Showing papers on "Annealing (metallurgy) published in 1978"

Cathodic Deposition of CdTe from Aqueous Electrolytes

Abstract: of well‐defined composition has been deposited cathodically from an aqueous solution of and . Films with a rest potential of −0.3V vs. SCE are p‐type semiconductors. The rate of deposition increases with stirring rate; it is proportional to the concentration but independent of the concentration. Films deposited at room temperature are amorphous, those deposited at higher temperatures are partly crystalline, the degree of crystallinity increasing with deposition temperature. Grain sizes are in the range 500–1000A. Annealing at 350°C causes the crystallite size to increase to ≥0.5 μm.

Time‐resolved reflectivity of ion‐implanted silicon during laser annealing

Abstract: The time‐resolved reflectivity at 0.63 μm from arsenic‐implanted silicon crystals has been measured during annealing by a 1.06‐μm laser pulse of 50‐ns duration. The reflectivity was observed to change abruptly to the value consistent with liquid silicon and to remain at that value for a period of time which ranged from a few tens of nanoseconds to several hundreds of nanoseconds, depending on the annealing pulse intensity. Concurrently, the transmission of the primary annealing beam dropped abruptly. These observations confirm the formation of a metallic liquid phase at the crystal surface during the annealing process.

Surface defects and the electronic structure of SrTi O 3 surfaces

Abstract: The electronic properties of various types of SrTi${\mathrm{O}}_{3}$ surfaces have been studied by using ultraviolet-photoemission and electron-energy-loss spectroscopy, low-energy electron diffraction and Auger spectroscopy. Vacuum-fractured surfaces exhibit weak photoemission in the region of the bulk band gap, which is probably due to residual surface defects. When surface defects are produced by Ar-ion bombardment, a much stronger band of surface states appears in the band-gap region. These states arise from the creation of ${\mathrm{Ti}}^{3+}$-O-vacancy complexes and are predominantly of $d$-electron character. Two surface defect phases are seen, one due to surface disorder and the other to changes in surface composition. The latter phase is stable under annealing to at least 1100 K. Exposure to ${\mathrm{O}}_{2}$, however, depopulates the band-gap surface states on both vacuum-fractured and ion-bombarded surfaces. Models for the detailed structure of the defect surface states are discussed.

Photovoltaic properties of ZnO/CdTe heterojunctions prepared by spray pyrolysis

Abstract: An extended investigation has been made of the electrical and photovoltaic properties of heterojunctions prepared by spray‐pyrolysis deposition of thin ZnO films on single‐crystal p‐type CdTe. The principal experimental variables were the substrate temperature and the postdeposition temperature for annealing in H2. Under actual sunlight the optimum cell showed an open‐circuit voltage of 0.54 V, a short‐circuit current of 19.5 mA/cm2, and a solar efficiency (referred to the active area) of 8.8%, the highest value obtained to date for an authentic heterojunction on CdTe. The nature of the forward transport mechanism has been investigated, and a tunneling model in which bulk and interface deep traps control the forward characteristics is shown to provide good correlation with the experimental data.

Grain Growth Mechanism of Heavily Phosphorus‐Implanted Polycrystalline Silicon

Abstract: Grain growth phenomena of heavily phosphorus‐implanted polycrystalline silicon films owing to high temperature annealing are investigated by transmission electron microscope. Phosphorus doping in excess of is found to enhance grain growth. This growth is broken down into primary and secondary recrystallization. Isochronal annealing reveals the activation energies for these as 2.4 and 1.0 eV, respectively. The driving force of the primary recrystallization is found to be the interface energy. Therefore, the elementary process behind the primary recrystallization is attributed to silicon diffusion across the grain boundary region.

The deformation behavior of a vanadium-strengthened dual phase steel

Abstract: A study has been made of the mechanical properties of dual phase (martensite plus ferrite) structures produced when a V containing HSLA steel is cooled in a controlled manner from either the austenite or austenite plus ferrite phase fields Such a heat treatment results in the pearlite regions and carbide particles of the standard V steel being replaced by martensite; this leads to a decrease in the yield stress and an increase in ductility while the tensile strength is essentially unchanged The fatigue of dual phase steels is slightly superior in the high strain life (ductility controlled) region and slightly inferior in the low strain life (yield dominated) region when compared to standard V steel The replacement of the pearlite and cementite particles which can nucleate cracks, by more ductile martensite islands results in improved Charpy impact properties The strength and the ductility of the dual phase materials is shown to be in agreement with a theory of composites with two ductile phases This theory then allows one to understand the relative importance of various microstructural features in controlling strength and ductility In this way it is found that the key to the superior elongation (at a constant tensile strength) is largely due to the high strength (fine grained), highly ductile ferrite matrix

