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Monolayers of submicron size silica (SiO₂) particles (550 and 300nm) were rapidly deposited on sapphire substrate (Ø 2in.) by spin coating. The time to prepare the monolayer film was only 25s, 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.