Showing papers in "Thin Solid Films in 1980"
TL;DR: In this article, the dependence on composition of optical properties and photoinduced changes in thin films of AsxS100−x with x between 15 and 45 was investigated and it was suggested that the origin of these effects is attributable to transformations of AsS and S-S bonds in films containing an excess of chalcogen.
Abstract: The dependence on composition of optical properties and photoinduced changes in thin films of AsxS100−x with x between 15 and 45 were investigated. The optical band gap and the single oscillator fitting constants show extreme at the stoichiometric composition x = 40 and they vary almost linearly with sulphur content in specimens containing an excess of chalcogen. In contrast, irreversible and reversible photoinduced changes of the optical properties accompany a characteristic transition at x ≈ 30. This suggests that the origin of these effects is attributable to transformations of AsS and SS bonds in films containing an excess of chalcogen. This speculation is supported by thermal analyses.
406 citations
TL;DR: In this article, it was determined from thermal stability tests that the contribution to the carrier density made by the addition of tin was at most (3−4) × 1020 cm−3; i.e. the efficiency of generation of free carriers by the adding of tin is only a few tens of per cent.
Abstract: Indium oxide films were deposited onto soda-lime glass substrates. The lowest resistivity found for indium tin oxide (ITO) films was 2 × 10 −4 Ω cm with a carrier density ne of 1 × 1021 cm−3 and a mobility μH of 30 cm2 V−1 s−1 at the optimized doping level (5 wt.%) and substrate temperature (400 °C), whereas it was 4 × 10 −4 Ω cm with ne = 4 × 1020 cm−3 and μH = 72 cm2 V−1 s−1 for pure indium oxide films. The characteristic features of ITO films are their high carrier density and low mobility in comparison with ordinary electron-beam-deposited ITO films. It was determined from thermal stability tests that the contribution to the carrier density made by the addition of tin was at most (3–4) × 1020 cm−3; i.e. the efficiency of generation of free carriers by the addition of tin is only a few tens of per cent.
246 citations
TL;DR: In this paper, a first approximation model based on the concept of rapidly collapsing thermal spikes is proposed for the film-forming process and the layer properties observed by a first-approximation model.
Abstract: Ion beam deposition techniques offer interesting possibilities for the preparation of metastable quasi-amorphous films owing to a high local activation and rapid quenching on an atomic scale. This is demonstrated in the context of new results obtained with the following materials: (1) i-carbon with diamond-like properties; (2) hard BN coatings;(3) hydrogenated dopable a-Si. The film-forming processes and the layer properties observed are interpreted by a first approximation model based on the concept of rapidly collapsing thermal spikes.
240 citations
TL;DR: In this paper, the packing of long-chain diacetylene monocarboxylic acid in the form of Langmuir-Blodgett (LB) multilayers was investigated using electron diffraction and small angle X-ray techniques.
Abstract: The state of order and the packing of cadmium salts of long-chain diacetylene monocarboxylic acid in the form of Langmuir-Blodgett (LB) multilayers were investigated using electron diffraction and small angle X-ray techniques. The diacetylene moiety can be polymerized by exposure to UV light giving rise to the corresponding polymer without destruction of the LB assembly. Crystallinity in both the monomer and the polymer is restricted to the —(CH2)n—segments for which regular subcells have been worked out. No evidence for regular packing can be found in the regions where the cadmium ions and the carboxylate groups must be located. Some phase transitions in the monomer as well as in the polymer layers were observed. The crystallographical relationship between the different modifications and the mechanism of phase transformation are discussed in relation to the solid state polymerization mechanism.
225 citations
TL;DR: In this article, the authors showed that the hillock formation observed in the present case has been explained on the basis of thermal stress relaxation occuring by diffusion creep, with the additional effect of the high surface diffusion of silver atoms on an oxygen-covered silver surface.
Abstract: Thin silver films deposited onto quartz substrates by cathodic sputtering showed hillock growth on annealing in vacuum and in atmospheres of oxygen, helium and argon. Further heating in an oxygen atmosphere caused hole growth and finally led to agglomeration in the films, whereas no hole formation or agglomeration was observed on annealing the films in vacuum and in helium or argon atmospheres. The phenomenon of hillock formation observed in the present case has been explained on the basis of thermal stress relaxation occuring by diffusion creep, with the additional effect of the high surface diffusion of silver atoms on an oxygen-covered silver surface. The hole growth observed as a result of annealing in an oxygen atmosphere could be suitably explained by surface diffusion of silver atoms while the agglomeration occurs during the process of achieving a minimum energy configuration.
