Post Annealing In Vacuum Research Articles

Selective Laser Melting Additive Manufactured Tantalum: Effect of Microstructure and Impurities on the Strengthening-Toughing Mechanism.

The balance between the strength and the toughness of pure tantalum (Ta) fabricated with selective laser melting (SLM) additive manufacturing is a major challenge due to the defect generation and affinity for oxygen and nitrogen. This study investigated the effects of energy density and post-vacuum annealing on the relative density and microstructure of SLMed tantalum. The influences of microstructure and impurities on strength and toughness were mainly analyzed. The results indicated that the toughness of SLMed tantalum significantly increased due to a reduction in pore defects and oxygen-nitrogen impurities, with energy density decreasing from 342 J/mm3 to 190 J/mm3. The oxygen impurities mainly stemmed from the gas inclusions of tantalum powders, while nitrogen impurities were mainly from the chemical reaction between the molten liquid tantalum and nitrogen in the atmosphere. The proportion of <110> texture decreased after vacuum-annealing at 1200 °C, while that of the <100> texture increased. Concurrently, the density of dislocations and small-angle grain boundaries significantly decreased while the resistance of the deformation dislocation slip was significantly reduced, enhancing the fractured elongation up to 28% at the expense of 14% tensile strength.

Revival of Smooth MgO(100) Surface: Ar Ion‐Beam Milling and Postvacuum Annealing in Oxygen Atmosphere

A recreation procedure for achieving the smooth and clean surface morphology of the degraded MgO(100) substrates is presented. The surfaces of the degraded MgO(100) substrates are treated with Ar ion‐beam milling (IBM) and annealing in O2 atmosphere. After each treatment, the changes in the MgO(100) substrate surface morphology are characterized using X‐ray diffraction (XRD), a 3D optical profilometer, atomic force microscopy, and Fourier‐transform infrared (FTIR) spectroscopy and compared with a fresh MgO substrate. It is shown that before any treatment, XRD and FTIR spectra show peaks corresponding to hydroxyl and carbonate groups in the degraded samples, whereas after treatment, XRD and FTIR spectra are comparable with the fresh sample. Further, after treatment, the surface roughness Rav value for two used/degraded samples reduces from 129 and 186 nm to 3.96 and 7.91 nm, respectively, after combined Ar IBM and annealing treatment. It is shown that the surface quality of the treated MgO(100) substrate improves in comparison with as it was before any treatment and can be reused for the good quality thin‐film deposition.

Influence of Reactive Oxygen Gas on Sputtered-Vanadium Oxide Films under Post-Annealing in Vacuum

Vanadium oxide thin films were deposited on glass substrates by O2 reactive-RF magnetron sputtering from a vanadium (V) target without substrate-heating. The percentages of O2 gas were 10%, 7.5%, 6.0%, 5.0% and 2.5%. The total gas flow rate (O2/Ar) was kept at 25 sccm. As-deposited films were experienced post-annealing process at different temperatures and times. The crystallinity and chemical bonding states of films were examined by X-ray diffraction and Raman spectroscopy. The condition in annealing to active crystallinity depended on an earlier composition of the films. As O2-gas percentages were 10% and 7.5%, after annealing, the as-deposited VxOy films were transformed into crystalline V2O5 films. With decreasing in O2 percentage to 5.0% and 2.5%, the films were transformed into V2O3 and VO films, respectively. The films deposited with 6.0% O2 were crystallized to VO2 with phase B after annealing with 500 °C 15 h. By applying a longer time to 30 h at the high temperature 500 °C in annealing, VO2 films revealed only phase M formation.

