Effect Of Annealing Research Articles

Creation of Room-Temperature Sub-100 nm Antiferromagnetic Skyrmions in an Antiferromagnet IrMn through Interfacial Exchange Coupling.

Antiferromagnetic (AFM) skyrmions are magnetic vortices composed of antiparallell-aligned neighboring spins. In stark contrast to conventional skyrmions based on ferromagnetic order, AFM skyrmions have vanished stray fields, higher response frequencies, and rectified translational motion driven by an external force. Therefore, AFM skyrmions promise highly efficient spintronics devices with high bit mobility and density. Nevertheless, the experimental realization of intrinsic AFM skyrmions remains elusive. Here, we show that AFM skyrmions can be nucleated via interfacial exchange coupling at the surface of a room-temperature AFM material, IrMn, exploiting the particular response from uncompensated moments to the thermal annealing and imprinting effects. Further systematic magnetic characterizations validate the existence of such an AFM order at the IrMn/CoFeB interfaces. Such AFM skyrmions have a typical size of 100 nm, which presents pronounced robustness against field and temperature. Our work opens new pathways for magnetic topological devices based on AFM skyrmions.

Effect of Annealing on the Interface and Microstructural Properties of Al/Cu Composites Processed by Hot Pressing and Subsequent Cold Rolling

Effect of Annealing on the Interface and Microstructural Properties of Al/Cu Composites Processed by Hot Pressing and Subsequent Cold Rolling

Effect of intercritical annealing on the microstructure and mechanical properties of a PH 13-8 Mo maraging steel

One method of achieving exceptional ductility and toughness of PH 13-8 Mo maraging steels is to perform aging at high temperatures or for prolonged dwell times, which is referred to as overaging. The increase in ductility and toughness is primarily related to the formation of high amounts of reverted austenite during aging. An alternative approach to elevate the reverted austenite content is to perform intercritical annealing, i.e., annealing in the dual phase field of martensite and austenite, prior to aging. Due to partitioning of substitutional elements during intercritical annealing, the freshly formed martensite is enriched in Ni after cooling. As a result, the formation of reverted austenite is facilitated, and high phase fractions can be achieved even at moderate aging temperatures. This study aims to shed light on the full potential of implementing intercritical annealing in the heat treatment route of PH 13-8 Mo maraging steels by thoroughly investigating the effect of this heat treatment adaption on the microstructure, mechanical properties and austenite stability. Overall, it is demonstrated that the addition of intercritical annealing enables to achieve a well-balanced microstructure showing a promising combination of strength, ductility and toughness. By performing intercritical annealing for shorter dwell times, high reverted austenite contents comparable to those after overaging can be reached. Resulting from a moderate aging temperature, fine β-NiAl precipitates, which were detected by atom probe tomography, are formed within martensite, leading to considerably higher strength compared to after overaging. However, the high matrix strength restricts the mechanically induced transformation of reverted austenite to martensite, as found by in-situ high-energy X-ray diffraction tensile tests.

On the effect of high-temperature annealing on the microstructure and mechanical properties of a hot-rolled 90W7Ni3Fe tungsten heavy alloy

We previously reported on commercial 90W7Ni3Fe (90W, wt. %) tungsten heavy alloy (WHA) plates, which were hot-rolled (HR) at 900 °C to thickness reductions of 62 %, 74 % and 87 % (62R, 74R and 87R), and an as-sintered (AS) 90W plate. In contrast to 62R and 74R, the 87R WHA was given a final processing heat treatment (HT) at 1400 °C/3 h (87RHT). HR deforms the WHA microstructure into an anisotropic brick (W) and mortar (NiWFe ductile phase) composite architecture. Fracture toughness tests showed that after the processing HT, the 87RHT plate experienced stable crack growth, with an average elastic-plastic fracture toughness of KJm ≈ 116 ± 20 MPa√m, somewhat higher than the AS KJm ≈ 97 ± 18 MPa√m. This compares to elastic fracture toughness of KIm ≈ 35 ± 2 MPa√m in the 62R and 74R conditions, absent a final HT. Here, we report on the microstructures and mechanical properties of four new WHA conditions following an additional recovery anneal at 1300 °C/24 h. The recovery anneal results in similar average elastic-plastic toughness of KJm ≈ 125 ± 12 MPa√m in all four processing conditions, which is slightly higher than for the AS and 87RHT WHA, and much higher than for the 62R and 74R WHA, without the processing HT. Scanning electron microscopy and electron backscatter diffraction showed that the final 1300 °C/24 h anneal recovers the hardening microstructures in the 62R and 74R WHA. The lower strength promotes crack tip microcracking dilatational shielding, which increases the WHA fracture toughness. The implications of these results to the design of WHA are briefly discussed.

