Low-temperature Vacuum Annealing Research Articles

Влияние температуры нагрева в вакууме на морфологию структурных составляющих предварительно наводороженного титанового сплава ВТ22

The possibility of controlling the process of structure formation in the titanium transition grade alloy VT22 (Ti—5.5Al—4.3V—4.2Mo—0.8Cr—0.8Fe) by thermal hydrogen treatment (reversible alloying with hydrogen) has been investigated. It is shown that a large volume fraction of the β-phase, inherent in (α+β) — titanium alloys of the transition class (at least 40% in the studied alloy), provides suppression of the martensitic transformation already with the introduction of 0.1% (wt.) of hydrogen, and with the introduction of 0.3% (wt.) of hydrogen, only the metastable β-phase is fixed in the structure. During subsequent vacuum annealing, by controlling the development of the β→α-transformation, it is possible to form different types of structures in the alloy: from bimodal to equilibrium dispersed. Dispersed (α+β) — structure with an α-particle size no more than 0.5 μm is formed only during low-temperature (625—700°C) vacuum annealing.

Формирование градиентных структур в титановом сплаве при обратимом легировании водородом

The possibility of transforming a large-plate structure and creating a gradient structure in samples of titanium alloy VT23 during thermal hydrogen treatment has been studied. It is shown that by varying the concentration-time parameters of hydrogenation annealing, it is possible to regulate the depth of hydrogen penetration and purposefully form the structure of near-surface layers. Subsequent low-temperature vacuum annealing makes it possible to transform the coarse-plate structure into a finely dispersed one with a hardness of up to 40 HRC. It was established that the thickness of a layer with a finely dispersed structure during unidirectional hydrogenation with a barrier coating is twice as large as during volumetric nonequilibrium hydrogenation in the absence of a coating.

Microstructure and Mechanical Properties of a High-Strength Ti-4Al-2Fe-3Cu Alloy Fabricated by Sintering and Hot Extrusion

A Ti-4Al-2Fe-3Cu (wt pct) alloy containing only low-cost alloying elements was fabricated by vacuum sintering a blend of TiH2, Al, Fe, and Cu powders at 1200 °C for 1 hour followed by hot extrusion at the same temperature. The as-extruded alloy exhibited a microstructure consisting of mainly α/β lamellar colonies and Ti2Cu as a minor phase. The average colony size and lamella thickness were 118 and 12 µm, respectively, and Fe and Cu were predominantly distributed in the β lamellae. The as-extruded alloy had a high tensile yield strength (YS) and ultimate tensile strength (UTS) of 1248 and 1270 MPa, respectively, but a limited ductility (elongation to fracture: 2.3 pct). Annealing at 750 °C for 4 hour caused the average colony size and lamella thickness of the alloy to increase to 145 and 17 µm, respectively, and the volume fraction of the β phase decreased with the annealing. These microstructural changes resulted in a slight decrease of the YS and UTS to 1221 and 1253 MPa, but a clear increase of the ductility with the elongation to fracture reaching 4 pct. This work demonstrates that a combination of relatively low-temperature vacuum sintering, hot extrusion, and annealing can be effectively utilized to fabricate a low-cost Ti-4Al-2Fe-3Cu alloy with high strength and appreciable tensile ductility.

Effect of Moisture Exchange Caused by Low‐Temperature Annealing on Device Characteristics and Instability in InSnZnO Thin‐Film Transistors

AbstractThin‐film transistors (TFTs) in practical operations are inevitably impacted by moisture and temperature. An investigation on the joint effect of environmental moisture and working temperature on device characteristics and instability is becoming necessary. However, few related studies have been performed. In this work, a low‐temperature (LT) annealing in air is proposed to simulate the working conditions of TFTs in display applications. The effect of moisture exchange caused by LT annealing on device characteristics and instability of InSnZnO (ITZO) TFTs is systematically investigated. Combined with X‐ray photoelectron spectroscopy analysis, TCAD design simulation, and the measurement of relative humidity (RH) change on the device surface, a model considering water diffusion and water ionization is proposed. The negative shift of the transfer curve is attributed to the extra electrons released from the water ionization and the positive‐bias‐stress‐induced instability is mainly attributed to the generation of interstitial/substitutional hydrogens and aggregation of hydrogen ions at the backchannel. The temperature and the RH on the device surface jointly determine the moisture diffusion direction. Furthermore, the model is verified by an LT vacuum annealing. The results and the model will be beneficial for the further reliable design of ITZO TFTs in commercial applications.

