Conventional Annealing Research Articles

Irradiation induced enhancement of ferromagnetic τ-phase in MnAl alloy thin films on Si substrate

Ferromagnetic L10 MnAl phase was achieved in as-grown MnAl alloy thin films by using 250 keV H+ ion irradiation without conventional post annealing. The magnetic properties and crystallinity of MnAl thin film got modified with increase in irradiation fluence. The magnetic coercivity was found to be maximum (2500 Oe) at the fluence of 5 × 1014 ions cm−2. The hysteresis curve for the sample irradiated by H+ ions with fluence of 5 × 1016 ions cm−2 exhibited highest saturation magnetization (130 emu/cc) among all irradiated films. The increase in irradiation fluence led to larger grain growth as confirmed from AFM results. The magnetic domain pattern observed by MFM images confirmed the presence of ferromagnetic τ-phase in irradiated samples. The present study establishes that the H+ ion-irradiation can be an effective technique to tailor the structural as well as magnetic properties of MnAl thin films.

Normally-Off AlGaN/GaN Heterojunction Metal-Insulator-Semiconductor Field-Effect Transistors With Gate-First Process

In this letter, AlGaN/GaN heterojunction metal-insulator-semiconductor field-effect transistors with gate-first process were developed for normally-off operation with p-GaN cap layers and SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> dielectrics. To avoid the effect of the annealing process on the gate, a low-temperature ohmic contact technique was developed at an annealing temperature of about 500 °C for 20 min in N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ambient. With the assistance of inductively coupled plasma dry etching, a contact resistance of 1.45 Ω · mm and sheet resistance of 1080.1 Ω/□ were obtained in the recessed region. Owing to the inset of the SiNx layer, the threshold voltage of the fabricated device was enhanced to approximately 2 V, and good pinch-off was observed with the gate voltage up to 16 V. Compared with the conventional high-temperature ohmic annealing process, the gate leakage current was suppressed significantly in both reverse and forward directions. Good device performance was confirmed with a maximum channel electron field-effect mobility of 1500 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> .

Modulating the crystallization process of Fe82B12C6 amorphous alloy via rapid annealing

Crystallization is a uniform behavior for amorphous alloys while it can be fairly complex. For Fe-B-C alloys with high Fe content, the precipitation of α-Fe is ahead of the Fe-metalloid compounds with temperature increasing. It is found that the crystallization products of Fe-B-C amorphous alloys with Fe content lower than 82% can be modulated by appropriate annealing. The Fe82B12C6 alloy is eutectoidally crystallized with the simultaneous precipitation of α-Fe and Fe-metalloid compounds under conventional annealing. It is a diffusion controlled three-dimensionally growth with a constant nucleation rate. However, only α-Fe nanocrystals with a low volume fraction form under rapid annealing, which is evidenced by the results of X-ray and electron diffractions along with the magnetometry. The transmission electron microscopy bright-field images show that the α-Fe nanocrystals obtained by rapid annealing have two different morphologies. One is dendritic with a large characteristic length and the other is equiaxed-like.

First results of humidity sensors based on CeO2 thick film deposited by a new deposition technique from a suspension of nanoparticles

In this paper, we show the possibility to deposit a CeO2 thick film on (111) silicon substrate from a suspension of CeO2 nanoparticles by a new process of thick layer deposition in order to realize a humidity sensor. This new technique is derived from the spin-coating technology. The suspension is based on ultra-fine grinding of CeO2 firstly in a stirred media mill coupled then in a sonication cell. Suspension viscosity has been adjusted with carbopol polymer and its rheological properties have been analyzed in order to cover completely the silicon substrate by the CeO2 layer. Then, the impact of a conventional annealing on the crystallinity of the CeO2 film has also been investigated by Raman spectroscopy and by scanning electron microscopy. Finally, gold interdigitated electrodes have been screen printed on the thick film surface in order to realize a sensor and first promising results on the humidity sensitivity have been highlighted.

Oxygen-deficient WO3via high-temperature two-step annealing for enhanced and highly stable water splitting.

