Photo-thermionic emission and photocurrent dynamics in low crystallinity carbon nanotubes

Abstract

Within this work, it is studied the photo-thermionic and photocurrent behavior of two kinds of carbon nanotube arrays, grown by chemical vapor deposition. One kind is fabricated by using a co-catalyst bilayer approach and other by a catalyst-free route by using a porous alumina membrane as a template. The carbon nanotubes fabricated by both approaches exhibit low crystallinity. To compute the thermal properties of the nanomaterials, a photothermal experiment was measured at 1064 nm wavelength, and numerical simulations were conducted to analyze the photo-thermionic emission dynamics. The high absorbance of the carbon nanotubes leads to reach temperatures above 1500 K, with time response in the millisecond order and emission currents in the nanoampere range. On the other hand, the photodetector behavior was confirmed by a single pulse experiment that induces fast photocurrent recognition associated to a photodiode. Our results highlighted the coexistence of stable states related to high-power and high-speed electronic conversion energy dependent on the growth mechanism of carbon nanotubes.