Laser annealing of boron-implanted silicon

Abstract: The properties of boron‐implanted silicon annealed by high‐power Q‐switched ruby laser radiation are compared with results obtained by conventional thermal annealing. Laser annealing of the implanted layer results in significantly increased electrical activity, as compared to thermally annealed implanted silicon. This correlates well with transmission electron microscopy and ion‐channeling measurements which show a dramatic removal of displacement damage as a result of laser annealing. A substantial redistribution of the implanted boron concentration profile occurs after laser annealing which cannot be explained by thermal diffusion in the solid.

Structure and Stability of Low Pressure Chemically Vapor‐Deposited Silicon Films

Abstract: The structure of silicon films deposited by low pressure, chemical vapor deposition in the 600°C temperature range has been investigated by x‐ray diffraction and transmission electron microscopy. There is a critical temperature near 600°C, above which the deposited films are polycrystalline and below which amorphous films are obtained. This temperature is close to that used to deposit films for integrated circuit applications. When the films are polycrystalline, the texture dominates. The polycrystalline films are reasonably stable upon annealing to temperatures up to approximately 1100°C. The initially amorphous films, however, easily crystallize. Crystallization has been observed to be well advanced after annealing at 800°C. Large stresses are built into the amorphous films, while the stresses in the polycrystalline films are lower.

Physical and electrical properties of laser‐annealed ion‐implanted silicon

Abstract: The use of a laser as a tool for annealing of ion‐implantation damage is described. The principal results obtained are as follows: (1) electrical measurements show that activity comparable to that of a 1000 °C 30‐min anneal can be obtained; (2) TEM measurements show that complete recrystallization of the damaged layer occurs during the laser anneal; (3) impurity profiles obtained from SIMS measurments show that the dopant atoms remain in the LSS profile during annealing. Simple diodes were fabricated to examine the feasibility of the method for device fabrication.

Periodic regrowth phenomena produced by laser annealing of ion‐implanted silicon

Abstract: We have discovered that interference effects extant during pulsed laser irradiation annealing of ion‐implanted silicon produce periodic property variations in the annealed material that mimic the interference pattern. These are manifest at near‐annealing threshold power densities as surface ripple and at higher power densities may be revealed by etching. The surface ripple observed at low power densities is correlated with the occurrence of polycrystalline silicon regions in the annealed material. Our observations suggest that surface melting and epitaxial regrowth are responsible for the annealing effect.

Theoretical analysis of thermal and mass transport in ion‐implanted laser‐annealed silicon

Abstract: Experimentally observed laser‐induced redistributions of ion‐implanted dopants in silicon are explained theoretically in terms of diffusion in the molten state. Calculations of thermal and mass diffusion in silicon show that the redistribution of a dopant file after pulsed‐laser annealing is dependent on the time the dopant region remains molten and on the value of the mass‐diffusion coefficient for the particular dopant.

Comparative study of annealed neon‐, argon‐, and krypton‐ion implantation damage in silicon

Abstract: Comparative annealing studies were carried out upon Si layers implanted with Ne+, Ar+, and Kr+ ions. Ion doses were in the range 6×1014/cm2–6×1015/cm2, and ion energies were chosen so that the matrix damage had approximately the same depth for each ion type. Annealing was carried out in a N2/dilute O2 ambient or in vacuum at 600, 900, or 1100 °C. Implanted layer structures were studied using electron‐microscope and ion‐backscattering techniques. The orientation of the Si substrate and ion‐beam heating effects were found to be important in determining layer‐annealing behavior. The latter depended weakly, if at all, upon the nature of the annealing ambient. Layer recrystallization was studied as a function of implanted ion type and dose, and the effects of inert gases trapped in the Si lattice were examined. The suitability of implantations for device gettering applications were considered. Crystallographic defects produced by annealing ranged from polycrystals and microtwins to simple dislocation networks. Faceted gas bubbles invariably occurred in annealed layers, and their geometry gave information regarding low‐energy planes in Si. Electron diffraction and He+‐ion channeling effects produced by twins in recrystallized layers have also been examined.

