Argon Annealing Research Articles

Reactions of Laser-Ablated Iron Atoms with Oxygen Molecules in Condensing Argon. Infrared Spectra and Density Functional Calculations of Iron Oxide Product Molecules

Reaction of laser-ablated Fe atoms with oxygen molecules in a condensing argon stream produced FeO, FeO2, FeO3, FeO4, Fe2O, Fe2O2, and Fe2O4 molecules, which are identified from oxygen isotopic shifts and multiplets in matrix infrared spectra. The Fe + O2 reaction gives symmetrical bent, symmetrical cyclic, and asymmetrical bent FeO2 isomeric products with triplet, triplet, and quartet isotopic absorptions, respectively, using statistically mixed 16,18O2 as the reagent. The major reaction product symmetrical bent OFeO iron dioxide molecule (150 ± 10°) is characterized by stretching fundamentals at 945.8 and 797.1 cm-1, and the asymmetric bent FeOO form exhibits a 1204.5 cm-1 absorption. The cyclic isomer Fe(O2) produced spontaneously during annealing in solid argon absorbs at 956.0 cm-1. Oxygen and iron isotopic absorptions show that FeOFe is a symmetrical bent (140 ± 10°) molecule. Rhombic Fe2O2 absorbs at 517.4 cm-1. Evidence is presented for isomers of FeO3, FeO4, and Fe2O4. Density functional theory was used to calculate energies, structures, and frequencies for product molecules to support their identification.

Improvement of Czochralski Silicon Wafers By High‐Temperature Annealing

High‐temperature annealing in hydrogen, argon, and oxygen ambients improves the electrical performance of Czochralski Si wafers considerably. The gate oxide integrity of such wafers can approach values close to 100% yield after annealing for 1 to 2 h at 1200°C in argon and hydrogen ambient which is related to a significant reduction of near‐surface crystal defects as compared to nonannealed polished wafers. The perfection of epitaxial wafers is, however, not obtained. The high‐temperature treatment deteriorates the surface of polished wafers depending on the ambient used. A protective oxide layer grown during annealing in an oxygen ambient prevents roughening due to desorption of . A more pronounced roughening occurs by annealing in hydrogen or argon which is tightly connected to the chemical composition of the surface. A hydrogen terminated reconstructed Si (100) surface is observed after annealing in hydrogen. An oxygen‐denuded zone is formed close to the surface during high‐temperature annealing preventing oxygen precipitation in this region of the wafer. The oxygen precipitation in the bulk of the wafers depends significantly on the details of the annealing process. A precipitation behavior similar to nonannealed Si wafers can be obtained by appropriate process parameters.

Manifestation of oxygen order-disorder effects in EuBa 2 − kSr kCu 3O 6 + z

We report here on the structural and AC susceptibility measurements of EuBa 2 − k Sr k Cu 3O 6 + z ( k = 0, 0.4, 0.6, 0, 8 and 1). The samples were subject to two types of heat treatment: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. Whereas the orthorhombicity decreased as a function of Sr ( k) for the [O] samples, it increased for the [AO] samples for k > 0.4. Further, the slope dT c dk decreased remarkably after the [AO] treatment. This slope was found to be different from that observed in the case of YBa 2 − kSr k Cu 3O 6 + z . A maximum increase in the intergranular coupling was found for k = 0.6 after the [AO] treatment. The result cannot be attributed only to a change in the ionic size of the rare earth as expressed by several authors. We propose that in addition to the cation disorder (Sr/Ba), there may be an oxygen disorder in the basal plane. The results observed are the outcome of an interplay between cationic (Sr/Ba) disorder and oxygen disorder. The [AO] treatment seems to enhance certain properties by reducing this oxygen disorder.

