Showing papers on "Annealing (metallurgy) published in 1972"

Room‐Temperature Electrical Properties of Ten I‐III‐VI2 Semiconductors

Abstract: The room‐temperature electrical properties of ten I‐III‐VI2 (I=Cu, Ag; III=Al, Ga, In; VI=S, Se) compounds are presented. The resistivities of eight of these compounds are rapidly changed by annealing under maximum and minimum chalcogen pressures. The Cu compounds can readily be made p type, a feature lacking in the analogous II‐VI compounds. However, the Cu compounds with energy gaps of 1.7 eV or above have not been made n type.

Ultrafine-grained microstructures and mechanical properties of alloy steels

Abstract: Ultrafine-grained microstructures can be developed in a variety of alloy steels by coldworking followed by annealing in theα +γ region. Because the annealing temperatures are relatively low and the recrystallized structure is two-phase, grain growth is restricted. Specimens with grain sizes in the range 0.3 to 1.1 μ.m (ASTM 20 to 16) were obtained in manganese and nickel steels by annealing 1 to 400 hr at temperatures between 450° and 650°C (840° to 1200°F). The expected improvement in yield strength through grain refinement was observed in almost all alloys. Other tensile properties depend on factors such as grain size, austenite stability, and specimen geometry, that determine which of three types of plastic behavior will occur. Transformation of austenite during straining improves the mechanical properties of ultrafine-grained specimens.

Thermal behavior of annealed organic glasses

Abstract: The influence of annealing processes on the thermal behavior of organic glasses in the glass-transition interval has been investigated and analyzed quantitatively. In detailed annealing studies of atactic polystyrene and Aroclor 5460, the absorption of thermal energy superposed on the increase in the specific heat at the glass transition, observed with suitably chosen heating rates, was followed by the differential thermal method. It is concluded that the absorption of thermal energy observed under these conditions parallels the extent of molecular relaxation that has taken place during the annealing period. It is not necessary to postulate a first-order process to account for the energy absorption. Moreover, such a postulate leads to severe conceptual difficulties regarding the development of crystallinity in crystallizable materials. The areas and the shapes of the endotherms are considered in terms of the original physical properties of the quenched glasses and the anticipated equilibrium properties. Relationships between the extent of energy absorption and time-dependent processes such as volume relaxation are discussed.

Transition Bands and Recrystallization in Metals

Abstract: Transition bands are regions of high lattice distortion which result from inhomogeneous deformation in metals. During annealing of cold-worked metals, nucleation of recrystallization is frequently observed to occur within these bands. An analysis has been made of some of the conditions under which transition bands may develop during deformation, and of the factors which influence their microstructure. A model is proposed for the mechanism by which nucleation of recrystallization occurs in transition bands during annealing. The dependence of these processes on crystallographic orientation is then discussed and related to the formation of recrystallization textures in b.c.c. metals.

Formation of Amorphous Silicon by Ion Bombardment as a Function of Ion, Temperature, and Dose

Abstract: The dose (fluence) of 200‐keV boron, phosphorous, and antimony ions required to produce a continuous amorphous layer in silicon is determined as a function of target temperature. EPR measurements are used to monitor the process which is also then related to annealing effectiveness. The continuous amorphous layer recrystallizes at 550°C, after which only the implanted ions within that layer are completely electrically active. Carrier concentration profiles indicate the position of the amorphous layer and allow an approximate determination of the distribution with depth of damage. At the low dose rates used, reasonable agreement with a simple model for the formation of amorphous silicon as a function of ion, temperature, and dose is obtained.

TiO2 Film Properties as a Function of Processing Temperature

Abstract: Thin film was produced at 150°C by chemical vapor deposition using hydrolysis of tetraisopropyl titanate. Films were amorphous as grown, but annealing in air caused crystallization, with anatase formed beginning at 350°C and rutile at 700°C. Density and index of refraction increased substantially with increasing anneal temperature, while etch susceptibility in and decreased. Comparison with literature data showed two groups of processes. One group yields films having properties that gradually approach those of rutile with increasing process temperature. The other group gives rutile directly at moderate temperatures. Deposition of amorphous film, followed by etching and annealing is suggested as a means for pattern definition.

