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

Abstract

The growth of particle size has been measured in a low-pressure argon-silane plasma using high-resolution transmission 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 particles. 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: (i) 'rapid' formation of crystalline clusters (as shown by dark-field high-resolution transmission electron microscopy) with concentrations of up to 1010 cm-3; (ii) formation of aggregates, of diameters up to 50 nm, by coagulation (during coagulation the particle concentration decreases dramatically); and (iii) growth of the particles with a constant concentration by surface deposition of SiHx 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.