Multilayered silicon/silicon nitride thin films deposited by plasma-CVD: Effects of crystallization

Multilayered (45 to 100 layers) thin films with alternating layers of hydrogenated amorphous silicon (2-4 nm thick) and silicon nitride (6 nm thick) were deposited on Corning 7059 glass by Plasma-Enhanced Chemical Vapor Deposition process. Ellipsometry and Transmission Electron Microscopy (TEM) were used to characterize these multilayers. Visible photoluminescence at room temperature was observed from the multilayers after their exposure to a few pulses of an excimer Laser. The origin of the visible luminescence is consistent with quantum confinement effects. Ellipsometry and High Resolution TEM (HRTEM) showed the formation of crystalline phases after the laser treatment. Crystallization was found to occur in the amorphous silicon layers thus limiting the crystallite sizes to approximately the layer thickness i.e. < 4 nm. TEM diffraction patterns further showed a 1-dimensional superlattice structure in the crystallized multilayer samples.