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 silicon on a graphite surface. On an as-cleaved graphite surface, hydrogenated amorphous silicon islands were formed only along the graphite steps, indicating that the precursors can migrate on the atomically flat graphite surface until they are pinned by the islands nucleated along 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 surface of graphite treated with the hydrogen plasma, a high density of bright spots was observed by scanning tunneling microscopy. These spots were suggested to act as pinning sites for the aggregation of surface migrating precursors into hydrogenated amorphous silicon nucleation centers.