Fabrication of highly transparent and superhydrophobic silica-based surface by TEOS/PPG hybrid with adjustment of the pH value

Preparation of superhydrophobic silica-based thin film with high transmittance (T%) in the visible light region by adjusting different pH value of mixing solution has been developed. The hybrid films were coated by the mixing solution which included precursor solution (sol–gel process) and polypropylene glycol (PPG) polymer solution. Rough surfaces were obtained by removing the organic polymer at high temperature and then the hydrophobic groups bonded onto the films were obtained by the reaction with hexamethyldisilazane (HMDS). Characteristic properties of the as-prepared surface of the films were analyzed by contact angle measurement, scanning electron microscopy (SEM), atom force microscopy (AFM), UV–VIS scanning spectrophotometer and Fourier transform infrared (FT-IR) spectrophotometer. The experimental parameters were mainly varied by the pH value (0, 1, 2.3, 6 and 8) of the mixing solution. The result showed that the contact angle of the film was greater than 150° and the transmittance of the film was greater than 90% simultaneously when the pH value of mixing solution was adjusted to 1. In addition, the highly transparent superhydrophobic surfaces was obtained by adding 20 μL acid solution into the mixing solution, which the contact angle of the film was 156.3° as well as the transmittance of the film at the 600 nm visible light was 97.9%.     

Pulsed laser deposited hard TiC, ZrC, HfC and TaC films on titanium: Hardness and an energy-dispersive X-ray diffraction study

Thin films of TiC, ZrC, HfC and TaC were pulsed laser ablation deposited onto sandblasted pure titanium substrate at a laser beam fluence of 3 J/cm². Deposition temperature was room temperature or 500 °C. The films were investigated by scanning electron microscopy, energy-dispersive X-ray diffraction (EDXD) and hardness measurements. The smooth and compact films of 200 to 600 nm thickness were obtained, consisting of tens nanometer particles. The rocking curve EDXD analysis revealed the films are textured. Intrinsic hardness of the films decreases generally with an increase in substrate temperature and in molecular weight of carbides.     

Anatase TiO2 films obtained by cathodic arc deposition

TiO₂ thin films were prepared on glass substrates at different temperatures employing an unfiltered cathodic arc device. The temperature values were varied from room temperature to 400 °C. The crystalline structure of the films was determined by X-ray diffraction. The surface morphology was studied by scanning electron microscopy and atomic force microscopy. Transmittance in UV-visible region was also measured. All films deposited at temperatures lower than 300 °C were amorphous, whereas films obtained at higher temperatures grew in crystalline anatase phase. Phase transition amorphous-to-anatase was observed after post-annealing at 400 °C. The average transmittance value for all films was higher than 80%, a comparison among the films obtained at different temperatures showed a transmittance value slightly higher for films obtained at highest temperatures. Grain size for as-deposited crystalline films was determined approximately in 20 nm, with a surface roughness of about 2 nm.     

Deposition and characterization of CuInSe2 films for solar cells using an optimized chemical route

CuInSe₂ (CISe) thin films have been deposited on glass using successive ionic layer adsorption and reaction (SILAR). The as-deposited films are treated at 400 °C in argon atmosphere and etched in KCN solution to remove detrimental secondary phases. The preparation and temperature of the precursor solutions, the duration of the reaction cycles and the duration of the annealing stage have been optimized. The films have been characterized employing grazing incident X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive scanning spectroscopy. Relevant semiconductor parameters have been calculated. Photoelectrochemical tests confirm p-type conduction. The films are crystalline and the stoichiometry can be improved by renewing the precursor solution after completing half of the cycles, annealing for 90 min and later etching in KCN. The quality of the material seems to be promising for application in solar cell devices.     

Structural, optical and hydrophilic properties of nanocrystalline TiO2 ultra-thin films prepared by pulsed dc reactive magnetron sputtering

TiO₂ ultra-thin (15 nm) films were deposited on silicon wafers (100) and glass slides by pulsed dc reactive magnetron sputtering in an ultra-high vacuum (UHV) system. The effects of substrate temperature, from room temperature to 400 °C, on structural, optical, and hydrophilic properties of the obtained films have been investigated. The structure of the films was characterized by grazing-incidence X-ray diffraction, high-resolution transmission electron microscopy, and atomic force microscopy. The optical properties were determined by UV-vis spectrophotometer and spectroscopic ellipsometry. The hydrophilic properties of the films, after exposed to ultraviolet illumination, were analyzed from contact angle measurements. The results suggested that the substrate temperature at 300 °C was critical in the crystalline phase transformation from amorphous to anatase in the TiO₂ films. The obtained films exhibited good qualities in the optical properties, in addition to excellent photo-induced hydrophilic activities.     

