We fabricated thermally evaporated 30 nm-Ni/(20 nm or 60 nm)a-Si:H/Si films to investigate the energy-saving property of silicides formed by rapid thermal annealing (RTA) at temperatures of 350˚C, 450˚C, 550˚C, and 600˚C for 40 seconds. A transmission electron microscope (TEM) and a high resolution X-ray diffractometer (HRXRD) were used to determine the cross-sectional microstructure and phase changes. A UVVIS-NIR and FT-IR (Fourier transform infrared spectroscopy) were employed for near-IR and middle-IR absorbance. Through TEM and HRXRD analysis, for the nickel silicide formed at low temperatures below 450˚C, we confirmed columnar-shaped structures with thicknesses of 20~30 nm that had δ-Ni2Si phases. Regarding the nickel silicide formed at high temperatures above 550˚C, we confirmed that the nickel silicide had more than 50 nm-thick columnar-shaped structures with a Ni31Si12 phase. Through UV-VIS-NIR analysis, nickel silicide showed almost the same absorbance in the near IR region as well as ITO. However, in the middle IR region, the nickel silicides with low temperature showed similar absorbance to those from high temperature silicidation.