Pre-annealing Process Research Articles

Reduction in Temperature-Dependent Fiber-Optic Gyroscope Bias Drift by Using Multifunctional Integrated Optical Chip Fabricated on Pre-Annealed LiNbO3

The refractive index change obtained after annealed proton exchange (APE) in lithium niobate (LiNbO3) crystals depends on both the proton exchange process carried out in hot acid and the structure of the crystals. In devices produced by the APE method, dislocations and lattice defects within the crystal structure are considered to be primary contributors to refractive index discontinuities and waveguide instability. In this study, the effects of pre-annealing LiNbO3 crystals at 500 °C on multifunctional integrated optical chips (MIOCs) were investigated through interferometric fiber-optic gyroscope (IFOG) system-level tests. It was observed that the pre-annealing process resulted in an improvement in the optical throughput of MIOCs (from %34 to %51) and the temperature-dependent bias drift stability of the IFOG (from 0.031–0.038°/h to 0.012–0.019°/h). The angle random walk (ARW) was measured as 0.0056 deg/√h.

Strategies for inhibiting the growth defects of CZTSe thin film

Growth defects are imperfections that appear during crystal formation.It is found that there are particle migration and crystalline phase decomposition behaviors during the crystal growth of CZTSe. By studying different annealing process paths, a selenium-free pre-annealing process strategy was proposed. It has been observed that under the condition of pre-annealing at 350℃ without selenium, the migration behavior of each element can be effectively controlled as the temperature increases. This process facilitates the formation of alloy phases and inhibits the generation of heterophase during the crystallization process. Simultaneously, the low-temperature pre-annealing treatment helps to reduce the decomposition of CZTSe during the annealing process, thereby minimizing defects. The large grains formed can also mitigate the carrier recombination issue caused by grain boundaries. In addition, the impact of pre-annealing temperature on crystallization quality was investigated. It was observed that there is a temperature threshold for enhancing crystallization, which should not exceed 400℃. As a result, the efficiency of the cells prepared using this strategy increased by nearly 50 %.

The Effect of Niobium Addition and Pre-Annealing on the Tensile Properties of 52CrMoV4 Spring Steel.

In this study, the effect of niobium addition and a specific preheating process on the microstructure and tensile properties of 52CrMoV4 steel used in leaf springs was investigated. Flat and leaf spring materials were used to accomplish this aim. The flat materials under investigation were kept in a furnace for 90 min at 900 °C. A homogeneous microstructure was aimed for with the use of this pre-annealing heat treatment in addition to the standard process before rolling used to create NbC. Leaf spring production was carried out with flat materials that possessed various Nb contents, with or without pre-heating. Grain size measurement and tensile tests were performed on the flat and leaf springs. Additionally, scanning electron microscopy images were captured from the fractured surfaces after the tensile tests were carried out. The current study highlights the importance of Nb addition as an alloying element and the effect of the selected pre-annealing process in optimizing the grain structure and enhancing the tensile properties of leaf springs. The leaf spring with a Nb ratio of 0.0376 that was pre-annealed exhibited a finer grain structure (G = 11.3), greater tensile properties (YS = 1550 N/mm2 and UTS = 1688.6 N/mm2), and deeper tear valleys and larger dimples, indicating higher energy consumption during fracturing, according to the SEM images produced, in contrast with the other materials studied.

Impact of Pre-Annealed ZrO2 Interfacial Layer on the Ferroelectric Behavior of Hf0.5Zr0.5O2

