In situ simple method for measuring size and density of nanoparticles in reactive plasmas

A laser-light-scattering (LLS) method for measuring the size and density of nanoparticles generated in reactive plasmas has been developed. The size and density of the nanoparticles are determined from their thermal coagulation that takes place after turning off the discharge. The measurable size and density range of the LLS method is np⪆1013(m−3∕2)×dp−5∕2L−2ng−1, where np, dp, L, and ng are the density, size, and diffusion length of the nanoparticles, and the density of a background gas, respectively. The method has been demonstrated by measurement of the size and density of nanoparticles formed by the radio-frequency discharge of dimethyldimethoxysilane Si(CH3)2(OCH3)2 diluted with Ar. Using a simple optical setup for the LLS measurement, nanoparticles are detected down to ≈1nm in size when they are generated at a density of ≈1012cm−3. The developed method is widely applicable to other systems in which thermal coagulation takes place.