Surface morphology of nanostructured anatase thin films prepared by pulsed liquid injection MOCVD

Nanostructured anatase thin films were prepared by chemical vapor deposition feeding a metal organic precursor in a pulsed liquid injection mode. The films were deposited at 500 °C on stainless steel substrates using a single molecular titanium isopropoxide liquid solution as the precursor, without any reactant gas. An effective pulsing injection mechanism for the precursor supply provides uniform concentration of the precursor in the vapor phase, allowing the formation of titanium dioxide layers from small micro-doses of the metal organic precursor. Energy-dispersive spectroscopy, scanning electron microscopy and X-ray diffraction studies show the formation of crack-free nanostructured anatase thin films, highly oriented, formed basically by stepwised nanostructures with a uniform coverage and no detectable carbon contamination. Surface crystallinity, composition, nanostructure and morphology are discussed in terms of the experimental parameters used in the deposition process.     

Polypropylene films modified by air plasma and feather keratin graft

Polypropylene (PP) films were grafted respectively with two different processes: air plasma graft (APG) and post-plasma grafting (PPG) using feather keratin. The graft results were compared by measuring contact angles, printability, ageing test and surface chemical composition analysis. The results showed that the surface hydrophilic and printing properties of the PP films after PPG were better than after APG. The contact angles went down from 34.7° to less than 10° and could sustain to 28° at the end of the test (30 days). The analyses of the C1s and N1s peaks by X-ray photoelectron spectroscopy (XPS) illustrated that polar groups, especially nitrogen-containing groups C–NH_x and CO–NH, were introduced on the PP surface after PPG. The mechanisms of PPG were briefly discussed.     

Amorphous hafnium oxide thin films for antireflection optical coatings

Hafnium oxide (HfO₂) thin films were grown on silicon and quartz substrates by radio frequency reactive magnetron sputtering at temperature < 52 °C. X-ray diffraction of the films showed no structure, suggesting that the films grown on the substrates are amorphous. The optical properties of these films have been investigated using spectroscopic ellipsometry with wavelength range 200-1400 nm and ultraviolet-visible spectrophotometer techniques. Also, the effects of annealing temperatures on the structure and optical properties of the amorphous HfO₂ (a-HfO₂) have been investigated. The films appeared to be monoclinic structure upon high temperature (1000 °C) annealing as confirmed by X-ray diffraction. The results show that the annealing temperature has a strong effect on the optical properties of a-HfO₂ films. The optical bandgap energy of the as-deposited films is found to be about 5.8 eV and it increases to 5.99 eV after the annealing in Ar gas at 1000 °C. The further study shows that the measurement of the optical properties of the amorphous films reveals a high transmissivity (82%-99%) and very low reflectivity (< 8%) in the visible and near-infrared regions at any angle of incidence. Thus, the amorphous structure yields HfO₂ film of significantly higher transparency than the polycrystalline (68%-83%) and monoclinic (78%-89%) structures. This means that the a-HfO₂ films could be a good candidate for antireflection (AR) optical coatings.     

