Showing papers on "Annealing (metallurgy) published in 1970"

Stress and Volume Relaxation in Annealing Flat Glass

Abstract: Laboratory simulation of the industrial process of annealing sheet glass has yielded data on the genesis of stresses in initially stress-free glass. The experimental results differed from expectations based on classical annealing theory in that stresses began to develop in the annealing range even when the glass was being cooled at a constant rate, i.e. even in the absence of any changes of temperature gradients within the glass. Typically, these stresses account for 40% of the total residual stress in glass annealed according to a linear schedule. The remaining 60% are the well-known thermoelastic stresses that arise later in the annealing process from the decay of temperature gradients in the glass. The stresses observed to arise in glass as it is being cooled at a constant rate are attributed to volume relaxation effects which, in parts of the annealing range, generate stresses rapidly enough that they are not dissipated by stress relaxation. A mathematical model of annealing is proposed that takes account of both stress and structural relaxation. The model fits the experimentally observed evolution of stresses during linear cooling. It also suggests that (with the activation energies of stress and structural relaxation about the same) the actual rate, at any given temperature, of structural relaxation is about 4 times lower than that of stress relaxation.

The strength and oxidation of reaction-sintered silicon nitride

Abstract: The structure of reaction-sintered silicon nitride is studied using scanning electron and optical microscopy at various stages during nitriding, for a range of nitriding and compacting conditions. The strength is then evaluated and interpreted in terms of the microstructure. It is found that fracture always occurs in a brittle manner by the extension of the largest pores. The effects of prolonged annealing in air above 1000† C on both the structure and strength are investigated. At 1400† C, cristobalite is formed. If the temperature is then maintained above 250† C, the strength is enhanced, but below this temperature the oxide layer cracks and reduces the strength.

Channeling study of boron‐implanted silicon

Abstract: The channeling technique has been used to determine the lattice location of boron implanted into silicon by using the B11 (p,α) nuclear reaction. Approximately 30% of the boron lies on substitutional sites after a room‐temperature implantation of 3×1015/cm2. The substitutional content decreases with annealing temperature up to 700 °C and then increases at higher annealing temperature. This explains a reverse annealing behavior observed in the carrier concentration. Nearly all of the boron lies on substitutional sites after annealing at 1100 °C. The nonsubstitutional boron atoms do not occupy the normal tetrahedral interstitial sites. For annealing temperatures up to 500 °C they appear to lie along atomic rows, but they do not lie midway between row lattice sites. After higher‐temperature annealing their location appears less well‐defined.

Recovery of low temperature electron irradiation-induced damage in n-type gaas

Abstract: Undoped n-type GaAa was irradiated near 5 and 77 °K with electrons having incident energies between 0.46 and 1.30 MeV. The recovery of the electrical resistivity and the Hall coefficient upon annealing from 4 to 520 °K was monitored. Changes which occurred upon annealing below 200 °K could be reversed by ionizing radiation. A small amount of irreversible ionization-induced recovery was observed after irradiation near 5 °K. Major irreversible recovery stages were centered near 235 (stage I), 280 (stage II) and 520 °K (stage III). Recovery in stage I and II obeyed first order kinetics. The activation energies of stages I and II were determined as 0.72 and 0.83 eV, respectively. The carrier concentration changes per unit irradiation dose corresponding to the three recovery stages differed in their energy dependence indicating that the defects which are removed in stage III have the lowest threshold energy. The carrier concentration changes per unit irradiation dose corresponding to stages I and III ...

Grain boundaries as sinks for dislocations

Abstract: A thermal grooving technique has been used to measure the relative grain boundary energy of deformed and annealed copper. The relative grain boundary energy after annealing at 600°c is a function of amount of previous strain, but is always higher than that of material annealed at 1000°c. Annealing at 900°c leads to a return of the energy towards the equilibrium value. On the basis of the above results a mechanism is proposed for the action of grain boundaries as a sink for dislocations.

The Influence of Austenite Strength Upon the Austenite-Martensite Transformation in Alloy Steels

Abstract: The resistance of austenite to plastic deformation (austenite flow stress) was measured using a high temperature tensile apparatus. The flow stress was then correlated with the Ms temperature as determined magnetically during subsequent cooling. In one part of the study, the flow stress of the austenite was varied only by work hardening the austenite, allowing the austenite composition, which is known to affect Ms, to be held constant. A decrease in Ms temperature with increasing austenite flow stress was observed. This observation was supported by the observation of a decrease in the amount of austenite transformed at 25°C. In the other part of the study, a series of alloy steels of different chemical compositions was tested. A decrease in Ms temperature with increasing austenite flow stress was again observed. Strengthening of austenite by plastic deformation was shown not to change the chemical driving force for transformation. The effect of deformation on Ms temperature thus results from its influence on either the nucleation or the growth process. While the effect of austenite deformation on martensite nucleation is uncertain, specific nucleation models can account for only approximately one-third of the nonchemical free energy change which accompanies transformation. A proposal, consistent with the observations, was made that the energy expended for the deformation of austenite during martensite plate growth could reasonably account for a substantial part of the nonchemical free energy change.

