Discovery of a metastable van der Waals semiconductor via polymorphic crystallization of an amorphous film.

Here we report on the growth of thin crystalline films of the metastable phase GeTe 2 . Direct observation by transmission electron microscopy revealed a Te-Ge-Te stacking with van der Waals gaps. Moreover, electrical and optical measurements revealed the films exhibted semiconducting properties commensurate with electronics applications. Feasibility studies in which device structures were fabricated demonstrated the potential application of GeTe 2 as an electronic material.