Optical characterization of boron-doped nanocrystalline Si:H thin films

We report on the optical properties of boron-doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films grown on glass substrates by plasma-enhanced chemical vapor deposition (PECVD), using X-ray diffraction (XRD), Raman scattering, and optical transmission measurements at room temperature. Wavelength-dependent optical constants (refractive index and extinction coefficient) are deduced from the optical transmission spectra by the well-known Tauc–Lorentz (TL) model with an empirical modification, instead of the conventional envelope method. The refractive-index behavior (magnitude and dispersion) below the interband absorption edge can be well described by the one-oscillator Wemple–DiDomenico model, which also reveals structural information of these nc-Si:H samples. The extinction coefficients are very close to those obtained independently by the Forouhi–Bloomer (FB) model. New physical significance implicit within the TL model has been tentatively discussed on the basis of the refractive-index results of the B-doped nc-Si:H in this work, and intrinsic nc-Si:H as well as many other Si-related materials in the literature.