In situ investigation of polymorphous silicon deposition

Polymorphous silicon (pm-Si:K) consists of an amorphous silicon matrix in w hich silicon crystallites with nanometer sizes are embedded. This material combines the optical absorption of amorphous silicon (a-Si:H) with electric al transport properties close to those of microcrystalline silicon (mu c-Si :H). pm-Si:H. thin films were prepared by radio frequency plasma enhanced c hemical vapor deposition To get a better insight in the growth process, we measured the plasma electrically and by means of optical emission spectrosc opy. The optical properties of the films were measured by spectroscopic ell ipsometry (SE). The results are consistent with the proposal that the growt h precursors of pm-Si:H differ from those of mu c-Si:H and a-Si:H and that the silicon particles are formed in the gas phase. High resolution transmis sion electron microscopy (HRTEM) revealed the presence of crystallites with diamond and hexagonal structure embedded in the amorphous matrix. The ambi polar diffusion length in pm-Si:H is a factor of three longer than in optim ized a-Si:H as concluded from diffusion induced time resolved microwave con ductivity (DTRMC) measurements. (C) 2000 Elsevier Science B.V. All rights r eserved.