Fast crystallization and void precipitation in laser pulse annealing of thin germanium films

A flash-excited dye laser of moderate power has been used to irradiate thin amorphous Ge films prepared by vacuum evaporation. TEM examination shows that complete crystallization of thermally isolated films up to a few hundred angstroms thickness occurs for a single laser pulse of ∼80 mJ/cm2. The crystals formed are up to ∼1 μ across and include precipitated voids whose origin is discussed in terms of a high-temperature fast-crystallization process.