Effect Of Pre-annealing Research Articles

Effects of Pre-Annealing on the Radiation Resistance of ZnO Nanorods

Ion implantation is usually used for semiconductor doping and isolation, which creates defects in semiconductors. ZnO is a promising semiconductor and has a variety of applications, such as for use in transparent electronics, optoelectronics, chemical and biological sensors, etc. In this work, ZnO nanorods were grown on Si (100) substrates by the process of chemical bath deposition and then annealed in an O2 atmosphere at 350 and 600 °C for 1 h to introduce different kinds of defects. The as-grown nanorods and the nanorods that annealed were irradiated simultaneously by 180 keV H+ ions at room temperature with a total dose of 8.0×1015 ions/cm2. The radiation effects of the H+ ions, effects of the pre-existed defects on the radiation resistance, and the related mechanisms under irradiation were investigated. The crystal and optical properties of the ZnO nanorods after H+ ion irradiation were found to depend upon the pre-existed defects in the nanorods. The existence of the appropriate concentration of oxygen interstitials in the ZnO nanorods caused them to have good radiation resistance. The thermal effects of irradiation played an important role in the property variation of nanorods. The temperature of the nanorods under 180 keV H+ ion bombardment was around 350 °C.

The Effect of Pre-Annealing on the Evolution of the Microstructure and Mechanical Behavior of Aluminum Processed by a Novel SPD Method.

A novel continuous process of severe plastic deformation (SPD) named continuous close die forging (CCDF) is presented. The CCDF process combines all favorite advances of multidirectional forging and other SPD methods, and it can be easily scaled up for industrial use. Keeping constant both the cross section and the length of the sample, the new method promotes a refinement of the microstructure. The grain refinement and mechanical properties of commercially pure aluminum (AA1050) were studied as a function of the number of CCDF repetitive passes and the previous conditioning heat treatment. In particular, two different pre-annealing treatments were applied. The first one consisted of a reheating to 623 K (350 °C) for 1 h aimed at eliminating the effect of the deformation applied during the bar extrusion. The second pre-annealing consisted on a reheating to 903 K (630 °C) for 48 h plus cooling down to 573 K (300 °C) at 66 K/h. At this latter temperature, the material remained for 3 h prior to a final cooling to room temperature within the furnace, i.e., slow cooling rate. This treatment aimed at increasing the elongation and formability of the material. No visible cracking was detected in the workpiece of AA1050 processed up to 16 passes at room temperature after the first conditioning heat treatment, and 24 passes were able to be applied when the material was subjected to the second heat treatment. After processing through 16 passes for the low temperature pre-annealed samples, the microstructure was refined down to a mean grain size of 0.82 µm and the grain size was further reduced to 0.72 µm after 24 passes, applied after the high temperature heat treatment. Tensile tests showed the best mechanical properties after the high temperature pre-annealing and 24 passes of the novel CCDF method. A yield strength and ultimate tensile strength of 180 and 226 MPa, respectively, were obtained. Elongation to fracture was 18%. The microstructure and grain boundary nature are discussed in relation to the mechanical properties attained by the current ultrafine-grained (UFG) AA1050 processed by this new method.

Effect of Preannealing on Microstructural Evolution and Tensile Properties of a Novel Nickel‐Based Superalloy

The effect of preannealing (PA) on microstructural evolution and tensile properties of a novel nickel‐based alloy GH4065 is investigated. Particularly, the study of PA in disc superalloys is reported herein for the first time. The detailed strengthening mechanisms of specimens under different heat treatment cycles are identified by electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) observations. The results reveal that the PA treatment after deformation improves the homogeneity of the microstructure due to static recrystallization (SRX). Multimodal size distributions and the morphology of γ′ precipitates are found after the PA + solution + aging (PASA). Also, the distributions of secondary and tertiary γ′ precipitates are optimized due to the PA. The tensile strength of GH4065 alloy after PASA is higher than that of as‐forged (AF) alloy and solution + aging (SA) alloy attributed to the improved microstructure during PA treatment. Compared with the SA specimens, the specimens of GH4065 alloy after PASA treatment lead to significant strengthening as the yield strength increased to more than 150 MPa, which is mainly due to the contribution from annealing twins and microtwins strengthening, as well as the grain refinement and γ′ precipitation strengthening.

