TiO2 Thin Films Obtained via Two-Phase Dip-Coating: Impact on Surface Roughness and Application to Heterostructures.

Titanium dioxide (TiO2) thin films were deposited by remote‐plasma atomic layer deposition (RPALD). The process window was determined in the range from 150 to 300 °C for atomic layer deposition of TiO2 thin film. The crystal structure and grain size of the TiO2 thin films deposited by RPALD was controlled via the variations of the deposition temperature and post‐deposition thermal annealing. The as‐deposited TiO2 thin film grown at 150 °C was amorphous whereas the TiO2 thin films grown above 200 °C were polycrystalline, consisting of anatase phase. As the deposition temperature increased, the grain size of the anatase phase progressively decreased. Meanwhile, when annealed at 900 °C, the amorphous TiO2 thin film deposited at 150 °C crystallized into anatase structure. The film deposited at 200 °C retained the anatase structure up to 900 °C while incurring minimal grain growth. However, the post‐annealed TiO2 thin films deposited at 250 and 300 °C partially transformed to the rutile structure, resulting in a mixture of anatase and rutile phases. It is speculated that the relatively large grain size of the films deposited below 200 °C likely suppressed the anatase → rutile transformation during annealing as the reduction of total fraction of grains boundaries, which acted as primary nucleation sites for the rutile transition, delayed the anatase → rutile transformation.

In this study, we deposited TiO2 thin films onto borosilicate glass by ultrasonic spray pyrolysis at 350 and 450 °C. The aim of study is to determine the effect of deposition temperature on photocatalytic activity of TiO2 thin films and to investigate the performance of TiO2 thin films on photocatalytic degradation of methyl tert-butyl ether (MTBE), acetone, acetaldehyde, and heptane as functions of different operating parameters. TiO2 thin films deposited at 350 and 450 °C have a thickness value of 190 and 330 nm, respectively. All as-prepared TiO2 films possess an anatase crystalline structure. According to the X-ray photon spectroscopy (XPS) study, the TiO2 thin film deposited at 350 °C showed a higher amount of oxygen vacancies and hydroxyl groups on the film surface after UV treatment. The aged-TiO2 thin film deposited at 350 °C showed a water contact angle (WCA) value of 0° after 10 min UV irradiation, showing superhydrophilic surface behavior. The TiO2 film deposited at 350 °C exhibited the highest amount of conversion of MTBE (100%). The results also showed that TiO2 films are capable of photocatalytic degradation of MTBE (100%) and acetaldehyde (approx. 80%) in humid air conditions and high airflow rate. The visible-light-activity of TiO2 thin films was tested with 5 ppm MTBE and acetone. TiO2 thin films deposited at 350 °C with a surface area of 600 cm2 showed 60% of MTBE and 33% of acetone degradation under VIS light.

Evolution of damage fraction due to dense ionizing irradiation on TiO2 film

Extrusion-based 3D printing (E3DP) is a popular additive manufacturing technique known for its versatility in creating prototypes and functional parts. However, achieving high surface quality has posed challenges regarding accuracy and finish. To address this issue, this study aims to enhance the surface quality of E3DP components fabricated by the fused filament fabrication (FFF) method and polylactic acid (PLA) material by applying neosanding postprocessing. The research investigates the impact of key neosanding process factors on surface roughness, namely neosanding spacing, neosanding speed, and flow rate. To ensure a comprehensive evaluation, each factor is examined at four levels, covering a wide range of values relevant to the neosanding process. Surface roughness is quantified using the average roughness parameter (Ra) and measured using both stylus profilometer and confocal profilometry methods. The results highlight a substantial decrease in surface roughness achieved through the neosanding method. At default factor levels of the neosanding method, the stylus profilometer method achieves an impressive 83% reduction in surface roughness, while the confocal profilometry method achieves an 80% reduction. Among the neosanding process factors, neosanding spacing significantly influences surface roughness values. Understanding and optimizing this factor is crucial for achieving desired surface quality in FFF-produced PLA parts. This study makes a valuable contribution to the field by optimizing surface roughness in FFF-produced PLA parts through neosanding postprocessing. By exploring the influence of neosanding tool factors and comparing measurement methods, manufacturers can enhance the surface quality of FFF-manufactured parts, paving the way for broader applications across various industries.

