Subsequent Thermal Annealing Research Articles

THE INFLUENCE OF ELECTRON IRRADIATION ON THE STABILITY OF α-Fe2O3 NANOPARTICLES TO NATURAL AGING PROCESSES

The influence of the modification of α-Fe2O3 nanoparticles by electron irradiation on their stability to natural aging processes during a long-term (three years) storage has been studied. Nanoparticles of this type (obtained by chemical vapor deposition with subsequent thermal annealing) were chosen due to the wide range of their practical applications. The changes in the properties of α-Fe2O3 nanoparticles during natural aging, depending on the irradiation dose, were investigated by X-ray diffraction and Mössbauer spectroscopy. It is found that modification by electron irradiation provides stability of α-Fe2O3 nanoparticles to hydration processes and phase transformations during a long-term storage; an increase in the irradiation dose increases the resistance to structural disordering during aging, thus retaining the nanoparticle properties for a long time.

Improvement in the aged silicon solar cells parameters by thermal annealing

In this paper, to simulate and accelerate the effects of aging, solar cells were exposed to the different doses of co60 gamma radiation. The current–voltage (I–V) characteristics of mono-crystalline solar cells under AM1.5 illumination condition were studied before and after the gamma irradiation. Experimental results showed that the solar cell parameters such as open circuit voltage (Voc), short circuit current (Isc) and efficiency (η) decrease with the increase of the gamma radiation doses. The effect of subsequent thermal annealing on solar cells degraded by gamma irradiation is investigated. A significant improvement in the electric parameters of by low doses gamma irradiated silicon solar cells is observed after the thermal annealing.

Synthesis of V2AlC thin films by thermal annealing of nanoscale elemental multilayered precursors: Incorporation of layered Ar bubbles and impact on microstructure formation

Periodically stacked nanoscale V/C/Al multilayered thin film precursors were deposited by magnetron sputtering using elemental targets. Their temperature-dependent phase transformation during subsequent thermal annealing in argon towards V2AlC MAX phase formation was investigated. Compositional and microstructural analyses at the nanoscale revealed undulation growth of the nanolayers and preferential incorporation of Ar atoms into amorphous carbon nanolayers within the as-deposited multilayered precursors. Single-phase and basal-plane-oriented V2AlC films were formed at annealing temperatures above 560 °C. The incorporated Ar atoms migrated and aggregated into high-density nanoscale Ar clusters/bubbles located essentially at grain boundaries after annealing, displaying pronounced layered distribution characteristics especially adjacent to the substrate/film interface. The heterogeneous incorporation of argon atoms or clusters in heterostructured films composed of multicomponent sublayers likely represents a common phenomenon during thin film nucleation and growth, while its impact on the macroscopic properties of films remains to be explored.

On-surface synthesis of enetriynes

Belonging to the enyne family, enetriynes comprise a distinct electron-rich all-carbon bonding scheme. However, the lack of convenient synthesis protocols limits the associated application potential within, e.g., biochemistry and materials science. Herein we introduce a pathway for highly selective enetriyne formation via tetramerization of terminal alkynes on a Ag(100) surface. Taking advantage of a directing hydroxyl group, we steer molecular assembly and reaction processes on square lattices. Induced by O2 exposure the terminal alkyne moieties deprotonate and organometallic bis-acetylide dimer arrays evolve. Upon subsequent thermal annealing tetrameric enetriyne-bridged compounds are generated in high yield, readily self-assembling into regular networks. We combine high-resolution scanning probe microscopy, X-ray photoelectron spectroscopy and density functional theory calculations to examine the structural features, bonding characteristics and the underlying reaction mechanism. Our study introduces an integrated strategy for the precise fabrication of functional enetriyne species, thus providing access to a distinct class of highly conjugated π-system compounds.