Effects of Pre-annealing on the Performance of Solution-processed Indium Zinc Oxide Thin-film Transistors

We report on thin-film transistors (TFTs) with indium zinc oxide (IZO) channel layers fabricated via a pre-annealing process at various temperatures. The solution-processed IZO semiconductor matched the pre-annealing well at temperatures as low as 120 °C, and showed good performance: field-effect mobility of 7.9 ㎠/Vs, threshold voltage of 1.4 V, subthreshold slope of 0.48 V/dec, and a current on/off ratio of 2.9 x 10SUP7/SUP. To investigate the static response of IZO TFTs with preannealing at 120 °C, simple resistor load–type inverters were fabricated by connecting a resistor (10 MΩ).

Effect of Pre-Annealing on Thermal and Optical Properties of ZnO and Al–ZnO Thin Films

Zinc oxide (ZnO) nanoparticles were synthesized by a simple solution route method using zinc acetate as the precursor and ethanol as the solvent. At a temperature of 60[Formula: see text]C, a clear homogenous solution is heated to 100[Formula: see text]C for ethanol evaporation. Then the obtained precursor powder is annealed at 600[Formula: see text]C for the formation of ZnO nanocrystalline structure. Doped ZnO particle is also prepared by using aluminum nitrate nonahydrate to produce aluminum (Al)-doped nanoparticles using the same solution route method followed by annealing. Thin film fabrication is done by air evaporation method using the polymer polyvinyl alcohol (PVA). To analyze the optical and thermal properties for undoped and doped ZnO nanocrystalline thin film by precursor annealing, characterizations such as UV, FTIR, AFM, TGA/DTA, XRD, EDAX and Photoluminescence (PL) were also taken. It was evident that precursor annealing had great influence on thermal and optical properties of thin films while ZnO and AZO film showed low crystallinity and intensity than in the powder form. TGA/DTA suggests pre-annealing effect improves the thermal stability, which ensures that Al ZnO nanoparticle can withstand at high temperature too which is the crucial advantage in the semiconductor devices. UV spectroscopy confirmed the presence of ZnO nanoparticles in the thin film by an absorbance peak observed at 359[Formula: see text]nm with an energy bandgap of 3.4[Formula: see text]eV. A peak obtained at 301[Formula: see text]nm with an energy bandgap of 4.12[Formula: see text]eV shows a blue shift due to the presence of Al-doped ZnO nanoparticles. Both ZnO and AZO bandgap increased due to precursor annealing. In this research, PL spectrum is also studied in order to determine the optical property of the nanoparticle embedded thin film. From PL spectrum, it is observed that the intensity of the doped ZnO is much more enhanced as the dopant concentration is increased to 1[Formula: see text]wt.% and 2[Formula: see text]wt.% of Al in ZnO.

Erratum to: Effect of Pre-annealing on Sintering of Stainless Steel Fiber Felt

Erratum to: Effect of Pre-annealing on Sintering of Stainless Steel Fiber Felt

Effect of Pre-annealing on Sintering of Stainless Steel Fiber Felt

Stainless steel fiber felt is a class of unique porous metal materials. This study investigates the effect of pre-annealing on the sintering of stainless steel fiber felt through quantitative characterization of sintered joints based on synchrotron radiation experiments. The sintered joint size was found to follow a marked normal distribution in fiber felt samples sintered with and without pre-annealing. However, pre-annealing prior to sintering led to a significant reduction in the total number of sintered joints as well as a reduction in the percentage of large sintered joints. Consequently, fiber felt samples sintered with pre-annealing achieved less than half the tensile strength of those sintered without pre-annealing. Delamination through fracture of sintered joints was pronounced in fiber felt samples sintered with pre-annealing, while failure occurred mainly through fracture of individual fibers in those sintered without pre-annealing. It was concluded that sintering without pre-annealing is necessary for the fabrication of high-strength fiber felt products and the reasons are briefly discussed.