This work systematically investigates the impact of a pre-annealed ZrO2 interfacial layer on the ferroelectric behavior of Hf0.5Zr0.5O2 (HZO) capacitors. The remanent polarization (2Pr) value of HZO capacitors, including configurations such as W/HZO/TiN/p+ Si, W/HZO/(pre-annealed) ZrO2/TiN/p+ Si, W/HZO/SiO2/TiN/p+ Si, and W/HZO/SiO2/p+ Si, exhibits significant variations. The W/HZO/(pre-annealed) ZrO2/TiN/p+ Si capacitor demonstrates superior ferroelectric performance, with a 2Pr value of ~32 µC/cm2. Furthermore, by optimizing the thickness combination of HZO and the pre-annealed ZrO2 interfacial layer, a capacitor with a 10 nm HZO and 2 nm ZrO2 achieves the largest 2Pr value. The pre-annealing process applied to ZrO2 is found to play a very important role in inducing the orthorhombic phase and thus enhancing ferroelectricity. This enhancement is attributed to the pre-annealed 2 nm ZrO2 interfacial layer acting as a structural guide for the subsequent HZO orthorhombic phase, thereby improving the ferroelectric performance of HZO capacitors. These findings provide a comprehensive explanation and experimental verification of the impact of pre-annealed ZrO2 on ferroelectric devices, offering novel insights for the optimization of ferroelectric properties.

Effects of a Preannealing Process on the Morphology of Developed Kinks in Mille-Feuille Structured Cu/A5052 Alloy Fabricated by Accumulative Roll Bonding: Criteria for Kink Formation

Cu/A5052 dissimilar metal laminates (DMLs) were fabricated by an accumulative roll bonding process. The Cu/A5052 DML consisted of hard and soft layers, in other words, high and low shear modulus layers, which is called a mille-feuille structure (MFS). The Cu/A5052 DML with the MFS showed kink deformation during monotonic compression. Kink formation was analyzed by in-situ optical microscopy and digital image correlation. The development behavior and morphology of the ortho-type kink depended on the annealing conditions prior to the compression tests. Based on the observations and measurements, criteria for kink formation in the DML with the MFS were proposed.

Impact of pre-annealing process on electrical properties and stability of indium zinc oxide thin-film transistors

This paper examined the effects of no treatment versus plasma treatment, and femtosecond laser irradiation as pre-annealing processes on indium zinc oxide (IZO) films and annealing at high temperatures. The plasma pre-annealed multilayer stacked IZO TFTs showed better electrical properties with mobility enhancement from 2.45 to 7.81 cm2/Vs, but exhibited diminished on–off current ratio (Ion/Ioff). The IZO thin-film transistor (TFT) prepared with femtosecond laser pre-annealing with low pulse energy generation (power of 3 W at 700 nm wavelength) for 100 s has also exhibited significantly improved electrical performance, the saturation mobility increased to 4.91 cm2/Vs, the Ion/Ioff ratio was enhanced from 4.5 × 105 to 2.1 × 106, the threshold voltage improved from − 1.44 to − 0.25 V, and the subthreshold swing was reduced from 1.21 to 0.61 V/dec. In conclusion, IZO TFTs with improved performance can be prepared using a femtosecond laser pre-annealing process, which has great potential for fabricating low-cost, high-performance devices.

Synthesis of n-type SnSe polycrystals with high and isotropic thermoelectric performance

p-type SnSe has the ultrahigh thermoelectric ZT over 2 at 773 K, as single crystal with a significantly anisotropic structure or polycrystals. In this study, a facile route of synthesizing n-type polycrystalline SnSe, which has high and isotropic thermoelectric performance, is proposed using simple ball milling, pre-annealing and spark plasma sintering processes, in sequence. The pre-annealing process effectively changes the major carrier from hole to electron and increases the crystallinity and grain size of the SnSe powder. The addition of SnCl2 as a dopant enables the electron concentration to be controlled in the range of 1.3 × 1016 cm−3 to 1.7 × 1018 cm−3 at 300 K. As a result, a remarkable ZT of 0.84–0.86 at 773 K was achieved for n-type polycrystalline SnSe0.92 with 4 wt% SnCl2, regardless of the sintering direction.

