MoS2 nanoparticle formation in a low pressure environment

Formation of MoS2 nanoparticles at pressures between 0.5 and 10 Torr has be en studied. Two different chemistries for the particle nucleation are compa red: one based on MoCl5 and H2S, and the other based on MoCl5 and S. In bot h cases particle formation has been studied in a thermal oven and in a radi o-frequency discharge. Typically, the reaction rates at low pressures are t oo low for an efficient thermal particle production. At pressures below 10 Torr no particle production in the oven is achieved in H2S chemistry. In th e more reactive chemistry based on sulfur, the optimal conditions for therm al particle growth are found at 10 Torr and low gas flows, using excess of hydrogen. In the radio-frequency discharge, nanoparticles are readily forme d in both chemistries at 0.5 Torr and can be detected in situ by laser ligh t scattering. In the H2S chemistry particles smaller than 100 nm diameter h ave been synthesized, the sulfur chemistry yields somewhat larger grains. B oth in thermal and plasma-enhanced particle syntheses, using excess of hydr ogen is beneficial for the stability and purity of the particles. (C) 1999 American Institute of Physics. [S0021-8979(99)05217-2].