Mechanics of Defects in Dislocation-Free Silicon Single Crystals

The problems of defect mechanics in dislocation-free silicon single crystals are relevant and technically significant due to the intensive development of microelectronics, which imposes increasingly high demands on minimizing the level of micro- and nanodefects in silicon wafers used to manufacture microelectronic chips. The solution of these problems is associated with the study of the regularities of thermomechanical processes both at the stage of growing silicon single crystals and at subsequent thermal annealing of wafers cut from them. The article provides an overview of theoretical and experimental work aimed at developing ways to control these processes. This includes the development of physical concepts of defect formation in dislocation-free single-crystal silicon and the development of mathematical models corresponding to different temperature ranges, implemented both during the growth of a single crystal and during thermal annealing of wafers cut from it. Thus, near the crystallization temperature, the processes of fast recombination and diffusion transfer of intrinsic point defects (vacancies and interstitial silicon atoms) are simulated, while at lower temperatures, the processes of their agglomeration into microdefects (pores and clusters of interstitial silicon atoms) are simulated. The verification of such models is illustrated for two experimental processes of growing silicon single crystals with a diameter of 150 mm by the Czochralski method, as well as for the process of rapid high-temperature thermal annealing of silicon wafers cut on their basis.

Green chemistry synthesis and structural and optical study of Dy2(CO3)3→ Dy2O3 transition

This paper presents preliminary results of Dy2(CO3)3→Dy2O3 transition have been successfully obtained by Chemical Bath Deposition technical and subsequent thermal annealing temperature at ~600 °C. Two different temperatures of ~20°C and ~90 °C ± 2 °C are chosen to carry out the nanocrystalline growth. The crystalline phase is investigated by applying X-Ray Diffraction (XRD) and some optical properties; Transmittance, Reflectivity, Normalized Absorbance, real (n) and imaginary (k) parts refractive index. The crystalline phase of these inorganic nanomaterials for Dy2(CO3)3 is orthorhombic phase, while for Dy2O3 it is cubic. Grain size average values located at ranged ~2.8-3.4 nm for Dy2(CO3)3 and ~6.5-9.6 nm for Dy2O3. Vibrational modes are identified by Raman spectroscopy, modes at ~150-1800 cm-1 frequency range assigned to internal vibrations of ion: v1-symmetric stretching (~1098 cm-1) v3-asymmetric -C-O stretching situated at ∼1063 cm-1, were observed corresponding to orthorhombic crystalline phase. The Fg+ Ag and A1g modes, corresponding to cubic phase Dy2O3. Multiple absorption bands with different relative intensities are observed at UV-Vis-NIR region, assigned to 4fs→4fs intra-electronic transitions and band gap energy. Absorption measurement were assigned to the transitions from ground state (6H15/2) to different excited states such as 4I13/2→4F7/2, 4I15/2, 6F3/2, 6F5/2, 6F7/2→6H5/2, 6F9/2→6H7/2, 6F11/2→6H9/2 and 6H11/2 of Dy3+ cation. Tauc’s plot reveals band gap situated at range ~4.66-5.17 eV for Dy2(CO3)3 and ~4.26-4.80 eV for Dy2O3 respectively.

Rough Surface Enhanced Interfacial Synthesis of Core‐Shell Magnetic Fluorescent Microspheres for Enhanced Latent Fingerprint Visualization

AbstractDeveloping latent fingerprints is extremely significant for personal identification and criminal investigation. Sub‐micrometer core‐shell structured magnetic fluorescent composite which combines the merits of noncontact magnetic responsiveness and strong fluorescence emission is highly desired for the visualization of latent fingerprint on various substrates with high resolutions. However, it remains a great challenge to synthesize uniform magnetic fluorescent composites with well‐defined structure and functionalities due to the uncontrollable heterogeneous growth. Herein, a urea‐assisted rough interface precipitation method is proposed to controllably synthesize uniform core‐shell structured magnetic fluorescent composite microspheres (Fe3O4@mesoSiO2@Y2O3:Eu3+). The composite microspheres with magnetic core and mesoporous silica shell (Fe3O4@mesoSiO2) possess huge guest‐host interface, numerous nucleation sites, and rough surface morphology, facilitating the efficient adsorption of Y3+/Eu3+ ions, and further controllable interface deposition of metal (Y, Eu) hydroxides induced by slow release of OH− and CO32− anions via the in‐solution decomposition of urea. After subsequent thermal annealing, the obtained Fe3O4@mesoSiO2@Y2O3:Eu3+ microspheres possess high magnetization for convenient magnetic manipulation, strong fluorescence intensity and negligible quenching effect, enabling a superior performance in latent fingerprint visualization with high contrast and resolution on various substrates.