Effect of Magnetic Pulsing and Low-Temperature Vacuum Annealing on the Soft Magnetic Properties of Hitperm Amorphous/Nanocrystalline Alloy

We studied soft magnetic properties of FeCoHfBCu amorphous/nanocrystalline alloy treated by medium-frequency magnetic pulsing (frequency 1500-2000Hz, field intensity 200-250Oe) and vacuum annealing at low temperature. The results of Mössbauer spectroscopy and transmission electron microscope show that the treating of magnetic pulsing with a medium frequency can introduce the nanocrystallization of amorphous FeCoHfBCu, precipitation of nm phase α-Fe(Co). And, with the increasing of pulsed frequency and field itensity, the crystalized volume friction increases from 24.71% to 35.2%. The low-temperature vacuum annealing for 100°C/30min of magnetic pulsed samples further improved the soft magnetic properties of nanocrystalline alloy. As compared with the amorphous state, the magnetic coerelvity decreaced from 103.4A/m to 34.0A/m, the saturated magnetization decreased from 160.47emu/g to 149.32emu/g.

SERS of a-C Thin Film on Ag, Au, Ag<sub>0.52</sub>-Au<sub>0.48</sub> Alloy Nanoparticle Arrays with Normal Particles Size Distribution Formed by Vacuum Thermal Evaporation

This paper presents the results of experimental studies of arrays of Ag0.52Au0.48 alloy nanoparticles. Arrays were formed by vacuum-thermal evaporation on an unheated substrate and subsequent low-temperature vacuum annealing. The TEM images of the obtained nanoparticle arrays and corresponding histograms of particle size distribution are shown. The transmission spectra of these arrays showing the displacement of the plasma frequency as a function of the mean particle size are obtained. Spectra of Raman scattering from a thin film of amorphous carbon in presence of AgAu particles are obtained, and a comparative analysis of Raman scattering amplification factors for pure Ag, pure Au and Ag0.52Au0.48 alloy nanoparticles is presented.

Reducing the contact and channel resistances of black phosphorus via low-temperature vacuum annealing

Contact and channel resistances of black phosphorus were improved via low-temperature vacuum annealing.

Enhancing ambipolar carrier transport of black phosphorus field-effect transistors with Ni-P alloy contacts.

Reducing power consumption and leakage current in complementary metal-oxide semiconductors (CMOSs) has gained importance for further increasing the transistor density. An effective strategy to achieve this is to use ambipolar carrier transport that can exploit both holes and electrons in a single transistor. We report the enhancement of ambipolar behavior in black phosphorus (BP) field-effect transistors (FET) by forming a low-resistance Ni2P alloy contact via low-vacuum annealing at 250 °C, where the transformation of BP into Ni2P alloy selectively occurred at the source/drain electrodes with the BP channel remaining pristine. The N-channel current on/off ratio and field-effect electron carrier mobility of BP FETs were improved by 98% and 1290%, respectively. Our results suggest that high-performance ambipolar BP FETs with low-resistance ohmic contacts can be achieved via low-temperature vacuum annealing for next-generation CMOS applications.

Influence of a static magnetic field on the formation of silicide phases in a Cu/Si(100) structure upon isothermal annealing

It is experimentally shown that the process of the solid-phase synthesis of copper silicide is sensitive to magnetic fields. Upon low-temperature vacuum annealing of a Cu/Si(100) thin-film structure, a static magnetic field with moderate strength stimulates the alloying of silicon in copper and suppresses synthesis of the Cu3Si phase.

Разработка биоматериала на основе нанокомпозита ГАП/TiOy с разной стехиометрией

At present, composite materials based on bioactive hydroxyappatite (HAP) are intensively developed. To achieve better mechanical properties, different additives are used, for example, titanium, zirconium, etc. In the present study, a dispersion-hardened composite material based on nanocrystalline HAP and nanocrystalline titanium monoxide (TiOy, y=0.92, 1.23) is prepared by low temperature annealing in vacuum. As an additive, titanium monoxide with different mass ratios and stoichiometries (10 or 20 mass % of substoichiometric TiO0.92 or superstoichiometric TiO1.23) is used. For the preparation of nanocrystalline powders and mixing of initial components, a planetary ball mill was used. According to scanning electron microscopy (SEM) data, using of the ball milling for mechanical mixing of nanopartilces allows one to prepare denser material with a particle shape, which facilitates cold pressing and sintering. It has been established that introducing of the TiOy additive leads to a reduction of the starting temperature of the composite material hardening by 200 to 250 оС. The phase composition and properties of the end product (microhardness, density) depend on the stoichiometry and on the amount of additives. For the content of 20 mass % of substoichiometric TiO0.92 phases Ti4.5O5 and Ti6O11 are found by means of XRD studies. The phase Ti4.5O5 is an ordered phase and is more stable as compared to other phases of Ti-O system., while the phase Ti6O11 has easy slip crystallographic planes. Presence of such two phases positively influences mechanical properties of the composite. According to SEM, BET and microhardness data, the composites prepared are nanodispersed ones and show an increased density and microhardness as compared to HAP without additives.

