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Showing papers on "Amorphous solid published in 1984"


Book
01 Jan 1984
TL;DR: In this paper, the glass transition theories for glass transition factors that determine the glass-transition temperature glass-forming systems and ease of glass formation are discussed. But they do not consider the effects of defects.
Abstract: Part 1 Preparation: definitions preparation of amorphous materials. Part 2 the glass transition theories for the glass transition factors that determine the glass-transition temperature glass-forming systems and ease of glass formation. Part 3 Structure: microscopic structure - experimental techniques, short-range order, medium-range order, structural modelling macroscopic structure - experimental techniques, examples of macroscopic structure. Part 4 Atomic dynamics: vibrational excitations computational methods experimental probes low-frequency modes and low temperature properties two-level systems ionic conduction. Part 5 Electrons: electronic density of states localization transport properties small polarons optical properties. Part 6 Defects: types of defect defect-controlled properties.

1,591 citations


Journal ArticleDOI
02 Aug 1984-Nature
TL;DR: Amorphous solids are made mainly by cooling the liquid below the glass transition without crystallizing it, a method used since before recorded history1, and by depositing the vapour onto a cold plate2, as well as by several other methods as discussed by the authors.
Abstract: Amorphous solids are made mainly by cooling the liquid below the glass transition without crystallizing it, a method used since before recorded history1, and by depositing the vapour onto a cold plate2, as well as by several other methods3,4. We report here a new way—by ‘melting’ a solid by pressure below the glass transition of the liquid—and apply it to making a new kind of amorphous ice. Thus, ice I has been transformed to an amorphous phase, as determined by X-ray diffraction, by pressurizing it at 77 K to its extrapolated melting point of 10 kbar. At the melting point, the fluid is well below its glass transition. On heating at a rate of ∼2.6 K min−1 at zero pressure it transforms at ∼117 K to a second amorphous phase with a heat evolution of 42±∼8 J g−1 and at ∼152 K further transforms to ice I with a heat evolution of 92±∼15 J g−1. In one sample, ice Ic was formed and in another, existing crystals of ice Ih grew from the amorphous phase. Heating below the 117 K transition causes irreversible changes in the diffraction pattern, and a continuous range of amorphous phases can be made. Similar transformations will probably occur in all solids whose melting point decreases with increasing pressure if they can be cooled sufficiently for a transformation to a crystalline solid to be too slow.

1,076 citations


Journal ArticleDOI
TL;DR: In this paper, three structural models of amorphous carbon with differing percentages of threefold and fourfold-coordinated atoms were constructed and analyzed, along with a purely fourcoordinated amorphus Ge model which was scaled to diamond bond lengths.
Abstract: Three structural models of amorphous carbon with differing percentages of threefold- and fourfold-coordinated atoms were constructed and analyzed, along with a purely four-coordinated amorphous Ge model which was scaled to diamond bond lengths. The radial distribution function and interference function, $F(k)$, of the model containing 14% four-coordinated atoms were in best agreement with the experimental results of Boiko et al., although the functions containing 48% four-coordinated atoms were in best agreement with the results of Kakinoki et al. The unavoidable planar nature of the entirely three-coordinated model caused its $F(k)$ to be in poor agreement with experiment. Raman and vibrational density-of-states (DOS) spectra were also calculated for the models. The presence of disorder in the three-coordinated model produced a downward shift in frequency of the principal Raman peak and DOS band edge from the position seen in graphite. With the addition of four-coordinated atoms, there was a gradual transition from graphitelike spectra to diamondlike spectra, rather than spectra with a mixture of distinct features typical of graphite and diamond. In addition, there was a further downward shift in frequency of the main Raman peak and in that of the "disorder peak" seen in microcrystalline and amorphous carbon. The spectra of the model containing 14% four-coordinated carbon was in best agreement with recent Raman scattering experiments. These results suggest a structure for amorphous carbon consisting of three-coordinated planar regions with occasional four-coordinated atoms allowing changes in orientation of the planes. The positions of the peaks in the spectra suggest that the proportion of four-coordinated atoms is not likely to exceed 10%.