Effects of Material and Processing Parameters on the Dielectric Strength of Thermally Grown SiO2 Films

Abstract: The influence of several material and processing parameters on the dielectric trength of thermally grown films on silicon has been assessed. This was accomplished by statistically analyzing the breakdown characteristics of a large number of MOS capacitor structures, which had been fabricated in various ways. Although the results of this investigation are only qualitative, they clearly demonstrate that the effective breakdown strength of these films is strongly dependent on: purity, structural perfection and thickness; the presence of a passivating phosphosilicate glass layer; the presence and reactivity of the metal electrode; and, the duration of the post‐ metallization heat treatment. The morphology of certain micron‐size defects which develop in the MOS structure during annealing is described in some detail, since these faults are apparently responsible for oxide shorting in some instances.

Damage produced by ion mplantation in silicon

Abstract: Silicon specimens were irradiated with Ne+, B+, P+ and Sb+ ions. The energy was 80kV, and the doses in the range 1013 to 1016 ions/cm2. The resulting structural damage was investigated by both scanning and transmission electron microscopy. The SEM electron channelling pattern method was used to determine the variation of gross damage with ion type, dose, depth below the surface, and annealing treatment. The TEM method was used to study the detailed nature of the defects formed by the annealing. These included dislocations, rod-like structures, micro-twins, semi-polycrystalline material, misoriented zones, etc. The results are briefly compared with known electrical properties of implanted silicon, and some correlations noted.

Physical metallurgy and magnetic measurements of SmCo 5 -SmCu 5 alloys

Abstract: The magnetic properties of the hexagonal intermetallic compounds involving the rare-earth and 3d transition metals have been reported in the literature. These alloys look promising as fine-particle permanent magnets. A large number of samples in the system SmCo 5-x Cu x were prepared by induction melting under a protective atmosphere, and annealed at various temperatures. An outstanding feature of these alloys is their high intrinsic coercive force. After annealing at low temperatures, they show coercive forces above 20 kOe and an energy product of about 8 × 106G.Oe. The most important factors determining the coercive force appear to be the chemical composition, the cooling rate, the alignment of the SmCO 5 -rich phase, and the annealing treatment. Examination by electron microscopy and electron probe techniques suggests a spinodal decomposition of a supersaturated solid solution into two phases, one rich in SmCo 5 and the other rich in SmCu 5 .

RF Sputtered Aluminum Oxide Films on Silicon

Abstract: The physical and electrical properties of aluminum oxide films deposited on silicon by rf sputtering from an alumina target in an argon atmosphere were investigated as a function of sputtering power density in the range from 0.5 to 3 W/cm2. The deposition rates ranged from 20 to 80 Aa/min. The density, index of refraction, and dielectric constant of the films increased while the etch rate decreased with increasing power density. The surface charge at the aluminum oxide‐silicon interface was typically larger than 1012 e/cm2. This charge increased with increasing sputtering power density and could be reduced to by annealing. The films exhibited trapping instabilities at room temperature but no polarization was observed under bias‐temperature stress. The characteristics of composite layers of thermally grown silicon dioxide and sputtered aluminum oxide layers on silicon were also investigated and found to exhibit low surface charge densities, no hysteresis, and a "contact potential" as well as charge stored at the interface between the two insulators.

Polycrystalline Ferrite Films for Microwave Applications Deposited by Arc‐Plasma

Abstract: The arc‐plasma spray deposition has been successfully applied to fabrication of planar ferrite microwave integrated circuits. Powdered commercial sintered microwave ferrites were deposited at rates up to 2 mils/min on 1 sq in. dielectric substrates by arc‐plasma spray deposition. Process controls produced densities >99% theoretical and also maintained stoichiometric agreement between deposited films and starting material. Annealing expanded <0.1 μ grains to useful sizes of 1 to 20 μ and controlled cation distribution. Special annealing techniques were necessary for ferrites having volatile products such as Ni–Zn compounds. Magnetic and microwave properties of several deposited Mg–Mn ferrites and CeYIG agreed closely with bulk values. Remanence ratios up to 0.87 were noted. Practical application of arc‐plasma deposition required material compatibility studies at high temperature. These considerations often superseded microwave properties as criteria for material section.