Absorption coefficient measurements for vacuum‐deposited Cu‐ternary thin films

Abstract: The absorption coefficients, α, of polycrystalline CuInS2 and CuInSe2 thin films have been determined at room temperature using transmission measurements. For each of these semiconductors, an absorption edge corresponding to the direct band‐gapl transition (1.54±0.02 eV for CuInS2 and 1.00±0.02 eV for CuInSe2) is observed in the α vs hν spectrum. In p‐type CuInS2 thin films, another edge is evident at lower energies (1.41×1.42 eV) and is attributed to transitions from a copper vacancy band to the conduction band. The effects of annealing on the absorption coefficient spectra of these chalcopyrite materials are presented. An additional absorption region, appears in the CuInSe2 spectra at higher energies (hν∠1.28 eV), and is critically dependent on the Se concentration of the films. This effect is discussed in terms of band structure, film stoichiometry and structural characteristics of the films.

A laser‐scanning apparatus for annealing of ion‐implantation damage in semiconductors

Abstract: The feasibility of annealing ion‐implantation damage by means of a continuous high‐power laser is demonstrated. An apparatus for the scanning of a semiconductor sample is described and a first‐order set of optimum conditions for annealing ion‐implanted Si is given. A preliminary comparison between laser and thermal annealing shows comparable results in terms of electrical activity of the annealed samples.

Electron field emission from ferromagnetic europium sulfide on tungsten

Abstract: The emission process from W-EuS junction field emitters was studied by combination of several experimental methods: measurement of emission current, spin polarization, energy distribution, and energy-selective spin polarization as function of emitter temperature for different annealing conditions. The results show that with critical annealing a stoichiometric crystalline EuS layer can be obtained; the interface of such a layer on tungsten acts as a spin filter below the EuS Curie temperature. With emitters annealed at higher temperatures, evidence for electron trapping and the formation of spin clusters has been obtained.

Some features of laser annealing of implanted silicon layers

Abstract: Comparative investigation of the process of the structure reordering of disordered implanted silicon layers after thermal (800°C, 30 min) and pulse laser annealing have been carried out. The new laser method of annealing implanted layers has a number of interesting features which provide great efficiency and locality of semiconductor doping without considerable heating of the base material and redistribution of implanted impurities. On the base analysing of investigation of kinetics of layer photostimulated recrystallization and calculation of temperature fields the possible mechanisms of laser annealing are also discussed.

Method for making defect-free zone by laser-annealing of doped silicon

Abstract: This invention is a method for improving the electrical properties of silicon semiconductor material. The method comprises irradiating a selected surface layer of the semiconductor material with high-power laser pulses characterized by a special combination of wavelength, energy level, and duration. The combination effects melting of the layer without degrading electrical properties, such as minority-carrier diffusion length. The method is applicable to improving the electrical properties of n- and p-type silicon which is to be doped to form an electrical junction therein. Another important application of the method is the virtually complete removal of doping-induced defects from ion-implanted or diffusion-doped silicon substrates.

cw argon laser annealing of ion-implanted silicon

Abstract: We report on the annealing behavior of ion‐implanted silicon exposed to cw argon laser radiation. The quality of the annealing was studied using channeling, in situ reflectivity, phase‐contrast microscopy, and electrical resistivity. Strong dependence of anneal quality on laser power, crystal orientation, and implant dose is reported. Reflectivity measurements with a focused probing laser show that the onset of annealing occurs just below the melting point, and the annealing extends into the region where a thin layer of liquid silicon is formed at the crystal surface. We conclude that the physical mechanism responsible for crystal recovery is similar to the solid‐state epitaxial regrowth observed for over‐annealed samples.

A comparative study of laser and thermal annealing of boron‐implanted silicon

Abstract: Transmission electron microscopy has been used to study the effects of high‐power laser pulses on as‐grown and boron‐implanted silicon. No defects (dislocations, dislocation loops, and stacking faults) were observed in either as‐grown or boron‐implanted (doses 3×1015 and 2×1016 ions cm−2) silicon after pulsed laser treatment. In thermally annealed specimens, on the other hand, a significant amount of damage was retained even after annealing at 1100 °C for 30 min. After thermally annealing the implanted laser‐treated specimens at 600 and 900 °C for 30 min, no defects were observed for low‐dose specimens; however, in high‐dose specimens, precipitation of boron occurred after 600 °C annealing and it increased after annealing at 900 °C. These results and the electrical measurements on these samples suggest that the boron atoms in the precipitates are electrically inactive.

