Hirotsugu Nagayama

A New Process for Silica Coating

Silica film was deposited on the surface of soda lime silicate glass by immersing it in hydrofluosilicic acid solution supersaturated with silica gel at low temperature. The composition and the structure of these films were evaluated using ESCA, IRRS, fluoric acid etching test, and sodium leaching test, and they were compared with those of various silica films prepared by other methods. The results showed that these films made at low temperature had a dense structure and a great alkali barrier effect. By heat‐treatment, the structure of this film became denser, getting close to that of fused silica. It was also found that the degree of supersaturation and the solution temperature had a great influence on the deposition rate.

Retention of Water Droplets by Hydrophobic Surfaces

Advancing contact angles and critical tilting angles at which water droplets begin to slide were measured on the silicon wafer treated with 1,3,5,7-tetramethylcyclotetrasiloxane with a view to understanding water retention by hydrophobic solid surfaces. Microscopic information on the surface was obtained by diffuse reflectance Fourier transform infrared spectra of SiO 2 particles used as a model substrate. The critical tilting angles and the contact angles could be related in terms of the interaction between water and the solid surface. The increase of the critical tilting angle and the decrease of the contact angle after immersion in boiling water is ascribed to an increase in the interaction caused by partial hydrolysis of the Si-H groups

SiO2 Film Grown On Glass In Aqueous Solution

Si02 film deposition on a glass was made by LPD method (Liquid Phase Deposition). This process involes the deposition and growth of Si02 layer on glass surface while immersing it in hexafluorosilicic acid (H2SiF6) solution supersaturated with silica. In this study, the influence of the impurities and H2SiF6 concentration in the solution on Si02 film properties was investigated by use of SIMS, ICP, Ellipsometry,IRRS and etch rate measurement. The results showed that LPD based Si02 film composition was scarcely affected by the concentration of such impurities as Na, K and Ca contained in the solution. Furthermore it was found that higher H2SiF6 concentration led to Si02 film with lower refractive index and lower etch rate. To have proper understanding of these apparently inconsistent results, the specific role of fluorine contained in the solution and the film was discussed.