Rutile titanium oxide (TiO2) thin films require more energy to crystallize than the anatase phase of TiO2. It is a prime candidate for micro-optoelectronics and is usually obtained either by high substrate temperature, applying a substrate bias, pulsed gas flow to modify the pressure, or ex situ annealing. In the present work, we managed to obtain high enough energy at the substrate in order for the particles to form rutile TiO2 at room temperature without any intentional substrate bias in a continuous gas flow. The rutile TiO2 thin films were deposited by a reactive radiofrequency magnetron sputtering system from a titanium target, in an argon/oxygen gas mixture. Investigations regarding the film’s structure and morphology were performed by X-ray diffraction (XRD), X-ray reflectivity (XRR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX), while the optical properties were investigated by means of ellipsometry.

This study describes the DLyte dry electropolishing of heat- treated Ti6Al4V samples (vertical, horizontal and semi-sphere samples) produced by laser powder bed fusion technology. The Ti6Al4V samples were divided and build-in zones according to the Argon inlet and outlet as well as the start and end areas of the powder distribution within the building plate. The as-build Ti6Al4V samples were investigated for their suitability in medical bone implant applications and were found to have a surface roughness that exceeds the standards of a bone implant irrespective of the zone in which they are built. This necessitates additional post surface finishing procedures to achieve the desired surface finish for bone implants. DLyte dry electropolishing was employed for surface finishing to enhance the surface condition of Ti6Al4V as-build samples. The Ti6Al4V as-build samples were polished according to their zones in which they were build. The efficacy of polishing was assessed based on different time intervals (30, 60 and 120 minutes) and the decrease in surface roughness. The results show that after 30 minutes of polishing there was a lower reduction in surface roughness and the higher surface reduction was observed after 120 minutes of polishing. It was noted that as the polishing time increased, the surface become progressively smoother.

Oxygen Partial Pressure Dependence of the Properties of TiO2 Thin Films Deposited by DC Reactive Magnetron Sputtering

This paper reports a study on the photodetection properties of TiO2 thin film deposited on chemically textured p-Si substrate and is compared to those deposited on pristine p-Si substrate. The structural properties of both the heterostructures were investigated using XRD analysis. FESEM images confirmed the deposition of TiO2 thin film on chemically pyramidal textured Si substrate. The average total reflectance of the textured Si substrate was reached to ~ 7.6% in the wavelength range of 300–900 nm. It was further decreased to ~ 6.5% after the deposition of 55 nm thick TiO2 on the top of the textured Si substrate. A systematic study was carried out to correlate the structural, optical and electrical properties of both the heterostructures. The electrical parameters of the heterojunction diodes were measured and compared under dark and illuminated conditions using UV and solar simulated light. UV as well as visible light detection property of the heterostructure of TiO2 thin film deposited on pyramidal textured Si substrate was improved compared to the one deposited on pristine Si by the factor 2.0 and 1.86, respectively, under the bias of − 2 V.

The structural and electrical characteristics of Ba0.5Sr0.5TiO3 (BST) thin films deposited by inverted cylindrical magnetron rf sputtering have been investigated. This unconventional sputter deposition technique consisting of a hollow cylindrical composite target of BST, high argon/oxygen gas pressure 53.2 Pa (400 μm), and 750 °C substrate temperature was employed for depositing low-loss BST thin films. The films were postannealed in a tube furnace at 780 °C for 8 h in flowing oxygen. Atomic-force microscopy revealed anisotropic grain growth with a columnar grain structure protruding from the surface with a 0.25 μm grain size. X-ray diffractometry shows the films to be purely (h00) oriented for certain deposition parameters. The lattice parameter of the best film was slightly larger than that for bulk BST. Other deposition conditions yielded films having many of the BST powder peaks. Capacitance versus voltage characteristics have been measured from 50 MHz to 20 GHz. Device Q values >600, beyond the resolution of the device/measurement system, were realized with a 6.7% tunability at 10 GHz for the best films.

