Initial Annealing Temperature Research Articles

Influence of the annealing temperature of (n) poly-Si/SiOx passivating contacts on their firing stability

Several works have been published recently regarding firing stability of passivating contacts featuring P-doped polysilicon on an interfacial oxide (poly-Si/SiOx). Therein, a degradation was reported if the (n) poly-Si/SiOx structure was capped by a dielectric passivation layer during firing due to creation of additional defects in the interfacial oxide. In part A of this study it is shown, that P-doped (n) poly-Si/SiOx structures capped by a SiNy or SiNy/AlOz stack only degrade during firing at moderate temperatures if they previously have been annealed below the optimum annealing temperature Topt. It was found that this degradation is stronger the colder the annealing temperature was below Topt. In part B of this study it is shown, that at excess firing temperatures also samples annealed at or above Topt degrade. Again, this degradation depends on the initial annealing temperature in a similar way that the degradation is stronger the colder the annealing temperature was below Topt. Furthermore, a saturation of the measured surface recombination density was observed for set firing temperatures above 900°C, which points to a saturation of the underlying defect creation mechanism in the interfacial oxide.

Thermodynamic Theory of Phase Separation in Nonstoichiometric Si Oxide Films Induced by High-Temperature Anneals

High-temperature anneals of nonstoichiometric Si oxide (SiOx, x < 2) films induce phase separation in them, with the formation of composite structures containing amorphous or crystalline Si nanoinclusions embedded in the Si oxide matrix. In this paper, a thermodynamic theory of the phase separation process in SiOx films is proposed. The theory is based on the thermodynamic models addressing various aspects of this process which we previously developed. A review of these models is provided, including: (i) the derivation of the expressions for the Gibbs free energy of Si oxides and Si/Si oxide systems, (ii) the identification of the phase separation driving forces and counteracting mechanisms, and (iii) the crystallization behavior of amorphous Si nanoinclusions in the Si oxide matrix. A general description of the phase separation process is presented. A number of characteristic features of the nano-Si/Si oxide composites formed by SiOx decomposition, such as the local separation of Si nanoinclusions surrounded by the Si oxide matrix; the dependence of the amount of separated Si and the equilibrium matrix composition on the initial Si oxide stoichiometry and annealing temperature; and the correlation of the presence of amorphous and crystalline Si nanoinclusions with the presence of SiOx (x < 2) and SiO2 phase, respectively, in the Si oxide matrix, are explained.

Dewetting regimes in ultra-thin nanocrystalline Ag films

Annealing-induced dewetting in ultra-thin metallic films continues to be a hot topic because of their prospects for developing versatile components in different optoelectronic applications. In this work, we present a brief but significant study about the effects of high vacuum annealing on the dewetting of sputtered ultra-thin Ag films. Results suggest that the activation threshold of different dewetting regimes is strongly dependent on the initial film thickness and annealing temperature. This enables the fabrication of Ag nanostructures with different microstructural features, which can be tuned by choosing adequate thickness and annealing conditions. This study shows that dewetting-regime engineering to achieve different Ag nanostructures can be a useful method to design optoelectronic components with perspectives to potential applications Thin-Film Solar Cells (TFSCs) and Surface-Enhanced Raman Spectroscopy (SERS).

On the critical strain of thermal-mechanical processing to tailor grain boundary character distribution in INCOLOY 925 alloy

Through a series of thermal-mechanical processing (TMP) routes with various ratios of cold rolling and subsequent high-temperature annealing, the samples with different critical strain states were prepared to explore the evolution of grain boundary character distribution (GBCD) in INCOLOY 925 during grain boundary engineering (GBE). The GBE microstructure was characterized using the electron backscatter diffraction to study the influence of TMP parameters on the evolution of GBCD and the penetration of random high angle grain boundaries. The results show that the different states of pre-strain correspond to the variational formation mechanism of grain boundary network (GBN). The strain induced boundary migration is the predominant mechanism with the rolling reduction lower than critical strain. With the slight increase of strain, the recrystallization nucleation can be initiated to generate the strain-free grains at a certain annealing temperature. Moderate strain is needed to ensure adequate growth for twin related domains (TRDs). Besides, with the increase of strain and temperature, the dominant mechanism of GBCD gradually transfers from the new twinning mechanism to the Σ3 regeneration mechanism. Specifically, the TMP sample with 10% rolling reduction followed by annealing at 1075 °C for 10min shows relatively higher grain size difference ratio and average grains numbers in the TRDs, indicating that a larger initial grain size can increase critical strain and delay the nucleation of strain-free grains during TMP treatment. The moderately higher grain size shows an opposite effect on the formation of GBN. Finally, an estimation model of critical strain, as a function of initial grain size and annealing temperature, was constructed based on the artificial neural network, and the predicted results show a high consistency with the actual microstructure evolution.

