Photocurrent Study of Locally Grown and Solution-deposited Carbon Nanotubes

International audienceCarbon nanotubes (CNTs) present extraordinary properties that make them a particularly attractive option for a variety of applications in electronics. CNTs can display either metallic or semi-conducting behavior according to their chirality and diameter and are predicted to display photocurrent in the latter case. Optical switching or modulation in electronic components can thus be envisioned. Here, we report an investigation of photocurrent generation parameters in CNTs as a preliminary step to optically switched RF components. The fabrication and characterization of the CNT test structures are presented. Two approaches are explored. The first type of structures is made through a three-step process. Quartz substrates are scratched with sharp metallic objects to produce catalytic nanoparticles. Aligned CNTs are then grown by chemical vapor deposition (CVD) in a quartz tube furnace. Finally, Titanium-Gold coplanar waveguides are fabricated on top of the CNTs, to allow for reproducible electrical contact and high-frequency measurement. As a complementary method, other samples have been fabricated using CNT-solution deposition techniques. DC photocurrent measurement is performed using a lock-in amplifier setup and a continuous-wave laser. We highlight how various parameters affect the photo/thermo-conductivity. We report and propose explanations for the rather different responses obtained depending on the type of CNTs produced