Nickel-induced crystallization of amorphous silicon

SCHMIDT, J. A.; BUDINI, N.; RINALDI, P.; ARCE, R. D.; BUITRAGO, R. H.

Puerto Iguazú, Misiones, Argentina

Simposio; XIX Latin American Symposium on Solid State Physics; 2008

Sociedad Latinoamericana de Física

We use the nickel-induced crystallization of hydrogenated amorphous silicon (a-Si:H) to obtain large grained polycrystalline silicon thin films on glass substrates. We deposited a-Si:H by plasma enhanced chemical vapor deposition at 200 ºC, preparing intrinsic (i), slightly p-doped (p-), strongly p-doped (p+) and strongly n-doped (n+) samples. Each sample was divided in several pieces, over which we sputtered increasing Ni concentrations. After a de-hydrogenation step, the samples were annealed at different temperatures and for different periods. The crystallization kinetics was followed by optical microscopy and scanning electron microscopy observations, X-ray diffraction, and reflectance measurements in the UV region. We present experimental results on the evolution of the crystallization process with the thermal treatments for the intrinsic and doped samples. We discuss the influence of the dopant atoms on the nucleation and growing steps of the crystallization process, proposing a model of growth. We present a correlation between the crystallization and the electrical properties of the samples. The large grain sizes obtained, around 26 µm for the intrinsic and p- samples, and the good electrical transport properties are very encouraging for the preparation of low-cost thin film polycrystalline silicon solar cells of structure glass/n+/p-/p+.