Low-temperature dynamic vacuum annealing of ZnO thin film for improved inverted polymer solar cells

Low temperature dynamic vacuum annealing was developed for preparing ZnO cathode buffer layer to improve the performance of IPSCs.

Capacitive Properties of MIS Structures with SiO<sub>x</sub> and Si<sub>x</sub>O<sub>y</sub>N<sub>z</sub> Films Containing Si Nanoclusters

he negative differential capacity has been observed in case of MIS structures with SiOx and SixOyNz films containing Si nanoclusters. It has been shown that existence of negative differential capacity depends on charge state of Si nanoclusters or electron traps in the insulating matrix. In case of SixOyNz films the two peaks have been revealed in C-V characteristics connected with Si nanoclusters and electron traps. The low-temperature annealing of SixOyNz films in hydrogen passivates the electron traps caused by Si dangling bonds and as a result the peak in C-V characteristics connected with electron traps disappears. The following low-temperature annealing in vacuum caused the some effusion of hydrogen from the film and appearance of electron traps and connected with them capacity shoulder on C-V characteristics. It has been shown, that the frequency and temperature dependences of the negative differential capacitance in C-V curves can be successfully used for the determination of nanoclusters and traps parameters for the samples with the nanoclusters embedded in SiO2 or SixOyNz films.

The effect of low temperature thermal annealing on the magnetic properties of Heusler Ni–Mn–Sn melt-spun ribbons

We report the effect of low temperature vacuum annealing (823K; 550°C) on the elemental chemical composition, structural phase transition temperatures, phase structure, and magnetic properties of Ni50.6Mn36.3Sn13.1 as-solidified ribbons. Their elemental chemical composition, highly oriented columnar-like microstructure and single-phase character (L21-type crystal structure for austenite) remain unchanged after this low temperature annealing. Annealed ribbons show a reduction of interatomic distances which lead to a small change in the characteristic phase transition temperatures (~3–6K) but to a significant rise of ~73 and 63% in the saturation magnetization of the martensite and austenite phases, respectively, that can be strictly ascribed to the strengthening of ferromagnetic interactions due to the change in interatomic distances.

磁控溅射工艺引起硅表面超薄钝化层电子结构变化

During fabrication of TCO/SiO x /n-Si (SIS) photovoltaic devices, deposition of TCO films by sputtering damages the electronic structure of the SiO x /c-Si interface, leading to higher interface recombination rate and lower open circuit voltage of the obtained photovoltaic device. Enhancing the interface recombination rate is equivalent to decreasing the diffusion length in the bulk and reducing the short circuit current. It is obvious that damage to the interface can seriously affect the overall performance of the device. Usually, researchers are only concerned with the effect of passivation before TCO film deposition by sputtering, or with the overall performance of the fabricated device; thus, the damage incurred by sputtering during device fabrication is often overlooked. The damage incurred by sputtering on the efficient silicon-based heterojunction solar cells, especially the SIS devices, is rarely considered. In this letter, we report the investigations of the damage incurred by the energetic particle beams in the plasma (atoms/ions and UV glow) on the atomic bonding and electronic states in both ultra-thin silicon oxides and SiO x (1.5-2.0 nm)/c-Si(150 μm) samples interface. The analysis was performed by using vacuum thermal annealing, effective minority carrier lifetime measurements (by using μ-PCD), and surface X-ray photoemission spectroscopy (XPS). The damage was observed in the process of magnetron sputtering deposition of the ITO thin film. We also investigated the effective passivation function of the ITO thin films silicon surface. The results show that the samples lifetime was reduced by more than 90% (from 105 μs to 5 μs) after the sputtering deposition of the ITO thin film. However, vacuum annealing at 100-400°C for 30 min partially eliminated the damage to the SiO x /c-Si interface and improved the passivation effect of the thin oxide layer on the crystalline silicon. Vacuum annealing at 200°C for 30 min restored the lifetime to nearly 30 μs; this annealing temperature corresponds to the typical temperature for the preparation processes of most efficient crystalline silicon heterojunction photovoltaic devices. However, vacuum annealing at 500-700°C for 30 min yielded a lifetime of about 3 μs. The analysis performed by comparing the results of XPS depth profiling revealed that the gaseous unstable material SiO is generated at the SiO x /c-Si interface under this annealing condition, which damages the SiO x /c-Si interface and augments the unsaturated bond silicon oxide SiO x (0 x <2), increasing the density of interface states, resulting in the lifetime attenuation. Therefore, low-temperature vacuum annealing can partially reduce the sputtering-induced structural damage, which prompts studying the effects of magnetron sputtering damage, and is also helpful for constructing the SIS photovoltaic devices and improving their performance.

