopy, low‐temperature photoluminescence (PL), and deep level transient spectroscopy (DLTS). The spectroscopic measurements of the residual donors and acceptors indicate that the pronounced increase in carrier concentration which is observed with increasing As flux (for a constant Ga flux) results from incorporation of additional residual S donors from the As source material, and not from reductions in the Si acceptor concentration or residual C acceptor concentration. The increase in carrier concentration with As flux is considerably more pronounced when using an alternative source of As, which introduces both S and 3 additional donor species. The C acceptor concentration increases with As flux using either As source, although the increase is much stronger with the alter...

CO bond angle changes in photolysis of carboxymyoglobin.

Abstract: Previous studies [Chance, B., Fischetti, B., & Powers, L. (1983) Biochemistry 22, 3820-3829] of the local structure changes around the iron in carboxymyoglobin on photolysis at 4 K revealed that the iron-carbon distance increased approximately 0.05 A but was accompanied by a lengthening of the iron-pyrrole nitrogen bonds of the heme (approximately 0.03 A) that was not as large as that found in the deoxy form. Further analysis of these data together with comparison to model compounds indicates that the Fe-C-O bond angle in carboxymyoglobin is bent (127 +/- 4 degrees), having a structure identical, within the error, with the "pocket" porphyrin model compound FePocPiv(1-MeIm)(CO) [Collman, J. P., Brauman, J. I., Collins, T. J., Iverson, B. L., Lang, G., Pettman, R., Sessler, J. L., & Walters, M. A. (1983) J. Am. Chem Soc. 105, 3038-3052]. On photolysis, this angle decreases by 5-10 degrees. In addition, correlation is observed between the increase in the length of the Fe-C bond and the decrease of the Fe-C-O angle. These results suggest that the rate-limiting step in recombination is the thermal motion of CO in the pocket to achieve an appropriate bonding angle with respect to the iron. These changes constitute the first molecular picture of the photolysis process, as well as the structure of the geminate state, and are important in clarifying nuclear tunneling parameters.

Structure and reactivity of multiple forms of cytochrome oxidase as evaluated by X-ray absorption spectroscopy and kinetics of cyanide binding

Abstract: The extended X-ray absorption fine structure (EXAFS) data show differences between the active site structures of different cytochrome oxidase preparations. In the resting (as isolated) state of the Yonetani preparation, the bridging atom between Fe3+a3 and Cu2+a3 is present [Powers, L., Chance, B., Ching, Y., & Angiolillo, P. (1981) Biophys. J. 34, 465], whereas in another preparation (e.g., Hartzell-Beinert), this atom seems to be bound only to Fe3+a3 in a significant fraction of the molecules. Both preparations bind cyanide in a multiphasic fashion, suggesting that the resting cytochrome oxidase is not homogeneous but rather is a mixture of several forms. The proportion of these forms as detected by cyanide binding kinetics differs for different preparations. However, upon reduction and reoxidation (conversion to the "oxygenated" form) the cyanide binding kinetics become monophasic and all preparations of the oxygenated form bind cyanide at the same rate. Thus, a combination of structural and kinetic approaches seems necessary for evaluation of the nature of the active site of cytochrome oxidase in its various forms.

Submicron, vacuum ultraviolet contact lithography with an F2 excimer laser

Abstract: An F2 excimer laser at 157 nm has been used for the first time as an exposure source for high resolution photolithography. At this short wavelength, conventional glass and quartz mask substrates are opaque, and therefore alkaline‐earth halides and sapphire were used as mask substrates. The masks were patterned by electron beam lithography, and mask features as narrow as 150 nm have been replicated and represent the smallest features yet produced by contact photolithography.

High resolution electron beam lithography on CaF2

Abstract: We have fabricated 30‐nm lines on 200‐nm centers in CaF2 using a scanning transmission electron microscope. The lines were written by electron beam radiolysis of a fine grain polycrystalline CaF2 film and reaction to CaO followed by development in H2O.