608 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that bulk specimens (0.4-4 g mass) of the alloy Pd40Ni40P20 have been undercooled consistently to the glass state with no detectable superficial crystallinity, in a molten flux of dehydrated boron oxide.
Abstract: Bulk specimens (0.4-4 g mass) of the alloy Pd40Ni40P20 have been undercooled consistently to the glass state, with no detectable superficial crystallinity, in a molten flux of dehydrated boron oxide. The minimum dimension of the most massive glass specimen, so formed, was 1.0 cm. The absence of crystallinity in the specimens was confirmed by X-ray diffraction, scanning electron microscopy, and calorimetry.

539 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that amorphous Si melts at a temperature at least 50 K below the crystalline value, and the initial liquid layer solidifies to form coarse-grained polycrystalline Si.
Abstract: Measurements during pulsed laser irradiation indicate that amorphous Si melts at a temperature 200 \ifmmode\pm\else\textpm\fi{} 50 K below the crystalline value. Below energy densities required to melt the amorphous layer fully, the data are interpreted in terms of an explosive crystallization. The initial liquid layer solidifies to form coarse-grained polycrystalline Si. A thin, self-propagating liquid layer travels through the remaining amorphous Si at a velocity of 10-20 m/s, producing fine-grained polycrystalline Si.

514 citations


Journal ArticleDOI
TL;DR: In this article, an equation expressing the volume fraction,x, of crystals precipitating in a glass heated at a constant rate, α, was derived and the validity and usefulness of this equation was ascertained by applying it to a Li2O·2SiO2 glass.
Abstract: An equation expressing the volume fraction,x, of crystals precipitating in a glass heated at a constant rate, α, was derived. When crystal particles grow m-dimensionally,x is expressed as In [- ln(1 -x)] = -n (nα - 1.052mE/RT + Constant whereE is the activation energy for crystal growth andn is a numerical factor depending on the nucleation process. When the nuclei formed during the heating at the constant rate,α, are dominant,n is equal tom + 1, and when the nuclei formed in the previous heat-treatment before thermal analysis run are dominant,n is equal tom. The validity and usefulness of this equation was ascertained by applying it to a Li2O·2SiO2 glass. A method for determining the values ofn andm from DSC curves was proposed and it was concluded that the modified Ozawa-type plot is very useful and convenient to obtain the activation energy for crystal growth.

453 citations


Journal ArticleDOI
TL;DR: In this article, the energy levels of defect states in amorphous silicon nitride have been calculated and the results are used to identify the nature of trap states responsible for charge trapping during transport and the charge storage leading to memory action.
Abstract: The energy levels of defect states in amorphous silicon nitride have been calculated and the results are used to identify the nature of trap states responsible for charge trapping during transport and the charge storage leading to memory action. We argue that the Si dangling bond is the memory trap in chemical vapor deposited memory devices and is also the center in plasma‐deposited nitride responsible for hopping at low electric fields and for charge‐trapping instabilities in amorphous silicon‐silicon nitride thin‐film transistors.

402 citations


Journal ArticleDOI
TL;DR: In this paper, a silicon-related intrinsic defect called triplet-to-singlet transitions in the SiO2 optical absorption band was identified. But the most probable model for this center is a silicon atom with only two neighboring oxygens.

286 citations


Journal ArticleDOI
TL;DR: The real and imaginary parts of the complex index of refraction of a hydrogenated amorphous carbon (a•C:H) film have been determined for photon energies between 145 and 49 eV from measurements of reflectance R and transmittance T.
Abstract: The real and imaginary parts, n and k, of the complex index of refraction of a hydrogenated amorphous carbon (a‐C:H) film have been determined for photon energies between 145 and 49 eV from measurements of reflectance R and transmittance T Both n and k, and consequently e1 and e2 (the real and imaginary parts of the dielectric constant), show a considerable variation with subsequent annealing of the a‐C:H film up to Ta=750 °C, with the most rapid changes occurring for Ta=450 °C and above The optical gap Eopt is observed to decrease from 22 eV to 0 as the film is annealed, signaling the development of graphitic short range order in the film Using an effective medium approximation to model the optical properties of the film, we find that the as‐deposited film contains amorphous diamond‐like, graphitic, and polymeric components With annealing, the amorphous diamond‐like and polymeric components decrease, the amorphous graphitic component grows, and a void component appears We discuss the local order