The Strength and Fracture Toughness of Polycrystalline Magnesium Oxide Containing Metallic Particles and Fibres

Abstract: The transverse rupture strength of hot-pressed and annealed composites of magnesium oxide and dispersed metallic phases (nickel, iron, cobalt) increases with increasing volume fraction of metal and annealing temperature. The strengthening effect of the metal is attributed to an inhibition of grain growth while flaw healing occurs during the annealing of the composites.

Structure and electrical characteristics of epitaxial palladium silicide contacts on single crystal silicon and diffused P-N diodes

Abstract: Pd2Si contacts to single crystal silicon have been made by depositing Pd at room temperature and annealing at a succession of elevated temperatures. The silicide initially formed is a single crystal, even at room temperature. Its crystal structure is uniquely related to that of the underlying silicon with the basal plane of Pd2Si making an excellent match, with respect to silicon atom positions, with the (111) plane of silicon. Understanding this epitaxy leads to an appreciation of the excellent electrical characteristics of these contacts which are shown to be superior to alloyed aluminum. For comparison, barrier height measurements reproduce earlier results of Kircher on Pd2Si formed during a high temperature (200°C) deposition of Pd.

Relaxation phenomena in amorphous selenium-tellurium alloys

Abstract: Amorphous specimens of selenium-tellurium alloys containing 0–35 at% Te were held for various times at temperatures ranging from room temperature to 318°K. Changes with time in the microhardness, density, small-angle X-ray scattering and heat capacity were determined. The hardness of crystalline specimens containing 0–100 at% Te and the density of crystalline specimens containing 0–30 at% Te were also measured. The microhardness and density of the amorphous specimens increased with time at room temperature to approximately constant values. With increasing time of annealing, the intensity of small-angle scattering decreased. Peaks developed in the heat capacity versus temperature curves; their height increased with time and decreased with temperature of annealing. The peaks moved to higher temperatures with increasing tellurium concentration. Changes in the enthalpy were determined from the heat capacities. The increases in microhardness, density and height of the heat capacity peaks reflect relaxation towards a more stable structure of smaller molecular mobility. The decrease in small-angle X-ray scattering indicates the disappearance of inhomogeneities in the density during the early stages of annealing. At a later stage, the enthalpy decreased with the most rapid change occurring over a narrow time interval. A spectrum of activation energies centered around 23 kcal (gram-atom) −1 was derived. The effects of composition, temperature and time of annealing on the various properties are explained in terms of structural changes and relaxation kinetics.

Positron lifetimes and trapping probabilities observed separately for vacancies and dislocations in aluminium

Abstract: The annihilation characteristics of positrons in aluminium have been studied for the distinct cases of annihilation in the perfect lattice and annihilation after trapping at vacancies or dislocations. A controlled production of vacancies and dislocation in single crystal aluminium specimens was achieved with a quenching and annealing procedure. The annihilation lifetime in the perfect lattice is 166+or-2 ps, whereas it is 246+or-4 ps for positrons trapped in vacancies and 250+or-30 ps for positrons trapped in dislocations. The mean lifetime is found to increase with increasing dislocation density, but saturation is not attained with the dislocation densities obtainable by the quenching process. The trapping probabilities are (0.23+or-0.05)*1015 s-1 for vacancies and (0.08+or-0.05)*1015 s-1 for dislocations.

Spheroidization of Tubular Voids in Al2 O3 Crystals at High Temperatures

Abstract: Cracks introduced into single-crystal sapphire broke up after annealing, first into channels of cylindrical voids and ultimately into rows of spherical pores, with the thicker gap spacings in the original crack remaining open. Breakup of the cylindrical voids on subsequent annealing conformed to the models for surface-diffusion-controlled material transport. At the temperatures of measurement, the magnitudes of the calculated surface diffusivities agree well with values reported previously.

