Showing papers on "Amorphous solid published in 1971"
TL;DR: In this article, the authors investigated the electrical conduction process in amorphous solids, using as a basis the ionization of local defects by an applied field, and showed that the Poole-Frenkel effect is a limiting case of a more general analysis that can be extended to cover the experimentally available range of field stress and temperature.
Abstract: The nature of the electrical conduction process in amorphous solids, using as a basis the ionization of local defects by an applied field, is investigated. It is shown that the Poole-Frenkel effect is a limiting case of a more general analysis that can be extended to cover the experimentally available range of field stress and temperature. At low temperature conduction is by tunnelling emission out of the defects into the quasi-conduction band of the host material whereas at high temperatures thermal emission becomes dominant. Between the two regions a thermal-field emission process has been identified with the characteristic of ln J ∝ T −⅓.
560 citations
TL;DR: In this paper, optical properties of non-crystalline Si, SiO and SiO x (x = 1·5) were analyzed for the energy region 1 to 26 eV and the results indicated that amorphous substances of all intermediate compositions between Si and Si O 2 can be formed and that these materials are not simple mixtures of Si and O 2 but rather the two atom species are blended on an atomic scale.
503 citations
TL;DR: In this article, a theory of the a.c. conductivity suitable for hopping conduction in the pseudogap of amorphous semiconductors is developed, and expressions applicable under various conditions are derived.
Abstract: The literature on experiments on a.c. conductivity in various disordered semiconductors is briefly summarized. A theory of the a.c. conductivity, suitable for hopping conduction in the pseudogap of amorphous semiconductors, is developed, and expressions applicable under various conditions are derived. Comparing some of the results with available experimental data, the concentration of localized states in the pseudogap of several materials is estimated.
486 citations
TL;DR: In this paper, the phase change from amorphous to crystalline state is not only a thermal phenomenon but is directly influenced by the creation of excess electron-hole carriers by either the light, or, for the electrical device, by the electric field.
Abstract: We have observed a high-speed crystallization of amorphous semiconductor films and the reversal of this crystallization back to the amorphous state using short pulses of laser light and evidenced by a sharp change in optical transmission and reflection. This optical switching behavior is analogous to the memory-type electrical switching effect in these materials which has received wide attention1 since the observation by S. R. Ovshinsky2 of both threshold and memory switching in amorphous semiconductors. In this letter, we propose a model which closely relates the optical and electrical switching behavior, and shows that the phase change from amorphous to crystalline state is not only a thermal phenomenon but is directly influenced by the creation of excess electron-hole carriers by either the light, or, for the electrical device, by the electric field. The reversibility of the phenomenon in this model is obtained through the large difference in crystallization rates with the light on or off.
393 citations
357 citations
TL;DR: In this paper, the amorphous form of Si and several related, tetrahedrally bonded semiconductors (Ge, GaAs, GaP, InSb) were studied in the presence of Raman scattering.
Abstract: Raman scattering has been studied in the amorphous form of Si and several related, tetrahedrally bonded semiconductors (Ge, GaAs, GaP, InSb). All vibrational modes of the material can take part in the scattering process, and the Raman spectrum is a measure of the density of vibrational states. The amorphous phases are found to have vibrational spectra very similar to the corresponding crystals, reflecting the similarity in short-range order of the two phases.
306 citations
TL;DR: In this article, the authors examined the hopping conduction process under conditions of high temperatures, high fields and a non-uniform distribution of hopping sites and showed that the field dependence of the Mott T −¼ law can yield information about the trap density distribution.
Abstract: The hopping conduction process is examined under conditions of high temperatures, high fields and a non-uniform distribution of hopping sites. It is shown that the field dependence of the Mott T −¼ law can yield information about the trap density distribution. A new mechanism of conduction, considering the emission of charge carriers from donor centres into traps, is examined and shown to yield a characteristic of ln σ∞T −1/7. The electrical properties of amorphous carbon and germanium are examined. It is shown that carbon exhibits a pure hopping process whilst germanium shows the characteristics of donor emission into traps.
273 citations
TL;DR: In this article, As2Se3 and As2S3 are shown to be reversible by thermal cycling to higher temperatures, and a mechanism is proposed to explain the photodecomposition reactions and the thermally induced reversibility in As 2Se3.