187 citations
161 citations
TL;DR: In this paper, the elestic stiffness parameter E f (1−ν f ) and the thermal expansion coefficient αf were obtained for four different silicides (TiSi2, TaSi2 and MoSi2) and for two different nitrides (chemically vapor-deposited Nitrox Si3N4 and r.f. plasma SiN) from stress-temperature measurements on identical films deposited on two different substrate materials.
Abstract: The elestic stiffness parameter E f (1−ν f ) and the thermal expansion coefficient αf were obtained for four different silicides (TiSi2, TaSi2, MoSi2 and WSi2) and for two different nitrides (chemically vapor-deposited Nitrox Si3N4 and r.f. plasma SiN) from stress-temperature measurements on identical films deposited on two different substrate materials. The values determined for αf and E f (1−ν f ) were quite similar for all silicides and averaged 15 ppm °C−1 and 1.1 × 1012 dyncm−2 respectively. The thermal mismatch of these silicides is such that, once safely formed, the silicide film should be able to withstand high temperature processing steps without cracking. For the nitrides the α values were essentially the same (approximately 1.5 ppm°C-1), although the larger value of E f (1−ν f ) chemically vapor-deposited Si3N4 film (3.7 × 1012 as opposed to 1.1 × 1012 dyn cm-2) indicates that it is somewhat stiffer than the SiN film.
151 citations
TL;DR: In this article, a rather comprehensive review is given of the electrical and photoelectrical transport properties of Langmuir-Blodgett (LB) built-up monolayers and multilayers.
Abstract: A rather comprehensive review is given of the electrical and photoelectrical transport properties of Langmuir-Blodgett (LB) built-up monolayers and multilayers. Both conventional (fatty acid) and unconventional materials are included. It is shown that this field has undergone enormous progress in the last few years; many promising scientific areas have opened up and a wide range of device applications can now be considered. The feasibility of several devices using insulating LB films has in fact been demonstrated, and it is now possible to design complex structures and supermolecular “organizates” to fulfil specific “active” electrical functions, and to fabricate them predictably. An extensive review is given of the possible device applications for LB films; these extend from a whole range of electronic devices utilizing the thinness and perfection of insulating LB films, to complex supermolecular structures designed for such purposes as solar energy conversion and high temperature superconductivity. The last possibility is discussed in some detail and is concluded to be a very promising area for future research.
137 citations
TL;DR: In2O3: Sn films were prepared by an activated reactive evaporation technique developed for this purpose as mentioned in this paper, which was characterized by transmission electron microscopy, electron diffraction, electrical resistivity and measurements of transmittance as a function of wavelength.
Abstract: In2O3: Sn films were prepared by an activated reactive evaporation technique developed for this purpose. The films were characterized by transmission electron microscopy, electron diffraction, electrical resistivity and measurements of transmittance as a function of wavelength. The electrical resistivity is found to be strongly dependent on process parameters such as the tin content and the deposition temperature. In contrast, the transmittance is found to be only weakly dependent on various process parameters. Under optimum conditions, films with an electrical resistivity of 7 × 10−5 Ω cm with an integrated (0.4–1.2 μ) transmittance of over 90% were obtained.
136 citations
TL;DR: A comparison of the properties of In2O3(Sn) films with those of transparent conducting films produced by other techniques is made in this paper, where a novel activated reactive evaporation technique is developed for use with resistively heated EVaporation sources.
Abstract: High quality films of In2O3 and tin-doped In2O3 were prepared by a novel activated reactive evaporation technique developed for use with resistively heated evaporation sources. Transparent conducting coatings of In2O3 have a sheet resistance of 80 Ω/□ with an optical transparency of more than 95% in the 0.4–1.6 μm wavelength range. Thin (0.4 μm) In2O3(Sn) films have a sheet resistance of 25 Ω/□ and an optical transparency as high as 99% at some wavelengths with an average transmission between 0.4 and 1.6 μm of 96%. Thicker films have a sheet resistance as low as 2.2 Ω/□. A comparison of the properties of In2O3(Sn) films with those of transparent conducting films produced by other techniques is made.