Magnetomigration in granular Co-Cu films

The effect of an applied dc inhomogeneous magnetic field on the structure and the composition of granular Co-Cu films is studied during their deposition by an ion-plasma method and during low-temperature vacuum annealing. Magnetomigration, which consists in the oppositely directed mass transfer of paramagnetic and diamagnetic phases, is detected in both cases. The magnetomigration effect is clearly detected at a temperature of 200–220°C and an applied magnetic field of 500–550 Oe due to a fine-grained structure of the films and, correspondingly, a high granular medium mobility.

Oxidation states of GaAs surface and their effects on neutral beam etching during nanopillar fabrication

We have investigated a new process for fabricating GaAs sub-20 nm nanopillars that uses a top–down combination of a bio-template and damage-free neutral beam etching. A two-dimensional array of nanoparticles composed of a protein shell embedded with a metal oxide core was formed on the top of a GaAs surface treated by neutral beam oxidation. Because of device requirements, three low-temperature oxygen techniques were investigated for removing the protein shell prior to the etching process: oxygen radical, oxygen neutral beam, and low-temperature oxygen annealing in vacuum (LT-OAV). X-ray photoelectron spectroscopy was used to monitor the effects of the different treatments on the GaAs surface. While the three processes could efficiently remove a protein shell, subsequent oxidation of the GaAs surface showed some differences in the oxide layer composition. Therefore, LT-OAV was selected considering its lower gallium oxide formation. A hydrogen radical process was then performed at temperatures lower than 400 °C to remove the oxide layer prior to etching. This process completely removed arsenide oxide and only residual gallium oxide was found on the surface afterwards. Etching was performed using a pure chlorine neutral beam of GaAs samples with metal oxide core etching masks. We found that control of the Ga-oxide amount on the surface is the key parameter for controlling the diameter and the density of nanopillars. Finally, high-aspect ratio nanopillars using stacked layers of GaAs and AlGaAs were obtained and showed no damage layer.

Effects of annealing process on characteristics of fully transparent zinc tin oxide thin-film transistor

Annealing effect on the performance of fully transparent thin-film transistor (TTFT), in which zinc tin oxide (ZnSnO) is used as the channel material and SiO2 as the gate insulator, is investigated. The ZnSnO active layer is deposited by radio frequency magnetron sputtering while a SiO2 gate insulator is formed by plasma-enhanced chemical vapor deposition. The saturation field-effect mobility and on/off ratio of the TTFT are improved by low temperature annealing in vacuum. Maximum saturation field-effect mobility and on/off ratio of 56.2 cm2/(V·s) and 3 × 105 are obtained, respectively. The transfer characteristics of the ZnSnO TFT are simulated using an analytical model and good agreement between measured and the calculated transfer characteristics is demonstrated.

Enhanced Performance of CdS Quantum Dot Sensitized Solar Cells by Low Temperature Vacuum Annealing

Enhanced Performance of CdS Quantum Dot Sensitized Solar Cells by Low Temperature Vacuum Annealing

Effects of vacuum annealing on the optical and electrical properties of p-type copper-oxide thin-film transistors

We have investigated the effects of vacuum annealing on the optical and electrical properties of the p-type copper-oxide thin-film transistors (TFTs). The vacuum annealing of the copper-oxide thin-film was performed using the RF magnetron sputter at various temperatures. From the x-ray diffraction and UV-vis spectroscopy, it is demonstrated that the high-temperature vacuum annealing reduces the copper-oxide phase from CuO to Cu2O, and increases the optical transmittance in the visible part of the spectrum. The fabricated copper-oxide TFT does not exhibit the switching behavior under low-temperature vacuum annealing conditions. However, as the annealing temperature increases, the drain current begins to be modulated by a gate voltage, and the TFT exhibits a high current on–off ratio over 104 as the vacuum annealing temperature increases over 450 °C. These results show that the vacuum annealing process can be an effective method of simultaneously improving the optical and electrical performances in p-type copper-oxide TFTs.

EFFECT OF LOW-TEMPERATURE VACUUM ANNEALING ON THE MAGNETIC PULSED AMORPHOUS Fe 52 Co 34 Hf 7 B 6 Cu 1 ALLOY

The nanocrystalline Fe52Co34Hf7B6Cu1 soft magnatic alloys composed of bcc-Fe nanocrystals embedded in a residual amorphous matrix were obtained by the magneto-crystallization of melt-spun ribbons. In order to improve the soft magnetic properties of double-phase Fe(Co)-based nanocrystalline alloy, the nanocrystalline alloy specimens were vacuum annealed for 30 min at 100, 200 and 300 . The results showed that the treatment of magnetic pulsing on the amorphous alloy resulted in the nanocrystallization, the grain size of precipitated α-Fe(Co) nanocrystallized phase was 5—10 nm. The low-temperature vacuum annealing of magnetic pulsed specimens further improved the soft magnetic properties of nanocrystalline alloy. The influence of annealing at 100 for 30 min on the properties is most obvious.