Optoelectronic properties and device physics of individual suspended carbon nanotubes

2015-04-15Carbon nanotubes (CNTs) have been studied extensively over the last two decades due to their remarkable mechanical, electronic, and thermal properties. Despite these numerous studies, there are still several important aspects of CNTs that are not well understood. The advance in fabricating ultra‐clean, nearly defect‐free, suspended single‐walled carbon nanotubes has been developed. This allows us to study many interesting physical phenomena due to CNTs’ one‐dimensional nature. ❧ Raman spectra are collected from CNTs at different gate voltages. When metallic CNTs are doped with an applied gate voltage, non‐adiabatic Kohn anomaly is shut off, and large modulations in Raman intensity are observed. A relationship between the strength of the non‐adiabatic Kohn anomaly and the intensity modulation of the Raman G- band is established. Possible structural phase transition is also proposed as an underlying mechanism for a Raman shift anomaly in 2D band. ❧ CNTs can be made into a p-n junction photodiode using dual gate FET structure. Photocurrent spectra are collected and a few exciton transitions can be distinguished. A gate voltage dependence on photocurrent intensity is observed and explained. ❧ In addition to CVD grown suspended CNTs, surfactant‐wrapped CNT solutions are also studied for photoluminescence (PL) and electroluminescence. We developed a PL imaging system to efficiently find CNTs that have emission energy in the Si detector range