Electric-field-enhanced metal-induced crystallization of hydrogenated amorphous silicon at room temperature

A novel simple method of crystallization of hydrogenated amorphous silicon (a-Si:H) thin films is described. Namely, we studied a metal-induced crystallization enhanced by a dc electric field in sandwich p--i--nstructures. The samples were fabricated from wide-bandgap a-Si:H with high hydrogen content (13--51 at.% H). Macroscopic islands of a-Si:H (up to ~1 mm in diameter) in the region between upper (CrNi) and lower (ITO) contacts crystallize instantaneously when a sufficiently high dc electric field ({greater than or equivalent to}10 Vcm) is applied. The crystallization sets in at room temperature and ambient atmosphere and is spatially selective. A proposed microscopic mechanism of such an easy macroscopic crystallization consists in easy diffusion of Ni and/or Ni silicides (representing nucleation sites) through a dense network of voids in hydrogen-rich a-Si:H.