| Summary: | Amorphous carbon (a-C) films are attracting considerable attention to due their large optical band gap (E<sub>opt</sub>) range of 1−4 eV. But the hopping conducting mechanism of boron doping a-C (a-C:B) is still mysterious. To exploring the intrinsic reasons behind the semiconductor properties of a-C:B, in this work, the boron doping a-C (a-C:B) nano-film was prepared, and the growth rate and E<sub>opt</sub> changing were analyzed by controlling the different experimental conditions of magnetron sputtering. A rapid deposition rate of 10.55 nm/min was obtained. The E<sub>opt</sub> is reduced from 3.19 eV to 2.78 eV by improving the substrate temperature and sputtering power. The proportion of sp<sup>2</sup>/sp<sup>3</sup> increasing was uncovered with narrowing the E<sub>opt</sub>. The shrinking E<sub>opt</sub> can be attributed to the fact that boron atoms act as a fluxing agent to promote carbon atoms to form sp<sup>2</sup> hybridization at low energy. Furthermore, boron atoms can impede the formation of σ bonds in carbon atom sp<sup>3</sup> hybridization by forming B−C bonds with high energy, and induce the sp<sup>3</sup> hybridization transfer to sp<sup>2</sup> hybridization. This work is significant to further study of amorphous semiconductor films.
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