Effect of low-temperature annealing on electric resistivity and mechanical anisotropy of Al-Si binary alloy fabricated by laser-powder bed fusion

Al-12mass%Si binary alloy was fabricated by laser-powder bed fusion (L-PBF). The effect of low temperature annealing (LTA) less than 573 K on electrical and mechanical properties, microstructure, and residual stress of L-PBF Al-12mass%Si was investigated. Due to LTA, electrical resistivity at 77 K and 293 K changed from 34 nΩm down to 10 nΩm and from 68 nΩm down to 45 nΩm, respectively. The lattice constant of α-Al phase increased around 0.0005 nm by LTA according to X-ray diffraction. The change was associated with the decrease in the concentration of solid-solution Si of around 3.4 mass% by electrical resistivity measurement and 3 mass% by X-ray diffraction, when the annealing temperature was 473 K. Whereas, Vickers hardness increases around 145 HV compared with that for the as-built value of 141 HV, and then, decreases down to 126 HV and saturates. TEM/EDS observations confirmed the precipitation of fine Si within the α-Al phase. The decrease in annealing temperature increases the time to reach the Vickers hardness peak. 0.2% proof stress obtained by compression tests shows anisotropy, which can be attributed to the anisotropy on residual stress, which still exists after LTA.

Light-emitting diodes with Ge(Si) nanoislands embedded in photonic crystals

Room temperature lateral p+–i–n+ light-emitting diodes (LEDs) with photonic crystals embedded in the i-region were fabricated on structures with Ge(Si) self-assembled islands and their optical properties were investigated. The use of preliminary amorphization and solid phase epitaxy of the implanted p+ and n+ contact regions made it possible to reduce the impurity activation temperature from 800 °С–1100 °С to 600 °С, which corresponds to the growth temperature of Ge(Si) islands. This resulted in a significant reduction of the detrimental effect of the high-temperature annealing used for diode formation on the intensity and spectral position of the luminescence signal from the islands. It was shown that significant enhancement (more than an order of magnitude) of room temperature electroluminescence of Ge(Si) islands in the spectral range of 1.3–1.55 μm can be achieved due to their interaction with different modes of the photonic crystals. The measured radiation power of the obtained diodes in the spectral range of 1.3–1.55 μm exceeds 50 pW at a pump current of 8 mA, which is an order of magnitude higher than the previously achieved values for micro-LEDs with Ge(Si) nanoislands. The obtained results open up new possibilities for the realization of silicon-based light emitting devices operating at telecommunication wavelengths.

Effects of Severe Plastic Deformation and Subsequent Annealing on Microstructures of a Ni50.6Ti49.4 Shape Memory Alloy

High-pressure torsion (HPT) was applied to the Ni50.6Ti49.4 (at. %) alloy ingot up to 1/4, 2, 16, 32 and 48 turns under a pressure of 6.0 GPa. The samples were examined by X-ray diffraction (XRD), transmission electron microscope (TEM) and microhardness measurement. The results indicate that martensitic transformation and formation of amorphous phase occurred during the HPT process. As the HPT turns increased, more amorphous phase formed. The fraction of amorphization was analyzed based on the X-ray results. The microhardness increased with the HPT turns, which may be related to strain-induced martensite transformation, formation of the amorphous phase, increased dislocation densities and grain refinement. Differential scanning calorimetry (DSC) test revealed that shape memory alloys can be produced by HPT and post-HPT annealing from a NiTi ingot.