Improved Negative Bias Stress Stability of IZO Thin Film Transistors via Post-Vacuum Annealing of Solution Method

Post-vacuum-annealed amorphous indium zinc oxide (a-IZO) nanostructure thin-film transistors (TFTs) were fabricated by a simple solution-based method. The number of oxygen-related defects in the IZO films was reduced by post-vacuum annealing, as revealed by X-ray photoelectron spectroscopy results. The refractive index studies of as-prepared films indicate the reduced film surface porosity. With the optimal post-vacuum treatment temperature of 250°C, the field-effect mobility and subthreshold slope (S) of TFTs (2.81 cm2/V s and 0.72 V/dec, respectively) improved compared to those of as-prepared IZO TFTs (0.38 cm2/V s and 3.79 V/dec, respectively). The negative bias stress tests of the vacuum-annealed devices was enhanced relatively high electrical stability due to fewer oxygen deficiencies in the IZO films.

Mechanism of the performance improvement of TiO2-x-based field-effect transistor using SiO2 as gate insulator

RF magnetron sputtered titanium oxide (TiO2-x) thin films were used as active channel layer to fabricate field-effect transistors (FETs). In the as-prepared FETs, poor FET performance was found, with a low on-to-off current ratio of ∼500 and a high sub-threshold slope. It is attributed the existence of Si-O-Ti cross-linking bonding at TiO2-x/SiO2 interface, which was probed by X-ray Photoelectron Spectroscopy (XPS) measurement. A remark improvement of sub-threshold slope and on-to-off current ratio was observed due to post annealing in vacuum at 300 °C for 30min. By using the electron energy loss spectroscope (EELS) analysis, oxidization of TiO2-x layer closing to SiO2 layer region was found, suggesting that Si-O-Ti cross-linking bonding at TiO2-x/SiO2 interface breaks due to post annealing treatment.

Effect of GZO thickness and annealing temperature on the structural, electrical and optical properties of GZO/Ag/GZO sandwich films

The GZO/Ag/GZO sandwich films were deposited on glass substrates by RF magnetron sputtering of Ga-doped ZnO (GZO) and ion-beam sputtering of Ag at room temperature. The effect of GZO thickness and annealing temperature on the structural, electrical and optical properties of these sandwich films was investigated. The microstructures of the films were studied by X-ray diffraction (XRD). X-ray diffraction measurements indicate that the GZO layers in the sandwich films are polycrystalline with the ZnO hexagonal structure and have a preferred orientation with the c-axis perpendicular to the substrates. For the sandwich film with upper and under GZO thickness of 40 and 30 nm, respectively, it owns the maximum figure of merit of 5.3 × 10 −2 Ω −1 with a resistivity of 5.6 × 10 −5 Ω cm and an average transmittance of 90.7%. The electrical property of the sandwich films is improved by post annealing in vacuum. Comparing with the as-deposited sandwich film, the film annealed in vacuum has a remarkable 42.8% decrease in resistivity. The sandwich film annealed at the temperature of 350 °C in vacuum shows a sheet resistance of 5 Ω/sq and a transmittance of 92.7%, and the figure of merit achieved is 9.3 × 10 −2 Ω −1.

The properties of ZnO/Cu/ZnO multilayer films before and after annealing in the different atmosphere

ZnO/Cu/ZnO multilayers were prepared on glass substrates by simultaneous RF magnetron sputtering of ZnO and dc magnetron sputtering of Cu. The influence of post growth annealing on the structural, electrical and optical properties of the multilayer was investigated. The experimental results show that the properties of the multilayers are improved with post annealing in vacuum and deteoriated in air, nitrogen or oxygen atmospheres. X-ray diffraction measurement indicated that the multilayers are c-axis oriented similar to ZnO wurzite structure. The multilayers heat treated up to 200 °C under vacuum maintained a transmittance over 85% and sheet resistance about 9.46 Ω/sq which further increases with increase of the annealing temperature.