Deep Learning-based Risk Prediction Model for Postoperative Healthcare-associated Infections

Objective To develop a risk prediction model combining pre/intraoperative risk factors and intraoperative vital signs for postoperative healthcare-associated infection(HAI)based on deep learning. Methods We carried out a retrospective study based on two randomized controlled trials(NCT02715076,ChiCTR-IPR-17011099).The patients who underwent elective radical resection of advanced digestive system tumor were included in this study.The primary outcome was HAI within 30 days after surgery.Logistic regression analysis and long short-term memory(LSTM)model based on iteratively occluding sections of the input were used for feature selection.The risk prediction model for postoperative HAI was developed based on deep learning,combining the selected pre/intraoperative risk factors and intraoperative vital signs,and was evaluated by comparison with other models.Finally,we adopted the simulated annealing algorithm to simulatively adjust the vital signs during surgery,trying to explore the adjustment system that can reduce the risk of HAI. Results A total of 839 patients were included in this study,of which 112(13.3%)developed HAI within 30 days after surgery.The selected pre/intraoperative risk factors included neoadjuvant chemotherapy,parenteral nutrition,esophagectomy,gastrectomy,colorectal resection,pancreatoduodenectomy,hepatic resection,intraoperative blood loss>500 ml,and anesthesia time>4 h.The intraoperative vital signs significantly associated with HAI were in an order of heart rate>core body temperature>systolic blood pressure>diastolic blood pressure.Compared with multivariable Logistic regression model,random forest model,and LSTM model including vital signs only,this deep learning-based prediction model performed best(ACC=0.733,F1=0.237,AUC=0.728).The simulation via simulated annealing algorithm reduced the incidence of postoperative HAI.Moreover,the incidence decreased most in the case of reducing the initial annealing temperature and choosing the last 20% of surgery procedure. Conclusions This study developed a risk prediction model for postoperative HAI based on deep learning,which combined pre/intraoperative risk factors and intraoperative basic vital signs.Using simulated annealing algorithm to adjust intraoperative vital signs could reduce the incidence of postoperative HAI to some extent.

TU-DAMD employment for molecular characterization of Salvia judaica and Salvia palaestina species

Genetic diversity in perennial Salvia judaica Boiss (Judean sage) and Salvia palaestina Benth (Palestinian sage) species using touch-up directed amplification of minisatellite region DNA (TU-DAMD) has been performed in two separated sets; in the first set (set A) the initial annealing temperature was increased from 50 °C to 55 °C, whereas, in the second one (set B), it increased from 55 °C to 60 °C by 0.5 °C/cycle during the first 10 PCR amplification cycles. Fifteen DAMD primers have been tested for each set. Set (A) produced 89.39% polymorphism level (P%) with polymorphic information content (PIC) average of 0.33 and marker index (MI) average of 3.96. Whereas, in set (B) these values were recorded to be 94.02%, 0.34 and 3.98 for P%, PIC and MI, respectively. Data showed that the two mentioned sets successfully highlighted high polymorphism level between the two studied Salvia sp. This work studies genetic diversity of S. judaica and S. palaestina species using TU-DAMD test as a novel molecular marker.

MA Cation-Induced Diffusional Growth of Low-Bandgap FA-Cs Perovskites Driven by Natural Gradient Annealing.

Low-bandgap formamidinium-cesium (FA-Cs) perovskites of FA1-xCsxPbI3 (x < 0.1) are promising candidates for efficient and robust perovskite solar cells, but their black-phase crystallization is very sensitive to annealing temperature. Unfortunately, the low heat conductivity of the glass substrate builds up a temperature gradient within from bottom to top and makes the initial annealing temperature of the perovskite film lower than the black-phase crystallization point (~150°C). Herein, we take advantage of such temperature gradient for the diffusional growth of high-quality FA-Cs perovskites by introducing a thermally unstable MA+ cation, which would firstly form α-phase FA-MA-Cs mixed perovskites with low formation energy at the hot bottom of the perovskite films in the early annealing stage. The natural gradient annealing temperature and the thermally unstable MA+ cation then lead to the bottom-to-top diffusional growth of highly orientated α-phase FA-Cs perovskite, which exhibits 10-fold of enhanced crystallinity and reduced trap density (~3.85 × 1015 cm−3). Eventually, such FA-Cs perovskite films were fabricated into stable solar cell devices with champion efficiency up to 23.11%, among the highest efficiency of MA-free perovskite solar cells.