Abstract: Electromagnetic radiation approximately equal to band‐gap energy has been established as responsible for the dissociation of amorphous As2Se3 and As2S3. The dissociation is accompanied by an optical densification observable as a ``photographic'' effect in thin films of these materials. The dissociation can be expressed by the following equations: As2Se3→ lim hvxAs+As2−xSe3, 0
259 citations
TL;DR: In this paper, a detailed investigation of two systems, polystyrene and poly(orthomethylstyrene) in the glassy and liquid states is undertaken, with the single parameter B as an exponentially decreasing function of T. The pressure coefficients for the two transition temperatures are discussed.
Abstract: An apparatus based on Bridgman's bellows method, originally devised for fluids, has been constructed for use with solid samples. Mercury is employed as the confining liquid. The operating range is 0≤t≤200 °C and 1≤P≤2000 bar. Calibration with benzene and mercury shows an accuracy of ±2×10−4 cm3/g in the measurement of the specific volume change. A detailed investigation of two systems, polystyrene and poly(orthomethylstyrene) in the glassy and liquid states is undertaken. The P‐V‐T results in both states can be well represented by the Tait equation, with the single parameter B as an exponentially decreasing function of T. Similar to the earlier result for polystyrene, a β‐relaxation region is observed in terms of the isothermal compressibility of the methylated polymer with Tβ/Tg≃0.70 for both. The pressure coefficients for the two transition temperatures are discussed. For the glass transition, the Ehrenfest‐type equation appears to be obeyed by the low‐pressure glasses (formed by cooling the liquid at a...
257 citations
TL;DR: In this paper, the authors evaluated the Hall conductivity in the Random Phase Model of Amorphous Solids appropriate to the diffusive, short mean free path regime and found that the Hall mobility is small in magnitude, temperature insensitive, and exhibit the same anomalies in sign as found in the localized regime.
Abstract: Kubo's formula for the electrical conductivity is used to evaluate the Hall conductivity in the Random Phase Model of Amorphous Solids appropriate to the diffusive, short mean free path regime. The Hall mobility is found to be small in magnitude, temperature insensitive, and to exhibit the same anomalies in sign as found in the localized regime: namely, negative for a non-degenerate distribution of holes on electrons due to diffusive motion about a closed path of three sites.
248 citations
IBM1
TL;DR: In this article, the interband gap of 9.0 eV in amorphous SiO2 was shown to be insensitive to band edge selection rules, and a gap of 8.9 ± 0.2 eV was seen in photoinjection measurements.
TL;DR: In this article, various silicon nitride films have been prepared from, N2,, and in an rf-promoted glow discharge reaction using infrared absorption, aided by ultraviolet absorption, the inclusion of excess silicon or of oxygen in the films is readily followed.
Abstract: Various "silicon nitride" films have been prepared from , N2, , and in an rf‐promoted glow discharge reaction. These films are described primarily through the use of infrared absorption. Aided by ultraviolet absorption, the inclusion of excess silicon or of oxygen in the films is readily followed. Changes in index of refraction, etch rates in HF acid, and electrical conductivity of the films are correlated with the optical absorption study. Comparisons of these films with those formed by pyrolysis or by reactive sputtering are made. Some reproducible physical properties of an amorphous film are stated.
TL;DR: In this paper, the equilibrium density, binding energy and elastic constants of amorphous metals are investigated using the approximation of pairwise central interatomic potentials, and the importance of the internal displacements is found to make significant contributions to the shear elastic constant.
TL;DR: In this paper, the formation of amorphous or crystalline damaged regions by ion bombardment or neutron irradiation of Ge and Si is discussed, and it is concluded that the individual damaged regions produced by high-energy ions or by primary knock-on atoms from fission neutron collisions are crystalline.
Abstract: The formation of amorphous or crystalline damaged regions by ion bombardment or neutron irradiation of Ge and Si is discussed. Several experiments have demonstrated that Ge and Si become amorphous when bombarded to high fluences with ions of 20–200 keV energy, but remain crystalline after low ion fluences (<1014/cm2) or after fission neutron irradiations up to very high fluences. The present results indicate that a fission neutron fluence of 5 × 1035 n/cm2 at ∼50 °C and at a flux of 6 × 1012 n/cm2/sec produces no amorphism in Ge or Si, but that microcrystals appear after annealing at 450 °C. It is concluded that the individual damaged regions produced by high-energy ions or by primary knock-on atoms from fission neutron collisions are crystalline. When these damaged regions are created rapidly enough so that overlap occurs before appreciable annealing of point defects takes place, the damaged regions become amorphous. The critical defect concentration required for spontaneous transformation to am...
