Ultrathin microc-Si films deposited by PECVD

The crystalline fraction of microcrystalline silicon films 18-200 nm thick, deposited by VHF plasma and by chemical transport deposition (CTD) was characterized by Raman and optical measurements. On a p-type CTD sample, thinner than 20 nm, a crystalline fraction as large as 78%, to our knowledge the largest obtained by VHF plasma on p-type films in this thickness range, was measured. Transmission electron microscopy shows crystallites extending to the interface with the substrate. Electrical conductivities in the range 10(-2)-10(0) S/cm, and 10(-1)-10(1) S/cm after annealing at 250 degreesC, were measured. Weak dependence of crystalline fraction and electrical properties on thickness was observed.