When grown according to the conventional one-step annealing process at 550 °C, WO3 exhibits low photocurrent density and inferior photocurrent retention. In contrast, after a two-step annealing process at first 550 °C and second 700 °C, WO3 contains a higher concentration of oxygen deficiencies acting as shallow donors, thus leading to improved charge separation. Importantly, this results in a substantial photocurrent increase and higher material stability, two criteria that are of utmost importance for efficient photoelectrochemical water splitting.

A Comparative Study of the Curing Effects of Local and Global Thermal Annealing on a FinFET

Recently, localized thermal annealing has been spotlighted as an effective method to cure aged devices. The degraded gate oxide can be successfully cured by local annealing, which utilizes Joule heat inherently generated in the device. But, despite this advantage, there has been no study comparing the curing effects with various other annealing methods. In this study, the curing effects of local annealing and a conventional global annealing method applied to SOI FinFETs are compared. The measured electrical characteristics are discussed to evaluate the damage curing with respect to curing level and variability.

Effect of Millisecond Annealing Temperature of Ni1-&lt;italic&gt;x&lt;/italic&gt;Pt&lt;italic&gt;x&lt;/italic&gt; Si Formation on Leakage Current Characteristics of Static Random- Access Memory Cells

The importance of optimizing the millisecond annealing (MSA) temperature for Pt-doped NiSi ( ${\mathrm {Ni}}_{{1}-{x}}$ Pt x Si) contact formation was highlighted by implementing and characterizing the ${\mathrm {Ni}}_{{1}-{x}}$ Pt x Si films in the static random-access memory (SRAM) cells fabricated with a 28-nm design rule. MSA at 750 °C–900 °C effectively reduced the junction leakage current compared to that with the conventional rapid thermal annealing, because of its efficient suppression of Ni diffusion in the junction region. Moreover, with an increase in the MSA temperature, the beneficial effects of maintaining a low junction leakage, such as interface flattening and grain size increase, were observed. However, the increase in the MSA temperature deteriorated the statistical distribution of the standby leakage current of the SRAM cells by producing more encroachment and spiking defects; this was attributed to the build-up of a high initial film stress and large stress relaxation during the subsequent back-end processes.

Effects of annealing conditions on the oxygen evolution activity of a BaTaO2N photocatalyst loaded with cobalt species

Precise engineering of the cocatalyst-photocatalyst interface and optimization of the cocatalyst dispersion are essential for improving the activity of particulate semiconductor photocatalysts. Herein, we report the effects of varying the conditions used to load cobalt oxide (CoOx) as a cocatalyst on the O2 evolution activity of a particulate BaTaO2N photocatalyst, based on trials in an aqueous silver nitrate solution under visible light irradiation. Annealing under an N2 flow after loading the Co species increased the O2 evolution rate threefold compared to that obtained following conventional annealing under an NH3 flow. Subsequent annealing under an H2 atmosphere exposed the BaTaO2N surface as a result of the aggregation of CoOx particles, and further enhanced the photocatalytic O2 evolution by a factor of two, yielding an apparent quantum efficiency of 0.55% at 420 nm. These results indicate the importance of intimate contact between cocatalyst particles and the photocatalyst, as well as the necessity of exposing the photocatalyst surface to make it available for reduction reactions during photocatalytic water oxidation.

Accelerated Carbide Spheroidisation and Refinement in Spring Steel 54SiCr6

Reduction of processing time is the goal of every business. In some cases, speeding up manufacturing processes is impossible or takes place at the expense of quality. The purpose of soft annealing is to obtain globular carbides in the microstructure. However, it is one of the most time-consuming heat treatment operations. Even its optimised versions require several hours of time. “Accelerated Carbide Spheroidisation and Refinement” (ASR) is an alternative process which can be performed using induction heating or thermomechanical treatment. It only takes several minutes to complete and has a beneficial effect on resultant mechanical properties. In this experiment, the impact of various microstructures in 54SiCr6 spring steel on hardening behaviour was explored. For this purpose, specimens with two different microstructures containing spheroidised carbides were produced by ASR accelerated annealing and by conventional soft annealing. Another initial microstructure, with lamellar pearlite, was obtained by hot rolling. It was found to have a certain effect as well. Quenched and tempered microstructures were observed using electron microscopy (SEM). Their mechanical properties were measured. The effects of various initial microstructures on resultant mechanical properties after cryogenic treatment were studied as well.