Temperature-Dependent Compressive Deformation Behavior of Commercially Pure Iron Processed by ECAP

To explore the temperature dependence of deformation behavior of BCC structural materials and the relevant effect of pre-annealing, commercially pure iron (CP Fe) produced by equal-channel angular pressing (ECAP) is selected as the experimental material. The influences of deformation temperature T and pre-annealing on deformation behavior, surface deformation characteristics and substructures of ECAP Fe were systematically studied. The results show that ECAP Fe undergoes a remarkable strain softening stage after a rapid strain hardening during uniaxial compression, and the softening degree and the yield strength σ YS first decrease and then increase with raising temperature. Pre-annealing at 400 °C effectively weakens the strain softening degree and increases σ YS. To understand the influence of deformation temperature on deformation behavior, as well as the relevant pre-annealing effect, deformation and damage characteristics and dislocation structures are studied in detail. In a word, the strain softening of ECAP Fe is associated not only with internal structural instability, but also with temperature, and pre-annealing at 400 °C improves high-temperature mechanical properties of ECAP Fe.

Optimisation of recrystallisation texture and magnetic properties in Fe–6·5 wt-%Si thin sheets by preannealing method

Fe–6·5 wt-%Si thin sheets were produced by conventional rolling and annealing processes, and the effect of preannealing before final annealing on recrystallisation texture was investigated using macro- and microtexture analysis. It is found that the suitable temperature and time of preannealing can decrease detrimental γ recrystallisation texture, resulting in an optimisation of magnetic induction. The effects of preannealing can be attributed to its weakening the dynamic advantage of γ recrystallisation nuclei with respect to others.

Investigation of the free volume change of Fe41Co7Cr15Mo14C15B6Y2 bulk metallic glass using the cyclic thermal dilatation test

In heating process, the free volume of bulk metallic glass (BMG) changes with temperature. This change, however, is too small to be directly investigated by thermal dilatation (DIL) test. In cyclic heating, the free volume change results in a difference between the thermal expansion during heating and reheating processes, i.e., Δ(δV(T)/V0), which can be obtained by the cyclic DIL test. In this paper, the sample diameter and pre-annealing effect on the free volume change of Fe41Co7Cr15Mo14C15B6Y2 BMG are investigated by the Δ(δV(T)/V0) and ΔδV/V0¯, where ΔδV/V0¯ is the average value of Δ(δV(T)/V0) in the low temperature range and represents the total free volume released in the cyclic DIL test. The as-cast samples with a smaller diameter have a larger ΔδV/V0¯. After pre-annealing below the glass transition temperature for 2hours, a peak that is attributed to the free volume generation in glass transition process occurs in the Δ(δV(T,ta)/V0) curve and becomes sharper as the pre-annealing time ta is prolonged. ΔδV(ta)/V0¯ is fitted by a stretched exponential relaxation function with a characteristic relaxation time τ of 14194±2808s and a Kohlrausch exponent βkww of 0.34±0.04. The βkww of Fe41Co7Cr15Mo14C15B6Y2 BMG is markedly lower than that of Pd- and Zr‐based BMGs, and deserves a further investigation.

Effect of pre-annealing treatment on the compressive deformation and damage behavior of ultrafine-grained copper

Abstract The effect of short-term pre-annealing treatment on the compressive deformation and damage behavior of ultrafine-grained (UFG) copper produced by equal channel angular pressing (ECAP) has been studied by mechanical tests and microstructural observations. It is found that a controlled 10-min pre-annealing treatment on the UFG copper below the recrystallization temperature can result obviously in a higher strength (higher flow stress level) and a higher flow stability (lower stress softening rate) under uniaxial compression, as compared to the case of as-ECAPed sample. Observations of surface and interior deformation damage features indicate that, compared to the as-ECAPed copper sample, the pre-annealed ECAPed copper at less than recrystallization temperature may exhibit a better compressive plastic deformation capacity, namely, the destructive deformation morphology of large-scale shear bands normally observed in compressed as-produced UFG copper sample would not appear in compressed pre-annealed sample, except for a relatively smooth surface morphology featuring some ‘step’ reliefs with a few discontinuous shear bands and non-propagation voids. Finally, the deformation mechanism of different kinds of severe plastic deformation (SPD) processed UFG materials as well as their pre-annealing effects are further discussed, and a general rule is summarized as follows: an appropriate selection of pre-annealing temperature and annealing time is needed for improving both strength and ductility of SPDed materials with a microstructure comprising equiaxed grains and well-defined grain boundaries.