Continuous modulation of VO2 film’s phase transition threshold and transmittance via n-AZO/n-VO2 heterojunction

To solve the irreconcilable contradiction between the phase transition threshold and the optical property of VO2 film, an n-AZO/n-VO2 heterojunction, in which AZO is Al-doped ZnO, was constructed with the radio frequency (RF) magnetron sputtering and the post annealing. The effects of annealing on the composition and properties of vanadium oxide films have been investigated, as well as the effects of annealing and AZO layer thickness on the phase transition performance of the n-AZO/n-VO2 heterojunction. The results indicate that the V2O5 film will gradually transform into VO2 (M) through V6O13 and VO2 (B) during the reduction annealing at 500 °C. The phase transition temperature (Tc) of VO2 (M) film increases with the annealing temperature. In the heterojunction formed by the ohmic contact between AZO and VO2 layers, the free electrons will be injected into the VO2 layer from AZO layer, which reduces the heterojunction’s Tc from 69.2 to 41.5 °C. The first-principles calculations were performed with the Vienna Ab initio Simulation Package (VASP) to assist in the influence mechanism explanation. In addition to modulating Tc, the AZO layer in the heterojunction also plays an antireflection role, increasing the maximum visible transmittance of VO2 film by ∼ 10 %.

Fe-based amorphous powder cores with low core loss and improvement of permeability

Fe-based amorphous powder cores of Fe–Si–B–Cr–C magnetic powder and phenolic binder were fabricated, and the effects of annealing and compaction pressure on the soft magnetic properties and core loss were investigated. The formation of Fe–B and α-Fe (Si) phases was confirmed at the annealing temperature above 773 K. The density gradually increased from 5.3 to 5.5 g/cm3 as annealing temperature increased, resulting in the saturation magnetization 4πMs increased to 1.0 T at 773 K. The effect of compaction pressure was studied by using samples annealed at 723 K. Both the density and 4πMs enhanced with compaction pressure from 980 to 1960 MPa. The real part of permeability µ’ remained constant for the frequency up to 2 MHz. The initial value of µ’ increased from 25 to 38 with compaction pressure. Consequently, at Bm of 50 mT and frequency of 100 kHz, the considerably low core loss of 67 kW/m3 was obtained. The low core loss and moderately high permeability of Fe–Si–B–Cr–C amorphous powder core across a wide frequency range indicate its potential for application in high frequency electronic components.

Effect of annealing and roughness on the magnetic-optical, adhesive, nano-mechanical, and electrical properties of Co60Fe20Dy20 films

The structural, magnetic, optical, and adhesion properties of Cobalt-Iron-Dysprosium (CoFeDy) films were investigated in this study. Glass substrates were coated with a Co60Fe20Dy20 alloy via sputtering, with a thickness ranging from 10 nm to 50 nm. Subsequently, the films underwent annealing at temperatures of 100 °C, 200 °C, and 300 °C for one hour. X-ray diffraction (XRD) analysis confirmed the amorphous nature of the deposited CoFeDy films under four distinct conditions. Notably, a thickness-dependent increase in low-frequency alternate-current magnetic susceptibility (χac) was observed. After annealing at 300 °C, CoFeDy films exhibited the highest χac compared to other temperatures. Surface roughness exhibited a decreasing trend with rising annealing temperature, as observed through atomic force microscopy (AFM) experiments. The maximum surface energy of CoFeDy films was achieved at a thickness of 50 nm following annealing at 300 °C. Higher surface energy was indicative of stronger adhesion efficiency. Furthermore, lower resistance and sheet resistance values were obtained through annealing at higher temperatures, suggesting that increasing thickness and reducing electron transport barriers enhanced electron conductivity. As film thickness increased, transmittance decreased due to the thickness effect, suppressing the photon signal. Consequently, rougher surfaces were associated with improved performance in magnetism, electrical adhesion, and optics, attributed to reduced domain pinning, enhanced carrier conductivity, and minimized light scattering.

