Femtosecond laser-induced CNT heterojunction as visible light photodetector

Abstract

Carbon nanotubes (CNTs) are one of the most promising materials for advanced electronic applications, due to its extraordinary chemical and physical properties. Non-linear interactions between photons and carbon bonds provide the possibility to fabricate unique photonic devices. In this paper we present the new technological route of single walled CNTs (SWCNTs) modification using femtosecond (fs) laser pulses to produce junctions in nanotubes through multiphoton oxidation of the carbon lattice with nanoscale resolution. SWCNTs were deposited onto Si/SiO2 substrate using gas-phase process based on thermal decomposition of ferrocene in the presence of carbon monoxide. Source and drain 100/20 nm Au/Ti electrodes were fabricated by photolithography, the gate electrode was p++ Si substrate. Samples were irradiated via fs laser with different energy fluence. Fs laser pulses at low energies were used to perform photocurrent measurements. Not modified SWCNTs and structures modified upon fs laser demonstrate a huge difference for light induced charge generation. We observed significant changes in optical and electrical properties of SWCNTs after the modification. Varying the parameters of power and laser scanning speed we can change the level of local oxidation of SWCNT and photocurrent in produced photodetectors.