Annealing effects on microstructure and properties of Ta-Al thin film resistors

The Ta-Al thin film resistor has been used as a heating element of the thermal bubble inkjet printhead with several millions of thermal cycle operations between room temperature and about 350 °C. In this paper, the thermal stability of Ta-Al alloy films was investigated by the variation of phase transformation, microstructure and resistivity at annealing temperatures of 450-650 °C for 1 h. Three kinds of Ta-Al films were prepared with average Ta/Al atomic composition ratios of about 2/1, 1/1 and 1/2, respectively. The Ta-Al film with composition ratio of about 1/1 exhibits amorphous-like microstructure with nanocrystalline grains embedded in an amorphous matrix. The thermal stability is strongly related to the composition and microstructure in Ta-Al alloy. The best thermal stability of Ta-Al films occurs in Ta-rich alloy up to 650 °C and the worst occurs in Al-rich alloy with phase transformation as low as 450 °C. The amorphous-like Ta-Al alloy is stable up to 550 °C, but then exhibits polycrystalline multiphase formation at 650 °C. The resistivity of Ta-Al films is also related to the annealing temperature. The resistivity of Ta-rich Ta-Al film increases to about 13.5% from as-deposited to after annealing at 450 °C while that is doubled in the Al-rich Ta-Al film. In contrast, the resistivity of the amorphous-like Ta-Al film increased by about 6.1% at 450 °C and then remains nearly stable at 1.5% variation on annealing at 450-550 °C. The as-deposited amorphous-like Ta-Al film has the merits of high resistivity, smooth morphology and good thermal stability at annealing temperatures of up to 550 °C. These attributes are beneficial for the thermal bubble inkjet application with thermal cycling at maximum temperatures below 400 °C.     

Synthesis-structure relations for reactive magnetron sputtered V2O5 films

V₂O₅ films were grown onto MgO (100) substrates by reactive magnetron sputtering between 26 °C to 300 °C to establish a detailed synthesis-structure relation. The effect of deposition temperature on structural characteristics and surface morphology was characterized using X-ray diffraction, Raman spectroscopy, atomic force microscopy and scanning and transmission electron microscopy. Films prepared at room temperature are amorphous while those deposited above 80 °C exhibit a polycrystalline structure with the orthorhombic symmetry of the V₂O₅ phase.     

Supercapacitor behavior of CuO-PAA hybrid films: Effect of PAA concentration

The Cu-poly(acrylic) acid (PAA) thin films were deposited at room temperature by a simple and cost effective polymer assisted deposition (PAD) method. The solution containing Cu salt and PAA was spin coated to yield the thin films with desired properties. The Cu-PAA films were annealed at 400 °C in ambient air for 4 h to obtain CuO-PAA phase. The effect of PAA concentration on the film properties is studied and characterized by employing various techniques. The structural and surface morphological studies are carried out using X-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. Fourier transform infrared spectroscopy (FT-IR) and FT-Raman spectroscopy are employed to investigate the hybrid film formation. Wetting behavior is studied by measuring the contact angle of water on the film surface. Cyclic voltammetry (CV) studies were carried out to investigate the specific capacitance of CuO-PAA films in aqueous 1 M H₂SO₄ electrolyte. Hybrid films deposited with 2 mM PAA exhibits highest specific capacitance of 65 F g⁻¹.     

Tribological properties of pulsed laser deposited Mo-S-Te composite films at moderate high temperatures

Tribological investigations of Mo-S-Te composite films were conducted on films grown at room temperature by pulsed laser deposition. The chemistry and microstructure of the films were characterized by X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, and micro Raman spectroscopy. The films showed a granular morphology and a preferred basal plane growth of 2H-MoS₂ parallel to the substrate after annealing at high temperatures. The friction coefficients of the films were 0.05 at 300 °C and 0.10 at 450 °C for more than 10,000 cycles in air. Smeared hexagonal MoS₂ lubricant films were observed inside wear tracks while the tribochemical formation of wear debris occurred both inside and outside the wear tracks. The Te additives for increasing the film durability were proposed to slow oxidation of the lubricants at elevated temperatures by thermally-induced tellurium migration to the surface and the subsequent formation of the Te diffusion barrier. This mechanism could be significantly effective in high-temperature tribotests because of the increased tellurium mobility at high temperatures.     

Effect of annealing temperature on the structure and optical properties of sputtered TiO2 films

TiO₂ thin films were deposited by DC reactive magnetron sputtering. Some TiO₂ thin films samples were annealed for 5 min at different temperatures from 300 to 900 °C. The structure and optical properties of the films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and ultraviolet-visible (UV-vis) spectrophotometry, respectively. The influence of the annealing temperature on the structure and optical properties of the films was investigated. The results show that the as-deposited TiO₂ thin films are mixtures of anatase and rutile phases, and possess the column-like crystallite texture. With the annealing temperature increasing, the refractive index and extinction coefficient increase. When the annealing temperature is lower than 900 °C, the anatase phase is the dominant crystalline phase; the weight fraction of the rutile phase does not increase significantly during annealing process. As the annealing temperature rises to 900 °C, the rutile phase with the large extinction coefficient becomes the dominant crystalline phase, and the columnar structure disappears. The films annealed at 300 °C have the best optical properties for the antireflection coatings, whose refractive index and extinction coefficient are 2.42 and 8 × 10⁻⁴ (at 550 nm), respectively.     

