Amorphous germanium under pressure: intriguing phase transformation pathways and stable phases on pressure release

Description
This seminar is organized within the framework of WATER project. http://www.water.imm.cnr.it This presentation discusses our recent results using both nanoindentation and diamond anvil cells that resolve some raging controversies in the literature. For example we observe different transformation pathways if the applied pressure is hydrostatic or sheer and if the pressure is released rapidly or slowly. Rapid unloading leads to an intriguing a-Ge to diamond cubic transformation that we suggest is explosive recrystallisation.  We observe for the first time an R8 phase on slow pressure release that our collaborating theorists suggest should be semiconducting with a small band gap.  Annealing reveals hexagonal and ST12 germanium phases that ultimately anneal to the diamond cubic phase.