Showing papers on "Amorphous solid published in 1981"
TL;DR: The effect of thermal and structural disorder on the electronic structure of hydrogenated amorphous silicon is investigated by measurement of the shape of the optical absorption edge as a function of temperature and thermal evolution of hydrogen as discussed by the authors.
Abstract: The effect of thermal and structural disorder on the electronic structure of hydrogenated amorphous silicon is investigated by measurement of the shape of the optical absorption edge as a function of temperature and thermal evolution of hydrogen. The data are consistent with the idea that the thermal and structural disorder are additive, and suggest that the disorder, rather than the hydrogen content, is the fundamental determining factor in the optical band gap.
974 citations
TL;DR: In this paper, the authors used macroscopic diffusion equations for heat and mass transport, cast in a finite-difference form to allow for the temperature and spatial dependences of the thermal conductivity, absorption coefficient, reflectivity, and other quantities.
Abstract: Pulses of radiation from ruby and Nd:YAG $Q$-switched lasers have been used recently to anneal the lattice damage caused by ion implantation of semiconductors. Other similar applications include the laser-induced diffusion of thin dopant films deposited on the surface of samples, recrystallization of doped amorphous films deposited on single-crystal substrates, and the removal of precipitates present after conventional high-temperature dopant diffusion. All of these processes can be understood in terms of models and calculations based on macroscopic diffusion equations for heat and mass transport, cast in a finite-difference form to allow for the temperature and spatial dependences of the thermal conductivity, absorption coefficient, reflectivity, and other quantities. Results of calculations on silicon with the models show that the near-surface region of a sample can melt and stay molten for times of the order of 100 nsec during which dopant diffusion in the liquid state and nonequilibrium segregation during ultrarapid recrystallization are sufficient to explain the major features of the experimental results. In this paper, a description of the model used in our heat-transport calculations is given. Results of the modeling are illustrated by a variety of calculations which should be of particular interest to experimentalists working with pulsed-laser annealing. These results include, e.g., the effects of pulse duration, shape, and energy density, the effects of assumptions made about the latent heat of amorphous silicon, the effects of substrate heating, the role played by the absorption coefficient in determining melt-front penetration, and the duration of surface melting.
396 citations
TL;DR: In this article, an analysis of the welding process based on the reptation picture of polymer dynamics due to de Gennes was presented. But the analysis was restricted to the case when two pieces of the same amorphous polymer are brought into contact at a temperature above the glass transition, the junction surface gradually heals until, at very long contact times, it is indistinguishable from bulk polymer.
Abstract: When two pieces of the same amorphous polymer are brought into contact at a temperature above the glass transition, the junction surface gradually heals until, at very long contact times, it is indistinguishable from bulk polymer. We have developed an analysis of this welding process based on the reptation picture of polymer dynamics due to de Gennes. The theory predicts the number of bridges (pieces of polymer chain) per unit area spanning the original junction surface as a function of time. At fixed time the number of bridges (σ) also depends on the molecular weight (M) of the chains. If the initial contact is between surfaces which have been equilibrated against a gas phase, we find that σ∼t1/2M−3/2. Alternatively, if the contacting surfaces contain many chain ends, such as may be found at brittle fracture surfaces in glassy polymers, we find that σ∼t1/4M−1/4 at short times. The theory may be compared to available measurements on strength development in healing interfaces leading to the conclusion that...
333 citations
15 Apr 1981
TL;DR: In this article, the optical constants of amorphous solid water were determined at 10 K and 80 K from a Kramers-Kronig analysis of the transmission spectra taking into account reflection and interference losses.
Abstract: Absorption spectra from 4000 to 1200 cm −1 of amorphous solid water and polycrystalline ice I c have been measured between 10 K and 140 K. Warm up and recooling of an H 2 O sample prepared at 10 K gives rise to both irreversible and reversible changes in the peak frequency, band width, and peak height as well as the integrated intensity of the OH stretching band. These spectral effects are related to structural differences. The structure of amorphous solid water also depends on deposition conditions. The optical constants of amorphous so water are determined at 10 K and 80 K from a Kramers-Kronig analysis of the transmission spectra taking into account reflection and interference losses. The astrophysical implication of the temperature dependence of peak frequency and band width of the 3250 cm −1 band in amorphous solid water is discussed briefly.