Nuclear methods in technology of Si:Er structures

Formation of optically and electrically active Er-related centers and redistribution of Er atoms in Si:Er structures were investigated at annealings in different atmospheres. It is shown that annealing in chlorine-containing atmosphere leads to an increase of photoluminescence intensity at wavelength of 1.54 μm as compared with annealing in argon or oxygen ambient. Annealing atmosphere also affects the behaviour of Er atoms and electrically active Er-related defects introduced by means of diffusion from film source. Silicon nitride films covering a surface of wafers were used to investigate the effect of annealing atmosphere on Er redistribution. Changes of concentration and penetration depth of Er atoms and electrically active Er-related centers dependent on annealing medium arose due to generation of excess vacancies and/or self-interstitials near surface.

Cationic substitution in mercury-based cuprates: generation of five superconductors

Five mercury-based superconductors, Hg1–xMxBa2CuO4+δ with MMn, Nb, Hg1–xMxBa2CaCu2O6+δ with M = Mn, Ge and Hg1–xNbxBa2Ca2Cu3O8+δ, have been synthesized. A significant decrease of the c parameter of the tetragonal cells of the Ge and Mn phases with respect to the unsubstituted mercury cuprates is observed for the Ge and Mn phases, whereas the Nb phases exhibit a ‘c’ parameter close to that of the unsubstituted cuprates, in agreement with the relative sizes of MnIV, GeIV and NbV. EDS analyses confirm that Mn, Ge and Nb have entered into the matrix of the cuprate in a homogeneous way. Magnetic studies of the as-synthesized phases and of the samples after argon and oxygen annealing show sharp transitions except for the 1201-Nb phase. The critical temperatures, Tc(midpoint), of these phases after optimisation are close to those of the unsubstituted mercury cuprates: 91 K for the 1201-Mn phase, 123–124 K for the 1212 Mn and Ge phases and 128 K for the 1223 Nb phase. The investigation of the AI-substituted mercury cuprates is also discussed.

Synthesis and characterization of a new mercury-based superconductor, Hg 0.5Tl 0.5Ba 2Ca 1- xSr xCu 2O 6+ δ

A new mercury-based superconductor Hg 0.5Tl 0.5Ba 2Ca 1- x Sr x Cu 2O 6+ δ ( x = 0.14, denoted as Hg, Tl-1212) was synthesized from the reaction of HgO, Tl 2O 3, Ba 2CuO 3+ x , and Ca 1- x Sr x CuO 2. X-ray powder diffraction analysis showed that the thallium completely substitutes for the mercury sites in the rock-salt [HgO δ] layer. The as-synthesized Hg, Tl-1212 has a T c of 122 K. Surprisingly the T c decreased to about 100 K upon annealing in an oxygen atmosphere at 350°C for 8 h while the argon annealing did not show any substantial change in T c under the same condition. The crystal symmetry was found to be tetragonal (P4/mmm) with lattice parameters a = 3.8496 (1) A ̊ and c = 12.6536 (4) A ̊ . The Hg, Tl-1212 is quite stable up to 450°C. The intra-critical current density of Hg, Tl-1212 is about twice larger than that of HgBa 2Ca 1- x Sr x Cu 2O 6+ δ ( x = 0.14). The substitution of Tl for Hg clearly stabilized the Hg, Tl-1212 phase as well as enhanced the pinning property.

Seebeck effect and neutron diffraction of NdSrBaCu 3O 6+z. Effect of argon annealing

We have performed neutron-diffraction and thermopower experiments on two samples of NdSrBaCu 3O 6+ z . One was a conventionally annealed sample at 450°C in oxygen [O] and the other was heated in argon at 850°C followed by oxygen annealing [AO]. The T c of the sample [O] was 68 K and that of [AO] was 78 K. The neutron data showed that the [O] sample had a higher impurity level arising from Nd entering the Sr/Ba sites that may result in a decrease in the carrier density ( p) which was also confirmed by our thermopower measurements. The increase in p and in-phase purity for the [AO] sample may account for the observed increase in T c.