281 citations


Journal ArticleDOI
TL;DR: In this paper, the forward current of all the junctions studied shows voltage and temperature dependence expressed as exp(−ΔEa f/kT) exp(AV), where ΔEa is the diffusion voltage and A is a constant.
Abstract: We have measured C‐V characteristics and temperature dependence of J‐V characteristics of undoped hydrogenated amorphous silicon (a‐Si:H) heterojunctions formed on p‐type crystalline silicon ( p c‐Si) substrates with different resistivities. It has been found that an abrupt heterojunction model is valid for a‐Si:H/p c‐Si heterojunctions, and the electron affinity of a‐Si:H has been estimated as 3.93±0.07 eV from C‐V characteristics. The forward current of all the junctions studied shows voltage and temperature dependence expressed as exp(−ΔEa f/kT) exp(AV), where ΔEa f and A are constants independent of voltage and temperature, being successfully explained by a multitunneling capture‐emission model. The reverse current is proportional to exp(−ΔEar/kT)(VD−V)1/2, where VD is the diffusion voltage and ΔEar is a constant. This current is probably limited by generation‐recombination process.

281 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that an irreversible change in the longitudinal sound velocity takes place between 10 and 17 GPa and that this change is stable at atmospheric pressure, and the Raman spectra of the retrieved sample indicate that it is also amorphous but differ noticeably from that of the original sample.
Abstract: Brillouin scattering from $a$-Si${\mathrm{O}}_{2}$ up to 17 GPa shows that an irreversible change in the longitudinal sound velocity takes place between 10 and 17 GPa and that this change is stable at atmospheric pressure. Raman spectra of the retrieved sample indicate that it is also amorphous but differ noticeably from that of the original sample.

Journal ArticleDOI
TL;DR: In this article, two experimental techniques are described for the determination of the change of specific volume of polymers with temperature and aging time, which allow measurements between − 160 °C and + 200 °C.
Abstract: Two experimental techniques are described for the determination of the change of specific volume of polymers with temperature and aging time, which allow measurements between − 160 °C and + 200 °C. Four technical amorphous polymers, PS, PVC, PMMA and PC have been investigated. Volume-temperature curves under constant rate of cooling are presented and interpreted with respect to relaxation processes known from other physical investigations. The rate dependence of dilatometric glass transition temperatures is compared with the time dependence of rheometric glass transition temperatures from shear creep data. Volume relaxation data at constant aging temperature are presented. Aging is found to proceed until very low temperatures in the glassy state for e.g. PMMA.

Journal ArticleDOI
K H J Buschow1
TL;DR: In this paper, the occurrence of compositional short-range ordering (CSRO) in amorphous systems is discussed with respect to its consequences for the hole model proposed earlier.
Abstract: Amorphous alloys of the types Zr1-xNix, Zr1-xCox, Zr1-xFex and Zr1-xCux were prepared by melt-spinning and studied by means of differential scanning calorimetry and X-ray diffraction. The crystallisation temperatures (Tx) and the activation energies for crystallisation ( Delta E) were determined. The former values were found to vary only slightly with concentration while the latter show a marked concentration dependence, which is particularly pronounced in Zr1-xNix. The occurrence of compositional short-range ordering (CSRO) in amorphous systems is discussed with respect to its consequences for the hole model proposed earlier. It is shown that the predictions of the hole model are only slightly affected by the occurrence of CSRO, owing to a gross cancellation of the effects of a decreasing hole formation enthalpy and decreasing configuration entropy. The relatively strong temperature dependence of the configurational entropy expected for alloy compositions with strong CSRO leads to an increase in the experimental values of the apparent activation energies. From the concentration dependence of the experimental activation energies indications can be obtained about the concentration dependence of CSRO. It appears that the regions with a maximum CSRO do not, in general, correspond to the concentrations at which intermetallic compounds occur, nor do they correspond in all cases to regions located around the deepest eutectic composition.

