Roles of hydrogen dilution on the microstructural and optoelectronic properties of B-doped nanocrystalline Si:H thin films

Abstract

We report on the roles of hydrogen dilution on the microstructural and optoelectronic properties of boron-doped nanocrystalline silicon thin films grown by plasma-enhanced chemical vapor deposition on glass substrates, through x-ray diffraction, scanning electron microscope, Raman scattering, optical transmission, temperature-dependent dark conductivity, and elastic recoil detection analysis (ERDA) measurements. The grain size, crystallinity, absorption coefficient, refractive index, and conductivity are found to decrease basically with increasing hydrogen dilution ratio ΔH. The Tauc’s optical band gap is found to increase with ΔH due to the quantum size effect. By the aid of hydrogen ion bombardment effect [J. Appl. Phys. 93, 1262 (2003)] as well as the hydrogen-induced annealing effect, the clear increase of hydrogen content with ΔH and the different hydrogen distribution from ERDA help us to elucidate the correlation of hydrogen dilution with the crystallinity and grain size. The argument has been further supported by a simple absorption model and the yielded refractive index and absorption coefficient.