Effect of argon dilution on the structure of microcrystalline silicon deposited from silane

The structure of the hydrogenated amorphous and microcrystalline silicon films deposited by radio-frequency (rf) glow discharge decomposition of silane diluted in argon has been studied by transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy techniques. It has been observed that argon acts not only as a passive diluent gas but also plays an important role in the growth of the amorphous or microcrystalline network. Calculation of the variation of equilibrium concentration of Ar*(P-3(0,2)) and Ar+ with argon dilution shows that at high argon dilution (>90%) equilibrium concentration of Ar* rises sharply with increase in argon dilution. Variation of structural properties with argon dilution suggests involvement of these excited states of argon in the growth process. A model has been proposed based on the energy exchange between the Ar* states and the growth zone of the materials to explain the structural changes observed in the presence of argon in the plasma. (C) 1996 American Institute of Physics.