3.1.1 Micro- reactors and gas sensors based on locally heated carbon nanotubes decorated with Ti nanoparticles

Abstract

In this work, we report design and fabrication of micro-sensors and reactors based on nanoparticledecorated carbon nanotubes.The reactors, having a volume of 100μl, were machined from one single Kovar ® piece in order to avoid leaks in the system due to additional welding.The connections for controlling pressure and atmosphere in the working chamber are provided by 1/4" Swagelok ® tubes placed at diametrically opposite positions from the testing chamber.The contacts were electrically insulated from the metallic body of the reactor using borosilicate sealing glass frit.Successively, the reactor was gold plated and hermetically sealed using a lid with Viton ® o-ring.The dielectrophoresis technique was used for deposition of CNTs over patterned electrodes.Titanium adhesion layers (30nm) and 150nm gold films were sputtered onto Si/SiO 2 substrates.Sequentially, the gold layers were electrochemically thickened until 1μm and the electrodes were patterned using photolithography and wet chemical corrosion.Before the deposition, a gap 1μm wide and 5μm deep was milled in the metallic line by focused ion beam.This procedure allowed us to fabricate sensors based on suspended nanotubes bridging the electrodes.Successively, the sputtering technique was used for CNTs decoration with Ti nanoparticles.The as-obtained sensors were electrically connected to the reactor by the wire-bonding technique.The sensors were tested using different gases and pressure ranges.The small chamber volume allowed the measurement of fast sensor characteristic times, with the sensors showing good sensitivity towards gas as well as high reproducibility.