Strategies for the synthesis of highly concentrated $Si1−yCy$ diamond-structured systems

Precursor chemistry and ultrahigh-vacuum chemical vapor deposition have been used to deposit $Si1−yCy$ thin films on (001) Si substrates. Films with carbon compositions ranging up to 20 at. % were deposited at substrate temperatures of 600–740 °C using gas mixtures of $SiH4$ with $C(SiH3)4$ or $C(SiH2Cl)4,$ which are (C–H)-free precursors incorporating $Si4C$ tetrahedra. The composition of the resulting materials was obtained by Rutherford backscattering spectrometry, including carbon resonance analysis. Cross-sectional transmission electron microscopy and infrared spectroscopy were used to provide microstructural and bonding information. Raman spectroscopy suggested that the substitutional C concentration obtained using this protocol was higher than that obtained by other methods. The addition of small amounts of $GeH4$ to the gas mixture had a remarkable effect on growth rates and film crystallinity.