Bilayer period effect on corrosion-erosion resistance for [TiN/AlTiN]n multilayered growth on AISI 1045 steel

The aim of this work is to study the electrochemical behavior, under a corrosion-erosion condition, of [TiN/AlTiN]_n multilayer coatings with bilayers periods of 1, 6, 12 and 24, deposited by a magnetron sputtering technique on Si (1 0 0) and AISI 1045 steel substrates.The TiN and AlTiN structure for multilayer coatings were evaluated via X-ray diffraction (XRD) analysis. Silica particles were used as an abrasive in the corrosion-erosion test within a 0.5 M H₂SO₄ solution at an impact angle of 30° over the surface. The electrochemical characterization was carried out using a polarization resistance technique (Tafel), in order to observe changes in the corrosion rate as a function of the bilayers number (n) or bilayer period (Λ). Corrosion rate values of 359 mpy in uncoated steel substrate and 1.016×10⁻⁶ mpy for substrate coated with [TiN/AlTiN]₂₄ under impact angle of 30° were found. This behavior was related with the mass loss curve for all coatings and the surface damage was analyzed using SEM images. These results indicate that TiN/AlTiN multilayer coatings deposited on AISI 1045 steel provide a practical solution for applications in erosive-corrosive environments.     

In vitro investigation of anodization and CaP deposited titanium surface using MG63 osteoblast-like cells

The aim of the present study was to investigate surface characteristics in four different titanium surfaces (AN: anodized at 270 V; AN-CaP: anodic oxidation and CaP deposited; SLA: sandblasted and acid etched; MA: machined) and to evaluate biological behaviors such as cell adhesion, cell proliferation, cytoskeletal organization, and osteogenic protein expression of MG63 osteoblast-like cells at the early stage. Surface analysis was performed using scanning electron microscopy, thin-film X-ray diffractometry, and a confocal laser scanning microscope. In order to evaluate cellular responses, MG63 osteoblast-like cells were used. The cell viability was evaluated by MTT assay. Immunofluorescent analyses of actin, type I collagen, osteonectin and osteocalcin were performed. The anodized and CaP deposited specimen showed homogeneously distributed CaP particles around micropores and exhibited anatase type oxides, titanium, and HA crystalline structures. This experiment suggests that CaP particles on the anodic oxidation surface affect cellular attachment and spreading. When designing an in vitro biological study for CaP coated titanium, it must be taken into account that preincubation in medium prior to cell seeding and the cell culture medium may affect the CaP coatings. All these observations illustrate the importance of the experimental conditions and the physicochemical parameters of the CaP coating.It is considered that further evaluations such as long-term in vitro cellular assays and in vivo experiments should be necessary to figure out the effect of CaP deposition to biological responses.     

Microstructure and tribological behavior of pulsed laser deposited a-CNx films

The a-CN_x films were deposited onto high-speed steel substrate by pulsed laser deposition at different nitrogen pressures. The tribological properties of the films in humid air and in vacuum were investigated using a ball-on-disk tribometer under various loads. The composition, microstructure and morphology of the films, wear tracks and paired balls were characterized by energy dispersive X-ray analysis (EDXA), X-ray photoelectron spectrum (XPS), Raman spectroscopy and scanning electron microscopy (SEM). With increasing the deposition pressure, the fraction of sp³ C bond reduces, the fraction of trapped nitrogen increases and the friction coefficient of the films declines both in humid air and vacuum. The friction coefficient of a-CN_x film decreases with increasing normal load. The tribological performances of the films in humid air are better than those of in vacuum. A transferred graphite-like tribo-layer is observed from a-CN_x film to the paired ball for both environments.     

Growth of SiO2 on InP substrate by liquid phase deposition

We have grown silicon dioxide (SiO₂) on indium phosphorous (InP) substrate by liquid phase deposition (LPD) method. With inserting InP wafer in the treatment solution composed of SiO₂ saturated hydrofluorosilicic acid (H₂SiF₆), 0.1 M boric acid (H₃BO₃) and 1.74 M diluted hydrochloric acid (HCl), the maximum deposition rate and refractive index for the as-grown LPD-SiO₂ film were about 187.5 Å/h and 1.495 under the constant growth temperature of 40 °C. The secondary ion mass spectroscope (SIMS) and energy dispersive X-ray (EDX) confirmed that the elements of silicon, oxygen, and chloride were found in the as-grown LPD-SiO₂ film. On the other hand, the effects of treatment solution incorporated with the hydrogen peroxide (H₂O₂) that can regulate the concentration of OH⁻ ion were also shown in this article. The experimental results represented that the deposition rate decreases with increasing the concentration of hydrogen peroxide due to the reduced concentration of SiO₂ saturated H₂SiF₆ in treatment solution.     

