Measuring Gas Temperature of a Microwave Plasma Chemical Vapor Deposition Reactor by Coherent Anti-Stokes Raman Scattering Spectroscopy

posted Jun 14, 2013, 8:38 AM by Timothy Fisher   [ updated Jun 18, 2013, 10:25 AM by Alfredo Tuesta ]

Student: Alfredo Tuesta

Faculty: Tim Fisher, Bob Lucht

Sponsor: National Science Foundation

Summary: Carbon nanostructures, such as carbon nanotubes and graphitic petals, have widely become the research topic for many due to their remarkable mechanical and electrical properties. Their potential applications in science and technology depend not only on the research conducted on their properties but also on an understanding of the chemical environment responsible for synthesizing them. In this study, the hydrogen (H­2) of the plasma in a Microwave Plasma Chemical Vapor Deposition (MPCVD) reactor is investigated by Coherent anti-Stokes Raman Scattering (CARS) spectroscopy using the second harmonic of a pulsed Nd:YAG laser at 532nm as the probe and pump beams and a broadband dye at 685nm as the Stokes beam. CARS spectroscopy is a spatially resolved optical technique extensively utilized to explore the concentration and temperature of Raman-active molecules such as H2, N2, and CO2 in combustion and plasma processes. Preliminary results reveal that for plasma generator powers of 300 W and 500 W at 10 Torr, the temperature range is approximately 700-1200 K while for plasma generator powers of 500 W and 700 W at 30 Torr, the temperature range is approximately 1100-1800 K. An improved understanding of the physics and chemistry of the synthesis environment will advance computational modeling efforts and the potential for mass production of nanodevices.