Low-temperature growth of crystalline silicon on a chlorine-terminated surface

We report on the role of surface termination during growth of crystalline silicon at low temperatures. Microcrystalline silicon was fabricated using plasma-enhanced chemical-vapor deposition with a hydrogen-diluted dichlorosilane $(SiH2Cl2)$/monosilane $(SiH4)$ mixture to study the role of hydrogen and chlorine in crystal formation. When varying the fraction of $SiH2Cl2,$ $x=[SiH2Cl2]/([SiH4]+[SiH2Cl2]),$ good crystallinity was obtained for $x=0$ and 1, whereas the crystallinity was markedly deteriorated for intermediate x. Optical emission spectroscopy of the plasma suggests that film precursors different from $SiHx$ fragments and atomic chlorine are generated for $x≠0$ and that atomic hydrogen is generated in all cases. Infrared reflection absorption spectroscopy indicates that the surface coverage is hydrogen for $x=0,$ chlorine for $x=1,$ and a hydrogen–chlorine mixture for intermediate x. These results imply that low-temperature growth of crystalline silicon is facilitated on a chlorine-terminated surface as well as on a hydrogen-terminated surface under the presence of atomic hydrogen. The cooperative roles of chlorine and hydrogen are proposed in the crystal growth of Si.