In situ observation of nucleation and subsequent growth of clusters in silane radio frequency discharges

Growth processes of clusters in low-pressure and low-power silane radio frequency discharges are studied by using the newly developed double-pulse-discharge method which realizes in situ measurement of their size and density in a size range of 0.5-4 nm. The clusters begin to be composed of two size groups at about 10 ms after the discharge initiation: clusters in the small size group have an almost constant average size of about 0.5 nm through the discharge period, while those in the large one grow at about 4 nm/s in a monodisperse way. Time evolution of the measured average sizes and densities in the groups is transformed into that of size distributions assuming that the density of SinHx clusters for the small group decreases exponentially with the increase in the number of Si atoms, n, of them, and the size distribution for the large group is the lognormal one. The results show that a critical cluster size for nucleation is SinHx (n similar to 4). (C) 2000 American Institute of Physics. [S0003-6951(00)01828-3].