Restoration and Transformation: The Response of Shocked and Oxidized Magnetite to Temperature

AbstractLarge impact craters on Earth are associated with prominent magnetic anomalies, residing in magnetite of the shocked target rocks and impactites. Shock experiments on magnetite suggest that up to 90% of magnetic susceptibility is lost at pressures >5 GPa, but can be partially restored by post‐shock thermal annealing. The magnetic property changes are caused by shock induced grain size reduction and fragmentation, as well as domain wall‐pinning at crystal lattice defects. A recent study of granitoids from the peak‐ring of the Chicxulub crater found that annealing may occur naturally, but can also be overprinted by high‐temperature hematite‐to‐magnetite transformation in non‐oxidizing environments. In this study, we isolate the effect of defect annealing and hematite‐to‐magnetite transformation using the evolution of hysteresis, isothermal remanent magnetization components and first order reversal curve (FORC) diagrams at different high‐temperature steps. We used a laboratory‐shocked magnetite‐quartz ore, a non‐shocked naturally oxidized granite, and a naturally shocked and oxidized granite. Our findings suggest that annealing of shock‐induced lattice defects partially restores some pre‐shock magnetic behavior and causes an apparent average bulk‐sample domain state increase. Hematite‐to‐magnetite transformation creates new fine‐grained magnetite that strongly overprints the original signal, and decreases the average bulk‐sample domain state. Where annealing and hematite‐to‐magnetite transformation both occur, the new magnetite masks the annealing‐induced property restoration and apparent domain state modification in the shocked magnetite. As magnetite oxidation is a ubiquitous process in surface rocks, these findings are fundamental to understand hematite‐to‐magnetite transformation as a potential overprint mechanism, and could have broad implications for paleomagnetic interpretations.

Effect of thermal annealing on the optical properties of 3D-printed nanostructured CuO films for flexible photovoltaic solar cells

In this work, the effect of thermal annealing on the optical and structural properties of 3D-printed nanostructured copper oxide films deposited on polyimide substrates is investigated for the first time. It was shown that both as-deposited and annealed at Ta = 160 °C films have mainly monoclinic CuO phase. XRD and Raman results show that these films also contain a small amount of Cu2O phase, and possibly an amorphous CuO as well as a metastable CuO2-like phases. At the same time, films annealed at 300 °C for 10 min are characterized by a pure CuO phase and have the best optical quality. The band gap of the investigated copper oxide films is equal to (1.53–1.64) eV, which is associated with indirect allowed optical transitions. The results obtained paves the way to the development of nanotechnologies for obtaining CuO films by the 3D printing method, suitable for flexible electronics, especially for solar energy.

Study of bulk damage of high dose gamma irradiated p-type silicon diodes with various resistivities

The bulk damage of p-type silicon detectors caused by high doses of gamma irradiation has been studied. The study was carried out on three types of n+-in-p silicon diodes with comparable geometries but different initial resistivities. This allowed to determine how different initial parameters of studied samples influence radiation-induced changes in the measured characteristics. The diodes were irradiated by a Cobalt-60 gamma source to total ionizing doses ranging from 0.50 up to 8.28 MGy, and annealed for 80 minutes at 60 °C. The Geant4 toolkit for simulation of the passage of particles through matter was used to simulate the deposited energy homogeneity, to verify the equal distribution of total deposited energies through all the layers of irradiated samples, and to calculate the secondary electron spectra in the irradiation box. The main goal of the study was to characterize the gamma-radiation induced displacement damage by measuring current-voltage characteristics (IV), and the evolution of the full depletion voltage (V FD) with the total ionizing dose, by measuring capacitance-voltage characteristics (CV). It has been observed that the bulk leakage current increases linearly with total ionizing dose, and the damage coefficient depends on the initial resistivity of the silicon diode. The effective doping concentration and therefore V FD significantly decreases with increasing total ionizing dose, before starting to increase again at a specific dose. We assume that this decrease is caused by the effect of acceptor removal. Another noteworthy observation of this study is that the IV and CV measurements of the gamma irradiated diodes do not reveal any annealing effect.