Ceramic joining III bonding of alumina via Cu/Nb/Cu interlayers

A method of ceramic-ceramic joining that exploits a multilayer interlayer designed to form a thin, potentially transient layer of liquid phase has been used to join alumina to alumina. Microdesigned multilayer Cu/Nb interlayers were used to achieve bonding at 1150 °C. Flexure strengths of as-bonded samples ranged from 119 to 255 MPa, with an average of ≈ 181 MPa. The ability to form ‘strong’ ceramic/metal interfaces is also indicated by instances of ceramic failure. Microstructural and chemical characteristics of fracture surfaces were evaluated using SEM, EDS and microprobe. The impact of post-bonding anneals of 10 h duration at 1000 °C in gettered argon on room-temperature joint strength was assessed. High strengths (198 to 238 MPa) were obtained. The retention of strength following annealing in low oxygen partial pressure argon differs from the behaviour previously observed in Cu/Pt bonded alumina. Effects of the anneal on interfacial microstructure were determined, and an explanation for this difference in behaviour is proposed.

Fe 3O 4(111) termination of α-Fe 2O3(0001)

Scanning tunnelling microscopy (STM) has been used to investigate the structure formed on an α-Fe 2 O 3(0001) substrate after argon ion bombardment and annealing in 1 × 10 −6 mbar of O 2 at 1000 K. The STM images recorded at positive sample bias reveal an hexagonal array, with a distance between (Fe) atoms of 6.0 ± 0.1 rA and steps in multiples of 4.8 Å. These results are consistent with formation of an Fe 3O 4(111) epitaxial layer terminating in a 1 4 monolayer of Fe atoms.

Imaging ion-bombarded III-V semiconductor surfaces: a scanning tunnelling microscopy study of InSb(100)

Scanning tunnelling microscopy (STM) has been used to produce images of InSb(100) prepared by in situ treatment of several cycles of low-energy argon ion bombardment and annealing. Electron diffraction studies, following annealing to 625 K, show the c(8*2) pattern associated with the In-rich reconstruction also observed during MBE growth. These STM images demonstrate the improved surface ordering with successive cycles resulting in atomically flat terraces over areas of the sample in excess of 1000 AA*1000 AA. The observed reduction of macroscopic morphological defects, such as In droplets, is discussed as a function of surface treatment.

An STM study of the InSb(100)-c(8 × 2) surface

Atomic resolution scanning tunneling microscopy (STM) images of InSb(100) prepared by in situ treatment of several cycles of low energy argon ion bombardment and annealing have been obtained. The STM images demonstrate how the structural quality of the surface improves dramatically with repeated bombardment and annealing cycles. After annealing to 625 K, atomically flat terraces were obtained over areas in excess of 1000 Å × 1000 Å and low energy electron diffraction (LEED) studies at room temperature revealed a sharp, stable c(8 × 2) pattern. Atomic resolution images indicate (4 × 1) unit cells in which occupied lone pair orbitals of Sb atoms in the second layer are imaged. The data obtained is consistent with the structural model presented for this surface on the basis of high resolution core level photoemission by John et al. [Phys. Rev. B 39 (1989) 1730] in which 3 4 of a monolayer of In dimers are on top of a complete monolayer-Sb-terminated surface.

Capillary instabilities in thin, continuous films

Abstract The agglomeration of continuous films was studied in 60 nm thick, polycrystalline, gold films deposited on polished fused silica substrates. Nucleation of holes in any particular sample showed nucleation frequencies characteristic of site saturation. The growth of the holes resulted in roughly circular agglomerated areas. The area fraction transformed was measured as a function of time for several temperatures in oxygen and argon. Using a Johnson-Mehl-Avrami analysis and assuming a constant hole growth rate, the time dependence of the agglomeration can be described. The growth rates, which contain important kinetic information, could thus be determined. Growth rates for anneals in argon and oxygen were found to be similar.