Zinc oxide (ZnO) grown on flexible substrate using dual-plasma-enhanced metalorganic vapor deposition (DPEMOCVD)

This study investigates the temperature dependence of zinc oxide (ZnO) grown on polyestersulfone (PES) flexible substrates using the dual plasma-enhanced metal–organic chemical vapor deposition (DPEMOCVD) system. The proposed method uses a direct voltage (DC) and radio-frequency (RF) plasma system. The group-VI precursor, oxygen (O₂), can be completely ionized by the DC plasma system. The effect of optimal DC plasma power on ZnO thin films is thoroughly investigated using X-ray diffraction (XRD). The experimental results indicate that the crystalline structure and optical and electrical properties of ZnO thin films grown on PES substrates are dependent on the deposition temperature. The optimum deposition temperature for ZnO thin films deposited on PES substrates is 185 °C, whereas the DC and RF plasma power is 1.8 W and 350 W, respectively. Additionally, the wettability characteristic regarding the UV irradiation time was assessed by measuring the water contact angle. Under the UV irradiation for 60 min, the ZnO film grown at 185 °C represents a low contact angle of 5°, which approaches to a superhydrophilic surface.     

Wear and oxidation resistance of combustion CVD grown alumina films

Alumina thin films were synthesized on Si (100) and Ni–20Cr substrates using combustion chemical vapor deposition. Aluminum acetylacetonate (0.005 M) dissolved in ethanol was used as the precursor solution. The films deposited at 900 and 1000 °C are found to be θ-alumina and those deposited at 1100 °C to be α-alumina. The scanning electron micrographs showed the films to be made up of crystallites of two different sizes and shapes. The coefficient of friction, of alumina coated Si samples, measured using a tribometer showed high value (~ 0.7) at initial passes and subsequently saturated to low value (~ 0.5) at higher sliding distances. It was observed that the tribological properties, of the films, are not affected significantly by the crystal structure and crystallite size. Oxidation resistance of alumina-coated Ni–20Cr specimens were studied using a thermo-gravimetric analyzer by exposing them to isothermal heating at 1000 °C in 20% O₂–Ar gas mixture. The results indicated that the coated specimens are 18 times more oxidation resistant, at initial stages, compared to uncoated specimens. The resistance slowly dropped to six times, where it reached a saturation value.     

Electrodeposition of black chromium from environmentally electrolyte based on trivalent chromium salt

Thin films of black chromium have been prepared by electrodeposition technique on steel substrates. Deposition of 1 µm thickness is conducted in a solution of chromium trivalent salt and oxidizing agent fluorosilicic acid (H₂SiF₆) operated at a current density 350 mA cm^− 2 at 25 °C and 1 min. The influence of H₂SiF₆ concentrations on the trivalent chromium electrodeposition was studied by the potentiodynamic technique. The phase structure and surface morphology of the deposited films were examined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The chemical composition of these thin films was determined by energy dispersive X-ray analysis (EDS) and X-ray photoelectron spectroscopy (XPS) analysis. The spectral reflectance in the visible light, for films coating was characterized. From the SEM analysis, it was found that the black chromium has nano lamellar morphology that leads to a strong dispersion level. The XRD results showed that chromium, chromium oxide and cobalt oxide are the main bulk chemical compounds in the films. However, from XPS analysis of these surfaces, it was possible to determine that the most external layers of the films are made of different kinds of chromium and cobalt compounds. The black chromium-cobalt alloy thin film has better optical properties to transform solar energy into thermal energy, and these properties remain practically constant even when heat treated to a high temperature, 400 °C for 24 h.     