Thermoreversible Gels of Poly(l-lactide)/Poly(d-lactide) Blends: A Facile Route to Prepare Blend α-Form and Stereocomplex Aerogels

The demand for biodegradable polymer-based aerogels with superior comprehensive properties has escalated in various fields of application, such as packaging, tissue engineering, thermal insulation, acoustic insulation, and environmental remediation. In this work, we report a facile strategy for enhancing the thermal and mechanical properties of polylactide (PLA) aerogels through the stereocomplex (SC) formation between the opposite enantiomers. Thermoreversible gelation of poly(l-lactide) (PLLA)/poly(d-lactide) (PDLA) blend in crystal complex forming solvent and the subsequent thermal annealing of the gel resulted in crystalline pure SC gel, which, upon solvent exchange with water and freeze-drying, furnished robust SC aerogel. It was found that the SC content could be tuned by varying the annealing temperature of the blend gel and that we could prepare blend aerogels with pure α crystalline form and a mixture of α and SC. Crystalline pure blend α aerogel showed fibrillar morphology, whereas SC aerogel exhibited unique interwoven ball-like microstructures interconnected by PLLA and PDLA chains. The structural evolution during SC formation at the molecular level and the micrometer length scale instigated better properties in the PLA aerogels. When compared with the homopolymer aerogels, the crystalline pure SC aerogel showed an enhanced melting temperature of 227 ± 2 °C (50 °C higher), better thermal stability (onset of degradation was delayed by ∼40 °C), enhanced mechanical strength (compression modulus of 3.3 MPa), and better sound absorption ability. The biodegradability of PLA and the superior properties induced by stereocomplexation make these aerogels potential candidates for applications such as tissue engineering scaffolds, packaging, acoustic insulation, etc.

Sulfonated polybenzimidazole engineering defect-induced N, S-codoped carbon-supported Co3C hybrid composite as high-efficiency electrocatalyst for oxygen evolution reaction

The exploitation of efficient OER electrocatalysts has become the key to realize the commercial-application of H2 production from electrocatalytic water splitting. In this research, the novel defect-induced N, S co-doped carbon-supported Co3C nanoparticles were successfully fabricated as OER electrocatalyst by combination of wet-impregnation treatment of Co/sulfonated polybenzimidazole (sPBI) and subsequent thermal annealing treatment, which was denoted as Co3C/CNS-X (X=700, 800, 900) electrocatalyst. Among them, Co3C/CNS-800 delivered the more favorable architecture due to its large specific surface area, high dispersion of Co3C nanoparticles and especially the generation of abundant defects sites, which not only improved its conductivity and the amounts of electrocatalytically active sites but also imparted the extremely important functionality in accelerating the interfacial electron-transfer and facilitated the adsorption ability of intermediates, thus exerting the extraordinary activities for catalyzing OER. What's more, there were some evidences demonstrating the generation of the strong interfacial interactions through the Co-N coordination bonds and the formation of more pyridinic-N species though annealing treatment, which allowed the structural stability to be further strengthened and simultaneously gave impetus to the O2 release for the reduction of OER overpotential. In recognition of these approvable structural characteristics, the Co3C/CNS-800 exhibited the lowest overpotential of 300 mV at an anodic current density of 10 mA cm−2, and a small Tafel slope of 70 mV dec−1 in 1 M KOH electrolyte as well as a long durability.

Amphiphilic Poly(vinyl alcohol) Membranes Leaving Out Chemical Cross-Linkers: Design, Synthesis, and Function of Tailor-Made Poly(vinyl alcohol)-b-poly(styrene) Copolymers.

Tailor-made poly(vinyl alcohol)-b-poly(styrene) copolymers (PVA-b-PS) for separation membranes are synthesized by the combination of reversible-deactivation radical polymerization techniques. The special features of these di-block copolymers are the high molecular weight (>70kDa), the high PVA content (>80wt%), and the good film-forming property. They are soluble only in hot dimethyl sulfoxide, but by the "solvent-switch" technique, they self-assemble in aqueous media to form micelles. When the self-assembled micelles are cast on a porous substrate, thin-film membranes with higher water permeance than that of PVA homopolymer are obtained. Thus, by using these tailor-made PVA-b-PS copolymers, it is demonstrated that chemical cross-linkers and acid catalysts can no longer be needed to produce PVA membranes, since the PS nanodomains within the PVA matrix act as cross-linking points. Lastly, subsequent thermal annealing of the thin film enhances the membrane selectivity due to the improved microphase separation.