283 citations
TL;DR: In this article, the authors used ion-induced reactions in thin film systems to form equilibrium and metastable compounds, amorphous layers, and solid solutions, which can be obtained by splat-cooling or high dose plantation.
275 citations
TL;DR: In this paper, the authors presented a model based on an asymmetric double-well potential having distributions of both the barrier height g(V) and the asymmetry f(Δ) such a model is justified by the random local environments in an amorphous material, and has the advantage that no low barrier cut-off is required, in contrast with the symmetric doublewell model.
Abstract: Peaks in the ultrasonic attenuation observed in amorphous materials are almost always explained in terms of a classical, thermally activated, structural relaxation process represented by a symmetric double-well potential with a broad distribution of barrier heights This model suffers from two drawbacks: a low barrier cut-off is required to produce a peak in the attenuation and the magnitude of the attenuation does not scale with the frequency of the acoustic waves, contrary to experimental evidence This paper presents a model based on an asymmetric double-well potential having distributions of both the barrier height g(V) and the asymmetry f(Δ) Such a model is justified by the random local environments in an amorphous material, and has the advantage that no low barrier cut-off is required, in contrast with the symmetric double-well model To illustrate the predictions of the model specific forms are assumed for the distribution functions: f(Δ) is taken as constant (valid for temperatures well
273 citations
TL;DR: In this article, structural defects are defined as regions in which the corresponding characterizing parameter deviates significantly from its average value, and two distinct classes of defects are found; positive (p-type defects) and negative (n-type defect) local density fluctuations; and regions of large shear stresses and large deviations from spherical symmetry.
Abstract: The possibility of defining structural defects in amorphous solids in terms of parameters such as atomic-level internal stresses and local symmetry coefficients was proposed in a previous paper (Egami, Maeda and Vitek 1980). Using a model amorphous structure generated by a computer, these parameters are statistically analysed in the present paper. It is shown that the stress and the symmetry coefficients are closely correlated and that spatial correlations of various kinds exist. The structural defects are then defined as regions in which the corresponding characterizing parameter deviates significantly from its average value. Two distinct classes of defects were found; (i) positive (p-type defects) and negative (n-type defects) local density fluctuations; and (ii) regions of large shear stresses and large deviations from spherical symmetry. Defects consisting of pairs of p-type and n-type defects separated by regions of large shear stresses are also common. The effect of annihilation of p- and n...
257 citations
TL;DR: In this paper, it is shown that thin-film field effect transistors (FETs) made from amorphous (a-) silicon deposited by the glow-discharge technique have considerable potential as switching elements in addressable liquid crystal display panels.
Abstract: It is shown that thin-film field effect transistors (FETs) made from amorphous (a-) silicon deposited by the glow-discharge technique have considerable potential as switching elements in addressable liquid crystal display panels. The fabrication of the elements and their characteristics with steady and pulsed applied potentials are discussed in some detail. Two important points are stressed: (i) a-Si device arrays can be produced by well-established photolithographic techniques, and (ii) satisfactory operation at applied voltages below 15VV is possible. Small experimental 7×5 transistor panels have been investigated and it is shown that with the present design up to 250-way multiplexing could be achieved. The reproducibility of FET characteristics is good and in tests so far no change has been observed after more than 109 switching operations.
255 citations
TL;DR: In this article, group theory was employed to interpret the observed spectra of crystalline α- and β-Si 3 N 4, which exhibited two broad peaks centered at about 400 and 900 cm −1.
Abstract: Vibrational excitations of α- and β-Si 3 N 4 were studied by Raman and infrared absorption spectroscopies. Group theory was employed to interpret the observed spectra of crystalline α- and β-Si 3 N 4 . Both Raman and IR spectra of amorphous Si 3 N 4 exhibit two broad peaks centered at about 400 and 900 cm −1 . Amorphous Si 3 N 4 was found to be of the non-molecular, random-network type.
247 citations
TL;DR: In this paper, a differential anomalous x-ray scattering technique has been developed for structural studies of disordered and amorphous systems, which is consistent with threefold coordinated models of the structure but not with the fourfold-twofold models.
Abstract: A differential anomalous x-ray scattering technique has been developed for structural studies of disordered and amorphous systems. The results on amorphous GeSe/sub 2/ are consistent with the twofold coordination of Se and the fourfold coordination of Ge. The results on amorphous GeSe are consistent with threefold coordinated models of the structure but not with the fourfold-twofold models.