Thermal stability and oxidation resistance of Ti-B-N, Ti-Cr-B-N, Ti-Si-B-N and Ti-Al-Si-B-N films

Films Ti-B-xN-y(Al,Si,Cr) with different compositions x = 25-33 at.% and y = 11-14 at.% were deposited by DC magnetron sputtering of TiBN, TiCrB, TiSiB, and TiAlSiB composite targets in a gaseous mixture of argon and nitrogen. The structure and phase composition of films were studied by means of X-ray diffraction, transmission electron microscopy, Raman and X-ray photoelectron spectroscopy. To evaluate the thermal stability and oxidation resistance, the Ti-B-N, Ti-Cr-B-N, Ti-Si-B-N, and Ti-Al-Si-B-N films were annealed at 600, 800, and 1000 °C in vacuum and at 600, 700, 800, and 900 °C in air, respectively. The elemental depth profiles for the oxidized films were obtained by focused ion beam equipped with secondary ion mass spectrometer. The Ti-B-N and Ti-Cr-B-N films demonstrated thermal stability up to 1000 °C. A threshold temperature of 800 °C was determined, below which these films acted as a diffusion barrier for Ni diffusion from metallic substrate. Annealing in the range of 600-800 °C improved mechanical and tribological characteristics of the films. The Ti-Cr-B-N and Ti-Al-Si-B-N films were more resistant against high-temperature oxidation than the Ti-B-N and Ti-Si-B-N films.     

Physical properties of chemical vapour deposited nanostructured carbon thin films

A simple thermal chemical vapour deposition technique is employed for the deposition of carbon films by pyrolysing the natural precursor “turpentine oil” on to the stainless steel (SS) and FTO coated quartz substrates at higher temperatures (700-1100 °C). In this work, we have studied the influence of substrate and deposition temperature on the evolution of structural and morphological properties of nanostructured carbon films. The films were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle measurements, Fourier transform infrared (FTIR) and Raman spectroscopy techniques. XRD study reveals that the films are polycrystalline exhibiting hexagonal and face-centered cubic structures on SS and FTO coated glass substrates respectively. SEM images show the porous and agglomerated surface of the films. Deposited carbon films show the hydrophobic nature. FTIR study displays C-H and O-H stretching vibration modes in the films. Raman analysis shows that, high ID/IG for FTO substrate confirms the dominance of sp³ bonds with diamond phase and less for SS shows graphitization effect with dominant sp² bonds. It reveals the difference in local microstructure of carbon deposits leading to variation in contact angle and hardness, which is ascribed to difference in the packing density of carbon films, as observed also by Raman.     

Fabrication of hydrophobic and antireflective coatings based on hybrid silica films by sol–gel process

This paper reports the synthesis of hydrophobic and antireflective coatings by sol–gel process at room temperature (25 °C), using tetraethylorthosilicate (TEOS) as a precursor and methyltriethoxysilane (MTES), phenyltriethoxysilane (PTES), vinyltriethoxysilane (VTES), and octyltriethoxysilane (OTES) as surface modifying agents. The silica sol was prepared by keeping the molar ratio of TEOS:RTES at 1:1, in acidic conditions with ethanol and 0.1 M HCl. All hybrid systems were enriched with titanium(IV) isopropoxide as the cross-linking agent. It was observed that the obtained silica films become hydrophobic with the introduction of the hydrophobic organic group. The higher value of static water contact angle (107 ± 3°) was obtained for the silica film prepared with TEOS + OTES. Under optimal synthesis condition, we obtained antireflection coatings, exhibiting a low reflection in the visible range.     

Nanocrystalline LiMn2O4 thin film cathode material prepared by polymer spray pyrolysis method for Li-ion battery

Nanocrystalline cubic spinel lithium manganese oxide thin film was prepared by a polymer spray pyrolysis method using lithium acetate and manganese acetate precursor solution and polyethylene glycol-4000 as a polymeric binder. The substrate temperature was selected from the thermogravimetric analysis by finding the complete crystallization temperature of LiMn₂O₄ precursor sample. The deposited LiMn₂O₄ thin films were annealed at 450, 500 and 600 °C for 30 min. The thin film annealed at 600 °C was found to be the sufficient temperature to form high phase pure nanocrystalline LiMn₂O₄ thin film. The formation of cubic spinel thin film was confirmed by X-ray diffraction study. Scanning electron microscopy and atomic force microscopy analysis revealed that the thin film annealed at 600 °C was found to be nanocrystalline in nature and the surface of the films were uniform without any crack. The electrochemical charge/discharge studies of the prepared LiMn₂O₄ film was found to be better compared to the conventional spray pyrolysed thin film material.