ATOMIC-FORCE MICROSCOPY AND SCANNING-TUNNELING-MICROSCOPY STUDIES ON THE GROWTH-MECHANISM OF A-SI-H FILM ON GRAPHITE SUBSTRATE

Based on analysis by atomic force microscopy, a nucleation and growth model is presented for the initial growth of hydrogenated amorphous si licon on a graphite surface. On an as-cleaved graphite surface, hydrog enated amorphous silicon islands were formed only along the graphite s teps, indicating that the precursors can migrate on the atomically fla t graphite surface until they are pinned by the islands nucleated alon g the steps. Hydrogen plasma treatment of graphite surfaces gave fine hydrogenated amorphous silicon islands on atomically flat terraces as well as homogeneous hydrogenated amorphous silicon films. On the surfa ce of graphite treated with the hydrogen plasma, a high density of bri ght spots was observed by scanning tunneling microscopy. These spots w ere suggested to act as pinning sites for the aggregation of surface m igrating precursors into hydrogenated amorphous silicon nucleation cen ters.