Construction of NiCo2O4@CNPs core-shell nanocomposites with 2D leaf-like structure for high-performance supercapacitor

Exploitation of NiCo2O4-based novel composite electrode materials with enhanced comprehensive properties is essential for high-performance supercapacitors. Herein, ultrathin NiCo2O4 nanosheets wrapped carbon nanoplates (NiCo2O4@CNPs) are fabricated by co-precipitation method and subsequent thermal annealing treatment. Characterization results indicate that 2D leaf-like NiCo2O4@CNPs is synthesized and NiCo2O4 nanosheets with thickness of 4 nm are tightly wrapped on CNPs. The NiCo2O4@CNPs is possessed of enhanced electrochemical properties in comparison to bare CNPs, bare NiCo2O4 and other NiCo2O4-based materials reported in literatures. The NiCo2O4@CNPs electrode shows higher specific capacitance (1265 F g−1 at 1 A g−1) and remarkable rate capability. Furthermore, the NiCo2O4@CNPs electrode has excellent cycling stability, and 97.3% of the initial specific capacitance still remains after 2000 cycles. Reasons for the enhanced electrochemical properties of NiCo2O4@CNPs were analyzed. In addition, the supercapacitor of NiCo2O4@CNPs//NiCo2O4@CNPs displays a high energy density of 32.4 Wh kg−1 at 435 W kg−1 and a high power density of 8676 W kg−1 at 14.4 Wh kg−1. The above results manifested that NiCo2O4@CNPs is an potential electrode material for fabricating high-performance supercapacitor.

Synthesis and high-temperature ferromagnetism of Fe-doped SiGe diluted magnetic semiconductor thin films.

Fe-doped SiGe (Si0.25Ge0.75:Fex, x = 0.01, 0.025, and 0.05) thin films were prepared by radio frequency magnetron sputtering and subsequent rapid thermal annealing on a Ge (100) substrate and their structural, magnetic and magneto-transport properties were investigated. Structural characterization using AFM, SEM, XRD, and HRTEM shows that the obtained samples are polycrystalline and their lattice constants increase with the Fe concentration. Analysis of their electronic and spintronic states using XPS and XMCD reveals that Fe dopants mainly exist as substitutional Fe2+ ions in the SiGe lattice, providing both local magnetic moments and hole carriers. Furthermore, magnetization measurements indicate that all the samples exhibit ferromagnetism, and their Curie temperature increases with the Fe concentration up to 294 K; meanwhile, magneto-transport measurements reveal a giant magnetoresistance (GMR) effect of over 800% and an anomalous Hall effect (AHE), as well as semiconducting behaviors, in the samples. Further analysis suggests that the ferromagnetism comes from a hole-mediated process originating from substitutional Fe dopants in the SiGe matrix and this is enhanced by the tensile strain in the films. The synthesis and high-temperature ferromagnetism of Fe-doped SiGe thin films may play a key role in group IV-based spintronic applications.

Thermal sensor based on si single crystal implanted with different parties P+ and B+ ions

The characteristics of existing temperature sensors based on silicon monocrystals are analyzed, and the reasons for the limited upper limit of temperature measurement are established. To increase sensitivity, expand the range of measured temperatures, and obtain a linear output characteristic of the temperature sensor, the authors propose to carry out phased implantation of P+ and B+ ions with decreasing energy in different directions of the Si(111) crystal followed by brief thermal, laser or IR radiation after each stage ion implantation. The distribution profiles of P and B atoms implanted into Si with a gradual decrease in energy are studied. The effect of subsequent thermal and IR annealing on the atomic distribution profiles and the characteristics of a thermal sensor was investigated. A p-i-n diode with a high concentration of electrically active atoms (NP=1021 cm-3, NB=2·1021 cm-3), with almost a step distribution of P and B atoms and a sharp boundary p-i and i-n was created areas with a high thermal sensitivity of 2.3 mV/K in a wide temperature range of 20-550 K.

