Showing papers on "Annealing (metallurgy) published in 1971"

The temperature dependence of stacking fault energy in Fe-Cr-Ni alloys

Abstract: The variation of intrinsic stacking fault energy (γi) in two austenitic Fe-Cr-Ni alloys has been determined from dislocation node measurements over the range 25‡ to 325‡C by means of high temperature transmission electron microscopy In both alloys γi increases with temperature Both reversible and irreversible effects have been observed in cyclic heating-cooling experiments After the first heating to elevated temperature the irreversible component is removed and thereafter cyclic annealing produces essentially reversible changes in γi The large reversible changes are best understood in terms of the variation in the stability of austenite with temperature The smaller irreversible effect appears to arise from the formation of substitutional solute atmospheres around partial dislocations at elevated temperature

High‐Temperature Annealing of Oxidized Silicon Surfaces

Abstract: The densities of fixed charge and trapping centers on thermally oxidized silicon surfaces have been measured by the MOS capacitance technique upon annealing in O2, N2, He, and vacuum at various temperatures from 600° to 1100°C. These surface characteristics are always determined by the conditions of the final high‐temperature process, except for , which will never increase in neutral ambients. In all atmospheres, higher annealing temperatures yield lower values. It was also found that the values are very sensitive toward trace amounts of water in the high‐temperature ambient. They decrease for increasing water vapor pressure. Effects of other impurities were not observed in this study. Based on saturation values and kinetic data a discussion is given of some models for both types of centers.

The isothermal annealing of boron implanted silicon

Abstract: Isothermal annealing studies of boron implanted silicon have been made at temperatures above 600°C for boron doses in the range of 1014 to 1015 ions/cm2. A 5 eV activation energy is obtained in the temperature range 600°C to 900°C. This value is the same as that associated with the generation and subsequent migration of vacancies in silicon. This indicates that the mechanism responsible for the increase in electrical activity of the implanted boron is due to the thermal generation of vacancies and the diffusion of these vacancies or vacancy complexes to interstitial boron atoms, which then become substitutional. The characteristic annealing times are dose dependent. No simple integral-order kinetic process will explain all the data. Good agreement between the data and a calculation is obtained if it is assumed that the characteristic annealing times are position dependent. Detailed data are presented which provide the time and temperature necessary to obtain complete electrical activity of boron ...

The Chemical Polishing of Sapphire and MgAl Spinel

Abstract: Based on air annealing studies at 1500°C, it appears that bulk and surface mechanical damage in sapphire and spinel may be greatly minimized. Such annealed surfaces can then be effectively polished chemically leaving essentially featureless surfaces. Preannealed sapphire orientations can be polished at 285°C in a mixture for 15 min while spinel orientations may be treated in a mixture at 250°C for the same length of time. (111) spinel and sapphire cannot be chemically polished by the procedures described but are presumably amenable to removal of most surface and mechanical saw and polish induced bulk damage via the high‐temperature annealing process.

On the annealing of damage produced by boron ion implantation of silicon single crystals

Abstract: Using the techniques of Rutherford scattering, electron microscopy and infra-red absorption, the damage produced by implantation of 100 to 400 keV boron (11B) ions in silicon single crystals, held at room and liquid nitrogen temperatures, has been examined, and the annealing behaviour investigated. The rapid annealing of disorder in the range between room temperature and 325°C, as observed by the Rutherford scattering of channelled analysing particle beams, correlates with a shrinkage of the 1. 8μ divacancy infra-red absorption band, and with a coarsening of some of the defects observed in the electron microscope. Amorphous zones observed in samples implanted with 1015 boron ions/sq. cm. at liquid nitrogen temperature do not anneal until temperatures in the vicinity of 450 °C are attained. The consequences of aggregation of point defects, first as small crystallographic clusters, for temperatures in the vicinity of 300 °C, and then as large circular dislocation loops following isochronal anneals ...

