Hydrogenated Amorphous Silicon (a-Si:H) Colloids

Colloidal particles of hydrogenated amorphous silicon (a-Si:H) were synthesized by decomposition of trisilane (Si3H8) in supercritical n-hexane (sc-hexane) at temperatures ranging from 380 to 550 °C. The reaction temperature, pressure and Si3H8 concentration have a significant influence on the average particle size, Si bond order and hydrogen content. The particle diameter could be varied from 170 nm to 1.7 μm, with hydrogen loadings between 10% and 58%. Raman spectroscopy of the particles revealed significant differences in Si bond order that correlated with hydrogen content, with the lowest reaction temperatures yielding particles with the least structural order and most associated hydrogen. Particles synthesized at temperatures higher than 420 °C had sufficient bond order to allow crystallization under the Raman laser probe.