Temperature Dependence of Thermoelectric Homogeneity of Noble Metal Thermocouples

This paper describes the results of low-temperature investigations of the thermoelectric inhomogeneity of conventional standardized noble metal thermocouples (types S and R, Au/Pt and Pt/Pd thermocouples) and of non-standardized Pt/Rh-alloyed thermocouples which have undergone initial annealing at 400 °C for 24 h. The investigations aim to verify the generally accepted practice of using a linear relationship between the inhomogeneity and the measured electromotive force (emf). Immersion profile measurements were carried out in a salt bath at temperatures of about 200 °C, 300 °C, 400 °C, and 500 °C. These temperatures are below the critical temperature range of the selective Rh oxidation of Pt/Rh-alloyed thermocouples. Therefore, the results of the homogeneity investigations should not be influenced by such reversible oxidations effects. Nevertheless, the results of the homogeneity tests at 500 °C showed a deviation from the linearity of the measured inhomogeneities of the thermocouples containing Pt/Rh alloys related to the measurements at 200 °C, 300 °C, and 400 °C. The results obtained with the Au/Pt and Pt/Pd thermocouples confirmed the above-mentioned assumption of the linear relationship between the magnitude of the inhomogeneities and the thermoelectric voltages measured. An additional investigation of a multi-wire thermocouple consisting of non-standardized Pt/Rh alloys (Pt5%Rh, Pt17%Rh, and Pt20%Rh) and a pure platinum thermoelement confirmed the results obtained with the standardized type S and R thermocouples and allowed conclusions to be drawn about re-ordering effects of the Pt/Rh-alloyed thermocouples, which are strongly related to the initial annealing temperature of 400 °C.

Gold-nanoisland-decorated titanium nanorod arrays fabricated by thermal dewetting approach

Solid-state dewetting is a simple and versatile technique for fabricating plasmonic-nanostructure-decorated platforms. However, understanding of the optical properties of these platforms and the effect of the three-dimensional (3D) morphology of the underlying substrate on the dewetting of metallic thin films is still needed for developing effective platforms for further applications. Herein, the authors report gold (Au)-nanoisland-decorated 3D titanium dioxide (TiO2) nanorod (TiNR) arrays fabricated through the thermal dewetting approach. It is demonstrated that the plasmonic behavior of the fabricated platforms can be manipulated by controlling both the initial gold film thickness and annealing temperature. Furthermore, the fabricated platforms exhibited Raman signal enhancement of up to ∼102 for the probe molecule methylene blue. The surface characteristics of the fabricated platforms were evaluated for biological interactions. For this purpose, osteogenic cells (Saos-2) were seeded on the samples. It was found that the cell behavior was improved on the anisotropic micro–nano pattern of TiNRs and gold-coated TiNR films because of features such as topography and surface chemistry. The authors’ results clearly offer simple but important guidance for the creation of surface-enhanced Raman spectroscopy platforms and tissue-integration devices as biomaterials for real-life applications.

Twin-induced stability and mechanical properties of pure magnesium

In the present study the effect of initial texture and annealing temperature on the microstructure and mechanical anisotropy of pure magnesium has been investigated. Evolution of microstructure after annealing was analysed by optical microscopy and SEM/EBSD. Magnesium samples with different initial textures were deformed at room temperature at a strain rate equal to 10−3 s−1 followed by subsequent annealing at 473 K and 673 K. The texture evolution, work hardening and microstructure have been examined after annealing treatment. It was found that the initial texture affects the main deformation mode as well as influences the texture upon annealing. During compression, samples deform by twinning, while slip becomes the dominant deformation mode for samples having c-axis perpendicular to the extrusion direction. Moreover, it was shown that the recrystallization temperature is critical for texture evolution and mechanical properties of the annealed magnesium samples. Annealing at 473 K does not initiate recrystallization in samples exhibiting twins whereas samples without twins undergo recrystallization strengthening particular texture components in ODF sections. However, annealing at 673 K leads to a strong grain growth lowering the yield strength of the material. It was shown that an intensive twinning can stabilize the microstructure of pure magnesium and improves its mechanical properties up to 473 K.

Recrystallization Kinetics of Fe-3%Si after Deformation at High Strain Rate and High Temperature

Recrystallization kinetics of Fe-3%Si with initial grain size 296~839µm at the temperature range 1223~1423K, strain range from 0.51 to 0.92, strain rate range 5~80s−1 was studied by isothermal compression test using Gleeble-2000. The effect of strain, strain rate, initial grain size and annealing temperature on the recrystallization kinetics were discussed. Avrami equation was used to describe the static recrystallization kinetics. Moreover, the effect of initial grain size and annealing temperature on the exponent in Avrami equation was discussed and the reason of the exponent deviating from the theory value is owed to the effect of static recovery. In all the experimental range the static recrystallization kinetics can be well predicted by Avrami equation.

