Boron thin films were deposited by pyrolysis of decaborane. The substrate was heated up to 1200 degrees C by infrared irradiation from a halogen lamp. The films were characterized by electron beam diffraction, XPS and electrical measurements. Spots and rings were observed in the electron beam diffraction patterns, which indicates that the films consist of alpha-rhombohedral boron. The activation energy of the conductivity was 0.1-0.3 eV from R.T. to 500 degrees C and 1.0-1.4 eV above 500 degrees C. This demonstrates that infrared radiation is an effective method in obtaining high quality boron films via the pyrolysis of decaborane.