Modification and Conversion of E-Beam Co-Evaporated Precursors for Fabricating High Critical Current ${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7-\delta}$ Films

Ex situ conversion of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</i> -beam co-evaporated precursors was studied in an effort to fabricate high critical current YBCO films using the BaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> process. The precursors were deposited on CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> buffered single crystal YSZ substrates. It was shown that an intermediate oxygenation annealing prior to the conversion modifies the precursor crystallinity and promotes c-axis epitaxial growth while randomly-oriented film formation is suppressed. With the modified precursors, a critical current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , 77 K & 0 T) of 2.1 MA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> measured by SQUID magnetometry was obtained in 1.8 mum thick YBCO films. The mechanism of the pre-annealing effect was investigated by characterization of the precursors, quenched films, and fully converted films using XRD, SEM, and TEM. Cross-sectional TEM was used to study the early nucleation of YBCO film at the precursor/substrate interface. The significant effect of the precursor modification indicated that, in addition to optimizing conversion processing parameters, modifying the precursor is an effective way to achieve the desired epitaxial film structure and to obtain higher critical currents, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> .

Pre-annealing effect of electroless Ni−B deposit as a diffusion barrier for electroplated Cu electrodes

Ni−B film of 1 μm thickness was electrolessly deposited on an electroplated Cu bus electrode. The film, which encapsulates the Cu bus electrodes, prevents Cu oxidation and serves as a diffusion barrier against Cu contamination of the transparent dielectric layer in a plasma display during the firing process at 580 °C. The microstructure of theas-deposited barrier film was amorphous phase and crystallized to Ni and Ni3B after annealing at 300 °C. The good barrier properties observed here can be explained by Ni3B precipitates at the grain boundaries acting as a fast diffusion path via pre-annealing at 300 °C before the firing process at 580 °C.

Hydrogen and deuterium incorporation and transport in hafnium-based dielectric films on silicon

Hydrogen and deuterium incorporation into nitrided and non-nitrided hafnium silicate films on Si during thermal annealing in H1- and H2-containing atmospheres was investigated. H1 profiling was accessed by means of nuclear resonant reaction profiling, whereas H2 incorporation was quantified by nuclear reaction analysis. The effects of preannealing in different atmospheres and temperatures were determined, as well as the losses of H1 and H2 from these structures during postannealing in vacuum. The results reveal a rather uniform depth distribution of incorporated H1, in striking contrast with previous studies on hydrogen in silicon oxide and oxynitrides and hafnium oxide films on Si. These results are discussed in terms of the defects present in each one of the structures studied here.

Defect relaxation at the origin of reduction in mobile proton generation at Si/SiO2/Si interfaces during annealing in H2

Previous work [Vanheusden and Devine, Appl. Phys. Lett. 76, 3109 (2000)] has reported that subjecting Si/SiO2/Si capacitors to a 450 °C preanneal in hydrogen impedes formation of protons in the buried oxide during the subsequent generation anneal at 600 °C in H2. In interpreting, a key role in proton generation was assigned to Si dangling bond (Pb-) type defects, yet with unusual assumptions as to their atomic hydrogen production nature. Here, an explanation of the preanneal effect is offered based on annealing induced structural relaxation of (Pb-type) interface defects residing in edge regions of the capacitor, affecting their atomic hydrogen generation efficiency through altering the spreads in the defect activation energies for passivation in H2 and dissociation. Thus the preannealing effect is seen as a direct result of the occurrence of substantial spreads in regions of enhanced strain.