Effects of post-deposition plasma treatments on stability of amorphous InGaZnOx thin-film transistors prepared with plasma-assisted reactive magnetron sputtering

Effects of post-deposition plasma treatments on the stability of amorphous InGaZnOx thin-film transistors (TFTs) prepared with plasma-assisted reactive magnetron sputtering were investigated. The temporal evolution in the electrical characteristics of as-deposited IGZO TFT and post plasma treated IGZO TFT that passed over 400 d after fabrication and were kept under 40% humidity at room temperature were measured, resulting in which no change in the electrical characteristics of post plasma treated IGZO TFT with mobility of 40 cm2 V−1 s−1 were observed. Positive-current-bias instability in post plasma treated IGZO TFTs was examined together with as-deposited IGZO TFTs. The results indicated that the stabilities of electrical characteristics caused by the positive bias stress is primarily attributed to defects in the bulk a-IGZO region for as-deposited IGZO TFTs. The stabilities of electrical characteristics in post plasma treated IGZO TFTs were considerably improved compared to that of as-deposited IGZO TFTs. From these results, it was shown that the post plasma treatment is considered to be effective for improving the stability of IGZO TFTs as well as conventional thermal annealing.

Hybrid Microwave Annealing for Fabrication of More Efficient Semiconductor Photoanodes for Solar Water Splitting

Hybrid microwave annealing (HMA) is proposed as an alternative to conventional thermal annealing (CTA) in a furnace to fabricate efficient semiconductor photoelectrodes for solar water splitting. Thus, the effects of HMA are investigated in comparison with CTA using spinel zinc ferrite as an example. The ZnFe2O4 photoanodes fabricated by HMA with a graphite susceptor provide less defective surface, better structural ordering and smaller feature size than photoanodes prepared by CTA. Besides, HMA does not impair conductivity of the F:SnO2 glass substrate. All these positive factors of HMA leads to ∼4 times higher photocurrents at 1.23 VRHE and lowered onset potential by ∼100 mV under 1 sun irradiation of an optimized ZnFe2O4 photoanode relative to that fabricated by CTA. The HMA could be an effective generic method to fabricate efficient photoelectrodes based on refractory semiconductors replacing incumbent CTA.

Multi- and single-step in situ microwave annealing as low-thermal-budget techniques for solution-processed indium–gallium–zinc oxide thin films

In this study, low-thermal-budget in situ microwave annealing of solution-processed indium–gallium–zinc oxide (IGZO) thin films was investigated as a potential alternative to the conventional high-thermal-budget annealing process. The low-temperature baking and high-temperature post-deposition annealing of the solution-processed IGZO film were continuously performed using the same microwave equipment, leading to a reduced heat treatment processing time and temperature. We compared the electrical characteristics of IGZO thin film transistors (TFTs) produced using single- and multi-step in situ microwave annealing methods with those of TFTs manufactured via the conventional annealing method and found that the proposed single-step microwave annealing method yielded TFTs with electrical characteristics better than those of the TFTs fabricated using the multi-step and conventional annealing methods. In addition, the reliability was evaluated by conducting positive and negative gate bias stress tests, in which the IGZO TFTs manufactured using the proposed heat treatment method proved superior to those fabricated via the conventional heat treatment method. We investigated the effects of heat treatment on the composition and energy band structures of the IGZO films by performing x-ray photoelectron spectroscopy analysis and found that the proposed in situ microwave annealing method is more effective than the conventional method in solution processing.