Static recrystallization after hot deformation of α iron

Abstract: The dependence of static recrystallization characteristics on deformation and annealing conditions has been examined for vacuum melted and zone-refined iron deformed in torsion at high temperatures in the α range. The kinetics of recrystallization are strongly accelerated by increasing deformation at low strains, but are virtually independent of strain in the “steady-state” region of the high temperature flow curve. In the latter case the kinetics of recrystallization are greatly influenced by the dynamic restoration process operative during hot deformation. In particular, for the same material, static recrystallization is faster in dynamically recovered than in dynamically recrystallized structures due to a decrease in growth rate with tie in the latter. This and other differences in the static recrystallization behavior of these two structures are discussed in terms of the differences in their microstructural features.

Thermally Stimulated Capacitance (TSCAP) in p‐n Junctions

Abstract: High‐frequency small‐signal capacitances of semiconductor junction vs temperature, from the initial conditions of filled and emptied traps in the junction depletion region, are used to determine the trap concentration and the thermal activation energies of trapped electrons and holes. Illustrations are given for silicon N + P diodes doped with gold impurity or irradiated with 1‐MeV electrons, showing the room‐temperature annealing for the latter.

Effect of annealing and temperature on the morphological structure of polymers

Abstract: During heat treatment of a semicrystalline polymer. various alterations of the morphological structure can occur. Two special cases are treated in more detail: the irreversible thickening of the polymer crystals during annealing and the reversible premelting effects occurring during heating of a well annealed sample. With regard to the thickening process. two mechanisms have to be taken into account: melting and recrystallization on the one hand and refolding in the solid state due to the high mobility of the chain molecules on the other. Which type of process predominates depends on crystallization conditions, heating rate and molecular weight. The changes in the morphological structure due to premelting can be analysed by x-ray small angle scattering studies. It is shown that the decrease of crystallinity within the so-called melting range is due to an increase of the thickness of the disordered surface layer.

Multiple endotherm melting behavior in relation to polymer morphology

Abstract: The two endotherms found during DSC analysis of annealed or drawn poly(ethylene terephthalate), PET, are discussed in greater. detail. Earlier workers proposed that the endotherms were the result of separate morphologies, i.e., extended-chain and folded-chain crystals, but more recently Roberts and others have presented data on the effect of DSC heating rate on annealed PET endotherm areas which indicate that the higher temperature endotherm is the result of recrystallization in the DSC. The present work explains the reasons for recrystallization, and presents data showing that samples cooled at various rates from the melt also exhibit recrystallization in the DSC, in much the same manner as samples annealed for different lengths of time. Further, by prolonged annealing before analysis, part of the recrystallization exotherm can be observed in the DSC scan. Drawn nylon 66 also exhibits recrystallization in the DSC, in a manner similar to annealed or slowly crystallized PET. The amount of material that recrystallizes is determined by the time and supercooling available between first melting and the ultimate recrystallization temperature, i.e., a temperature at which there is too little time and temperature driving force for further recrystallization to occur. Infrared absorption data show an increase in “regular” fold content during prolonged annealing of PET, while dynamic mechanical data show a marked decrease in a dispersion that is likely associated with the looser fold crystal morphologies. Annealed PET does superheat in the DSC, leaving unanswered the question as to whether any partially extended material is present along with the regular-fold material. For cold-drawn PET, the infrared data indicate disappearance of regular folds and the dynamic mechanical data indicate disappearance of the looser folds. Cold-drawn PET also superheats. These data indicate a likelihood of at least partially extended morphologies in cold-drawn PET; these observations do not apply to PET drawn at high temperatures or to polyethylene.

Influence of implantation temperature and surface protection on tellurium implantation in GaAs

Abstract: GaAs samples were implanted with tellurium at room temperature or at 150 °C and annealed to 750 °C with an SiO2 or Si3N4 protective layer. The highest electron concentrations and brightest photoluminescence were obtained for the hot implants with a Si3N4 protective layer.

Structural changes of drawn polyacrylonitrile during annealing

Abstract: Fibers and solvent-cast films of polyacrylonitrile have been investigated by x-ray small-angle and wide-angle measurements and dynamic-mechanical analysis. It has been found that the structure of this polymer is better described by a two-phase model consisting of more and less ordered regions. By the aid of x-ray methods, transition temperatures have been observed; there are indications that the molecules within the ordered regions are responsible for motion mechanisms. By annealing, the colloidal structure and thereby the mechanical behavior is influenced.