希土類元素-ニッケル系水素吸蔵合金の水素平衡特性のY, Mn置換の効果

The pressure-composition (P-C) isotherm of hydrogen in alloys is important for the practical use of hydrogen-absorbing alloys. A numerical expression method was developed for the plateau region of the P-C isotherm in LaNi5, LaNi4.8Mn0.2 and La0.8Y0.2Ni5 alloys with the CaCu5 structure.Samples were prepared by using argon arc melting and annealing. The desorption isotherms at 298 K were used for testing the numerical expression. The regular solution model with a term proportional to hydrogen composition as an excess chemical potential was applied to the solid solution and hydride phase region. A normal cummulative distribution function (ncdf) model with composition as frequency was applied to the plateau region.All the isotherms were expressed accurately with the models employed and characteristic parameters of the alloys were obtained. The changes in the micro-structural heterogeneity in the alloys by annealing and the Mn or Y substitution were in accordance with those in the standard deviation (σ) of the ncdf which presents the plateau slopes.Consequently, the normal cummulative distribution function model for the plateau region was found to be helpful for the development of the alloys because σ presents both the plateau slope and the micro-structural heterogeneity in the alloys.

Effect of annealing ambient on the removal of oxide precipitates in high-dose oxygen implanted silicon

The effect of annealing ambient on the precipitate removal processes in high-dose oxygen implanted silicon [separation by implantation of oxygen (SIMOX)] has been studied with transmission electron microscopy, electron energy-loss spectroscopy, and secondary ion mass spectroscopy. The rate of removal of oxide precipitates from the top silicon layer in SIMOX is higher during annealing in argon than in nitrogen. The removal is reduced in nitrogen due to the formation of an oxynitride complex at the precipitate surfaces which inhibits oxygen diffusion across the interfaces. Similar effects have been observed for oxide precipitation during nitrogen ambient annealing in bulk silicon.

Two-dimensional ordered stearic acid films on CdxHg1− xTe(111) substrates

Stearic acid (HST) Langmuir-Blodgett films (LBFs) were investigated on Si(111), GaAs(110) and Cd x Hg 1- x Te(111) substrates with ellipsometry, X-ray photoelectron spectroscopy (XPS), low energy electron diffraction and work function measurements. Silicon and GaAs surfaces were initially covered with amorphous native oxide layers while the Cd x Hg 1- x Te surface was structurally ordered owing to argon bombardment and annealing. For all the cases the hydrophobic nature of the substrate, Y-type bilayer formation and an inclination at 30° of the molecular axis to the surface normal were observed. Two-dimensional ordering of the HST bilayer with hexagonal symmetry and translational period 0.5 nm took place on Cd x Hg 1- x Te(111) substrates. XPS and work function experiments have demonstrated the perfection of this system. Surface terraces and a (2 x 2) adsorption phase seem to be the most probable reasons for LBF ordering on Cd x Hg 1- x Te(111) substrates.

Indium–tin oxide films radio frequency sputtered from specially formulated high density indium–tin oxide targets

High density ITO (indium–tin oxide) targets doped with Al2O3 and SiO2 manufactured in the Tektronix Ceramics Division have been used to rf sputter ITO films of various thicknesses on borosilicate glass substrates. Sputtering in an oxygen–argon gas mixture and annealing in forming gas, resulted in ITO films exhibiting 90% transmission at 550 nm and a sheet resistance of 15 Ω/sq for a thickness of 1100 Å. Sputtering in an oxygen–argon gas mixture and annealing in air increased sheet resistance without a large effect on the transmission. Films sputtered in argon gas alone were transparent in the visible and the sheet resistance was found to be 100–180 Ω/sq for the same thickness, without annealing.

The behaviour and properties of in-situ formed YBa/sub 2/Cu/sub 3/O/sub x/ thin films during reversible oxidation/deoxidation

The authors have reversibly oxygenated and deoxygenated in situ-formed thin films of YBa/sub 2/Cu/sub 3/O/sub x/ by means of low-temperature anneals in oxygen and argon. The transition shape for slightly deoxygenated material is consistent with the existence of two superconducting phases, which may be distinguished by different oxygen ordering. The authors investigated J/sub c/(B) as a function of oxygen content in samples whose oxygen content has been controlled by low-temperature anneals. The steep rise in J/sub c/ with T/sub c/. has been demonstrated and the effect on J/sub c/ of change in c investigated. It is confirmed that in situ-formed films which have low T/sub c/ as-deposited have anomalously high c values, but it is demonstrated that good films (that is, films which as deposited have c approximately 1.168 nm and T/sub c/ approximately 90 K) follow the bulk c vs. T/sub c/ relationship when deoxygenated and reoxygenated in low-temperature anneals. The cause of the c expansion is attributed to a defect, possibly the substitution of Ba for Y, introduced at the time of film deposition under conditions of low mobility. Some data have been obtained which suggest that films deposited on substrates at higher temperatures have c vs. T/sub c/ more consistent with bulk data.

