Stability of polydihydrosilane liquid films on solid substrates

The quality of polydihydrosilane liquid films is a key factor in the fabrication of solution-processed silicon films. This study investigates the stability of polydihydrosilane liquid films with a thickness L of ~ 40 nm on solid substrates by a comparison between the observed optical microscope images and the values of the Hamaker constant A_ALS for the air/liquid (polydihydrosilane)/solid substrate systems. A_ALS values for a series of SiO₂-based substrates were determined by adopting a simple spectrum method. We found that the micrographs of the polydihydrosilane films provide direct evidence of stability in accordance with the sign of A_ALS; a stable liquid film with A_ALS > 0 showed a continuous figure, while an unstable film with A_ALS < 0 exhibited an array of dots caused by the rupture of the film. The array of dots in the unstable liquid films has a slight orderly distribution with a period λ that is in accord with the characteristic wavelength of the undulation related to the spinodal-like decomposition in van der Waals unstable liquid.