Electrical conduction in evaporated amorphous silicon films

Abstract: We report the results of measurement and analysis of the electrical conductivity as a function of temperature and anneal for amorphous silicon films. The resistivity of the films between 77 and 300°K increasesc with annealing. Refractory electrodes were used. The extrapolated portions of T − 1 4 fits to the log of the conductivity give physically unreasonable parameters for the T − 1 4 formula.

Thermal stability of thin PtSi films on silicon substrates

Abstract: The thermal stability of PtSi is an important parameter in large‐scale integration processing schemes which involve postmetallization high‐temperature operations. For this reason, the effect of annealing on various properties of PtSi has been studied over the temperature range 800–900°C, for 200‐ and 900‐A‐thick PtSi films on single‐crystal silicon substrates. The as‐prepared films, produced by backsputter cleaning of Si surface followed by sputtering of Pt, in situ sintering at 700°C for 10 min, and etching to dissolve any unreacted Pt, were found to be single‐phase PtSi. The 200‐A‐thick PtSi films on (111) Si possess a strong degree of preferred orientation with grains which are triply positioned with (100) PtSi ∥ (111) Si and [010] PtSi ∥ 〈110〉 Si; the orientation remains unchanged upon further annealing. On going to higher thickness (900 A), the preferred orientation of PtSi changes to (010) type and then to a partial (111) type on annealing at 900°C. Rapid grain growth is observed on annealing in the range 800–900°C; the grain size increases from 0.01–0.25 μ in the as‐deposited film to several μ at 850°C. The grain growth is followed at 900°C by agglomeration, i.e., a changeover from continuous film to island‐type microstructure. The final stage of agglomeration, which has been observed in 200‐A PtSi at 900°C, is associated with a drastic increase in resistivity. The resistivity of as‐prepared PtSi films is estimated to be 15 (±5) μΩ cm. Partial agglomeration of 900‐A PtSi occurs at 900°C; it produces only a 10% increase in resistivity. It is concluded that for PtSi films 200–900 A thick, 800°C is a safe upper‐limit (and 850°C, absolute‐limit) temperature below which there is no agglomeration, no change in crystallographic orientation, and grain growth is not excessive.

Hillock Growth on Vacuum Deposited Aluminum Films

Abstract: Vacuum deposited aluminum films are extensively used as inter- and intra-connects on silicon integrated circuits for their advantageous electrical and metallurgical properties. Hillock growth occurs after annealing of the films in the form of aluminum projections normal to the film surface. The growth of these hillocks (as well as depressions) takes place during the heating and cooling portions of the annealing cycle caused by differences in expansion coefficient between film and substrate. Diffusional creep (with grain boundary diffusion) or grain boundary sliding is believed to occur in these films to relieve the thermally induced stresses which result in annealing hillocks and depressions. Foreign impurities such as Cu in the aluminum film or the surface anodization of the aluminum inhibit hillock growth. Both approaches are being explored to achieve essentially hillock free deposits. These results support either grain boundary sliding or oxide film voids (on the aluminum film) as possible nucleation s...

Generation of Dislocations Induced by Chemical Vapor Deposited Si3N4 Films on Silicon

Abstract: The correlation between the dislocation generation and the stress in the (100) Si substrate surface completely covered with CVD Si3N4 films is investigated in relation to the film deposition and subsequent annealing conditions. The stress in the Si3N4 films deposited at 940°C at the NH3 flow rate of 1000 cc/min, when measured at room temperature, is tensile with 1.2–1.8×1010 dyn/cm2, and straight dislocations along two sets of [011] and [01] directions are formed in the Si surfaces after heat treatments at temperatures above 1050°C. The stress is small when the films are deposited at the small NH3 flow rate and high deposition temperatures. The interfacial stress generating the dislocations is found to be the inherent intrinsic stress produced during the deposition of Si3N4 film. Some characters of generated dislocations are described.

