In situ monitoring of hydrogen desorption from silicon nanoparticles dispersed in a nonthermal plasma

In this paper, the authors discuss the use of Fourier transform infrared absorption spectroscopy to monitor the hydrogen surface coverage of silicon nanoparticles suspended in an argon-hydrogen nonthermal plasma. The absorption from surface silicon hydride groups is measured by growing nanoparticles from silane in a first plasma reactor and by passing them through a second plasma reactor intersected by an infrared beam. Using this setup, the authors obtain an in situ, in-flight measurement of the surface termination. They have found that hydrogen surface coverage declines at increasing plasma power. Control experiments performed on particles collected onto a substrate and exposed to the same plasma indicate that the loss of hydrogen is the result of a thermally induced desorption process. By using well-established kinetic rates for hydrogen interactions with silicon surfaces, the authors estimate the nanoparticle temperature to be in the 650-750K range. This work provides additional experimental evidence that dust suspended in a low-pressure partially ionized gas is heated to a high temperature, enabling the production of high-quality nanocrystals. (C) 2016 American Vacuum Society.