FePt Patterned Media Fabricated by Deep UV Lithography Followed by Sputtering or PLD

Continuous and patterned FePt films (40 nm) were fabricated on silicon (100) substrates using deep ultraviolet lithography with the wavelength of 248 nm followed by sputter deposition or pulsed laser deposition at room temperature, liftoff, and postannealing in vacuum. The structures and magnetic properties of the films were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, scanning electron microscopy, and alternating gradient force magnetometry. A buffer layer of Ag or MgO was inserted between the Si substrate and FePt to prevent a chemical reaction between Si and FePt. The phase transformation from face-centered cubic to face-centered tetragonal started after annealing at 400 degC for continuous films, while for the patterned FePt films, phase formation was retarded. High coercivities of 10-15 kOe have shown potential in hard magnetic applications. The effects of Ag and MgO top layers on the coercivities were also investigated

Electron field emission from TiO2 nanotube arrays synthesized by hydrothermal reaction

Conductive TiO2 nanotube arrays were grown on metal Ti substrates by hydrothermal reaction and subsequent postannealing in vacuum. The nanotubes were vertically grown and adhered well to the substrates. The crystal structure of the postannealed TiO2 nanotubes was identified to be oxygen-defective anatase. The nanotube arrays exhibited efficient electron field emission even at room temperature with rather low turn-on fields ∼280V per electrode distance of 100μm. The emission current density exceeded 0.15mA∕cm2 at an extraction voltage of 800V. The emission current was reproducible and stable in the lower voltage (&amp;lt;800V) region.

XAS characterization of growth parameter effects for pulsed laser deposited CoxTi1−xO2−δ films

Films of cobalt-doped titanium dioxide (CoxTi1−xO2−δ) can be stabilized in the thermodynamically unfavorable anatase phase if they are grown on appropriate substrates. We performed X-ray Absorption Spectroscopy (XAS) measurements at the oxygen, titanium, and cobalt edges of PLD grown samples. Our data shows the success of this substrate-induced stabilization of the anatase phase occurs only at elevated temperatures (∼ 700 °C or more) and elevated oxygen partial pressures (∼ 1 × 10−5 Torr or more). The effects of post annealing in vacuum are also considered.

Hydrogen and deuterium incorporation and transport in hafnium-based dielectric films on silicon

Hydrogen and deuterium incorporation into nitrided and non-nitrided hafnium silicate films on Si during thermal annealing in H1- and H2-containing atmospheres was investigated. H1 profiling was accessed by means of nuclear resonant reaction profiling, whereas H2 incorporation was quantified by nuclear reaction analysis. The effects of preannealing in different atmospheres and temperatures were determined, as well as the losses of H1 and H2 from these structures during postannealing in vacuum. The results reveal a rather uniform depth distribution of incorporated H1, in striking contrast with previous studies on hydrogen in silicon oxide and oxynitrides and hafnium oxide films on Si. These results are discussed in terms of the defects present in each one of the structures studied here.

In situ formation of titanium carbide in titanium powder compacts by gas–solid reaction

Porous titanium compacts of fine and coarse sponge titanium powders were reacted with methane gas to produce Ti–TiC in situ composites. The kinetics of titanium carbide formation during the reaction were studied in relation to powder size, reaction temperature and time, and methane flow rate. The titanium carbide was initially formed as a layer around each titanium powder and the rate of formation was found to be diffusion-controlled. Titanium hydride was also formed during the reaction but was easily removed by post-vacuum annealing. A significant reduction of chlorine content in the compact also resulted during the processing. High temperature vacuum sintering could densify the reacted compacts to over 95% theoretical density and, at the same time, alter the layered titanium carbide phase into rounded particles. It was possible to produce fully dense titanium base composites containing up to 30 vol% by the present gas–solid reaction-based processing.

Growth of EuCuO thin films on YSZ (100) substrates

Eu 2CuO 4 (ECO) thin films have been grown epitaxially on Y-stabilized ZrO 2 (YSZ) (100) substrates by magnetron rf sputtering method. The obtained ECO films are highly c-axis oriented and well crystallized, as shown by x-ray diffraction, rocking curves. The initial growth stage of ECO on YSZ was studied by AFM. An island growth mode was suggested. The changes in the c-axis length and the resistance behavior were studied on the films treated by post vacuum annealing. The post vacuum annealing removes the excess oxygen from the structure and reduces the c-axis length. As a result, the resistance of the films increases accordingly.