Recrystallization and grain growth in titanium: I. characterization of the structure

Abstract: Transmission electron microscopy, quantitative optical microscopy, and texture studies were made on swaged and recrystallized titanium wire of three impurity contents: zone refined, a special lot of intermediate purity, and commercial A-70. The electron microscopy studies revealed that a) during recrystallization a number of processes overlap, and b) during grain growth there occurs a decrease in the dislocation density within the grains along with the increase in the average grain size. The quantitative microscopy studies indicated that the linear intercept grain size distribution is approximately log normal and that for a given mean grain size the distribution is relatively independent of the combination of annealing time and temperature used to obtain it. Moreover, there exists a range of grain sizes in space, the numbers of grains in each class interval changing with increase in grain size. The so-called grain shape factor decreases with increase in mean grain size (annealing time) at a constant temperature and with decrease in temperature for a constant grain size. The texture of the as-swaged wire and the changes in the texture during grain growth are in qualitative accord with those previously reported for deformed and recrystallized titanium. Impurity content influences the degree of these various structural characteristics but not their substance.

Rapid Annealing of Frequency Change in Crystal Resonators Following Pulsed X-Irradiation

Abstract: A transient negative frequency change in AT-cut 125 MHz 5th overtone quartz resonators has been observed following exposure to an intense burst of x-rays. All natural, Z-growth synthetic, and swept Z-growth synthetic resonators suffer a significant initial negative frequency offset. At room temperature, the transient frequency change in natural quartz anneals in approximately ten minutes to a relatively stable negative offset. For the synthetic quartz resonators, appreciable annealing of the initial negative offset continues for a longer period, finally arriving at an offset which may be positive in the case of the Z-growth synthetic but negligibly small for swept Z-growth synthetic. The transient frequency change is attributed to a relaxation process, which anneals above 165°K (Stage I). This annealable relaxation is superposed on a more stable part (Stage II) which is removed only by heating the crystal well above room temperature. The kinetics of Stage I annealing obeys a t-2 relationship and is interpreted in terms of a one-dimensional diffusion limited annealing of uncorrelated defects. In particular, it is proposed that the annealing involves the trapping of monovalent cations, most probably H+, at substitutional aluminum sites in the crystal lattice. The activation energy governing the diffusion of the defect to the trapping center is estimated to be 0.80 ± 0.05 eV.

Energy Dependence of Displacement Effects in Semiconductors

Abstract: In a semiconductor, the formation of a space-charge region is a logical consequence of the creation of a defect cluster. The dependence of cluster size and defect density on neutron energy can be derived directly from neutron-scattering data and recoil range-energy relationships. The effect of clusters on macroscopic semiconductor properties (e.g., recombination rate, carrier removal) is more uncertain, but the shape of the dependence on cluster size is not strongly dependent on the constants used in the calculation. The relative effectiveness of 14- and l-MeV neutrons before annealing is predicted to be significantly larger for recombination rate (factor of 2.7) than for carrier removal (factor of 1.7). The annealing process can decrease this difference. Moreover, it is possible that the time scale on which annealing proceeds can be different for the larger clusters produced by 14-MeV collisions. In establishing relative damage factors between different energy neutrons, it is important to note that the relative damage curve can be a function of the property measured. In comparing the damage produced by reactor neutrons and 14-MeV neutrons, it is important to take into account the very large energy recoils (>300 keV) produced by inelastic interactions of 14-MeV neutrons. These are responsible for intense ionization as well as displacement production. If the contribution from these recoils can be shown to be negligible or to be equivalent to a number of lower-energy recoils not producing as much ionization, the effects of 14-MeV and reactor neutrons can be correlated.

Auger Spectroscopy Study on the Surface Composition of Copper–Nickel Alloys after Annealing and Sputtering

Abstract: The changes in surface composition of Cu–Ni alloys after various treatments have been observed by means of Auger electron spectroscopy. A retarding field analyzer consisting of four spherical grids was used. Samples of six different compositions were examined to obtain the calibration curve between the chemical composition and the peak-to-peak height of the derivative Auger peak. The sample surfaces were only polished with emery papers and rinsed in water and acetone. The apparatus was ion pumped to the mid 10−9-Torr range without baking so as not to affect the samples by heating. It was found that the Ni content on the sample surfaces for 80% Ni alloy decreases during the annealing process above 100 °C; and sputtering with argon ions of about 500 eV causes the nickel to become enriched in the surface layers. A slight increase of the nickel was observed on the surface of 38% Ni alloy after initial heating.