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We explored effects of the degree of supersaturation, which depends on solution concentration, pH, and temperature, on the development of microstructures of the TiO2 thin films deposited from the controlled hydrolysis of TiCl4 aqueous solutions. It was shown that, with precursor (TiCl4) solution of low degree of supersaturation, a porous flower-like dendritic structure was synthesized, while a densely packed particulate nanostructure was obtained with that of high degree of supersaturation. The former morphology was attributed to the directional growth of TiO2 crystals from the already-deposited films, whereas the latter to the bulk precipitated TiO2 nanoparticles nucleated in the solution, followed by their attachment and self organization. By establishing the processing–microstructure relations, this study provided a means of generating a wide spectrum of reproducible TiO2 microstructures using the low-temperature aqueous solution processing. [ABSTRACT FROM AUTHOR]

Current microelectronics devices based on flexible as well as rigid substrates demand high dielectric constant ( k) films to be grown on conductive substrate from a low-cost, low-temperature deposition technique. In this study, we produced high- k titania (TiO2) films through an affordable electrodeposition protocol from the electrochemical bath maintained at about 0°C. The deposition occurs through a rapid hydrolysis mechanism of titanium containing ions in the precursor solution aided by electrochemically generated hydroxyl ions formed near the cathode surface (copper (Cu) substrate). Upon attaining a sufficient supersaturation level, such hydrolyzed species precipitate to form a titania thin film on the cathode surface. While depositing from a highly acidic precursor solution, Cu substrate was protected by a cathodic potential (−3 to −5 V against the counter electrode). The resultant titania films show nanoparticulate structures evolved from nucleation and growth events of the in situ precipitated particles. Much higher deposition rate (about 1 μm/min) was observed compared with that of typical chemical bath deposition. The resultant films with a thickness of 1500 nm grown on Cu exhibit very high dielectric properties (e.g., k∼30, capacitance density >110 nF/in.2 at 100 kHz) and moderate breakdown voltage ( VB) (∼17.5 V). These properties indicate the potential of electrodeposited titania films to be used as a small-area thin-film capacitor for miniaturized electronic devices. [ABSTRACT FROM AUTHOR]

Both the electrical and mechanical properties of silica thin films deposited by liquid phase deposition (LPD) have been evaluated in this study. Silica thin films have been prepared on glass surface by immersing it in a supersaturated Hexafluorosilicic acid (H2SiF6)-based solution at a low temperature of 50°C. The as-deposited LPD silica films exhibit a low dielectric constant ( k) that varies from 1.7 to 2.7 depending on the film morphology and fluorine content of the film. Young's modulus of these films was measured in the range of 18.9–24.5 GPa by a nanoindentation technique. The combination of extremely low k and fairly high modulus made this low-temperature-processed LPD silica films a very promising candidate for an interlayer dielectric film for the next-generation semiconductor devices. [ABSTRACT FROM AUTHOR]

Titanium oxide (TiO2) thin films can be prepared by controlled hydrolysis of a titanium tetrachloride (TiCl4) precursor in an aqueous solution at temperatures below 100°C. As part of an effort to understand the formation of such TiO2 films, the kinetics of the nucleation, growth, and aggregation of TiO2 nanoparticles in aqueous solutions of TiCl4 were studied using dynamic light scattering and a transmission electron microscope (TEM). A higher degree of supersaturation, produced by a higher solution temperature, a higher concentration of TiCl4, or a higher pH, results in a shorter nucleation induction time, a faster initial growth/aggregation rate, and a larger aggregate size. The interfacial energy of TiO2 nanoparticles was found to be 0.072 J/m2 from the homogeneous nucleation theory. Further investigations by a high-resolution scanning electron microscope (SEM) and TEM for the as-deposited films showed the structure hierarchy organized from nanocrystalline particles precipitated in the supersaturated solution. As a result, the effect of solution conditions on the nucleation, growth, and aggregation of TiO2 nanoparticles can provide useful guidance for tailoring of microstructures of the TiO2 films. [ABSTRACT FROM AUTHOR]

Investigates the influence of dopant concentration on creep properties of Nd[sub 2]O[sub 3]-doped alumina. Use of high-resolution scanning transmission electron microscopy and ion mass spectroscopy; Analysis of stress and grain-size exponents; Increase of the dopant concentration.