Modulation of carbon nanotube yield and type through the collective effects of initially deposited catalyst amount and MgO underlayer annealing temperature

ABSTRACTRecently, the millimetre-scale, highly efficient growth of single-wall carbon nanotube (SWCNT) forests from iron (Fe) catalysts has been reported through the annealing of the magnesia (MgO) underlayer. Here, we report the modulation of the CNT yield (height) and average number of CNT walls for a Fe/MgO catalyst system through the collective effects of initial Fe amount and MgO annealing temperature. Our results revealed the existence of a well-defined region for high yield SWCNT forest growth in the domain of deposited Fe thickness and MgO annealing temperature. Through topographic examinations of the catalyst surface using atomic force microscopy, we confirmed that our results stem from the collective effects of increased amounts of surface-bound Fe through the amount of deposition and suppression of Fe subsurface diffusion, together govern the amount of surface-bound catalyst. The combination of these mechanisms determined the final nanoparticle size, density, and stability and could explain the three distinctly defined regions: low yield SWCNT growth, high yield SWCNT growth, and high yield multiwall CNT growth. Furthermore, we explained the observed borders between these three regions.

Impact of Dark Annealing on the Kinetics of Light- and Elevated-Temperature-Induced Degradation

Light- and elevated-temperature-induced degradation (LeTID) has been shown to have a significant detrimental impact on p-type multicrystalline silicon solar cells and, in particular, on passivated emitter and rear cells. Previous studies have shown that defect kinetics can be modulated for samples that are dark annealed prior to light soaking at elevated temperature. In this work, we show that while short annealing durations help accelerate both degradation and recovery rates to different extents, extended annealing instead instigates a retarding effect. Our results confirm that thermally induced degradation and regeneration mechanisms can be observed during dark annealing. The results also suggest that the response to this yet undetermined defect mechanism not only depends on the initial dark annealing temperature, but it is also highly dependent on the stage of the dark annealing degradation and regeneration cycle reached before beginning light soaking. Finally, we propose a refined model of three generalized modes to describe the changes in LeTID kinetics after dark annealing.

Analysis of Temperature andq-Parameter Dependency of FCM with Tsallis Entropy Maximization

The Tsallis entropy is aq-parameter extension of the Shannon entropy. By maximizing it within the framework of fuzzyc-means, statistical mechanical membership functions can be derived. We propose a clustering algorithm that includes the membership function and deterministic annealing. One of the major issues for this method is the determination of an appropriate values forqand an initial annealing temperature for a given data distribution. Accordingly, in our previous study, we investigated the relationship betweenqand the annealing temperature. We quantitatively compared the area of the membership function for various values ofqand for various temperatures. The results showed that the effect ofqon the area was nearly the inverse of that of the temperature. In this paper, we analytically investigate this relationship by directly integrating the membership function, and the inversely proportional relationship betweenqand the temperature is approximately confirmed. Based on this relationship, aq-incrementation deterministic annealing fuzzyc-means (FCM) algorithm is developed. Experiments are performed, and it is confirmed that the algorithm works properly. However, it is also confirmed that differences in the shape of the membership function of the annealing method and that of theq-incrementation method are remained.

The effect of PtxPb intermetallic metastable phase on the crystal orientation in PZT thin films

In this paper, the crystal orientations of Pb(Zr0.52Ti0.48)O3 (PZT) thin films prepared by sol–gel method were investigated by using various initial annealing temperature in the modified annealing process. The films were put directly into the muffle furnace when the temperature reached at 300–500 °C, it’s clear that this modified annealing process made the PZT films presented better (111)-orientation. A PtxPb intermetallic metastable phase was observed by X-ray diffraction, which is considered to be connected with the promotion of the (111) preferred orientation. The PZT thin film with 400 °C initial annealing temperature has the maximum (111) diffraction intensity, remanent polarization and dielectric constant.