Grain growth kinetics of 3 mol. % yttria-stabilized zirconia during flash sintering

Grain growth kinetics of dense 3 mol. % yttria-stabilized zirconia (3YSZ) ceramics during both DC flash sintering and conventional annealing were investigated using the grain size as a marker of microstructure evolution. The results indicated faster grain growth under greater current density. In contrast to conventionally annealed specimen, the grain boundary mobility was enhanced by almost two orders of magnitude with the applied electric current, revealing that joule heating alone was not sufficient to account for the experimental results. Instead, activation energy for grain growth decreased significantly due to electro-sintering. Systematic characterization of graded microstructure further indicated that local oxygen vacancies and specimen temperature were responsible for a grain size transition. Based on electrochemical reaction involved in flash sintering, grain size reduction at the cathode was proposed to be attributed to the local rearrangement of lattice cations and generated oxygen ions.

Effect of Microwave Annealing on Transparent In–Ga–ZnO Thin-Film Transistors With Graphene Source and Drain Electrodes

In this letter, we investigated the effects of microwave heat treatment on amorphous In–Ga–ZnO (a-IGZO) thin-film transistors (TFTs) with transparent graphene source and drain (S/D) electrodes. Microwave annealing (MWA) was simultaneously applied to post-deposition annealing of the a-IGZO channel layer and post-metallization annealing of the graphene S/D electrode, and then, the influence of MWA on the a-IGZO channel and graphene S/D electrode was evaluated and compared with conventional thermal annealing. We measured the ${I}$ – ${V}$ characteristics of the a-IGZO TFTs, analyzed the trap density of the channel layer, the interface trap density between the gate oxide and the channel, and the instability of device was evaluated. In addition, the effect of MWA on the contact resistance and process stability of transparent graphene electrodes was analyzed. As a result, we improved the electrical properties of the a-IGZO TFTs, simplified the annealing step, and reduced the thermal budget without damaging the graphene S/D electrode for transparent and flexible displays.

Low temperature annealing of metals with electrical wind force effects

Conventional annealing is a slow, high temperature process that involves heating atoms uniformly, i.e., in both defective and crystalline regions. This study explores an electrical alternative for energy efficiency, where moderate current density is used to generate electron wind force that produces the same outcome as the thermal annealing process. We demonstrate this on a zirconium alloy using in-situ electron back scattered diffraction (EBSD) inside a scanning electron microscope (SEM) and juxtaposing the results with that from thermal annealing. Contrary to common belief that resistive heating is the dominant factor, we show that 5 × 104 A/cm2 current density can anneal the material in less than 15 min at only 135 °C. The resulting microstructure is essentially the same as that obtained with 600 °C processing for 360 min. We propose that unlike temperature, the electron wind force specifically targets the defective regions, which leads to unprecedented time and energy efficiency. This hypothesis was investigated with molecular dynamics simulation that implements mechanical equivalent of electron wind force to provide the atomistic insights on defect annihilation and grain growth.

Room temperature H2 plasma treatment for enhanced passivation of silicon/TiO2 interface

Simultaneous requirement of excellent interface passivation and low thermal budget is a desirable feature for low cost Si based carrier selective solar cells. Accordingly, Titanium dioxide (TiO2), a widely used electron selective material, finds challenges related to thermal annealing like phase change and compatibility with thermal budget of hole transport layers. To address this, here we report a H2 plasma treatment process at room temperature which significantly reduces the surface recombination velocity (∼40 cm/s). Consequently, the reverse saturation current of the Si-TiO2 diode improves by a factor of 40, built-in potential improves by 100 mV, and the diode exhibits a near unity ideality factor. Using the same method, our Si-based double heterojunction solar cell results in an absolute increase of 2.4% in efficiency over devices with conventional thermal annealing. Given the ease of implementation and excellent performance, the proposed method is a promising alternative to thermal annealing for Si based heterojunction devices.

Low-temperature activation of boron ion in silicon substrate using B10H14+ cluster and by soft X-ray irradiation

To achieve an ultrashallow junction, a novel activation method for a B dopant in a Si wafer using a soft X-ray undulator in a synchrotron radiation facility was proposed. In addition, B10H14+ clusters were used to obtain high activation ratios and small junction depths. A low-sheet resistance of 245 Ω/sq was obtained using B10H14+ clusters and by soft X-ray irradiation at 490 °C. A p–n junction was fabricated at a treatment temperature of 440 °C without excessive dopant diffusion. The mechanism of low-temperature activation by soft X-ray irradiation is discussed in comparison with that of conventional furnace annealing and on the basis of the difference between B+ and B10H14+ clusters.