TL;DR: In this article, the existence of void networks in amorphous Ge films formed at substrate temperatures of 25 and 150 C and the absence of a void network in higher substrate temperatures at 200 and 250 C were shown.
Abstract: Electron micrographs have been obtained which clearly show the existence of a void network in amorphous Ge films formed at substrate temperatures of 25 and 150 C, and the absence of a void network in films formed at higher substrate temperatures of 200 and 250 C. These results correlate quite well with density measurements and predictions of void densities by indirect methods.
01 Mar 1971
TL;DR: In this article, the structural transformation of amorphous semiconductors to a more ordered state can be used for the same purpose if the structure transformation can be achieved fast and reversibly.
Abstract: ORDER-DISORDER transformations such as ordering of magnetic or ferroelectric domains are used in many information storage devices. The structural transformation of amorphous semiconductors from the amorphous to a more ordered state can be used for the same purpose if the structure transformation can be achieved fast and reversibly.1 Amorphous semiconductors have then the advantage over other information storage devices in that they can be cheaply produced and easily shaped in many different configurations. Furthermore, for semiconductors the difference between the physical properties of the amorphous and the crystalline state is particularly large. This enables one to retrieve and read the binary information, stored in the form of the structural state, with good signal to noise ratio despite extensive miniaturization.
TL;DR: In this article, the effect of thermal history on yielding behavior of atactic polystyrene, isotactic poly styrene, polycarbonate, and polymethyl methacrylate was examined by correlating the deformed microstructure with measured density changes and compressive stress-strain studies.
Abstract: The effect of thermal history on yielding behavior of atactic polystyrene, isotactic polystyrene, polycarbonate, and polymethyl methacrylate was examined by correlating the deformed microstructure with measured density changes and compressive stress‐strain studies. Electron micrographs of bulk polymers and thin films demonstrate the tendency for well‐annealed materials to undergo localized shear deformation at 100–1000‐A interspacings, and density measurements show an over‐all density increase of about 0.15% upon plastic deformation. Rapid cooling from the melt decreases both the material density (about−0.04%) and the tendency for plastic strain to localize into narrow bands. Compressive stress‐strain studies in which the strain rate, test temperature, and thermal history were systematically varied show a semilogarithmic relationship between nominal strain rate and yield stress. These data were analyzed according to an Eyring‐type exponential model where the ``shear activation volume'' and the ``activatio...
TL;DR: In this article, the dielectric β relaxation of polyvinyl chloride has been studied in the ranges of temperature, pressure and frequency, 296 to 353 K, 1 × 105 to 3 × 108 N m 2 and 1 to 105 Hz.
Abstract: The dielectric β relaxation of polyvinyl chloride has been studied in the ranges of temperature, pressure and frequency, 296 to 353 K, 1 × 105 to 3 × 108 N m–2 and 1 to 105 Hz. Detailed results are discussed in terms of current concepts of the α, β and (αβ) relaxations which occur in amorphous polymers and in small molecule glass forming systems.
TL;DR: In this paper, a study of room-temperature implantations of group III and group V ions into amorphous Si layers prepared by the previous implantation of Si ions into crystalline Si substrates was made.
Abstract: A study has been made of room‐temperature implantations of group III and group V ions into amorphous Si layers prepared by the previous implantation of Si ions into crystalline Si substrates. Neutron activation combined with anodic oxidation and HF stripping techniques was used to determine the proflies of the implanted ions for Ga71 and Sb121. Electrical evaluation of the implanted layers by Hall effect and sheet resistivity measurements in conjunction with layer removal techniques yielded profiles of the net electrically active species and the depth variation of mobility after annealing for 30 min in the temperature range 600°–900°C. The ion species studied were B11 (60–200 keV), Al27 (200 keV), Ga69&71 (140 and 280 keV), P31 (100–280 keV), As75 (280 keV), Sb121&123 (120 and 260 keV), and Bi209 (240 keV). The epitaxial regrowth of the amorphous phase at 600°C causes most of the implanted ions within this region to become electrically active and uncompensated for the ion species B, P, As, Sb, and Bi even for peak ion concentrations in excess of 1020 cm−3. For Al and Ga implants, the number of carriers was less than the number of implanted ions. The profiles obtained for these implantations into amorphous Si were compared with predictions based on the theory of Lindhard, Scharff, and Schiott.
TL;DR: In this paper, it was shown that conduction in amorphous germanium sandwich layers is by hopping in the temperature range up to 300°K, where the carriers are supplied by a large density of acceptor states (1018-1019 cm-3) near to the localized valence band.