Visible photoluminescence from Si ion-beam-mixed SiO 2/Si/SiO 2 layers deposited by e-beam evaporation

The SiO 2/Si (3 nm)/SiO 2 layers were deposited by e-beam evaporation, and ion-beam-mixing was performed with 1.5 × 10 16 ions/cm 2 of 55 keV at room temperature. The sample deposited by e-beam evaporation needs the pre-annealing before ion-beam-mixing as well as the post-annealing after ion-beam-mixing to obtain the nanocrystal-related photoluminescence, compared with the study of the sample deposited by ion beam sputtering which was not required the pre-annealing before ion-beam-mixing to obtain visible red photoluminescence. The pre-annealing effect on the photoluminescence of Si ion-beam-mixed SiO 2/Si (3 nm)/SiO 2 layer will be discussed.

Enhancement of Schottky barrier height on AlGaN/GaN heterostructure by oxidation annealing

The effect of preannealing of AlGaN under an oxygen ambient on the improvement of the Schottky barrier height on an AlGaN/GaN heterostructure was studied using synchrotron radiation photoemission spectroscopy. The oxidation annealing increased the Schottky barrier height from 0.59 to 0.84 eV, and dramatically reduced the reverse leakage current. The group-III elements (Ga, Al) outdiffused to the surface to form group-III oxides during the annealing, leaving group-III vacancies behind. The surface Fermi level shifted to the energy levels of group-III vacancies, leading to the enhancement of Schottky properties of AlGaN.

Nonstoichiometric deep levels in Mg-doped GaP epitaxial layers: Effects of pre-annealing of substrates

The effects of substrate pre-annealing on deep level density in Mg-doped GaP liquid-phase epitaxy (LPE) layers were investigated by photocapacitance measurement. With annealing under optimum phosphorus-vapor pressure, concentration of deep donor at EC — 1.9–2.1 eV increased in undoped GaP substrate. Deep level densities in Mg-doped layers were also affected by pre-annealing of the substrates. Densities of dominant deep levels at EV + 0.85 eV and EV + 1.5 eV were an order of magnitude reduced and, in contrast, the level at EC − 2.1 eV in Mg-doped layer increased with long pre-annealing. This level at EC − 2.1 eV is supposed to be involved with P-rich-type nonstoichiometric defects, such as phosphorus interstitial atoms diffused from the surface of the substrate.

Effect of Preannealing on Substitutional Gold Concentration in Silicon

Data are presented on the effect of long-term high-temperature heat treatment (750°C, 200 h; 950°C, 50 h; and 1050°C, 50 h) preceding Au diffusion on the acceptor behavior of Au in n-type Czochralski silicon. Detailed studies of Au diffusion reveal that the impurity gettering process depends strongly on the heat treatment conditions. The results are interpreted in terms of oxygen precipitation in Si.

Mechanism of pre-annealing effect on electromigration immunity of Al–Cu line

In this work, we have investigated effects of pre-annealing, which means annealing performed prior to electromigration (EM) test, on EM lifetime of Al–Cu lines. We also investigated the relationships between void formation and size of Cu precipitated area in the line under various pre-annealing conditions. It is found that EM lifetime decreases while the size of the Cu precipitated area increases with lengthening of the pre-annealing period. However, no void is observed after this pre-annealing treatment. The results indicate that the tiny voids generated by formation of Cu precipitation do not move during the pre-annealing period. In the case of EM testing, Cu precipitation occurs followed by void formation at the cathode area, probably due to diffusion of vacancies which are generated by Cu atom movement by electron wind. As a result, resistance of the line increases and eventually it fails completely. It is demonstrated that pre-annealing helps Cu atoms to accumulate at the grain boundary forming the Cu precipitates. However, in samples with no pre-annealing treatment, the accumulation of Cu atoms at the grain boundaries begins just after the start of the EM testing and then the Cu precipitates diffuse toward the anode. Since EM test conditions are the same for samples with and without pre-annealing treatment, the only variation is the incubation time to accumulate Cu atoms at the grain boundaries. This is the reason why EM lifetime of pre-annealed samples is shorter than that of samples with no pre-annealing treatment.