Nanostructural Misch-Metal Magnets with Eutectic Nd-Al Alloy and Enhanced Magnetic Properties by Pre-annealing Process

Nanostructural Misch-Metal Magnets with Eutectic Nd-Al Alloy and Enhanced Magnetic Properties by Pre-annealing Process

Growth mode control of CVD-grown WS2 monolayer flakes via O2 pre-annealing for organic surfactant oxidation

Chemical vapor deposition (CVD) using liquid solution precursors is a promising method for synthesizing uniform and large-area monolayers of transition metal dichalcogenides. Organic surfactants, such as iodixanol, are crucial additives for the uniform coating of substrates with liquid solution precursors. However, during the heating process of CVD, carbons from the incompletely decomposed organic surfactant suppress crystal growth unfavorably. Here, we investigate the role of such residual carbons in the crystal growth behavior of WS2 monolayers. The crystal growth modes were precisely manipulated by residual carbon oxidation and the precursor etching rate, which was implemented by introducing O2 pre-annealing into the CVD process. Without O2 pre-annealing, flakes of limited size and multilayers were synthesized owing to the carbonization of surfactant, whereas sufficiently oxidized residual carbons via O2 pre-annealing allow for crystal growth with a large monolayer size. Moreover, the growth modes of the flakes in terms of triangles and hexagons can be systematically controlled by the O2 amount for pre-annealing because the remnant O2 compensates for the role of H2, which manipulates the etching rate of the residual W precursors on the substrate. Our results pave the way for controlling the growth modes of CVD-grown WS2 by introducing an optimized O2 pre-annealing process.

The effects of Ni or Nb additions on the relaxation behavior of Zr55Cu35Al10 metallic glass

Many questions raised in the field of metallic glasses (MGs) are inherently attributed to β relaxation. Therefore, this study investigated the behavior of β relaxation in the Zr55Cu35Al10 MG by differential scanning calorimetry (DSC) under different heating rates. Minor additions of Ni and Nb into the base alloy and pre-annealing process were also carried out to highlight the features of β relaxation in the thermal curves. The results showed that the pre-annealing process led to the appearance of an endothermic peak under the glass transition temperature (Tg), which is a sign of reversible β relaxation in the glassy structure. Moreover, the peak position of the endothermic event was at 0.78 Tg, 0.83 Tg, and 0.87 Tg for Zr55Cu35Al10, (Zr55Cu35Al10)98Ni2, and (Zr55Cu35Al10)98Nb2, respectively, which indicated the crucial role of minor addition on the evolution of β relaxation. In addition, the pre-annealing process from 3 h to 48 h demonstrated that the endothermic peaks in the minor-added samples tended to shift to higher temperatures. Furthermore, structural characterization of MGs revealed various types of short-range and medium-range orders in the Ni- and Nb-added alloys, leading to a different relaxation behavior in the glassy structure.

Investigation of Cu2ZnSnS4 thin film with preannealing process and ZnS buffer layer prepared by magnetron sputtering deposition

Unlike traditional methods for fabricating a CdS buffer layer through chemical bath deposition in thin-film solar cells, this study fabricated a ZnS thin film by sulfurizing the Zn film that was deposited using a magnetron sputtering system at varied temperatures from 500° to 560 °C in a sulfurization furnace. The ZnS thin film have been used as a buffer layer on the Cu2ZnSnS4 absorption layer. In this study, the Cu2ZnSnS4 absorber layer was prepared by first depositing a copper–zinc–tin (CZT) precursor film with a metal stack order of Zn–Sn–Cu–Zn through magnetron sputtering, followed by a preannealing process on the CZT precursor, to promote the interdiffusion of elements for the transfer of the metal phase into the alloy phase. Experimental results revealed the increased crystallite size in the SEM observation, an enhanced Raman intensity at 336 cm−1, and a reduced FWHM value in the XRD study for the Cu2ZnSnS4 thin film fabricated at a sulfurization temperature of 510 °C for 20 min with a preannealing treatment of the CZT precursor at a temperature of 420 °C for 30 min. In addition, the improved optical transmittance to 81.3% and an increased optical band gap value to 3.28 eV due to the reduced grain boundaries was obtained for the ZnS film with improved crystallinity quality fabricated at a sulfurization temperature of 560 °C.