135 citations
TL;DR: In this paper, thin zinc telluride films were grown on amorphous substrates by the alternate evaporation of monolayers of zinc and tellurium with the aid of the ALO method, and they were characterized by a number of surface sensitive analysis techniques, by X-ray diffraction and by optical absorption.
Abstract: Thin zinc telluride films were grown on amorphous substrates by the alternate evaporation of monolayers of zinc and tellurium with the aid of the atomic layer evaporation (ALE) method. The films were characterized by a number of surface sensitive analysis techniques, by X-ray diffraction and by optical absorption. The films were found to be clean, smooth and featureless, and they crystallized with a preferential orientation in the (111) direction. There seemed to be no narrow-range “optimum” temperature affecting the quality of the crystals when grown by using ALE, in sharp contrast to the case in which the films were grown by codepositing the elements. The electronic structure of the films exhibited characteristics features of the bulk material, as deduced from the angle-resolved photoemission and optical absorption. In addition, some features which might be related to particular properties of the surface were present in the photoemission spectra.
TL;DR: The surface chemistry of InP substrates used for the fabrication of electronic devices (MIS structures) was examined by ESCA as discussed by the authors, where the effectiveness of several types of etchants and the features produced on the substrate surface were evaluated and discussed.
Abstract: The surface chemistry of InP substrates used for the fabrication of electronic devices (MIS structures) was examined by ESCA. Spectroscopic data on related materials such as indium metal, plasma-oxidized indium metal, In 2 O 3 , InPO 4 ( x H 2 O), P 4 O 10 , AlPO 4 , (C 6 H 5 O) 3 PO and (C 6 H 5 ) 3 P were collected so as to aid the assignment of components in the spectra of as-received and etched InP surfaces on the basis of the chemical shifts and the intensity ratios. Surface features of InP substrates from several batches were examined in the as-received and the chemically etched forms. The effectiveness of several types of etchants and the features thus produced on the substrate surface were evaluated and are discussed.
TL;DR: In this paper, a mass spectrometric investigation of the ionic and neutral species present during the deposition of a-Si: H using an r.f. glow discharge in silane (mixed with helium or hydrogen).
Abstract: We undertook a mass spectrometric investigation of the ionic and neutral species present during the deposition of a-Si: H using an r.f. glow discharge in silane (mixed with helium or hydrogen). A correlation between the neutral composition of the plasma and the nature of the IR vibrational modes in the deposited film is proposed. The ionic species extracted from the silane discharge are not characteristic of the direct ionization of SiH4. The predominance of the SiH3+ ion is attributed to the ion-molecule reaction SiH 2 + + SiH 4 → SiH 3 + + SiH 3 Secondary ions Si2Hn+ (n = 1−7) are also observed. Mass spectrometry of the ionic species resulting from the interaction of a hydrogen plasma with the a-Si: film suggests that atomic hydrogen plays an active role during the growth of the film.
IBM1
TL;DR: In this paper, the authors used a highly collimated monochromatic X-ray beam to measure the diffraction from a single monolayer and from odd numbers (up to 11) of layers of manganese stearate (MnSt2).
Abstract: We used a highly collimated monochromatic X-ray beam to measure the diffraction from a single monolayer and from odd numbers (up to 11) of layers of manganese stearate (MnSt2). The molecules were deposited in layers by the Langmuir-Blodgett technique. For the larger numbers of layers we can distinguish that the continuous diffraction pattern consists of several orders of (00l) Bragg peaks and “subsidiary” maxima which arise between these. Below the (001) peak some subsidiaries are larger than the largest Bragg peak. Qualitative explanations of the results are given. The diffraction patterns are quantitatively explained by calculations of the interference of X-rays reflected from layers whose electron density corresponds to the structure of MnSt2. Good fits to the data are obtained with parameters of the layers that are close to a priori estimates. The results also show that our silicon substrates were smoother for our films than glass microscope slides were.
TL;DR: In this article, thin Cu2−xSe thin films were evaporated and deposited on glass substrates by a vacuum evaporation method, and the films showed a low resistivity p-type conduction.
