Nanocrystalline Si:H films and nanocrystalline Si:H film based p -n junctions were fabricated by rapid thermal annealing (RTA) of amorphous silicon films deposited by hot-wire chemic al vapor deposition.Dependence of the structural and optical properties of the nanocrystalline Si:H films on the annea ling temperature is studied by Raman spectroscopy,X-ray diffraction,scanning electron microscopy and spectrophotomet er.The temperature dependent I-V characterization of the junctions is also studied.The Raman results show that the crystalline fraction of the films is gradually increased from 46.3% to 96%,and the full width at half maximum (FWHM) is gradually decreased from 19.7cm－1 to 7.1cm－1 as the RTA tem perature is increased from 700℃ to 1100℃.The X-ray diffraction results show that at the annealing temperature of 700℃,only a small peak corresponding to the Si(111) plane is observed in the spectrum. In contrast,as the annealing temperature increasing above 900℃,the spectra of the nanocrystalline silicon films show Si(111),Si(220) and Si(311) orientations.At the same time,the band gap of the de posited nanocrystalline silicon films is increased from 1.68eV to 2.05eV as the RTA temperature increasing from 700℃ to 1100℃.On the other hand,with the increasing of the band gap,the highest working temperature of the correspon ding p-n junctions is gradually increased from 180℃ to 300℃.