Lattice Damage, Optical and Electrical Properties Induced by H and C Ions Implantation in Nd:YLF Crystals

Neodymium-doped yttrium fluoride crystal has emerged as one of the most valuable functional materials, and has thus become a research hotspot and shown promising application value in recent years. In this work, utilizing 460 keV H and 6.0 MeV C ions implantation, the damage behavior, lattice structure change, spectral, and electrical characteristics of the Nd:YLF crystal induced by electronic and nuclear energy loss were investigated, utilizing complementary characterization techniques (X-ray diffraction, hardness and elastic (Young’s) modulus, micro-Raman, absorption, fluorescence spectra, and I–V characteristic curve). Thus, the annealing effect on the waveguide properties and the surface damage of the samples was discussed. The fabricated waveguide structure shows potential application in highly sensitive optoelectronic sensors.

ANNEALING EFFECT ON UV DETECTION PROPERTIES OF ZnO:Al STRUCTURES

The aim of this study was to develop low-powered, highly selective UV sensor to continuously monitor personalized UV exposure as well as to study annealing effect on UV detection properties of the sensors. ZnO:Al structures were obtained by chemical growth method followed by thermal annealing at 625 °C for 2 h. The studied samples exhibit maximal UV response of 620/488 at 25 °C/50 °C to 370 nm UV radiation before/after annealing, respectively. Thermal annealing of sensor (250 °C for 1 h) led to improvement in fall time from 3860 seconds to 262 seconds at 25 °C and highest responsivity (~48 mA/W) came out for 370 nm wavelength at 75 °C operating temperatures. Consequently, excellent selectivity for 370 nm UV illumination can be ascribed as due to thermal annealing effect which increases the crystallinity, grain size, and roughness of the sensing film. The PL measurements reveals the suppression of structural defects, increase in intensity after annealing and enhanced UV response due to presence of Al content in films. Overall, these structures showed magnificent UV properties, before and especially after additional thermal annealing. UV sensing mechanism of such nanomaterial-based sensor were explained with physio-chemical processes take place on the surface of these structures. The obtained results on annealed ZnO:Al films-based devices is superior to reported performances of other nanostructures, proving new results for UV sensing applications at different operating temperatures in various fields.

Effect of isothermal annealing on formation of self-assembled nanostructures in manganese spinel ZnMnGaO4

The effects of isothermal annealing on the self-assembled nanostructures of spinel manganese oxide ZnMnGaO4 were investigated using transmission electron microscopy and x-ray diffraction. The checkerboard nanostructures and zigzag nanostructures (named “Sierra” nanostructures) coexisted owing to the chemical phase separation of Mn3+ and Ga3+ ions by isothermal annealing at 575 °C. It was observed that the checkerboard nanostructures were dominant in short-time annealing and that the volume fraction of the Sierra nanostructures became more prominent as the annealing period increase. The interdiffusion of Mn3+ and Ga3+ is indicated to play an important role in gaining the total energy of the system by the reduction in the local strain caused by the formation of nanostructures. These results provide further insights into the fabrication of distinct types of nanostructures in complex transition-metal compounds.

High-quality dense ZnO thin films: work function and photo/electrochemical properties

Compact ZnO (wurtzite) thin films are prepared on four different substrates by (i) spray pyrolysis or (ii) pulsed reactive magnetron sputtering combined with a radio frequency electron cyclotron wave resonance plasma. Films are characterized by AFM, XRD, Kelvin probe, cyclic voltammetry, electrochemical impedance spectroscopy, and UV photoelectrochemistry. Film morphologies, defect concentrations, crystallite size, and orientation provided specific fingerprints for the electronic structure of ZnO close to the conduction band minimum. Fabricated films are referenced, if relevant, to a model system based on a wurtzite single crystal with either Zn-face or O-face termination. Kelvin probe measurements of the ZnO/air interface distinguished effects of annealing and UV excitation, which are attributed to removal of oxygen vacancies close to the surface. In turn, the work function, at the electrochemical interface, specifically addressed the growth protocol of the ZnO electrodes but not the effects of crystallinity and annealing. Finally, high photocurrents of water oxidation are observed exclusively on virgin films. This effect is then discussed in terms of photocorrosion, and work function changes due to UV light.Graphical

