Bismuth induced crystallization of hydrogenated amorphous silicon thin films: effect of annealing time

This paper investigates the effect of annealing time and Bismuth (Bi) interlayer on the crystallization of hydrogenated amorphous silicon (a-Si:H) thin films. Bismuth thin films, 50 nm in thickness, were deposited by physical vapor deposition on ⟨100⟩ oriented silicon substrates. Afterwards, a-Si:H films were elaborated by plasma enhanced chemical vapor deposition (PECVD) at fixed growth conditions to cover the Bi coated Si substrates. To investigate the role of the deposited Bi interlayer as a Metal Induced Crystallization (MIC) of amorphous Si thin films, annealing experiments were performed under N₂ atmosphere at 400 °C for different annealing times ranging from 2 h30 to 5 h. The effect of annealing time on the amorphous a-Si:H thin films in the presence of Bi interlayer has been evaluated in terms of crystallinity, preferential orientations, average surface roughness and atomic distribution using X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), scanning electron microcopies (SEM) and energy dispersive X-ray analysis (EDS). These results showed that a-Si:H thin films with high crystallinity could be obtained at annealing time (t_a) ≥ 2 h30. The electrical properties study of a-Si:H thin films revealed its correlation with their crystalline distribution which was enhanced due to the presence of the Bi interlayer.