Abstract: Cu2−xSe thin films were evaporated and deposited on glass substrates by a vacuum evaporation method. The films showed a low resistivity p-type conduction. Hole mobility measurements performed on films prepared on substrates at 40 and 200°C gave values of 2–5 cm2V-1s-1 and 8–15 cm2V-1s-1 respectively. The films prepared at 40°C have a carrier density of 1022 cm-3 which is one order of magnitude higher than the carrier density of the films prepared at 200°C. In order to employ the Cu2−xSe films as a window material in solar cells, the film was deposited on n-type silicon. The electrical and photovoltaic properties of the junction were mainly determined by the corresponding properties of the substrate material. A maximum solar conversion efficiency of 8.8% was obtained.
TL;DR: In this paper, the surface layer consists of the hard relatively coarse (a cross section of the order of 100 μm) injected particles in a soft matrix, which contribute to the hardening of the surface.
Abstract: Hardened surfaces were produced on 304 stainless steel by the recently developed process of injecting carbide particles into a shallow laser-melted surface layer. The injected TiC can alter the surface properties in two different ways. With processing conditions chosen to minimize the dissolution of the particles, the surface layer consists of the hard relatively coarse (a cross section of the order of 100 μm) injected particles in a soft matrix. With processing conditions chosen to promote the dissolution of the injected TiC, fine (a cross section of the order of 1 μm) dendritic carbides formed on cooling contribute to the hardening of the surface.
NEC1
TL;DR: In this paper, the alloying reaction in a thin nickel film deposited on a GaAs substrate was investigated using microprobe Auger spectroscopy, reflection high energy electron diffraction and transmission electron diffusion.
Abstract: The alloying reaction in a thin nickel film deposited on a GaAs substrate was investigated using microprobe Auger spectroscopy, reflection high energy electron diffraction and transmission electron diffraction. A nickel film reacts with the substrate above 200°C to form a metastable hexagonal reaction product with the composition Ni:Ga:As = 2:1:1, which is monocrystalline with the orientation relation 〈0001〉 hexagonal // 〈111〉 GaAs and 〈11 2 0〉 hexagonal // 〈110〉 GaAs. Above 400°C the metastable reaction product decomposes into NiAs and β-NiGa, both of which are also monocrystalline with the same orientation relation as the metastable reaction product. The role of nickel in GaAs contact systems is explained by the high reactivity of nickel with GaAs in the solid-solid phase.
TL;DR: In this article, a large volume microwave plasma generator was used for producing thin plasma-polymerized (PP) films as corrosion protection on metal substrates, which were tested in a simulated marine environment for periods of several weeks with no trace of corrosion.
Abstract: A large volume microwave plasma generator was used for producing thin plasma-polymerized (PP) films as corrosion protection on metal substrates. Through the control of plasma polymerization variables (“monomer” vapour, pressure, power density and substrate temperature), strongly adhering, pinhole-free and highly cross-linked coatings can be deposited on metal surfaces. Numerous monomer-metal combinations were tested and PP films were found to outperform “conventional” polymeric coatings in various corrosive media. Organosilicone films appear to hold particular promise as they have excellent mechanical properties and are stable up to high (>800°C) temperatures. Carbon steel substrates with coatings 2 μ thick were found to withstand a simulated marine environment for periods of several weeks with no trace of corrosion.
TL;DR: In this paper, the effect of argon ion bombardment during the evaporation procedure was studied experimentally, and it was shown that the small amount incorporated into the film by the bombardment is shown to have no significant influence on the process.
Abstract: The enhancement of film adherence resulting from argon ion bombardment during the evaporation procedure was studied experimentally. The observations point to the existence of an annealing effect caused by atomic rearrangement in bombardment-induced temperature spikes. This mechanism begins to be effective at a critical minimum bombardment intensity which is sufficient to ensure that practically all the deposited material is subjected to rearrangement soon after it has been condensed. The small amount of argon incorporated into the film by the bombardment is shown to have no significant influence on the process.
TL;DR: In this article, the main IR absorption bands of Si x C 1− x H z and Ge xC 1−x H z films produced with an r.f. glow discharge were observed and assigned, and the influence of neighbouring atoms on the frequency of Si and CH bond stretching vibrations was determined.
Abstract: We have observed and assigned the main IR absorption bands of Si x C 1− x H z and Ge x C 1− x H z films produced with an r.f. glow discharge. The influence of neighbouring atoms on the frequency of SiH and CH bond stretching vibrations was determined. Agreement between observed and calculated frequency shifts was obtained for Si x C 1− x H z films.