Fracture of aluminium-coated carbon fibres

Abstract: A degradation in the ultimate tensile strength (UTS) of aluminium-coated carbon fibres was associated with the formation of a reaction layer of aluminium carbide during annealing treatments ⩾ 475° C for high tensile fibres (HT) and ⩾ 550° C for high modulus fibres (HM). It was established that for a given annealing treatment, the UTS depended on the square root of the original coating thickness and proposed that fracture was controlled by cracks in the aluminium carbide, with a specific surface energy (γ) and intrinsic crack length (c0) of 2.33 J m−2 and ∼ 30 nm for HT fibres, and of 0.64 to 0.77 J m−2 and ∼ 20 nm for HM fibres.

Annealing of Te-implanted GaAs by ruby laser irradiation

Abstract: A single pulse of ruby laser radiation is shown to cause significant regrowth in the amorphous region of heavily ion‐implanted GaAs. The implanted Te atoms and the host material both show good channeling dips, suggesting essentially complete substitutionality of the Te. There has been only a minor redistribution of the tellurium atoms. The resulting local Te concentration in the laser‐irradiated sample is more than ten times the known maximum solubility of Te in GaAs.

Photorefractive effects and photoconductivity in LiNbO3:Fe

Abstract: The photoconductivity of LiNbO3: Fe-crystals oxidized and partially reduced by annealing treatments is studied in the visible and the near uv-region. The measurements yield information on the influence of Fe2 +- and Fe3 +-ions.

Influence of deposition conditions on sputter‐deposited amorphous silicon

Abstract: The electrical, optical, and photoelectronic properties of sputter‐deposited amorphous silicon films have been systematically related to deposition parameters for the case of pure Ar sputtering gas in an rf diode system. Variation of the sputtering gas pressure from 25 to 150 mTorr controllably and reproducibly increases the film resistivity 3 to 4 orders of magnitude and significantly decreases optical absorption for photon energies ≲1.6 eV. Similar film property improvements can be realized through the use of large substrate‐target spacings (∼10 cm) and substrate temperatures ≲500 °C. The film properties, however, are independent of deposition rate between 0.5 and 5 A sec−1. The influence of gas pressure and substrate‐target spacing has been linked to Ar bombardment of the growing film, which appears responsible for both high dangling‐bond densities and incorporated gas. The influence of substrate temperature could result from annealing of collision‐induced defects as the film grows, or from a decrease in the density of microvoids as reported by Paul et al. for amorphous germanium. The use of deposition conditions which minimize plasma interaction and maximize thermal reorganization results in remarkably good electrical and optical properties for nonhydrogenated amorphous silicon. Using the approach of Lewis et al. the addition of H2 to the Ar sputtering gas produces film properties which are further improved and quite similar to those observed for films prepared by plasma‐assisted decomposition of silane.

Influence of substoichiometry, hydrogen content and crystallinity on the optical and electrical properties of H x WO y thin films

Abstract: We have prepared HxWOy amorphous thin films both by evaporation of tungsten trioxide powder and by cathodic sputtering of a tungsten target in an argon/oxygen/hydrogen reactive gas mixture. The evaporated layers have the composition HxWO2.7 (0.2 < × < 0.5). Their oxygen content seems rather insensitive to the evaporation parameters. We do not observe any correlation between x and these parameters. Evaporated virgin layers are nearly transparent. Annealing,under vacuum leaves y unchanged, under oxygen increases y to 3. Annealing of the virgin layer under vacuum induces the growth of the 1.38 eV absorption band (giving blue coloration) and a decrease of the activation energy for conduction. Annealing the blue layers in oxygen destroys the 1.38 eV band and increases the activation energy for conduction. In both cases annealing at high temperature induces a microcrystalline phase with an absorption band centered about 0.72 eV (giving also a blue coloration) and a jump in electronic conductivity. As in the case of the 1.38 eV band, an increase of the intensity of the 0.72 eV band induces a decrease of the activation energy for conduction. The two bands are interpreted as polaronic like. They can be induced in transparent layers without any change in global composition by excitation of the hydrogen atoms from a “ passive” state to an “ active” state. In addition to the hydrogen content, the existence of the 1.38 eV band requires some substoichiometry. The study of the optical and electrical properties of amorphous HxWOy sputtered layers, supports our previous conclusions about the composition range (C) for the coloration capability of transparent thin films. In addition there is a composition range (B) where the virgin layers are blue, and a composition range (M) where they have a metallic like behavior. On the other side of (C), there is a range (C’) where uv illumination only induces a decrease in the activation energy for conduction, then a range (T) where the layers are completely nonresponsive. One can pass from (T) to (B) through (C') and (C) either at constant hydrogen content by increasing the departure from stochiometry, or at constant substoichiometry by increasing the hydrogen content.