Correlation of electron microscope studies with the electrical properties of boron implanted silicon

Abstract: A number of 1ω cm n-type silicon substrates have been implanted with boron at room temperature. Samples from these substrates were annealed at predetermined temperatures between 600°K and 1400°K and four-probe electrical measurements and transmission electron micrographs were taken. An attempt has been made to correlate the two studies and it is possible to explain the observed annealing behaviour in terms of precipitation during recrystallization, and migration of defects.

Magneto-optic properties of quenched thin films of MnBi and optical memory experiments

Abstract: Magnetic, magneto‐optic, and optical properties of thin films of MnBi prepared in the quenched high‐temperature phase have been measured. The saturation magnetization is reduced from normal phase by 23% and the coercive force is more than doubled at room temperature. In the visible spectrum region, there is no significant change in the optical absorption, but the strong wavelength dependence of the magneto‐optic Faraday rotation in the normal films is essentially eliminated. At the 6327‐A HeNe‐laser wavelength the room‐temperature Faraday rotation is reduced to one‐half of that of the normal films. These properties coupled with the low Curie temperature of 180°C make the quenched MnBi films well suited for optical memory applications. Experimental results of laser Curie‐point writing, erasing, and reading using the quenched films have been obtained. In comparing with the normal films, the laser writing power is reduced by a factor of four; unheated spots are not disturbed by the erasure field; and the margin between the writing temperature and the decomposition temperature is much increased. The measured activation energy and annealing time constant associated with the transformation of this high‐temperature phase to the normal phase indicates that the thermal stability of the quenched MnBi films is lacking for memory applications.

Anneal behavior of defects in ion-implanted GaAs diodes

Abstract: Doping of semiconductors by implantation of high-energy ions creates lattice damage which in general must be removed by annealing to form good qualityp-n junctions. Implantation of zinc or cadmium ions inton-type gallium arsenide substrates held at 400°C produces ap-n junction after the samples are annealed at elevated temperature (≥500°C for zinc, ≥600°C for cadmium). However, the resulting junctions are not abrupt; they contain a semiinsulating (I) layer and have ap-i-n structure. The thickness of the semiinsulating layer changes with annealing. For example, an implant of 1.3×1015 per sq cm, 20 kv, Zn+ ions produced a junction with an I layer of 28 μ thickness after annealing for 10 min at 600°C. An identically implanted sample, annealed for 10 min at 900°C, had an I layer thickness of 120 μ. A similar increase in I layer thickness with annealing was observed for samples implanted with 20 kv Cd+ ions at 400°C. Implantation of Zn+ and Cd+ ions into GaAs substrates held at room temperature produced junctions with much thinner I layers after annealing than those observed for the 400°C implants. The formation of the semiinsulating layer in the junction and its subsequent variation of thickness with annealing are attributed to deep diffusion of defects during the implantation or subsequent anneal, which produces compensation to the depth where the concentration of defects equals the substrate impurity concentration. The compensating centers are thought to be arsenic vacancy-substrate dopant atom complexes.

Evidence for vacancy motion in low temperature ion-planted Si

Abstract: Recent results have reported a strong implantation-temperature dependence between 125°K and room temperature for lattice disorder produced by 200-keV B implantation into Si. Using our previous annealing model incorporating implant temperature and dose rate, we have calculated a characteristic defect annealing time at the threshold of the crystalline to amorphous transition at 173°K for 1 μA/cm2 and find that it agrees very closely with that for neutral vacancy annealing. In addition, we have made measurements of the 1.8μ infrared absorption band, characteristic of the Si divacancy, following room temperature and 85°K implants of 400-keV B11 or Sb121 ions. Very few divacancies are observed immediately after 85°K implants, but annealing growth of divacancies occurs between 150 and 300°K yielding a density almost equal to that for the same ion Ruence at 300°K. These results strongly suggest that below 300°K neutral vacancy motion and trapping control both the implantation-temperature dependence of l...

Three‐Dimensional versus Crowdion Migration of Interstitials in Annealing Stage I of Irradiated Metals