Hydrogen embrittlement of titanium during microwave plasma assisted CVD diamond deposition

During diamond deposition on a titanium substrate using a gas mixture of H2–CH4 (196 : 4), hydrogen easily diffused into the substrate and led to significant microstructural coarsening and a severe loss in Charpy impact energy. In order to prevent the rapid diffusion of hydrogen into the substrate during diamond deposition, three techniques were studied. The first method was to use a post-vacuum annealing treatment to achieve dehydrogenation of a diamond coated titanium specimen. However, the Charpy impact energy could not be restored significantly even after a few hours of annealing. The second method was to apply a barrier interlayer between the diamond coating and titanium substrate. Results showed that even though the sputtered TiN coating and plasma nitrided layer could prevent the rapid diffusion of hydrogen and carbon into the titanium substrate, the deposited diamond coatings had poor adhesion to the substrate. A graded interlayer produced by plasma nitriding followed by plasma carbonitriding was effective in preventing the rapid diffusion of hydrogen and also improving the nucleation rate and adhesion of the diamond coating. The third method was to use a gas mixture of Ar–H2–CH4 instead of the conventional H2–CH4 . With the use of an Ar–H2–CH4 (180 : 16 : 4) mixture, a smooth and nanocrystalline diamond coating was deposited, and there was little change in the substrate microstructure or Charpy impact energy after diamond deposition.

Preparation and Characterization of Tin Oxide Films by Ion-Assisted Deposition

AbstractUndoped tin oxide films were grown on Si substrates by a reactive ion-assisted deposition technique in which oxygen ions were irradiated on depositing Sn particles. In order to investigate the oxidation from SnO to SnO2, the effects of initial oxygen contents and heat treatment on the final crystalline structure of tin oxide films were thoroughly examined. Oxygen to Sn metal ratio (No/Nsn) of as-deposited films were controlled from 1.1 to 1.9 by varying the relative arrival ratio (F) of oxygen ion to Sn particle from 0.025 to 0.1. Heat treatment was carried out in two different ways; one was post vacuum-annealing at 400 ∼ 600°C and the other was in-situ annealing 400 ∼ 500°C. Crystalline structure of as-deposited tin oxide films at room temperature was amorphous. After post-annealing at 400°C, only SnO phase was found below No/Nsn= 1.6 in x-ray diffraction and crystalline structure of the films comprising higher oxygen contents still appeared to be amorphous. Even though the films still showed SnO phase until Γ50 after 500°C post-annealing, however, mixed structures of SnO, SnO2, and intermediate Sn2O3/Sn3O4 were observed for the films Γ75 and Γ100 with higher oxygen contents. At 600°C annealing, perfect SnO2 phase was attained for the films having No/Nsn=1.9. On the other hand, pure polycrystalline SnO2 films could be obtained by in-situ annealing at low temperature. The values of No/Nsn and the chemical shifts with the variation of oxidation were carefully determined by the comparison of Sn MNN and O KLL Auger transitions. Surface microstructure of deposited films was also analyzed using a scanning electron microscopy (SEM) and an atomic force microscope (AFM).

Characterization of ceramic films and interfaces by electron microscopic and spectroscopic techniques

An understanding of the microstructural and chemical nature of thin films and film-substrate interfaces is of growing interest and importance. Of critical interest is the determination of the mechanisms for interfacial bonding and how it is affected by deposition methodology and conditions. In this study, Auger electron spectroscopy, in combination with inert-gas ion-milling and cross-sectional transmission electron microscopy, was employed to investigate the chemical and microstructural characteristics of a TiN film on an M50 steel substrate and the film-substrate interfaces formed during ion-plating at 100 and 500°C deposition temperatures. The results of both analytical technique indicated that the coating produced at 100°C was composed of a thin Ti layer (approximately 100 Å) and a thick TiN layer. Upon vacuum annealing at 500 ° C for 45 min, the Ti-rich interlayer was transformed into a TiC phase. The coating produced at 500°C consisted of a thin TiC layer and a relatively thick TiN layer. Ion-plating as well as post-vacuum annealing at 500°C resulted in grain growth and reduced defect density.