Fabrication of a large area monolayer of silica particles on a sapphire substrate by a spin coating method

Monolayers of submicron size silica (SiO2) particles (550 and 300 nm) were rapidly deposited on sapphire substrate (Ø 2 in.) by spin coating. The time to prepare the monolayer film was only 25 s, a very short time compared with previously reported methods used for assembling particles in monolayers. The concentration of SiO2 particles in the solution, the ambient humidity (relative humidity, RH) and the spin speed were all important parameters in achieving a large area monolayer film. A relatively high surface coverage and uniform monolayer film of SiO2 particles in the range of 60–81% from the center to the edge of the substrate (or the average is around 72%) was achieved by appropriate control of the above preparation parameters. We conclude that this method could be used in industrial applications, because of the speed and cost of the process.