Thermal embrittlement of 18 Ni(350) maraging steel

Abstract: The embrittlement of as-solutionized 18 Ni(350) Maraging steel was monitored as a function of heat treatment variables by means of Charpy impact tests The processing parameters of interest were annealing temperatures in the range of 1900° to 2400°F, intermediate holding temperatures in the range of 1300° to 1800°F, and the quenching rate The changes in fracture mode with heat treatment were characterized by replica and scanning electron microscopy The severity of thermal embrittlement increases with decreasing cooling rate from the annealing treatment upon direct quenching to room temperature Intermediate isothermal holding, particularly at 1500° to 1600°F, further accentuates the embrittlement A large grain size is beneficial to the toughness when rapid direct quenches from the annealing range are imposed but is detrimental upon air cooling or intermediate holding The major loss in toughness may be associated with the diffusion of interstitial impurity atoms (C+N) to the austenite grain boundaries during cooling or intermediate isothermal holding below 2000°F An advanced stage of the embrittlement is characterized by the discrete precipitation of Ti(C,N) platelets on these boundaries Thermal embrittlement is accompanied by change in fracture mode from transgranular dimpled rupture to intergranular quasi-cleavage

High‐Mobility Epitaxial Layers of PbTe and Pb1−xSnxTe Prepared by Post‐Growth Annealing

Abstract: Postgrowth annealing has been found to give layers of PbTe and Pb1−xSnxTe (with x ≈ 0.2) with much larger low‐temperature Hall mobilities than as‐grown layers. At temperatures down to about 50 °K the Hall mobilities are close to those of good bulk crystals. Below 50 °K there is a tendency to saturation at values greater than 105 cm2 V−1 sec−1. Structural studies indicate that both as‐grown and annealed specimens are single crystals with about the same concentration of low‐angle grain boundaries as the BaF2 substrates. It is suggested that the annealing process removes an excess of native defects.

Electrical and electron microscope studies of the annealing of tellurium-doped gallium arsenide

Abstract: Hall effect measurements and electron microscope examination of tellurium-doped gallium arsenide crystals annealed at various temperatures indicate that tellurium and copper (present as a contaminant) produce a high population of matrix point defects which are probably simple vacancies. Annealing at temperatures below 1000°C causes the growth of intrinsic prismatic vacancy loops on {111} and {100} planes in association with decorations of precipitated copper. Heating to temperatures above 1000°C caused the copper and tellurium (in extrinsic stacking faults) to move back into solution, eventually changing the semiconductor from n to p type, and leading to the disappearance of both prismatic loops and stacking faults.

Production and Annealing of Color Centers in rf Sputtered SiO2 Films

Abstract: Radio‐frequency sputtered SiO2 films can be made that contain a variety of optical absorption bands and electron spin resonance centers. In addition to absorption bands at 5.1, 5.8, and 7.6 eV that are typical of irradiated fused SiO2, two new absorption bands have been found. The G band at 5.4 eV and the H band at 6.55 eV are present in certain sputtered SiO2 films and develop further when they are annealed in forming gas or N2. The occurrence of these bands and the density of paramagnetic centers produced in SiO2 films when they are sputtered under different deposition conditions has been studied. The effect of annealing to 950°C in N2, O2, and forming gas on optical absorption bands and ESR centers has been determined. Absorption bands appear to be associated with oxygen deficiency in the sputtered SiO2 films since they will anneal completely at 930°C in oxygen. Hydrogen plays an important role in annealing of the B1 band at 5.1 eV, the E1′ band at 5.8 eV, and all the ESR centers. They anneal at 200°C lower temperatures in forming gas, compared to annealing in N2. The OH content, refractive index, Ar content, density, and etch rates of sputtered SiO2 films have also been measured. The properties of the film show the importance of plasma radiation and resputtering in determining film properties. Wide variations in optical absorption and ESR are observed in samples deposited under nominally identical conditions.

Preparation and electrical properties of amorphous InSb

Abstract: Layers of amorphous InSb are prepared by flash evaporation on cold substrates. The main properties of these layers are: The electrical band gap E g el increases from 0.17 eV in crystalline up to 0.65 eV in amorphous InSb. E g el , however, has no characteristic value, but can be varied by annealing below the transition temperature between 0.4 and 0.65 eV. The absorption edge as well as the photoconduction edge are shifted to higher photon energy in the amorphous state.