Journal ArticleDOI
TL;DR: In this article, the early stages of oxygen segregation at dislocation and precipitation in the bulk have been investigated by high-resolution electron microscopy in Czochralski grown silicon, and two kinds of precipitates are observed: a crystalline silica phase, coesite, and an amorphous phase.
Abstract: The early stages of oxygen segregation at dislocation and precipitation in the bulk have been investigated by high‐resolution electron microscopy in Czochralski grown silicon. Two kinds of precipitates are observed: a crystalline silica phase, coesite, and an amorphous phase. Both forms coexist after 650 °C heat treatment: the so‐called rodlike defects are in fact long 〈011〉 ribbons of coesite associated with interstitial dipoles. This crystalline form is favored by a high oxygen supersaturation and a low carbon content. Above 870 °C amorphous platelets of silica are formed on the {100} planes, whereas coesite is no longer observed but interstitial dislocation loops are always present. The strain produced by such precipitates is partially relaxed by Si interstitial emission, which explains the internal formation of dislocations. It is suggested that both forms are nucleated on two different species of nuclei. At 〈011〉 dislocation cores it is shown that the coesite phase is stabilized over a wide range of oxygen content or annealing temperature.


Journal ArticleDOI
TL;DR: The Nicalon SiC fiber offers the possibility of the development of composite materials for use above 1000° C as mentioned in this paper. But, the properties of the SiC fibres have not yet been investigated.
Abstract: The Nicalon SiC fibre offers the possibility of the development of composite materials for use above 1000° C. This study has compared two types of Nicalon fibre, one which was shown to be amorphous and the other microcrystalline with a SiC grain radius of 1.7 nm. Both fibres behaved in a brittle manner when tested in air and in argon up to 1300° C and their strengths fell above 1000° C. There were indications that new defects were created in the amorphous fibre when tested in air above 1000° C. The microstructural analysis showed that as well as SiC, both SiO2 and free carbon were present in both fibres. The segregations of free carbon had a mean radius of 2.0 nm in the amorphous fibre and were grouped into two populations of 1.5 and 2.2 nm in the microcrystalline fibre.

Journal ArticleDOI
TL;DR: In this article, measurements of the dc electrical conductivity, optical absorption edge and infrared optical absorption of GeO2-TeO2 glasses are reported, showing that the hopping of polarons seems to be the dominant process in the transport mechanism.
Abstract: Results of measurements of the dc electrical conductivity, optical absorption edge and infrared optical absorption of GeO2-TeO2 glasses are reported Conduction in these glasses is found to be electronic and the hopping of polarons seems to be the dominant process in the transport mechanism The electrical activation energy decreases with the increase of tellurium content and this decrease corresponds to a decrease in the optical energy gap The optical gap is of the order of 274 eV, somewhat lower than for many other oxide based glasses Most of the sharp absorption bands characteristic of the basic materials GeO2 and TeO2 are modified with the formation of broad and strong absorption bands in the process of going from the crystalline to the amorphous state Density measurements show the glasses to have a compact structure

Journal ArticleDOI
TL;DR: In this article, a drop calorimetric study of amorphous SiO 2, NaAlSi 3 O 8, KAlSi3 O 8, NaO 2 O 6, NaO 4 O 4, NaSiO 4 and KSiO 8 O 8 showed that the fictive temperature has negligible effect on the heat capacity above room temperature.