TL;DR: In this article, single-phase CuInS 2 thin films were prepared by r.f. sputtering and the asdeposited films were p type with resistivities in the range 10 −1 −10 1 ω cm.
Abstract: Single-phase CuInS 2 thin films were prepared by r.f. sputtering. The asdeposited films were p type with resistivities in the range 10 −1 −10 1 ω cm . X-ray and electron diffraction data are discussed. Rutherford backscattering and atomic absorption were used for analysis of the composition and the impurities in the thin films. Both the growth direction and the composition of the thin films could be varied by increasing the sulphur vapour pressure during sputtering. Grain size and resistivity data and the effects of post-deposition annealing are also presented.
TL;DR: In this paper, the growth rate and crystalline structure of tin oxide layers doped with antimony were studied as functions of the deposition parameters, independent of substrate type, dopant concentration, and time deposition.
Abstract: Transparent conductive tin oxide layers doped with antimony were produced by an inexpensive spraying method in the temperature range of 573–923 K. The substrates were soda glass and polished 〈111〉 silicon wafers. The growth rate and crystalline structure were studied as functions of the deposition parameters. The growth rate was independent of the substrate type, dopant concentration, and time deposition. As a function of temperature, the growth rate showed an activation energy of 0.48 eV at the lowest deposition temperatures, becoming constant at the highest deposition temperatures, for a constant reactant flux. The growth rate was a rising function of the flux rate of reactants for low flux rates, becoming flux independent at highest flux rates, at constant substrate temperatures. The crystalline structure of the films was a function of the substrate temperature only, resulting in structures that were amorphous below 623 K and polycrystalline above. The films showed preferential growth directions as a function of temperature but they developed no preferential growth direction in the highest temperature range. The crystalline size showed a tendency to increase as the deposition temperature was increased. The grain size was in the range of a few hundreds of angstroms.
TL;DR: In this article, the authors review the work of the past several years at University College London in applying Langmuir films to integrated optical components, particularly planar waveguides.
Abstract: In this paper we review the work of the past several years at University College London in applying Langmuir films to integrated optical components, particularly planar waveguides. The development of an improved process to produce low loss optical guides is described in some detail. The method of measuring the refractive index of the layer and the molecular length is also presented. A brief summary of typical applications to waveguiding, bulk optics and display is included.
TL;DR: In this article, the potential of photoresists based on monomolecular layers is described, where polymerization is controlled by the lattice imposed by aliphatic chains and the low dispersivity of the polymer obtained gives these resists a high contrast (γ = 1.5).
Abstract: The potential of photoresists based on monomolecular layers is described. In these organic solid films, polymerization is controlled by the lattice imposed by aliphatic chains, and the low dispersivity of the polymer obtained gives these resists a high contrast (γ = 1.5). Furthermore, owing to this polymerization control and to a suitable design of the molecules, the sensitivity and contrast of these resists can be varied independently. The ultrathin (30–1000 A) films of uniform and controllable thickness obtained by this technique make these resists very suitable for low energy electron beam microlithography. Very high resolutions can be achieved by using these films without the need for high contrast; e.g. a 600 A resolution was obtained on a thick substrate using a monomolecular resist with γ = 0.7.
TL;DR: In this paper, the effects of bias voltages on electrical properties such as the resistivity ϱ, the differential change in resistivity with respect to temperature dϱ/dT, the Hall coefficients and the superconductivity were studied in terms of the structural features of the films prepared.
Abstract: TiN films of the f.c.c. phase were grown by reactive r.f. sputtering on negatively biased substrates. The effects of the bias voltages on electrical properties such as the resistivity ϱ, the differential change in resistivity with respect to temperature dϱ/dT, the Hall coefficients and the superconductivity were studied in terms of the structural features of the films prepared. At sufficient substrate bias voltage (≈ 100 V) it was found that films with stable electrical properties could be produced.
TL;DR: In this article, the annealing properties of pure and antimony-doped tin oxide films were reported up to temperatures of approximately 400°C in various atmospheres and it was found that the chemisorption or desorption of oxygen, primarily from the grain boundaries, governs the changes in the electrical parameters of the films.