Improved High-Performance Solution Processed In₂O₃ Thin Film Transistor Fabricated by Femtosecond Laser Pre-Annealing Process

The low-temperature annealing process has a critical impact on the electrical performance of thin-film transistors (TFTs). This paper reports significant performance enhancements of TFTs using a femtosecond laser pre-annealing (FLA)-based preparation method. The solution-processed In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> films were fabricated by FLA at various laser irradiation times and then annealed on a hot-plate at 230 °C. When the FLA time was set to 30 s, the device exhibited high saturation mobility of 10.03 ± 0.64 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> of 3.4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> , low V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> of 0.14 ± 0.64 V, and small SS of 1.44 ± 0.37 V/dec. The FLA process improved the formation of M-O lattices effectively, which led to an improvement in mobility. Furthermore, the gate-bias-stress stability and time-dependent environmental stability were improved considerably by the FLA process. These results show that high-performance In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> TFTs can be prepared at low temperatures using FLA-centered annealing technology. This work suggests that the FLA preparation method has tremendous potential for the fabrication of low-cost, high performance, and flexible TFT devices.

Investigation of Zn/Sn ratio for improving the material quality of CZTS thin films with the reduction of Cu2-xS secondary phase

In this study, a sputtering system was adopted for the preparation of Cu2ZnSnS4 (CZTS) thin films with high material quality. The system precisely controlled the elemental ratio in a copper-zinc-tin (CZT) precursor for contributing to the grain growth of CZTS crystallites, and reduced the detrimental formation of the Cu2-xS secondary phase during the high-temperature sulfurization process.The CZT precursor was prepared in a layer sequence of Zn/Sn/Cu/Zn, as the Cu-capping layer could protect the underlying Zn/Sn bilayer from volatilization during the high-temperature sulfurization. The CZT precursors were subjected to the sulfurization process at varied temperatures ranging from 480 to 560 °C for 20 min to form the CZTS thin film. In this study, the Cu/(Zn + Sn) and Zn/Sn ratios in the CZTS film were studied by energy dispersive X-ray spectroscopy measurements, and both ratios revealed elevations with an increasing sulfurization temperature, owing to the thermal volatilization of Zn and Sn. Thus, the formation of the undesirable Cu2-xS secondary phase was enhanced, and the surface roughness and density of voids on the CZTS thin films were increased. For a reduced Zn/Sn ratio with a reduced sulfurization temperature, the improved CZTS thin-film quality was demonstrated by the increased X-ray diffraction (XRD) and Raman intensity, along with the reduction of the XRD linewidth of the (112) CZTS crystal phase. A CZTS thin film with a sulfurization condition of 500 °C for 20 min showed a low Zn/Sn ratio (at 1.1), along with the features of a dense and smooth thin-film surface. Moreover, a reduced photoluminescence spectra full width at half maximum (FWHM) value of 92.7 meV was observed.In addition, for further improving the grain growth of CZTS, a pre-annealing process of a CZT precursor was conducted at a temperature of 350 °C for 30 min. An enhancement of the CZTS crystallite size with the stoichiometric formation of a CZTS phase and a reduced Cu2-XS phase was observed, indicating the superior material quality of the CZTS thin films.

Oxidation Resistance Failure of Dilute CuAl alloys at 800 °C

Oxidation is a major failure mode for the application of Cu in industry. To address this issue, alloying Cu with Al presents a potential solution due to the Al2O3-rich thin film formed during a pre-annealing process. The low oxidation resistance (OR) of dilute CuAl alloys that are oxidized at high temperatures is a critical issue due to their long-term exposure to an aerobic environment. Thus, the ORs of dilute CuAl alloys with 0.2–2.0 wt.% Al pre-annealed in a hydrogen atmosphere were examined at 800 °C and compared with the case at 400 °C. The OR of dilute CuAl alloys at 800 °C can be distinctly improved at the initial oxidation stage as well as 400 °C. However, at 800 °C, the OR gradually declines as the oxidation progresses, which considerably differs from the observation at 400 °C with the stable OR. The results show that the decline of the OR at 800 °C starts from the oxide button formation at the surface, and the growth and coarsening of these buttons cause nonuniform oxide scale formation. As the oxidation proceeds, the remnant Al2O3-rich thin film does not move with the Cu2O/CuAl interface, which is induced by the impeded outward diffusion of Cu atoms. The slowed diffusion of Cu atoms originates from the remnant Al2O3-rich thin film and the Al2O3 particles that are newly formed in the CuAl alloys due to the internal oxidation of Al.