Metal‐dependent interface states in thin mos structures

Abstract: Admittance measurements of MOS structures with oxide layers 20 to 40 A thick have been made to determine interface‐state distributions for various metal contacts These distributions for Au, Cr, Cu, and Mg, exhibiting comparatively sharp characteristic peaks, increase rapidly with decreasing oxide thickness and sample annealing, thus indicating a strong influence of metal diffusion through the oxide on interface‐state formation

ELECTRON-IRRADIATION EFFECTS IN SILICON AT LIQUID-HELIUM TEMPERATURES USING ac HOPPING CONDUCTIVITY.

Abstract: Changes in ac hopping conductivity with electron irradiation have been measured in n-type silicon, p-type silicon, and high purity silicon. Irradiations were carried out at both 4.8 and 1.6 degrees kelvin, with measurements made at reference temperatures of 4.2 and 1.3 degrees kelvin, respectively. In the p-type crystals, the changes in ac hopping conductivity depended strongly on the concentration of chemical acceptors, indicating a concentration dependence on impurities of the defect production rate. The production rates at 1.6°K were generally very similar to those for a 4.8°K irradiation. No significant thermal annealing stages below room temperature were observed in any of the crystals. A small amount of ‘reverse annealing’, i.e. an increase in ac hopping conductivity was observed below 30°K. No radiation annealing effects due to a beam of either 300 MeV or.350 MeV electrons were observed, either at 4.5°K or at 1.45°K.

Short-Term Charge Annealing in Electron-Irradiated Silicon Dioxide

Abstract: The existence of a rapid annealing phase in the decay of space charge induced in silicon dioxide by pulsed irradiation has been demonstrated. This effect has been observed in MOS structures prepared from both wet and dry thermal oxides and also in several commercial N-channel MOSFET's. A simple model involving thermal release of the trapped positive charge from a distribution of oxide trapping levels conveniently approximates the major features of short-term annealing.

Altering the time cycle of heat treatment by preannealing prior to grain growth

Abstract: Preannealing is found to alter the time cycle of grain growth in lead and lead-tin alloys by modifying the kinetics of grain boundary migration. Aging at a low temperature prior to annealing at a high temperature shows the influence of residual strains in the early stage of grain growth. A model is proposed to explain the deviation of the growth kinetics from the theoretical t1/2 law when the samples are annealed immediately after primary recrystallization in terms of a superposition of a strain-induced and a surface tension-induced grain boundary migration. Preannealing by using multiple anneals at the same temperature enables simulation of many different alloys by changing the amount of impurities segregated at grain boundaries. In zone refined material, a good agreement between the Cahn theory and the experimental results is observed; in lead-tin alloys, grain growth kinetics are understood in terms of a superposition of the influences of the solute and of other lattice defects.

Crystallographic aspects of Fe−Ni and Fe−Ni−C dilute alloy martensites

Abstract: Two experimental techniques which can be used to determine accurately the habit plane and orientation of martensite plates in specimens of alloys normally containing no retained austenite are described. One depends upon the use of a parent crystal containing a sharp gradient of nickel concentration and the introduction of deformation twins in the martensite. The other, which can be used for measurements on homogeneous crystals completely transformed to martensite, depends upon the development of annealing twins in large grains of the parent austenite by a sequence of heat treatments prior to transformation. Results of measurements of the habit plane and orientation of plates formed in Fe−Ni and Fe−Ni−C alloys transformed to massivemartensite are reported. These results are compared with predictions of recent crystallographic theories.