Improved Memory Window and Robust Endurance for Ge P-Channel Ferroelectric FET Memory Using Microwave Annealing Followed by Rapid Thermal Annealing

Microwave annealing with subsequent rapid thermal annealing (MWA+RTA) is proposed for HfZrOx-based germanium (Ge) p-channel ferroelectric FET (p-FeFET) memory to concurrently improve the interfacial quality while obtaining the required polarization, leading to a memory window of 2.5 V by ±4 V operation, good read latency, robust endurance up to 107 cycles for 1 bit/cell operation and each stable state for 3 bits/cell (triple-level cell, TLC) operation up to 105 cycles for the first time. Reversing the annealing sequence (RTA+MWA) degrades the performance and attests to the importance of thermal budget control. The proposed annealing scheme makes the Ge FeFETs, even with planar structure, quite competitive compared to other Si-, SiGe- and Ge-based FeFETs in terms of low-voltage TLC capability with high reliability, enabling high-density embedded memory for future nodes.

Formation of n-type CoSi monosilicide film which can be used in instrumentation

There arises the formation of thin films of cobalt monosilicide (CoSi) deposited into the base surface of SiO2/Si (111) using magnetron ion-plasma sputtering and subsequent thermal annealing. It was found that, in addition to the formation of CoSi silicide, also there are Co and Si atoms that do not form bonds on the surface. Therefore, in this work, we studied the surface morphology and composition of a CoSi silicon target using a scanning electron microscope. The study, silicide CoSi, was chosen as the target and standard SiO2/Si (111) was used as the substrate. The surface morphology and composition of the CoSi silicon film obtained by scanning electron microscopy had been studied. The paper reports on a method, morphology of the surface of a CoSi silicon film obtained using Raman microscopy. The results obtained are based on the fact that they were obtained using a modern magnetron sputterer, a high-vacuum thermal heater and modern devices.

Synergy of Z-scheme heterostructure with interfacial S−O bonding in In2S3/BiOBr for efficient tetracycline hydrochloride degradation and Cr(VI) reduction

High-efficiency interfacial charge transfer is the key to achieve better spatial carrier separation, and thus to develop advanced heterogeneous photocatalysts for environmental remediation. However, It still remains a great challenge to design and exploit the effective charge transfer scheme. Herein, a novel Z-scheme In2S3/BiOBr with S−O covalent bonding was prepared by hydrothermal and subsequent thermal annealing methods. The obtained photocatalysts were systematically characterized and used for tetracycline hydrochloride degradation and Cr(VI) reduction in aqueous solution. As a result, the optimized In2S3/BiOBr heterostructure (IS/BOB-39) exhibited superior photocatalytic activities for tetracycline hydrochloride degradation and Cr(VI) reduction under simulated solar light irradiation compared with individual materials. The Z-scheme transfer mechanism was corroborated by trapping experiments, ESR and XPS analysis, which provided an effective transfer pathway for spatial separation of carriers. Moreover, the formation of chemical S−O bond between In2S3 and BiOBr, which acted as a specific bridge to expediently transmit interfacial electrons, showed a synergistic effect with Z-scheme transfer model on the significantly enhanced photocatalytic performance. In addition, the In2S3/BiOBr heterojunction presented excellent cycle stability, resulting from the tight heterointerface. This work provides a promising approach to design and fabricate high effect Z-scheme heterojunction in wastewater treatment.

In Situ Process Monitoring and Multichannel Imaging for Vacuum‐Assisted Growth Control of Inkjet‐Printed and Blade‐Coated Perovskite Thin‐Films

AbstractVacuum‐assisted growth (VAG) control is one of the most promising methods for controlling nucleation and crystallization of printed and coated large area lead halide perovskite‐based layers for optoelectronics. To coat or print homogeneous high‐quality perovskite thin‐films at high fabrication yield, real‐time process monitoring of the VAG is pivotal. In response, a 2.1‐megapixel multichannel photoluminescence (PL) and reflection imaging system is developed and employed for the simultaneous spatial in situ analysis of drying, nucleation, and crystal growth during VAG and subsequent thermal annealing of inkjet‐printed and blade‐coated perovskite thin‐films. It is shown that the VAG process, for example, evacuation rate and time, affects the film formation and provide detailed insight into traced PL and reflection transients extracted from sub‐second videos of each channel. Based on correlative analysis between the transients and, for example, perovskite ink composition, wet‐film thickness, or evacuation time, key regions which influence crystal quality, film morphology, and are base for prediction of solar cell performance are identified.