Effect of Initial Annealing Temperature on Microstructural Development and Microhardness in High‐Purity Copper Processed by High‐Pressure Torsion

The effect of the initial annealing temperature on the evolution of microstructure and microhardness in high purity OFHC Cu is investigated after processing by HPT. Disks of Cu are annealed for 1 h at two different annealing temperatures, 400 and 800 °C, and then processed by HPT at room temperature under a pressure of 6.0 GPa for 1/4, 1/2, 1, 5, and 10 turns. Samples are stored for 6 months after HPT processing to examine the self‐annealing effects. Electron backscattered diffraction (EBSD) measurements are recorded for each disk at three positions: center, mid‐radius, and near edge. Microhardness measurements are also recorded along the diameters of each disk. Both alloys show rapid hardening and then strain softening in the very early stages of straining due to self‐annealing with a clear delay in the onset of softening in the alloy initially annealed at 800 °C. This delay is due to the relatively larger initial grain size compared to the alloy initially annealed at 400 °C. The final microstructures consist of homogeneous fine grains having average sizes of ≈0.28 and ≈0.34 µm for the alloys initially annealed at 400 and 800 °C, respectively. A new model is proposed to describe the behavior of the hardness evolution by HPT in high purity OFHC Cu.

Microstructural evolution during thermal annealing of ice-Ih

We studied the evolution of the microstructure of ice-Ih during static recrystallization by stepwise annealing experiments. We alternated thermal annealing and electron backscatter diffraction (EBSD) analyses on polycrystalline columnar ice pre-deformed in uniaxial compression at temperature of −7 °C to macroscopic strains of 3.0–5.2. Annealing experiments were carried out at −5 °C and −2 °C up to a maximum of 3.25 days, typically in 5–6 steps. EBSD crystal orientation maps obtained after each annealing step permit the description of microstructural changes. Decrease in average intragranular misorientation at the sample scale and modification of the misorientation across subgrain boundaries provide evidence for recovery from the earliest stages of annealing. This initial evolution is similar for all studied samples irrespective of their initial strain or annealing temperature. After an incubation period ≥1.5 h, recovery is accompanied by recrystallization (nucleation and grain boundary migration). Grain growth proceeds at the expense of domains with high intragranular misorientations, consuming first the most misorientated parts of primary grains. Grain growth kinetics fits the parabolic growth law with grain growth exponents in the range of 2.4–4.0. Deformation-induced tilt boundaries and kink bands may slow down grain boundary migration. They are stable features during early stages of static recrystallization, only erased by normal growth, which starts after >24 h of annealing.

Effect of ferrite-martensite interface morphology on bake hardening response of DP590 steel

The effect of martensite spatial distribution and its interface morphology on the bake hardening characteristics of a dual phase steel was investigated. In one case, typical industrial continuous annealing line parameters were employed to anneal a 67% cold rolled steel to obtain a dual phase microstructure. In the other case, a modified annealing process with changed initial heating rates and peak annealing temperature was employed. The processed specimens were further tensile pre-strained within 1–5% strain range followed by a bake hardening treatment at 170°C for 20min. It was observed that industrial continuous annealing line processed specimen showed a peak of about 70MPa in bake-hardening index at 2% pre-strain level. At higher pre-strain values a gradual drop in bake-hardening index was observed. On the contrary, modified annealing process showed near uniform bake-hardening response at all pre-strain levels and a decrease could be noted only above 4% pre-strain. The evolving microstructure at each stage of annealing process and after bake-hardening treatment was studied using field emission scanning electron microscope. The microstructure analysis distinctly revealed differences in martensite spatial distribution and interface morphologies between each annealing processes employed. The modified process showed predominant formation of martensite within the ferrite grains with serrated lath martensite interfaces. This nature of the martensite was considered responsible for the observed improvement in the bake-hardening response. Furthermore, along with improved bake-hardening response negligible loss in tensile ductility was also noted. This behaviour was correlated with delayed micro-crack initiation at martensite interface due to serrated nature.

Combustion assisted synthesis of hardystonite nanopowder

In this study, single-phase hardystonite (Ca2ZnSi2O6) nanopowder was synthesized by combustion synthesis method from aqueous solution of Calcium nitrate, Zinc nitrate and Tetraethyl orthosilicate. In order to characterize the obtained powders, X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used. The effect of sucrose concentration on the purity and morphology of the obtained hardystonite powder, and its initial annealing temperature was investigated. The optimum sucrose to metal ratio was found to be 2:1. The average particle size and the maximum crystallite size of the produced hardystonite nanopowder were 220 and 40nm, respectively.

Peculiarities of grain growth in silver films

Grain growth in thin sliver films is studied experimentally. It is shown for the first time that notable grain growth is preceded by an incubation stage in which a film’s microstructure may be considered stable since the rate of grain growth is relatively low. The length of the incubation stage depends on the initial gran size and annealing temperature. The results are in agreement with the view that the effect of vacancy generation accompanying grain growth is an important factor inhibiting the latter.