Characterization of Surface States at the Si ‐ SiO2 Interface Using the Quasi‐Static Technique

Abstract: : The quasi-static technique is used to investigate the effect of processing parameters on the surface-state density at the silicon-thermally grown silicon dioxide interface. The determination of the constant required for the evaluation of surface potential from equilibrium C-V data is discussed. A rapid method of estimating the midgap density of surface states is also described. The dependence of surface-state density on substrate orientation, type of oxide growth, high-temperature annealing in nitrogen, low-temperature heat treatment in forming gas, and temperature of oxide growth are discussed. The interdependence between the fixed oxide charge and the surface-state density is also investigated. (Author)

Correlation of microstructure and strength during stage III annealing of irradiated vanadium

Abstract: The microstructure of Vanadium irradiated to a fluence of 1.0 × 1019 n/cm2 E < 1 MeV at a temperature of 55 °C was quantitatively analyzed after irradiation and post-irradiation annealing and correlated with changes in the strength as determined from microhardness measurements. Radiation anneal hardening during Stage III annealing was not accompanied by a change in the size or number of defect aggregates. It is shown that the strength changes and migration kinetics of Stage III are consistent with the migration of oxygen and/or carbon to the defect aggregates. It is suggested that the simultaneous observation of no growth of defect aggregates and radiation anneal hardening in Stage III can be used to differentiate between impurity migration and intrinsic defect migration.

Low temperature channeling measurements of ion implantation lattice disorder in single crystal silicon

Abstract: Lattice disorder for 200-keV Sb implantations into silicon has been studied by channeling effect analysis using 400 keV proton backscattering. Implantation and analysis were performed at low temperatures in the same system without warmup. In the temperature region between 85°K and room temperature the disorder production per incident ion at low doses is implantation temperature dependent. Approximately 18,000 silicon scattering centers per incident 200-keV Sb ion are observed for 90°K implantations, and this value is nearly a factor of three greater than at room temperature. Isochronal anneal curves of low fluence, low temperature implantations show, significant annealing below room temperature. The observed disorder production per incident ion decreases with increasing implantation temperature at temperatures 50 to 100°K lower than annealing occurs following 85 or 90°K implants. Strong similarities of the implantation temperature dependence and anneal behavior of the disorder exist for Sb and B ...

NEAR BAND EDGE OPTICAL ABSORPTION PRODUCED BY ION IMPLANTATION IN GaAs

Abstract: Ion implantation of 400‐keV Se+ and Xe+ in GaAs at room temperature has been found to induce a strong optical absorption in the photon energy range 0.5 eV ≤ hv ≤ Eg. This absorption is used as a measure of the ion‐bombardment damage in GaAs and is similar to that seen in neutron‐damaged GaAs. The fluence dependence and annealing of the damage are presented and compared to previous work. An annealing stage is seen near 230 °C and corresponds to the annealing observed in radiation‐damaged GaAs.

Carrier Profile Change for Phosphorus‐Diffused Layers on Low‐Temperature Heat Treatment

Abstract: The low‐temperature annealing of phosphorus‐diffused layers in silicon is described. The sheet resistance of the diffused layer is found to increase with time at temperatures of 450–800°C. Carrier profiles for slices which have reached an equilibrium value of sheet resistance indicate a substantial decrease in the surface concentration. An Arrhenius plot of this concentration gives a straight line with an activation energy of 0.33 eV. In addition to a decrease in surface concentration, anomalously fast diffusion near the junction causes a significant tail on the profile. A model is presented to account for these results.

Effects of pressure on amorphous polymers. III. Thermodynamic properties of densified polymethyl methacrylate

Abstract: Measurements of the temperature dependence of specific heat are presented for polymethyl methacrylate densified in various pressure‐temperature‐time cycles. It is found that treatment in the glass transition region produces samples with higher glassy specific heat (0. 38 vs 0. 35 cal/g °C) and lower heat content (difference in enthalpy of 2 to 5 cal/g) than the original material. The change in thermal properties is directly correlated with increased density and increased resistance to annealing. High‐pressure treatment in the glassy state is found to produce little change in the thermodynamic properties. Samples vitrified by rapid application of high pressure show complex specific‐heat‐temperature curves. The results are related to previously reported data on densification and annealing and are discussed in terms of theories of the glassy state and the glass transition.