Effects of applying tensile stress during annealing on the GMI and induced anisotropy of Fe-Cu-Nb-Si-B alloys

• GMI measurements also confirm amorphous – nanocrystalline phase transition. • Application of stress at annealing temperature induces large anisotropy. • Macroscopic contraction during conventional annealing. • Application of stress at annealing temperature can reduce embrittlement effects. Nanocrystalline Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 ribbon samples possess excellent soft magnetic properties. Three forms of annealing treatment were performed on amorphous Fe-Cu-Nb-Si-B ribbon samples. The microstructure of the ribbon samples is studied using synchrotron radiation XRD. It is seen that upon annealing, a microstructure of nanocrystalline phase embedded in a residual amorphous matrix is achieved. The application of tensile stress (i) at the annealing temperature till cooling down to room temperature and (ii) from room temperature throughout the annealing process till cooling down to room temperature both show a clear difference in the XRD peaks in the directions parallel and perpendicular to the ribbon directions indicative of an induced structural anisotropy. The transition from the amorphous phase to the nanocrystalline phase was also confirmed by the GMI and transverse field anisotropy measurements. The application of tensile stress at the annealing temperature induces an anisotropy similar to the conventional stress annealing process, with about 5% less strain. This could be a method of reducing the brittle fracture problem of nanocrystalline ribbon samples.

Nano-crystallisation and magnetic softening in Fe–B binary alloys induced by ultra-rapid heating

Magnetically soft nanostructures are known to be prepared by the primary crystallisation of Fe-based amorphous precursors containing Cu and/or Nb. These nonmagnetic additives are essential for accelerated nucleation and retarded crystal growth during crystallisation. However, it has recently been found that none of these additives are necessary for the preparation of similar nanostructures when ultra-rapid annealing (URA) is employed. As a result, a magnetically soft nanostructure with exceptionally high Fe contents is realized in a simple Fe–B binary system. An obvious question is the mechanism of the nanostructural formation in such a simple system. To answer this question, the crystallisation behaviour of amorphous precursors was investigated by means of in situ resistivity measurements with heating rates up to ~100 K s−1. The primary crystallisation temperature (Tp) in Fe86B14 is increased at least by ~100 K under URA. This brings Tp to the vicinity of the glass transition (Tg) predicted by Egami’s zeroth-order approximation, suggesting that an enhanced nucleation rate near Tg due to the contribution of homogeneous nucleation could be responsible for the nanostructural formation in Fe86B14. Contrarily, the effect of URA is absent from Fe80B14Nb6, and a magnetically soft nanostructure is realized by conventional annealing because the crystallisation reaction in this alloy takes place above Tg even with a low heating rate of ~1 K s−1. URA offers new possibilities for enhancing the saturation magnetization in nanocrystalline soft magnetic alloys through reductions of the amount of nonmagnetic additives.

Surface morphology and photoelectric properties of FTO ceramic thin films under a simple transparent cover-assisted laser annealing

A simple transparent cover-assisted laser annealing strategy, which used a coverglass or a PET sheet as the transparent cover, was proposed to improve photoelectric properties of fluorine-doped tin oxide (FTO) thin films. Pure laser annealing was also performed for comparison. Transparent cover-assisted laser annealing was found to be more effective for producing densely distributed particles, decreasing surface roughness and increasing grain size, thus enhancing transmittance and conductivity of the film. More importantly, compared with coverglass-assisted laser annealing, PET-assisted laser annealing enabled the film surface to be covered with more uniform and denser particles and exhibit a remarkable increase in grain size. Therefore the film had the highest total transmittance of 84.32%, the highest specular transmittance of 75.88%, a slightly decreased haze of 10.01% and the lowest sheet resistance of 7.36 Ω/sq. The simple PET-assisted laser annealing method may be a promising substitution for the conventional laser annealing treatment.