Ga2O3/GaN-based solar-blind phototransistors fabricated using a thermal oxidation process performed on the GaN p-n junction layers

In this article, β-Ga2O3/GaN-based solar-blind phototransistors are fabricated using a thermal oxidation process performed on the p-GaN layer of a p-GaN/n-GaN junction to form the β-Ga2O3/p-GaN/n-GaN heterostructure. The thermal-oxidized β-Ga2O3 films exhibit a (2̅01)-orientated crystal phase and high-resistivity property. The high-resistivity β-Ga2O3 layer can be converted into an n-type β-Ga2O3 layer through Si ion implantation and a subsequent thermal annealing process. The typical electron concentration and mobility of the Si-implanted β-Ga2O3 are as high as 3.2 × 1020 cm−3 and 177 cm2v−1s−1, respectively. The n-type β-Ga2O3 and unimplanted β-Ga2O3 layers serve as the collector associating with the p-GaN and n-GaN layers, which function as the base and emitter, respectively, to construct the heterojunction phototransistors (HPTs). The HPTs exhibit a distinct cut-off wavelength at around 260 nm, indicating that the photocurrents result from the β-Ga2O3 layers rather than the p-GaN and n-GaN layers. The HPTs also show a significant bias-dependent responsivity in the deep UV (λ < 260 nm) region. This increased responsivity can be attributed to band discontinuity, resulting in the accumulation of photogenerated carriers at the β-Ga2O3/p-GaN interface. The preliminary results suggest that the β-Ga2O3/GaN-based HPTs can be achieved through the thermal oxidation of a p-GaN/n-GaN epitaxial structure.

Tunable magnetic and magnetocaloric properties by thermal annealing in ErCo2 atomized particles

Processing magnetocaloric materials into magnetic refrigerants with appropriate shapes is essential for the development of magnetic refrigeration systems. In this context, the impact of processing on the physical properties of the materials is one of the important issues. Here, we investigate the crystallographic, magnetic, and magnetocaloric properties of gas-atomized particles of the intermetallic compound ErCo2, a giant magnetocaloric material for low-temperature applications. The results demonstrate that the physical properties of ErCo2 are significantly changed by atomization and subsequent thermal annealing. In the as-atomized particles, the magnetic transition temperature increases from 34 to 56 K, and the phase transition changes from first order to second order. The thermal annealing shifts the transition temperature back to the original one and restores the first-order phase transition characteristic. The changes in magnetic properties are closely related to those in crystallographic properties, suggesting the importance of the magneto-structural coupling. The magnetic entropy change −ΔSM of the particles can be tuned in size, shape, and peak temperature depending on the annealing conditions. The peak value of −ΔSM varies in the range of 9–33 J kg−1 K−1 for a field change of 0–5 T. All the ErCo2 atomized particles have magnetocaloric properties comparable or superior to other promising candidates for low-temperature magnetic refrigerants.

Control of perovskite film crystallization and growth direction to target homogeneous monolithic structures

Getting performant organo-metal halide perovskite films for various application remains challenging. Here, we show the behavior of solvent and perovskite elements for four different perovskites families and nine different initial precursor solution systems in the case of the most popular preparation process which includes an anti-solvent dripping-assisted spin coating of a precursor solution and a subsequent thermal annealing. We show how the initial solution composition affects, first, the film formed by spin coating and anti-solvent dripping and, second, the processes occurring upon thermal annealing, including crystal domain evolution and the grain growth mechanism. We propose a universal typology which distinguishes three types for the growth direction of perovskite crystals: downward (Type I), upward (Type II) and lateral (Type III). The latter results in large, monolithic grains and we show that this mode must be targeted for the preparation of efficient perovskite light absorber thin films of solar cells.