Boron-doped hydrogenated nanocrystalline silicon (nc-Si(B):H) films were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD). The effect of Ar/H 2 ratio on the characteristic of as-grown nc-Si(B):H films was investigated systematically with Raman scattering, XRD, XPS as well as Hall effect measurements. The experimental results indicate that the increase of Ar/H 2 ratio can enhance the concentration of B in the as-grown films. On the other hand, with the Ar/H 2 ratio increasing, the crystallinity of the films deteriorated sharply, and the electrical properties of the as-grown films decreased. Langmuir Probe was used to investigate the electron temperature (T e ) of microwave activated B 2 H 6 /Ar/H 2 plasmas. Finally, the microscopic mechanism of the enhancement in doping efficiency was elucidated in terms of the plasma reaction equations of B 2 H 6 and Langmuir probe testing result.