243 citations
TL;DR: In this article, a scaling model for the metal-insulator transition in amorphous materials is presented, which predicts a continuous phase transition at zero temperature with localized states and a correlation gap in the insulating phase.
Abstract: A scaling model is presented for the metal-insulator transition in amorphous materials which includes a localization, correlation, and screening. The model predicts a continuous phase transition at zero temperature with localized states and a correlation gap in the insulating phase.
TL;DR: In this paper, the optical and physical properties of various single films and multilayer systems are described and their history, the dip-coating procedure and especially the chemical processes are described.
TL;DR: In this article, a review covers results of recent O.M.R.D. measurements of recombination processes in layered semiconductors, II-VI compounds, at dep traps and in amorphous compounds.
Abstract: This review covers results of recent O.D.M.R. measurements of recombination processes in layered semiconductors, II–VI compounds, at dep traps and in amorphous compounds, and includes consideration of experimental aspects.
TL;DR: In this paper, a clear valency electron controllability with substitutional impurity doping in the hydrogenated amorphous silicon carbide has been found, and a new type of a•SiC:H/a•Si:H heterojunction solar cell was developed.
Abstract: A clear valency electron controllability with substitutional impurity doping in the hydrogenated amorphous silicon carbide has been found. The amorphous silicon carbide is produced by the plasma decomposition of [SiH4(1−X)+CH4(X)] with the dopant gas of a B2H6 or PH3 system. Electrical and optical properties of doped amorphous SiC films are briefly demonstrated. Utilizing this a‐SiC:H as a wide‐band‐gap window material, we have developed a new type of a‐SiC:H/a‐Si:H heterojunction solar cell. A typical cell performance is Voc = 0.887 V, Jsc = 12.33 mA/cm2, fill factor = 0.653, and the conversion efficiency of 7.14% under AM‐1 illumination.
TL;DR: In this article, the energy distributions of sputtered Nb and Cu atoms ejected from amorphous targets under low-energy Ar bombardment were calculated and the subsequent energy loss of the ejected atoms due to collisions in the sputtering gas was calculated.
Abstract: We have calculated the energy distributions of sputtered Nb and Cu atoms ejected from amorphous targets under low‐energy Ar bombardment. A formula based on elementary kinetic gas theory is used to calculate the subsequent energy loss of the ejected atoms due to collisions in the sputtering gas. The energy distributions of the sputtered atoms arriving at the substrate is compared with the distributions obtained using thermal evaporation techniques. This comparison indicates that the preparation of epitaxial metallic films, such as Layered Ultrathin Coherent Structures using sputtering techniques may have fundamental advantages over thermal evaporation.
TL;DR: In this paper, the collective translational structure of dilute suspensions under shear is investigated by light scattering, and it is shown that the equilibrium bcc Wigner lattice exhibits two major, reversible, disordering transitions.
Abstract: The collective translational structure of dilute suspensions (\ensuremath{\sim} 0.1% by weight) of charged, spherical, and colloidal particles under shear is investigated by light scattering. When subjected to increasing shear rate, the equilibrium bcc Wigner lattice exhibits two major, reversible, disordering transitions. Transition II occurs at low shear, is kink mediated and results in freely slipping two-dimensional hcp layers. At higher rates, transition I occurs where these two-dimensional layers melt via shear-induced fluctuations (phonons) to produce an amorphous structure. The amorphous structure has stringlike particle correlations which ultimately disappear.
TL;DR: The results of secondary ion mass spectrometric analysis of carbon films produced by rf plasma decomposition of hydrocarbon gases are also discussed in this article, where the results indicate that these films are predominantly amorphous, both singlecrystal and polycrystalline diffraction patterns have been obtained from both types that indicate formation of several different phases.
Abstract: Diamondlike carbon films produced both by ion‐beam technique and by radio‐frequency (rf) plasma decomposition of hydrocarbon gases (C4H10, C2H6, C3H8, and CH4) have been examined using the technique of transmission electron microscopy. Although these examinations indicate that these films are predominantly amorphous, both single‐crystal and polycrystalline diffraction patterns have been obtained from films of both types that indicate formation of several different phases. Some of these phases appear to be cubic and could be new forms of carbon. The results of secondary ion mass spectrometric analysis of carbon films produced by rf plasma decomposition of hydrocarbon gases are also discussed.
