Particle nucleation and growth in a low-pressure argon-silane discharge

The growth of particle size has been measured in a low-pressure argon-silane plasma using nigh-resoltion transmssion electronic microscopy. The results show that formation and growth of dust particles is an homogeneous process; the first generation size distribution is monodispersed; and the growth kinetics reveals a three-step process from molecular ions to large panicles. Together with measurements of particle concentration obtained by laser light scattering, these measurements give a clear indication that the growth proceeds through three successive steps: (1) 'rapid' formation of crystalline clusters (as shown by dark-field high-resolution transmission electron microscopy) with concentrations of LP to 10(10) cm(-3); (ii) formation of aggregates, of diameters up to 50nm, by coagulation (during coagulation the particle concentration decreases dramatically); and (iii) growth of the panicles with a constant concentration by surface deposition of SiH(x) radicals, whilst the numerical density remains constant. Laser-induced particle explosive evaporation has been performed using a XeCl (308 nm) laser. This experiment allowed detection of nanocrystallites and also the beginning of their coagulation and gave clear evidence of the temperature effect on particle formation.