Atomic layer deposition and characterization of biocompatible hydroxyapatite thin films

Atomic layer deposition (ALD) was used to produce hydroxyapatite from Ca(thd)₂ (thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) and (CH₃O)₃PO onto Si(100) and Corning (0211). Film crystallinity, stoichiometry, possible impurities and surface morphology were determined. The as-deposited films contained significant amounts of carbonate impurities however, annealing at moist N₂ flow reduced the carbonate content even at 400 °C. The as-deposited Ca-P-O films were amorphous but rapid thermal annealing promoted the formation of the hydroxyapatite phase. Mouse MC 3T3-E1 cells were used for the cell culture experiments. According to the bioactivity studies cell proliferation was enhanced on as-deposited ALD-grown Ca-P-O films and greatly enhanced on films annealed at 500 °C in comparison with reference cells on borosilicate glass or cell culture polystyrene.     

Deposition and characterization of magnetic Ti-Fe-C nanocomposite thin films

Nanocomposite (Ti_1−xFe_x)C_y films with different compositions have been deposited by dc magnetron sputtering at 450 °C. The sputtered films could dissolve as much as 20-30 at.% of Fe on the Ti sites which is far above the maximum solid solubility at equilibrium. The solubility was dependent on the carbon content and more carbon-rich films could dissolve more Fe without the formation of Fe-precipitates. The addition of Fe also reduced the grain size of the carbide particles. Upon annealing, α-Fe starts to precipitate and the amount and size of these precipitates can be controlled by the annealing procedure and from the total composition of the as-deposited films. Mechanical and tribological studies show that some compositions of the (Ti_1−xFe_x)C_y films have very good wear-resistant properties. These results together with magnetization measurements suggest that Ti-Fe-C films can be used as a wear-resistant magnetic thin film material.     

Fabrication and characterization of polyaniline-znO hybrid nanocomposite thin films

Polyaniline (PANI)-ZnO nanocomposite thin film has been successfully fabricated on glass substrates by using vacuum deposition technique. The as-grown PANI-ZnO nanocomposite thin films have been characterized using X-ray diffraction, Scanning Electron Microscopy, Atomic Force Microscopy, UV-visible spectrophotometer and Fourier Transform Infrared (FTIR) spectroscopy, respectively. X-ray diffraction of as-grown film shows the reflection of ZnO nanoparticles along with a broad peak of PANI. The surface morphology of nanocomposite films has been investigated using scanning electron microscopy and atomic force microscopy. The hypsochromic shift of the UV absorption band corresponding to pi-pi* transition in polymeric chain of PANI and a band at 504 cm(-1) due to ZnO nanoparticles has been observed in the FTIR spectra. The hydrogen bonding between the imine group of PANI and ZnO nanoparticle has been confirmed from the presence of the absorbance band at 1151 cm(-1) in the FTIR spectra of the nanocomposite thin films.     

Surface and mechanical characterization of TaN-Ag nanocomposite thin films

TaN-Ag nanocomposite thin films with Ag nano-particles dispersed in TaN matrix and surface were prepared by reactive co-sputtering of Ta and Ag in the plasma of N₂ and Ar. After deposition, the films were annealed using RTA (Rapid Thermal Annealing) at 350 °C for 2, 4, 8 min respectively to induce the nucleation and growth of Ag particles. C-AFM (Conductive-atomic Force Microscopy) and SSPM (Surface Scanning Potential Microscopy) were applied to characterize the emergence of Ag nano-particles on the surface of TaN-Ag thin films in this study. It is seen that Ag nano-particles may emerge in the matrix and on the surface of TaN and, possibly, grow. The results are compared with that obtained by FE-SEM (field-emission scanning electron microscopy). After comparison, C-AFM and SSPM are seen to be useful in characterizing the emergence and distribution of Ag particles. The results also show that the films' hardness and Young's modulus values would increase or decrease with the increase of annealing time, depending on Ag content and annealing time. This behavior is similar to that of TaN-Cu nanocomposite film. In addition, the increase of wear resistance of these coatings is proved.     

Structural characterization of thin amorphous Si films

We present a study of structural changes occurring in thin amorphous silicon (a-Si). The a-Si films were deposited on single-crystalline Si substrates held at room temperature or 200 °C by magnetron sputtering of a Si target in pure Ar atmosphere, and therefore the films were hydrogen-free. All samples were annealed in vacuum and subsequently studied by EPR and GISAXS. A strong decrease in the dangling bonds content at lower annealing temperatures, and then an increase of it at around 550 °C, suggested significant structural changes. In parallel the samples were studied by GISAXS which confirmed changes at the nanometric scale attributed to voids in the material. A nice correlation of the results of the two techniques shows advantages of this approach in the analysis of structural changes in a-Si material.     

Structural characterization of vacuum evaporated ZnSe thin films

Thermally evaporated ZnSe thin films deposited on glass substrates within substrate temperatures (T _s)at 303 K-623 K are of polycrystalline nature having f.c.c. zincblende structure. The most preferential orientation is along [111] direction for all deposited films together with other abundant planes [220] and [311]. The lattice parameter, grain size, average internal stress, microstrain, dislocation density and degree of preferred orientation in the film are calculated and correlated with T _s.     