TL;DR: X-Rayamorphous zeolites have been prepared which exhibit i.r. and catalytic properties typical for ZSM-5 materials and therefore must contain ZSM5 crystals of less than 8 nm size in an amorphous matrix.
Abstract: X-Ray-amorphous zeolites have been prepared which exhibit i.r. and catalytic properties typical for ZSM-5 materials and therefore must contain ZSM-5 crystals of less than 8 nm size in an amorphous matrix.
TL;DR: The coercive field of amorphous ferromagnetic alloys is determined by defect structures, surface irregularities, relaxation phenomena and intrinsic fluctuations of the material properties within the framework of micromagnetism.
TL;DR: In this article, 15 amorphous Fe-Ni base alloys containing P and/or B as additives were studied to determine their catalytic activity for the hydrogenation of CO to produce mainly C1 to C3 hydrocarbons.
TL;DR: In this paper, the status of ion-induced defects in semiconductors is reviewed, including the charge-state dependence of defects, novel defect migration mechanism and enhanced damage production mechanisms, where the main emphasis is on defects in silicon where a panorama of defects is emerging which encompasses the evolution of damage from vacancies and interstitials and their aggregates to stacking faults and dislocations to disordered zones and the development of an amorphous layer.
TL;DR: In this article, a sol-gel process was applied to polished silicon and heat treated at temperatures less than 450°C to convert the applied films to amorphous oxide films ranging in refractive index from approximately 163 to 217.
TL;DR: In this paper, the existence of weakly bonded H in $a$-Ge: H and Ge-rich $a-Si: H over Ge: H alloys was investigated and a preference ratio in excess of 5 for the attachment of H to Si over Ge was found.
Abstract: Hydrogen evolution and infrared vibrational absorption have been interpreted to show (1) the existence of weakly bonded H in $a$-Ge: H and Ge-rich $a$-Si-Ge: H alloys, and (2) a preference ratio in excess of 5 for the attachment of H to Si over Ge in the formation of such alloys. It is suggested that this may account for the inferior photoresponse of hydrogenated binaries compared to elements, and also for the superiority of $a$-Si: H over $a$-Ge: H. Some ideas on better compensators than H are advanced.
TL;DR: In this paper, the properties of amorphous hydrogenated silicon are reviewed, with special emphasis placed on results obtained by the method of reactive sputtering in an argon-hydrogen plasma.
TL;DR: In this paper, the photoluminescence, optical properties and photoconductivity of amorphous Si : C : H alloys prepared from the plasma decomposition of silane and ethylene are presented.
Abstract: Results on the photoluminescence, optical properties and photoconductivity of amorphous Si : C : H alloys prepared from the plasma decomposition of silane and ethylene are presented. Films deposited at substrate temperatures of 30 and 300°C have been studied with compositions ranging from 100 to 10% silicon. The photoluminescence spectra measured at 77 and 300 K show considerable discrepancies with respect to previously reported results. The emission is in the form of a single band which broadens and shifts towards higher photon energies as the carbon concentration is increased. The highest emission-peak energy of 2·05 eV is achieved for samples with 90 at.% C. The temperature quenching of the luminescence is reduced with increasing carbon concentration. For 90% C specimens there is less than a factor of 2 reduction in emission intensity between 77 and 300 K. As a consequence visible (yellow–orange) room-temperature luminescence can be clearly observed with the naked eye. The luminescence efficie...
TL;DR: In this article, a comparison of the Raman spectrum of amorphous MoS 3 and poorly crystalline MoS 2 has been performed using infrared and Raman spectroscopies.
TL;DR: In this paper, the in-phase and out-of-phase properties of a spin glass were investigated and it was shown that the properties of spin glass have a broad spectrum of relaxation times.
TL;DR: In this article, the first model of the collagen-apatite bond was proposed, and the transformation of carbonate ions into apatitic lattice can take place in two kinds of sites and under different forms.
TL;DR: Amorphous silicon films prepared by a discharge of 10% SiH4•90% H2 mixture are shown to have properties comparable to those prepared from 100%SiH4.
Abstract: Amorphous silicon films prepared by a discharge of 10% SiH4‐90% H2 mixture are shown to have properties comparable to those prepared from 100% SiH4. These films are found to be quite stable against prolonged light exposure.