Structural Investigations of Laser-Crystallized Hydrogenated Amorphous Silicon

We investigated the structure of hydrogenated amorphous silicon, thin films crystallized by short pulses from a XeCl excimer laser at fluences for which total melting of the films occurs. Atomic force microscopy revealed that films prepared using optimized process conditions, leading to hydrogen contents ≤ 5 at.%, are smoother after laser crystallization than those prepared by laser-dehydrogenation. The roughness of the laser-crystallized films increases with their thickness, and can be reduced by multiple exposure. A better smoothing is obtained by partially remelting the films after the first irradiation. Transmission electron microscopy shows that the grains in the laser-crystallized films have sizes that are comparable to the film thickness.