Journal ArticleDOI
TL;DR: In this article, it was shown that the carbon film is amorphous and does not contain graphitically bonded carbon atoms, and the atomic density of the film calculated from the energy loss due to the plasma oscillation of valence electrons is 1.7×1023 atoms/cm3, which is in good agreement with that of diamond.
Abstract: Carbon films were deposited using mass‐separated C+ ions of 300 and 600 eV. The films have diamond‐like characteristics such as transparency in the visible spectral region with wavelengths longer than about 650 nm and in the infrared, and high electrical resistivity. Transmission electron diffraction analysis shows that the film is amorphous and does not contain graphitically bonded carbon atoms. Kα x‐ray emission spectrum of the carbon in the film agrees well with that of diamond. In the x‐ray photoemission spectrum of the film, no characteristic energy loss due to π plasmon was observed. The atomic density of the film calculated from the energy loss due to the plasma oscillation of valence electrons is 1.7×1023 atoms/cm3, which is in good agreement with that of diamond. These results indicate that the film deposited using C+ ion beam consists of tetrahedraly bonded carbon atoms.

Journal ArticleDOI
TL;DR: Load-variant microhardness tests have been used to investigate the hardness behavior of ion-implanted (1 1 1) silicon wafers as mentioned in this paper, and it is concluded that the amorphous layer produced by implantation appears to show no variation of micro-hardness with load and has a hardness typically between 400 and 700 VHN.
Abstract: Load-variant microhardness tests have been used to investigate the hardness behaviour of ion-implanted (1 1 1) silicon wafers. A variety of ion doses, energies and species, including n-type, p-type and isovalent ions, have been implanted. At the high doses used (1 to 8 x 1017 ions cm2−), all implantations resulted in a surface amorphous layer being formed. The microhardness behaviour has been interpreted in terms of the presence of a surface layer of lower hardness than the substrate. The thickness of this layer has been investigated experimentally using Rutherford backscattering and the results correlated with simple theoretical predictions. Finally, the microhardness behaviour of a soft layer on a harder substrate has been modelled in order to try to predict the hardness variations arising from differing layer thicknesses and different indentation sizes. It is concluded that the amorphous layer produced by implantation appears to show no variation of microhardness with load and has a hardness typically between 400 and 700 Vickers (VHN). Further, the previously reported “critical dose” of ∼ 4 x 1017 ions cm−2 necessary to observe significant surface softening seems to correspond to the regime in which the amorphous layer shows a rapid increase with dose.

Journal ArticleDOI
TL;DR: In this paper, direct precipitation of fine powders of lead zirconate titanate (PZT) in the complete range of solid solution under hydrothermal conditions, starting from lead oxide and titania/zirconia mixed gels, is investigated.

Journal ArticleDOI
TL;DR: In this article, a review of applications of amorphous ribbons and wires to sensors and transducers is presented, where the basic principle of ammorphous sensor constitutions and the advantageous points are represented.
Abstract: Recent researches and developments of applications of amorphous ribbons and wires to sensors and transducers are reviewed. Various sensitive and quick response magnetic sensors with very small amorphous cores have been developed corresponding to strong demands in the fields of information devices, automobiles, power motor drives, industrial robots, and industrial measurement instruments. Relationship between amorphous material properties and the suitable applications to sensors and transducers, the basic principle of amorphous sensor constitutions, and the advantageous points of amorphous sensors are represented.

Journal ArticleDOI
TL;DR: In this paper, a neon ion beam has been used to regrow epitaxially a ~1700-AA{}-thick amorphous surface layer in silicon on sapphire at low temperatures.
Abstract: A neon ion beam has been used to regrow epitaxially a ~1700-\AA{}-thick amorphous surface layer in silicon on sapphire at low temperatures. The damaged layer was produced by implanting 80-keV silicon ions to a dose of $2\ifmmode\times\else\texttimes\fi{}{10}^{15}$ ions/${\mathrm{cm}}^{2}$ at room temperature. The channeling technique with 315-keV protons was used to investigate the depth distribution of the damage, and disorder depth profiles were extracted from the backscattering spectra using calculations based on multiplescattering theory. The epitaxial regrowth was quantitatively determined from the extracted profiles. Many of the parameters which influence the regrowth rate, such as dose, dose rate, target temperature, energy, and random or channeled direction for the annealing beam, were varied. The results were compared with energy deposition calculations which indicated strongly that the annealing rate depends on the energy deposited in elastic collisions by the annealing ion beam. A defect annealing model based on vacancy diffusion is discussed.