High‐Efficiency CsPbI2Br Perovskite Solar Cells with Dopant‐Free Poly(3‐hexylthiophene) Hole Transporting Layers

AbstractCsPbI2Br is emerging as a promising all‐inorganic material for perovskite solar cells (PSCs) due to its more stable lattice structure and moisture resistance compared to CsPbI3, although its device performance is still much behind this counterpart. Herein, a preannealing process is developed and systematically investigated to achieve high‐quality CsPbI2Br films by regulating the nucleation and crystallization of perovskite. The preannealing temperature and time are specifically optimized for a dopant‐free poly(3‐hexylthiophene) (P3HT)‐based device to target dopant‐induced drastic performance degradation for spiro‐OMeTAD‐based devices. The resulting P3HT‐based device exhibits comparable power conversion efficiency (PCE) to spiro‐OMeTAD‐based devices but much enhanced ambient stability with over 95% PCE after 1300 h. A diphenylamine derivative is introduced as a buffer layer to improve the energy‐level mismatch between CsPbI2Br and P3HT. A record‐high PCE of 15.50% for dopant‐free P3HT‐based CsPbI2Br PSCs is achieved by alleviating the open‐circuit voltage loss with the buffer layer. These results demonstrate that the preannealing processing together with a suitable buffer layer are applicable strategies for developing dopant‐free P3HT PSCs with high efficiency and stability.

Formation Mechanism and Gram-Scale Production of PtNi Hollow Nanoparticles for Oxygen Electrocatalysis through In Situ Galvanic Displacement Reaction.

Galvanic displacement reaction has been considered a simple method for fabricating hollow nanoparticles. However, the formation of hollow interiors in nanoparticles is not easily achieved owing to the easy oxidization of transition metals, which results in mixed morphologies, and the presence of surfactants on the nanoparticle surface, which severely deteriorates the catalytic activity. In this study, we developed a facile gram-scale methodology for the one-pot preparation of carbon-supported PtNi hollow nanoparticles as an efficient and durable oxygen reduction electrocatalyst without using stabilizing agents or additional processes. The hollow structures were evolved from sacrificial Ni nanoparticles via an in situ galvanic displacement reaction with a Pt precursor, directly following a preannealing process. By sampling the PtNi/C hollow nanoparticles at various reaction times, the structural formation mechanism was investigated using transmission electron microscopy with energy-dispersive X-ray spectroscopy mapping/line-scan profiling. We found out that the structure and morphology of the PtNi hollow nanoparticles were controlled by the acidity of the metal precursor solution and the nanoparticle core size. The synthesized PtNi hollow nanoparticles acted as an oxygen reduction electrocatalyst, with a catalytic activity superior to that of a commercial Pt catalyst. Even after 10 000 cycles of harsh accelerated durability testing, the PtNi/C hollow electrocatalyst showed high performance and durability. We concluded that the Pt-rich layers on the PtNi hollow nanoparticles improved the catalytic activity and durability considerably.

Effect of pre-annealing on microstructure, mechanical properties and current-carrying properties of Bi-2212 wires