Magnetic properties and surface crystallization induced by selective oxidation in Fe-B-Si amorphous alloy

The relationship between the annealing atmosphere and the magnetic properties of Fe78.5B13Si8.5 amorphous alloy has been studied, showing that annealing in nitrogen, argon, hydrogen and air significantly improved the iron loss of the amorphous ribbon, giving much better results than annealing in an H2 + H2O atmosphere. A boron-depletion zone with the alloy composition O to 3 mol % B and 9 to 11 mol% Si was detected by Auger electron spectroscopy under the oxide film formed during annealing in H2 + H2O. The iron crystalline phase is formed only on the ribbon surface after annealing in H2 + H2O. A mechanism is proposed explaining the deleterious effect of annealing in the H2 + H2O, whereby the H2O in this atmosphere selectively oxides boron in the amorphous alloy to form a B2O3 film and the boron-depletion zone, and the alloy in this zone is then crystallized into α-Fe. This surface crystalline layer induces out-of-plane magnetic anisotropy in the amorphous alloy ribbon (which was observed by transmission Mossbauer spectroscopy) and thus deterioration of the iron loss.

Effect of oxygen adsorption-desorption on some properties of high-Tc Bi[sbnd]Pb[sbnd]Sr[sbnd]Ca[sbnd]Cu[sbnd

The effect of further annealing in ambient argon at low temperature in the range of room temperature to 700°C on some properties of BiPbSrCaCuO was studied by the thermogravimetric analysis (TGA) etc. The annealing has a large influence on the superconducting properties. The transition temperature of low-Tc phase and the reversibility of superconducting phase after thermal cycles in ambient Ar and O2 are closely related to the reduced oxygen partial pressure in ambient Ar. Very low partial pressure of oxygen will cause the sample lose its superconductivity.

Structure and composition requirements for deoxygenation, dehydration, and ketonization reactions of carboxylic acids on TiO 2(001) single-crystal surfaces

The reactivities of TiO 2(001) single-crystal surfaces for acetic acid decomposition were studied by TPD and XPS. Surface structure and composition were varied by a combination of argon ion bombardment and annealing in order to investigate reaction selectivity and to identify the active sites responsible for adsorption and decomposition. Acetic acid adsorbed both molecularly and dissociatively at 200 K, but only dissociatively at 300 K. The molecular species desorbed readily below 300 K. Approximately 15% of the dissociatively adsorbed species (acetates) desorbed as acetic acid at 390 K via recombination with surface hydroxyls. The remaining acetates decomposed at higher temperatures via three different reaction pathways with selectivities dependent on surface composition and structure. Reduced surfaces containing Ti cations of lower valences favored direct deoxygenation of the acetates to fill the oxygen vacancies of the surface. This reaction occurred even at room temperature and deposited atomic carbon on the surface. Oxidized surfaces containing only Ti 4+ cations favored reactions to form volatile molecular products. On the {011}-faceted surface, surface acetates decomposed via net unimolecular dehydration to ketene. On the {114}-faceted surface, the bimolecular reaction of surface acetates to form acetone also took place. The reactions of propionates formed by dissociation of propionic acid were directly analogous to those of acetates: methyl ketene was produced by net unimolecular dehydration on the {011}-faceted surface and 3-pentanone was the bimolecular ketonization product on the {114}-faceted surface. Since the {011}-faceted surface exposes only Ti 4+ cations of fivefold oxygen coordination, these sites were determined to be responsible for the net unimolecular dehydration. Bimolecular ketonization required the coordination of two acetates to a common Ti 4+ cation on a stoichiometric surface. Of the single-crystal surfaces examined, only the {114}-faceted surface presented the necessary fourfold oxygen-coordinated Ti 4+ sites for this reaction.