Journal ArticleDOI
TL;DR: In this article, an amorphous zirconium-nickel phase was formed by annealing vapor deposited crystalline layers of elemental ZIRconium and nickel.
Abstract: We have formed an amorphous zirconium-nickel phase by annealing vapor deposited crystalline layers of elemental zirconium and nickel. Auger depth profiling and x-ray diffraction have been used to monitor the reaction. The thermodynamics of the process is explained in terms of a metastable free energy diagram which reflects the large negative heat of mixing between zirconium and nickel. The formation of an amorphous layer occurs via a diffusion limited reaction occurring at the zirconium-nickel interface.

Journal ArticleDOI
TL;DR: In this paper, the authors describe the time evolution of photochemical holes in organic glasses, showing a logarithmic increase of the hole widths in a time domain between minutes and about 104 min.
Abstract: Experimental data describing the time evolution of photochemical holes in organic glasses are reported. The photochemical system is 1,4‐dihydroxyanthraquinone (quinizarin) in ethanol/methanol glasses; its photochemistry is based on proton or deuteron transfer processes. The experiments show a logarithmic increase of the hole widths in a time domain between minutes and about 104 min. The experimental results yield a pronounced deuteration effect and little variation with temperature between 1.35 and 4.2 K. The data are interpreted in a semiquantitative way using current theories of spectral diffusion in amorphous solids. The fastest measured photochemical rates are on the order of seconds, leaving a ‘‘time independent’’ linewidth of about 0.4 cm−1 at 1.35 K.

Journal ArticleDOI
TL;DR: In this article, a detailed study of a new process to produce amorphous binary alloys by solid-state reaction of the elemental constituents from an initially thin-layer configuration is presented.
Abstract: We report on a detailed study of a new process to produce amorphous binary alloys by solid-state reaction of the elemental constituents from an initially thin-layer configuration. The Ni-Hf system was selected on the basis of the criteria that a fast diffuser (Ni) and a large binary heat of mixing drives the solid-state reaction at temperatures so low (∼ 300 °C) that nucleation and growth of the crystalline phases are suppressed and the amorphous phase becomes the lowest accessible state of free energy. Backscattering spectrometry, x-ray diffraction, and transmission electron microscopy are used to monitor the atomic composition profile and the microstructure of the samples. The kinetics of the amorphous phase formation is consistent with the diffusion-limited growth of a laterally uniform amorphous layer. The substantial and approximately linear composition gradient of the amorphous layer reflects the low atomic mobility of the atoms in the amorphous phase and the broad existence range of the amorphous phase in the binary Ni-Hf system. The latter is consistent with predictions based on the calculated equilibrium free-energy diagram of the system.

Journal ArticleDOI
TL;DR: Amorphous tungsten trioxide films, investigated by the Raman scattering method, are shown to be composed of a spatial network of tightly bound (WO6)n·mH2O clusters with a large number of terminal oxygen W=O and W-O-W bonds between clusters as mentioned in this paper.


Patent
14 May 1984
TL;DR: In this article, a film field effect transistor is proposed to operate at fast switching rates for use in video display applications, where the transistor includes a body of silicon semiconductor material having a structure more ordered than amorphous material and less ordered than single crystalline material.
Abstract: There is disclosed a film field effect transistor which can be operated at fast switching rates for use, for example, in video display applications. The transistor includes a body of silicon semiconductor material having a structure more ordered than amorphous material and less ordered than single crystalline material. The source and drain of the transistor comprise rectifying contacts formed on the body of silicon semiconductor material. Also disclosed are a method of making the transistor and an electronically addressable array system utilizing the transistor to advantage.

Journal ArticleDOI
TL;DR: The conductance/temperature behavior of poly(ethylene oxide)/LiClO4 electrolyte prepared under anhydrous conditions has been studied in this article, where light crosslinking has been shown to cause a small reduction in the conductivity, probably due to restricted backbone segmental motion.