Thermal stability of nanocomposite CrC/a-C:H thin films

The thermal stability of low-friction Me-C/a-C:H coatings is important for their potential applications in the tool and automotive industry. Recently we showed that CrC_x/a-C:H coatings prepared by unbalanced magnetron sputtering of a Cr target in Ar + CH₄ glow discharges exhibit a nanocomposite structure where metastable fcc CrC nanocrystals are encapsulated by an a-C:H phase. Here, we present the structural evolution of these nanocomposite CrC/a-C:H coatings during annealing. High-temperature X-ray diffraction in vacuum and differential scanning calorimetry (DSC) combined with thermo-gravimetric analysis in Ar atmosphere indicate decomposition of the formed metastable fcc CrC phase and subsequent formation of Cr₃C₂ and Cr₇C₃ and structural transformation of the a-C:H matrix phase towards higher sp² bonding contents at temperatures above 450 °C. Combined DSC and mass spectrometer analysis as well as elemental profiling after annealing in vacuum by elastic recoil detection analysis relate this transformation to the loss of bonded hydrogen at temperatures above 200 °C.Due to these structural changes the coefficient of friction depends on the annealing temperature of the nanocomposite a-C:H coatings and shows a minimum of ∼ 0.13 for T = 200 °C. The more complex tribochemical reactions, influenced by the hydrogen loss from the coating during in-situ high temperatures ball-on disc tests, result in coefficient of friction values below 0.05 for T < 120 °C.     

Synthesis and characterization of polyimide-based hybrid thin films from a novel colloidal core-shell nanocomposite particles

In this study, poly(4,4-(hexafluoroisopropylidenediphthalic anhydride)-co-oxydianiline) (6FDA-ODA) and a novel core-shell nanoparticle consisting of a core (SnO2/TiO2) and a shell (ZrO2/Sb2O3) with the composition (SnO2:TiO2:ZrO2:Sb2O3 = 18:5:3:4) were used to prepare polyimide/nanoparticles hybrid thin films. The resultant hybrid thin films were investigated by FTIR, TGA, DSC, TEM, SEM, AFM, alpha-step, UV-Vis, and n&k analyses. The results show that the prepared hybrid thin films had a good thermal stability. The size of nanoparticles was effectively controlled in the range of 8-10 nm in the hybrid thin films. These nanoparticles were evenly distributed across the hybrid thin films and no phase separation occurred. In terms of the optical properties, the prepared hybrid thin films had good transparency in the range of visible light. The cutoff wavelength had a blue shift as the content of the nanoparticles increased. The refractive index of prepared hybrid thin films increased with corresponding increases in nanoparticle content. Moreover, the prepared polyimide/core-shell nanoparticle hybrid thin films displayed excellent film formability and planarity.     

Structural characterization of thin ZnS films by X-ray diffraction

Structural properties of electroluminescent ZnS: Mn thin films grown by atomic layer epitaxy, which emit yellow light with an external efficiency as high as 2%, are investigated. The films grown at 500°C have a strong preferred orientation: one-half of the 00·1 plane normals are aligned within 7° from the normal of the glass substrate. The length of coherently diffracting domains (crystallite size) in the direction of the normal obtained from the Fourier analysis of a line profile ranges from 30 to 160 nm. The average relative strain in the same direction is calculated to be 10^?3. The estimated dislocation density is about 10¹⁰ cm^?2.     

Mechanical properties of nanocomposite thin films

The mechanical properties of nanocomposite thin films are reviewed. Two types of films are considered: artificially multilayered thin films and granular metal thin films. Artificially multilayered thin films, which are composed of alternating layers of two different materials, can display variations (reductions or enhancements) of the order of 15 to 30% in their elastic behavior as the bilayer repeat length is reduced below about 5 nm. Significant enhancements in the hardness of these materials are also observed for this range of bilayer repeat length. Granular metal films, which are composed of a thin film ceramic matrix embedded with metal granules of diameters as small as a few nanometers, display novel behavior in their hardness and apparent elastic behavior as measured by low-load indentation methods. This appears to be correlated with the percolation threshold of the metal.     

Biocompatibility of diamond-like nanocomposite thin films

Diamond-like nanocomposite (DLN) films consist of network structure of amorphous carbon and quartz like silicon. In the present work, DLN films have been synthesized on pyrex glass and subsequently, their biocompatibility have been investigated through primary and secondary cell adhesion, cytotoxicity, protein adsorption and murine peritoneal macrophage activation experiments. Variable degree of cell and protein response have been found based on variable film synthesis parameters but in overall, required biocompatibility has been established for all types of film-coating.     

Some remarks on Ag/C:H nanocomposite films

Nanocomposite films Ag/C:H were prepared using DC unbalanced magnetron sputtering operated in Ar and n-hexane mixture. Optical emission spectroscopy was used to monitor deposition process as witnessed by XPS quantitative analysis. UV-vis transmittance of Ag/C:H films as a function of Ag content show well-known anomalous optical absorption. FTIR (SEIRA) spectroscopy and HRTEM images were used to reveal an interface region between plasma polymer C:H and Ag nanocluster surface.     

