NOVELTY - A layer of amorphous silicon (a-Si:H) film is deposited on a cleaned glass substrate. The film sample is immersed in hydrofluoric acid, and oxide layer is removed, and dried using nitrogen. A layer of metal tin film is deposited to obtain a substrate/a-Si:H/tin structure. The sample is taken out and placed in a thermal treatment furnace. Nitrogen is supplied, and the sample is annealed, naturally cooled, and soaked in concentrated hydrochloric acid. The surface of metal tin is removed to obtain a tin-metal-induced polycrystalline silicon film.    USE - Conversion of amorphous silicon film to tin-metal-induced polycrystalline silicon film for solar batteries and thin-film transistors.    ADVANTAGE - The method provides polycrystalline silicon film having a crystal grain size of 70-200 nm.    DETAILED DESCRIPTION - A common glass substrate is cut, surface is washed using a detergent, and the substrate is ultrasonically cleaned using acetone and deionized water for 15 and dried in an oven. Using plasma-enhanced chemical deposition, a layer of amorphous silicon (a-Si:H) film is deposited on the glass substrate, to a thickness of 200-300 nm at a substrate temperature of 200 degrees C, a deposition pressure of 10-5 Pa, an air pressure of 50-250 Pa, and a radio frequency power of 13.56 MHz, using a gas source containing 100% silane or 99.999% silane diluted with hydrogen. The amorphous silicon thin film sample is immersed in 1% hydrofluoric acid for 10 seconds, and the amorphous silicon film surface of the oxide layer is removed, dried using nitrogen, and put in a vacuum evaporator cell. A layer of metal tin film is deposited to a thickness of 10-20 nm at a vacuum evaporation current of 60 A, a tin evaporation temperature of 1184 degrees C, a pressure of 1\10-3 Pa, and a tin raw material purity of 5N (99.999%) to obtain a substrate/a-Si:H/tin structure. The sample is taken out and placed in a thermal treatment furnace. Nitrogen is supplied for 1 hour, and the sample is annealed at 450 degrees C, naturally cooled to room temperature, and soaked in 37.5% concentrated hydrochloric acid for 2 minutes. The surface of metal tin is removed to obtain a tin-metal-induced polycrystalline silicon film.