Abstract In order to solve the problem of excessive porosity of Bi-2212 Cable in Conduit Conductor (CICC) after the overpressure heat treatment, which leads to a significant decrease of mechanical stability of the conductor, a pre-annealing of Bi-2212 wires with a total pressure of 50 bar has been carried out in this paper. After the pre-annealing, the density of oxide cores of Bi-2212 wires was close to the theoretical density, which avoided the problem of diameter reduction of the wires in Bi-2212 CICC during overpressure heat treatment. At the same time, the mechanical properties, microstructures and current carrying properties of pre-annealed wires have been also analyzed. It showed that after pre-annealing, the Bi-2212 wires had not only high yield strength σ0.2, which reached 167 Mpa, but also great tensile strainse, which reached 7.4 %. High yield strength of the wires could effectively avoid serious scratches on the surface of wires during the preparing process of Bi-2212 CICC. Large tensile strain of the wires could prevent the crack of the wires caused by large compressive deformation or twisting deformation of the wires during preparation of Bi-2212 CICC, so that the conductors with smaller pitch and low hysteresis loss could be prepared. In addition, the phase composition of oxide cores in Bi-2212 wires did not change obviously during the pre-annealing process, but the crystallinity of Bi-2212 powder of the cores increased significantly, which was beneficial to the simultaneous melting of Bi-2212 powder of the cores during the overpressure heat treatment and the improvement of the content of Bi-2212 phase of the final wires. As a result, the current carrying capacity of the wires was slightly improved, and its engineer critical current density (Je) reached 825 A/mm2 (4.2K, 12T), which could meet the requirements of future fusion systems. In summary, it is expected that Bi-2212 CICC with less surface defects of the wires, low hysteresis loss, high filling ratio and excellent current-carrying performance can be obtained by the pre-annealing method.

Enhanced luminescent performance with surface wrinkled Al-doped ZnO films

To improve the photoluminescence (PL) properties of ZnO films, researchers generally preferred cations doping such as Al, but the effects of Al doping on the increase in PL intensity of ZnO films were dissatisfactory usually when surface of films was smooth. In this work, a new and simple process was proposed for enhancing the PL intensity in the range of 375–600 nm of ZnO films. We prepared surface wrinkled Al-doped ZnO (AZO) films by sol–gel method with a quickly pre-annealing process. The wrinkle morphology was found to provide a larger absorption and luminescence area. Results showed that the wrinkle surface as compared with the smooth surface could raise the PL intensity of AZO films to 4 times, which made ZnO further close to the application for ultraviolet and visible luminescent devices.

Effect of pre-annealing process on semiconductor-to-metal transition properties of vanadium oxide thin films

Vanadium oxide (VOX) thin films were fabricated on the (0001) sapphire substrates by pre-annealing process and subsequent rapid thermal annealing (RTA). The XRD results showed that the intensity of VO2 peak was enhanced and the V2O5 peak was not much changed when pre-annealing process was added before RTA. In addition, the pre-annealing process lowered the roughness of thin film and made film surface smooth and uniform. After pre-annealing process and subsequent RTA, the semiconductor-to-metal transition (SMT) amplitude increased from 21.8 to 160 and the phase transition temperature (TC) of the film reduced to the minimum of 50 °C. Moreover, the increase rate of solar modulation ability reached 61%. This study demonstrates that the pre-annealing enhanced the SMT amplitude and solar modulation ability, and decreased the TC of VOX thin films simultaneously. Therefore, it is a promising way to fabricate thermochromic VOX thin films for smart windows.

Enhanced spectral absorption of bilayer WOx/SiO2 solar selective absorber coatings via low vacuum pre-annealing

Solar selective absorber coatings (SSACs) have been one of promising strategies for conversing solar radiation into heat source. To enhance the solar absorption properties, various strategies have been developed to fabricate the SSACs, involving multilayer structure, texturing surface, metal nitrides and carbides, etc., whereas these often entailed sophisticated processes and expensive material costs. Therefore, developing the simple method to yield platforms with excellent optical properties is highly desired. Here, we showed a simple and effective method to boost the optical absorptivity, namely low vacuum pre-annealing process. The resulting absorptance of WOx/SiO2 SSACs is significantly raised from 0.91 to 0.93, and the emittance remains around 0.055 only after annealing at below 300 °C for 10 h. The optical absorptivity of the pre-annealing SSAC is on par with most of absorbers, and it still remained excellent thermal stability in high-vacuum at 400 °C. This simple and efficient method could be a prospective strategy for booting the spectral absorption in the design of the desirable SSACs.