Preparation and characterization of carbon nanotube/polyetherimide nanocomposite films

Multi-walled carbon nanotube (MWCNT)/polyetherimide (PEI) nanocomposite films have been prepared by casting and imidization. A homogeneous dispersion of MWCNTs throughout the PEI matrix is observed by scanning electron microscopy of fracture surfaces, which shows not only a fine dispersion of MWCNTs but also strong interfacial adhesion with the matrix, as evidenced by the presence of many broken but strongly embedded carbon nanotubes (CNTs) in the matrix and by the absence of debonding of CNTs from the matrix. Differential scanning calorimetry and dynamic mechanical analysis show that the glass transition temperature of PEI increases by about 10 °C by the addition of 1 wt% MWCNTs. Mechanical testing shows that for the addition of 1 wt% MWCNTs, the elastic moduli of the nanocomposites are significantly improved by about 250% while the tensile strength is comparable to that of the matrix. This improvement is due to the strong interfacial interaction between the MWCNTs and the PEI matrix which favors stress transfer from the polymer to the CNTs.     

Structural, optical and electrical characterization of spray-deposited TiO2 thin films

Titanium oxide (TiO₂) thin films were deposited onto glass substrates by means of spray pyrolysis method using methanolic titanyl acetyl acetonate as precursor solution. The thin films were deposited at three different temperatures namely 350, 400 and 450 °C. As-deposited thin films were amorphous having 100–300 nm thickness. The thin films were subsequently annealed at 500 °C in air for 2 h. Structural, optical and electrical properties of TiO₂ thin films have been studied. Polycrystalline thin films with rutile crystal structure, as evidenced from X-ray diffraction pattern, were obtained with major reflexion along (1 1 0). Surface morphology and growth stages based on atomic force microscopy measurements are discussed. Electrical properties have been studied by means of electrical resistivity and thermoelectric power measurements. Optical study shows that TiO₂ possesses direct optical transition with band gap of 3.4 eV.     

Structural characterization and porosity analysis in self-supported porous alumina-silica thin films

In this study, alumina, silica and alumina-silica binary (36% mol silica) thin films are synthesized using the sol-gel technique. These form the basis for future gas separation membranes. The characterization of the synthesized oxides was performed using nitrogen physisorption, X-ray diffraction (XRD), Doppler-broadening measurements on the 511 keV annihilation photon peak, together with 3γ/2γ analysis, and Fourier transform infrared spectroscopy (FTIR) of adsorbed CO. It is found that silica is microporous, γ-alumina is mesoporous, and the binary material shows fingerprints of both the meso- and microporous nature of its constituents as well as of the respective crystal structures. These results open the possibility to also investigate thin supported porous films (a few microns thick), and especially the setting and drying aspects on porous supports for membrane production, using the positron annihilation technique.     

Transparent high refractive index nanocomposite thin films

This work reports the preparation of acetic acid-modified TiO₂ nanoparticles by sol–gel synthesis method. The nanoparticles can be incorporated directly into the polymer matrix to form transparent high refractive index nanocomposite thin films. The result shows that increasing the titania content in the hybrid nanocomposite thin films can significantly increase the refractive index. Hybrid nanocomposite thin film with refractive index value of 2.38 had been prepared. All prepared films also exhibit excellent optical transparency in the visible region.     

Structural and chemical characterization of precipitates in Al-2024/TiC composites

Structural characterizations based on transmission electron microscopy observations were carried out on as-fabricated and heat-treated Al-2024/TiC composites. These composites types reinforced with TiC particles were produced with a pressureless melt infiltration route at 1200 °C for 2 h under argon atmosphere. The composites were heat-treated at 530 °C during 150 min, cold-water quenched and subsequently artificial and natural aged at 190 °C for 12 h in an argon environment and at room temperature for 96 h, respectively. Different precipitate types were obtained and they were identified as CuAl₂, Al₃Ti, Ti₃AlC and Ti₃Al. Most of the precipitates were found to be uniformly distributed in the matrix and some regions show precipitates which have a cubic morphology (Ti₃Cu). High-resolution electron microscopy images were partially used for the characterization of the precipitates in these composites.     

Optical switch from silver nanocomposite thin films

Silver nanoparticles capped with sodium alginate were assembled into thin films by using the layer-by-layer dipping technique. Composite films were built by sequential dipping of a glass slide in either anionic alginate capped nanoparticles or cationic Poly(diallyldimethylammonium chloride) (PDADMAC). The growth of the film was characterized using UV-Vis spectroscopy by monitoring the increase in absorbance at 420 nm which correspond to the silver nanoparticles plasmon band. The final films formed onto glass slides displayed and interesting color shift upon exposure to water or to a less polar solvent such as ethanol. In this research, changes in spectral absorbance of the nanoparticles film were monitored as a function of ethanol content (0, 20, 40, 60, 80 and 100%) in water. The color shift from yellow to red color was explained by the changes in the dielectric constant of the silver nanoparticles surrounding medium which induce a shift in their plasmon band absorbance. These composite thin films displayed fast color change and could therefore be used in sensing application as well as for optical switches.