Defect-dependent environmental stability of high mobility transparent conducting In-doped CdO

Highly degenerate n-type CdO with high electron mobility is a promising transparent conducting oxide (TCO) for optoelectronic devices utilizing a spectrum in the Vis-NIR range. In particular, it has been shown that doped CdO thin films can show much superior transparency of >80% in the NIR region compared to conventional transparent conducting oxide (e.g., Sn-doped In2O3) thin films with a similar sheet resistance. However, CdO thin films typically experience rapid degradation in their electron mobilities when exposed to environmental conditions with H2O moisture. Here, we studied the effects of thermal annealing on the environmental stability of In-doped CdO (CdO:In) using a combination of different analytical techniques. CdO:In thin films with different In concentration (0%–8.3%) synthesized by magnetron sputtering were subjected to different post-thermal annealing (PTA) and then aged in different environmental conditions with varying relative humidity (RH) in the range of 0%–85%. Our results reveal that the degradation of CdO:In thin films can be primarily attributed to the oxygen vacancy-related defects at the grain boundaries, which can readily react with the OH− in the moisture. The moisture induced degradation can be mitigated by appropriate PTA at high temperatures (>400 °C) where grain boundary defects, primarily associated with Cd vacancies, can be passivated through hydrogen (H), thus enhancing their environmental stability. The present study provides a comprehensive understanding of the instability mechanisms and defect passivation in transparent conducting CdO:In thin films, which can also be relevant for other wide gap oxides.

Improving Solar Cell Efficiency through Controlled Annealing Effects of TiO2 Thin Films

In the scope of this research, the impact of thermal annealing on the electrical and optical characteristics of TiO2 thin films is investigated through empirical analysis. Varied annealing temperatures are applied during the production of TiO2 thin films, and their reflection, transmission, absorption, and crystalline structure attributes are meticulously gauged. Through systematic analysis, the optimal annealing temperature is determined to be 500 °C. Remarkably, TiO2 thin films fabricated under this specific temperature exhibit notably reduced reflection values. Moreover, comprehensive scrutiny extends to encompass both electrical and structural attributes, such as carrier density, resistivity, and crystal size, in addition to optical attributes. In the outcome, it is revealed that TiO2 thin films subjected to annealing at 500 °C exhibit the highest carrier density and the lowest resistivity. X‐ray diffraction analyses unveil the anatase phase of TiO2 thin films developed at this temperature. Notably, ascending annealing temperatures correlate with amplified crystal sizes and increased surface roughness. Furthermore, the TiO2 thin films are subsequently integrated into crystalline silicon solar cells via employment of the SCAPS (a Solar Cell Capacitance Simulator) software, culminating in a noteworthy 8% enhancement in solar cell efficiency.

Enhancing the Properties of Photo-Generated Metallized Nanocomposite Coatings through Thermal Annealing.

In this work, the effect of thermal annealing on silver nanoparticles@polymer (AgNPs@polymer) nanocomposite coatings was investigated. These photo-generated metallized coatings have a spatial distribution of metal nanoparticles, with a depth-wise decrease in their concentration. During annealing, both structural and morphological variations, as well as a spatial reorganization of AgNPs, were observed, both at the surface and in the core of the AgNPs@polymer coating. Owing to their increased mobility, the polymer chains reorganize spontaneously, and, at the same time, a hopping diffusion process, caused by the minimization of the surface energy, promotes the migration and coalescence of the silver nanoparticles towards the surface. The layer of discrete nanoparticles gradually transforms from a weakly percolative assembly to a denser and more networked structure. Consequently, the surface of the coatings becomes significantly more electrically conductive, hydrophobic, and reflective. The general trend is that the thinner the nanohybrid coating, the more pronounced the effect of thermal annealing on its spatial reorganization and properties. These results open up interesting prospects in the field of metallized coating technology and pave the way for integration into a wide variety of devices, e.g., efficient and inexpensive reflectors for energy-saving applications, electrically conductive microdevices, and printed electronic microcircuits.