Abstract: Formulas for the defect production rates are derived for the case that interstitials are highly mobile at the irradiation temperature thereby either recombining with vacancies or being trapped at impurities. Both the migration of interstitials in three dimensions and the linear migration of crowdions are considered. For the crowdion model the possibility of thermal conversion is included. Experimental observations of the defect production rates in f.c.c. metals at temperatures above stage I confirm qualitatively and quantitatively all the predictions of the model which assumes three-dimensional interstitial migration. The predictions of the crowdion model are by orders of magnitude in disagreement with the experimental results. Especially the very specific dependence of the defect production rates on the impurity concentration and irradiation temperature predicted by the crowdion model is not observed. In the Appendix the interpretation of the dislocation pinning experiments in terms of the crowdion model is criticized. Fur Elektronenbestrahlung wurde die Defektproduktionsrate fur den Fall berechnet, das die Zwischengitteratome bei der Bestrahlungstemperatur hochbeweglich sind und entweder mit Leerstellen rekombinieren oder sich an Fremdatome anlagern konnen. Sowohl dreidimensional wie eindimensional wandernde Zwischengitteratome wurden betrachtet. Fur letztere (Crowdionen) wird zusatzlich die Moglichkeit der thermischen Konversion zugelassen. Die experimentellen Ergebnisse der Defektproduktionsraten der k.f.z. Metalle bei Elektronenbestrahlung im Temperaturgebiet uber Stufe I stimmen sowohl qualitativ wie quantitativ gut mit dem Model uberein, das dreidimensionale Wanderung der Zwischengitteratome annimmt. Die Vorhersagen des Crowdionen-Modells sind im krassen Widerspruch zu den Experimenten. Insbesondere wird die fur dieses Modell vorhergesagte, sehr spezifische Abhangigkeit der Defektproduktionsraten vom Verunreinigungsgehalt und der Bestrahlungstemperatur nicht beobachtet. Im Anhang wird eine kritische Stellungnahme zur Deutung der Versetzungs-„pinning”-Experimente mit Hilfe des Crowdionen-Modells gegeben.

Transient annealing of defects in irradiated silicon devices

Abstract: The annealing of radiation-produced defects in semiconductor devices is discussed briefly for60Co gamma-ray and 1-MeV electron damage, and in detail for fast-neutron damage. The effects on the reordering processes of varying the material parameters and the irradiation conditions are considered. Transient annealing of neutron damage near room temperature has been investigated for a wide variety of devices, and the data are presented in generalized form to increase their usefulness to device and circuit designers. Based on the experimental results, physical models are suggested for the reordering processes which occur during the annealing of neutron damage. Electron density is shown to be the most important factor governing the rate of transient annealing. Annealing factors are estimated for very early times (1 µs) following neutron exposure. Suggestions are made to minimize the effects of transient annealing on devices.

PHOTOELECTRONIC PROPERTIES OF ION-IMPLANTED CdS.

Abstract: The photoelectronic properties of CdS successively implanted with 1.0‐, 0.5‐, and 0.3‐MeV P+ ions versus annealing cycles were studied. Diodes thus formed were highly photosensitive, with photoconductive gains between 102 and 104. Yellow electroluminescence was observed at 77°K. Short annealing creates centers with a sheet resistance thermal activation energy of 0.13 eV. Prolonged annealing creates states 0.75–0.8 eV below the band edge.

Radiation damage by implanted ions in GaAs and GaP

Abstract: The production of lattice disorder in GaAs and GaP by Te ions up to 40 keV has been investigated. For GaAs the build up of damage with implanted ion dose is linear until a saturation level is reached. For Gap, two linear regions are evident; a slow build up of damage to ⋍15 per cent of the saturation level, followed by a faster rate of increase up to the final 100 per cent level. Radiation annealing, for GaP samples, both by the heavy ion beam during implantation and by the helium beam during back-scattering measurements has been observed. The annealing temperatures required for re-ordering the lattice depend on the percentage of damage present. Samples damaged up to the saturation level require annealing at ⋍500°C, whilst 300°C is sufficient for samples damaged to ≲50 per cent of the saturation value.

Radiation-anneal hardening in niobium: an effect of post-irradiation annealing on the yield stress.

Abstract: The effect of low-temperature annealing on the yield stress of niobium following neutron irradiation was studied. The initial increase in yield stress upon irradiation was sensitive to the interstitial carbon content. A further increase in the yield stress (“radiation-anneal hardening”) was observed after two-hour anneals near 150 and 300 °C. When the annealing temperature was raised above 400 °C, the yield stress gradually recovered toward the preirradiation value. Changes in the density and size of the radiation-produced defect clusters were determined by transmission electron microscopy following post-irradiation anneals. An analysis of the observed hardening based on a dispersed barrier model and the density and size of defect clusters indicated that post-irradiation annealing strengthened the clusters as barriers to dislocation motion by as much as a factor of two. Previous resistivity and internal friction measuremements have shown that interstitial oxygen and carbon in irradiated niobium migrate to the defect clusters at the temperatures near 150 and 300 °C, respectively. Thus, the radiation-anneal-hardening peaks at these temperatures are attributed to the trapping of oxygen and carbon, respectively, at defect clusters. There is a reduced tendency for dislocation channeling (i.e., defect cluster removal by slip dislocations) in radiation-anneal-hardened niobium, suggesting that indeed the clusters have been strengthened.