Direct observation of crystallization in silicon by in situ high-resolution electron microscopy

We have studied the nucleation and growth of crystalline silicon by in situhigh-resolution electron microscopy. Amorphous silicon thin films, deposited onto oxidized silicon wafers by low-pressure chemical vapor deposition, were heated in the microscope in the nominal temperature range of 700–775°C. Many sub-critical crystal embryos exist at the a-Si/SiO2 interface, very few of which develop into viable nuclei. One nucleation event was recorded successfully at lattice resolution, allowing an estimate of the critical radius as 2.5±1.0 nm and the a-Si/c-Si interfacial energy as 600±200 mJ m−2. The crystal growth was followed for extended periods of time. It appeared to be characterized by sporadic growth bursts rather than a continuos advance of the crystal-amorphous phase interface. We specifically sought evidence for a ledge growth mechanism but did not find such behavior.