Group 4 metal oxides TiO2, ZrO2, and HfO2 were deposited on glass substrates at substrate temperatures ranging from 100 to 800 °C by reactive direct current magnetron sputtering using an Ar and O2 mixture as discharge gas. On the basis of the obtained cross-sectional and surface morphologies, crystallographic structures, and film properties, the homologous substrate-temperature dependence of the film structure and properties for the sputter-deposited metal oxide thin films are discussed. The x-ray diffraction measurements show the diffraction patterns characteristic of the anatase (tetragonal) structure at substrate temperatures below 400 °C and those of the rutile (tetragonal) structure at substrate temperatures above 600 °C for TiO2 thin films and the patterns attributable to the monoclinic structure with 〈−111〉 orientation for ZrO2 and HfO2 thin films. Scanning electron microscopy (SEM) observations show voided columnar structures with rough surfaces for TiO2 thin films and fine columnar structures with smooth surfaces for ZrO2 and HfO2 thin films, which is supported by the results obtained from atomic force microscopy (AFM) analysis. The quantitative data on the lattice strain, crystallite size, surface roughness, and refractive index are plotted against the homologous substrate temperature, Tsub/Tm (Tsub: substrate temperature and Tm: melting point of thin film materials). The lattice strain reaches approximately zero at Tsub/Tm = 0.3–0.35, suggesting that the residual stress is relaxed at this point, and the crystallite size reaches a plateau at the same range of Tsub/Tm. The surface roughness increases sharply after passing Tsub/Tm = 0.25–0.30, and the refractive index shows a rise at Tsub/Tm = 0.30–0.35. The images obtained by SEM and AFM are categorized based on the property transition observed in the quantitative property changes. The data obtained in this work are utilized to systematically study the effectiveness and appropriateness of the homologous (normalized) substrate temperature to explain the changes in structure, morphology, and properties of oxide thin films. Furthermore, it is suggested that the structure zone model, which is normally applied to sputtered metal films, is also applicable to sputtered oxide thin films.

Ionic liquid-mediated morphology and structure of CeO2 nanoparticles for silicon wafers ultra-precision chemical mechanical polishing applications

The influence of isotropically directed deposition flux on the formation of the thin film microstructure at low temperatures is studied. For this purpose we have deposited TiO2 thin films by two different deposition techniques: reactive magnetron sputtering, in two different experimental configurations, and plasma enhanced chemical vapor deposition. The obtained results indicate that films grown under conditions where deposition particles do not possess a clear directionality, and in the absence of a relevant plasma/film interaction, present similar refractive indices no matter the deposition technique employed. The film morphology is also similar and consists of a granular surface topography and a columnarlike structure in the bulk whose diameter increases almost linearly with the film thickness. The deposition has been simulated by means of a Monte Carlo model, taking into account the main processes during growth. The agreement between simulations and experimental results indicates that the obtained microstructures are a consequence of the incorporation of low-energy, isotropically directed, deposition particles.

Titanium dioxide (TiO2) has been exploited extensively as it shows remarkable performance in photocatalytic applications. TiO2 thin films can be deposited onto window glass which is workable for self-cleaning applications. In this article, we have studied the role of substrate temperature for spray pyrolysis (SP) of TiO2 thin films for studying self-cleaning applications. For thin film deposition, TiO2 sol is prepared by the sol-gel synthesis technique. The samples are deposited at room temperature and 250 °C, respectively. The samples are characterized via Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and UV-Vis spectroscopy to determine the morphology, surface roughness, and optical properties of the thin films. SEM and AFM results show that samples deposited at 250 °C (pre-heated samples) have uniform size distribution, and defined grain boundaries, respectively. The results also show that the pre-heated sample is highly transparent in the visible region of the solar spectrum when analyzed by the steady-state UV-Vis spectrophotometer. The wettability of the prepared thin films is measured, and the results show that the pre-heated sample shows a hydrophilic character. The self-cleaning property of prepared thin films is evaluated by the photodegradation of Rhodamine B dye. It is observed that the pre-heated substrates show better photoactivity in presence of UV light irradiation. Hence, due to their hydrophilic nature and better photoactivity, these pre-heated thin films deposited by spray pyrolysis can be employed as efficient coatings for self-cleaning glass applications.

Effect of multi stage abrasive slurry jet polishing on surface generation in glass

TiO2 thin films with an inverse opal-like structure have attracted considerable attention recently owing to their high potential for a range of applications. In this study, we demonstrated the possibility to deposit TiO2 thin films with an inverse opal-like structure from TiO2 nanoparticle-based slurry paste using a conventional spin-coating process. In addition, we also showed that the photoelectrochemical (PEC) performance of as-fabricated inverse opal-like TiO2 films can be further improved by the dip-coating process. In particular, dip-coated and untreated inverse opal-like TiO2 films exhibit photocurrent densities of ∼66.5 μA cm−2 and ∼40.9 μA cm−2 at 1.23 V versus RHE, respectively. A detailed physicochemical analysis revealed that photocurrent density enhancement (∼38.5%) in dip-coated inverse opal-like films can be attributed to a variety of factors including improved interconnection between TiO2 nanoparticles, higher crystallinity, decreased light reflection, and reduced charge carriers recombination. We strongly believe that these findings will be useful in the development of highly efficient third-generation solar cells, photocatalytic systems, electrochromic devices, and gas sensors.