Abstract: Pure and antimony-doped tin oxide films were prepared by spray pyrolysis. The annealing characteristics of these films up to temperatures of approximately 400°C in various atmospheres are reported. It was found that the chemisorption or desorption of oxygen, primarily from the grain boundaries, governs the changes in the electrical parameters of the films.
TL;DR: In this paper, optical absorption and emission spectroscopies were used for in situ investigations of process occuring in the plasma and at the electrode-gas interfaces which control the reactive sputter etching of indium targets and the reactive deposition of InN films in mixed Ar-N 2 glow discharges.
Abstract: Optical absorption and emission spectroscopies were used for in situ investigations of process occuring in the plasma and at the electrode-gas interfaces which control the reactive sputter etching of indium targets and the reactive deposition of InN films in mixed Ar-N 2 glow discharges. The sputtering parameters used were a d.c. target voltage of -2.5 kV, a total sputtering pressure P of 30–70 m Torr (4–9.3 Pa), N 2 mol.% C N 2 values of 0–100 and a target-to-substrate separation d of 3–6 cm. Under these conditions no indication of complete nitride formation at the target surface or of sputter ejection of InN molecular species was obtained. Increasing C N 2 at a constant value of P caused a decrease of the target sputtering rate R . This decrease was due primarily to a decrease in the ion current i T , which was caused by thermalization of low energy electrons in the plasma through excitation of vibrational modes in molecular N 2 . Atomic absorption provided a real-time monitor of R over the entire range of sputtering parameters. The optical emission intensity from sputtered indium atoms in the cathode glow was found to increase with C N 2 (even though R decreased) because of enhanced excitation through collisions with N 2 metastable species. The nitrogen concentration in the deposited films, as determined by X-ray photoelectron spectroscopy and X-ray diffraction, was found to depend strongly on C N 2 , P N 2 and d . The dependence on d was caused by the position of the growing film surface with respect to the negative glow region where most of the atomic nitrogen was formed through the reaction N 2 + + N 2 → N 2 + N + + N In discharges with short mean free paths this is the primary mechanism of nitrogen incorporation since indium does not chemisorb N 2 , only atomic nitrogen. InN films grown on glass substrates at about 80°C were found to be polycrystalline n-type semiconductors with a room temperature resistivity of 40 mΩ cm, a carrier concentration of about 5×10 18 cm -3 and an electron mobility of approximately 20 cm 2 V -1 s -1 . The refractive index at a wavelength of 1 μm and the room temperature direct band gap were found to be 2.85 and 1.7 eV respectively.
TL;DR: In this paper, the lateral charge transport has been observed in Langmuir multilayer films with a surface-active merocyanine dye by measuring the photoconduction in a gap cell configuration.
Abstract: Lateral charge transport has been observed in Langmuir multilayer films with a surface-active merocyanine dye by measuring the photoconduction in a gap cell configuration. The lateral photoconductivity Δσ ∥ is found to be 10 3 –10 4 times larger than the photoconductivity Δσ ⊥ in the normal direction evaluated for sandwich cells at higher levels of illumination. A square root dependence on intensity is observed for both photoconductivities at these higher intensity levels. On decreasing the light intensity, Δσ ∥ varies linearly, while Δσ ⊥ continues to obey the square root law. These results are consistent with the hopping model for multilayer systems which has so far been developed.
TL;DR: In this article, the preparation of Fe-Cu and Ni-Cu microlaminate composites by electron beam evaporation from two sources and alternating deposition onto a rotating substrate was dealt with.
Abstract: Microlaminate metal matrix composites offer considerable potential as high strength high toughness materials with isotropic properties in the plane of the sheet. In this paper we deal with the preparation of Fe-Cu and Ni-Cu microlaminate composites by electron beam evaporation from two sources and alternating deposition onto a rotating substrate. The thickness of the laminae was varied by changing the evaporation rates of the metals and the speed of rotation of the substrate. The deposits were characterized by optical microscopy, scanning electron microscopy and electron microprobe analysis to study the thicknesses of the laminae and interdiffusion of elements between the layers. X-ray diffraction was used to study the composition of the laminates. The microhardness and tensile strength at room and high temperatures of the laminates were studied and correlated with the thicknesses of the laminae and the microstructure. The results showed very marked increases in strength and hardness as the size of the laminae decreased below about 2 μm. Superplastic behavior was observed at a certain thickness of the laminae, strain rate and temperature.