Abstract: The current-voltage behaviour of amorphous germanium sandwich layers has been investigated in the temperature range 2°K to 79°K. The results obtained, in conjunction with those of Walley (1968) for the range 77°K to 300°K, are discussed in terms of a model for conduction in amorphous germanium. It is also shown that similar processes must be responsible for conduction in amorphous silicon.Following the analyses of Mott (1969) and Hill (1970) it is concluded that conduction in amorphous germanium (and silicon) is by hopping in the temperature range up to 300°K. The carriers are supplied by a large density of acceptor states (1018-1019 cm-3) near to the localized valence band. At low temperatures the current limiting process is field assisted emission from acceptors and this gives rise to power law (I ∝ V8) and exponential (I ∝ exp V½) behaviour in the current-voltage characteristics. Transport between the acceptors is via states in the localized part of the valence band. At higher temperatures the limiting...
01 Jan 1971
TL;DR: In this paper, the sputtering of an amorphous solid is considered analytically and the equations of motion of the changing surface topography derived, and the sputtered sputtering is analyzed.
Abstract: The sputtering of an amorphous solid is considered analytically and the equations of motion of the changing surface topography derived.
TL;DR: The influence of annealing on the optical, electrical and structural properties of thin amorphous Ge films deposited under well-defined conditions has been investigated in this paper, where the results below the onset of recrystallization are interpreted as due to a progressive elimination of defects and an evolution of the films towards an “ideal” Amorphous state.
TL;DR: In this article, a detailed discussion of donorlike and traplike states in disordered solids and the various transitions between them are discussed in the context of low and high-field conductivity under dc and ac conditions.
Abstract: A review is given of some electronic conduction processes in amorphous semiconductors and insulators. A detailed discussion is given of donorlike and traplike states in disordered solids and the various transitions between them are discussed in the context of low- and high-field conductivity under dc and ac conditions. Recent experimental and theoretical results are described relating to amorphous films of SiO, Ge, Si, and C. Some experimental results and theoretical interpretations of photoconductive studies on SiO are also given.
TL;DR: Barium titanate (BaTiO3) was deposited onto Pt foil, and onto thin-film Pt and Pt-Rh electrodes on sapphire, and counterelectroded to complete metal-dielectric-metal structures.
Abstract: Barium titanate (BaTiO3) was deposited onto Pt foil, and onto thin-film Pt and Pt-Rh electrodes on sapphire, and counterelectroded to complete metal-dielectric-metal structures. Dielectrics (5000–60 000 A) were deposited at substrate temperatures from 23 ° to 1000 °C, some fired in air at temperatures to 1400 °C after deposition, the films providing a wide range of dielectric constants (16–1900). Onset of BaTiO3 crystal growth was detected at 500 °C, a reduced BaTiO3 detected at 1000 °C, and constant Ba/Ti ratios measured over the deposition temperature range. Capacitance increase with temperature was essentially linear, with the fired dielectrics showing minimum slope. Tanδ varied from 0.005 for amorphous films to 0.065 for films with highest dielectric constants, with related dielectric strengths of 1.8×106 to ≈0.15×106 V/cm, respectively. Substrate, electrode, and process limitations for capacitor fabrication are defined.
TL;DR: In this article, the authors explored a possible application of this theory to the glassy state by introducing an assumption following a frequently used idea, namely, the freezing of one parameter, for example, an unoccupied volume ratio.
Abstract: A recently elaborated theory of the p‐V‐T properties successfully describes the behavior of amorphous polymers above the glass temperature. The improvement over earlier results arises from the introduction of a vacancy fraction which is obtained as a function of volume and temperature by a maximization of the partition function. We now explore a possible application of this theory to the glassy state by introducing an assumption following a frequently used idea, namely, the freezing of one parameter, (or more), for example, an unoccupied volume ratio. The natural quantity to consider is the vacancy fraction and its effect on the thermal expansion coefficient at the glass temperature. Experimental data at atmospheric pressure on a series of polymers, encompassing a wide range of Tg's, are examined and compared with theoretical predictions. The computed expansivities αg at T=Tg are uniformly smaller than is observed. We suggest as the primary reason for this discrepancy the assumption of a complete freezing of the hole fraction at the glass temperature, which should be replaced by a decreased dependence on volume and temperature as compared with the liquid. Additional factors are discussed.
TL;DR: The anomalous ellipsometric effects, which occur upon chemical adsorption of gases on clean silicon and germanium surfaces have been determined in the wavelength region 034-18 μm as mentioned in this paper.