Synthesis of SnS thin films via galvanostatic electrodeposition and fabrication of CdS/SnS heterostructure for photovoltaic applications

In this work SnS thin films were electrochemically deposited on ITO coated glass substrate by galvanostatic electrodeposition at different pH of the plating bath. The working electrode used in these studies was low cost high purity graphite rod. The as-deposited films were found to be smooth, pinhole free and well adherent to the substrate with no powdery deposition. EDX measurements revealed that all the SnS films were non-stoichiometric in nature with variation from Sn-excess to S-excess compositions. XRD pattern showed that all the SnS thin films had orthorhombic polycrystalline structure. The direct bandgaps of all the films were found to be in the range 1.54-1.58 eV. ITO/SnS/In structure exhibited linear current-voltage characteristics, establishing the ohmic nature of both ITO/SnS and SnS/In junctions. Furthermore, SnS layer was grown on CdS film using electrodeposition technique. The heterostructure ITO/CdS/SnS/In was characterized under dark and illuminated conditions. From forward biased I-V characteristics several junction parameters like barrier height, diode ideality factor and series resistance of the heterostructure were extracted using Cheung model.     

Structure evolution and stoichiometry control of Pb(Zr, Ti)O3 thick films fabricated by electrospray assisted vapour deposition

Well-crystallized and stoichiometric Pb(Zr, Ti)O₃ (PZT) films, typically ∼5 μm thick, with pure perovskite-type rhombohedral structures have been successfully prepared via an electrospray assisted vapour deposition (ESAVD) method. Control of the deposition temperature within a narrow range of 300-400 °C resulted in films with the most desirable phases. PZT films with close stoichiometric match with the expected composition ratio and uniform element distribution were obtained by adding the appropriate levels of excess Pb in the precursor solutions. The annealed films were uniform, dense, compact and adherent to the substrates. The dielectric constant, ?_r, and loss tangent, tan δ, of the fabricated PZT films measured at 10 kHz were 442 and 0.09, respectively. The ESAVD deposited PZT films showed a remanent polarization, P_r, of 15.3 μC/cm² and coercive field, E_c, of 86.7 kV/cm. These results demonstrate the clear potential of the ESAVD method as a promising technique for the fabrication of thick PZT films.     

Aligned synthesis of multi-walled carbon nanotubes with high purity by aerosol assisted chemical vapor deposition: Effect of water vapor

Aligned multi-walled carbon nanotubes (MWCNTs) with high purity and bulk yield were achieved on a silicon substrate by an aerosol-assisted chemical vapor deposition. The introduction of specific amounts of water vapor played a key role in in situ controlling the purity and surface defects of the nanotubes. The morphology, surface quality and structure of MWCNTs were characterized by secondary and backscattered electron imaging in a field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). Crystallinity and defects of the MWCNTs’ were investigated by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. In this work, water vapor was found to provide a weak oxidative environment, which enhanced and purified the MWCNTs’ growth. However, excessive water vapor would inhibit the MWCNTs growth with a poor surface quality. In addition, it has been found that the surface morphology of the CNTs can be modified intentionally through producing some surface defects by tuning the amount of the water vapor, which may offer more nucleation sites on the chemically inert CNT surface for various applications such as catalyst support.     

Reflection absorption infrared spectroscopy during atomic layer deposition of HfO2 films from tetrakis(ethylmethylamido)hafnium and water

Tetrakis(ethylmethylamido)hafnium and water are commonly used precursors for atomic layer deposition of HfO₂. Using reflection absorption infrared spectroscopy with a buried-metal-layer substrate, we probe surface species present during typical deposition conditions. We observe evidence for thermal decomposition of alkylamido ligands at 320 °C. Additionally, we find that complete saturation of the SiO₂ substrate occurs in the first cycle at ≈100 °C whereas incomplete coverage is apparent even after many cycles at higher temperatures. The use of this technique as an in situ diagnostic useful for process optimization is demonstrated.     

Multilayer growth of BaTiO3 thin films via pulsed laser deposition: An energy-dependent kinetic Monte Carlo simulation

An energy-dependent kinetic Monte Carlo approach was proposed to simulate the multilayer growth of BaTiO₃ thin films via pulsed laser deposition, in which the four steps, such as the deposition of atoms, the diffusion of adatoms, the bonding of adatoms, and the surface migration of adatoms, were considered. Distinguishing with the traditional solid-on-solid (SOS) model, the adatom bonding and the overhanging of atoms, according to the perovskite structure, were specially adopted to describe the ferroelectric thin film growth. The activation energy was considered from the interactions between the ions, which were calculated by Born-Mayer-Huggins (BMH) potential. From the simulation the relative curves of the each layer coverage and roughness vs total coverage were obtained by varying the parameter values of the incident kinetic energy, laser repetition rate and mean deposition rate. The relationship between growth modes and the different parameters was also acquired.     

Crystallization and surface segregation in CuIn0.7Ga0.3Se2 thin films on Cu foils grown by pulsed laser deposition

This work reports unexpected crystallization and segregation behavior of CuIn_0.7Ga_0.3Se₂ (CIGS) thin films deposited on flexible Cu foils by pulsed laser deposition. A composite-type microstructure containing nanometer-scaled CIGS crystallites embedded in amorphous Cu-rich matrix is observed even at the high temperature of 500 °C. The findings are attributed to very fast condensation of the ablated species and random nucleation induced from the amorphous matrix. Cu-rich particulates tend to precipitate on the film surface, and their average size, shape, number density and composition exhibit a strong dependence on the substrate temperature up to 500 °C. The similar crystallization properties of the films on Cu foils and glass substrates are noticeable to the use of Cu foils for flexible solar cells.