The spontaneous metal-sitting structure on carbon nanotube arrays positioned by inkjet printing for wafer-scale production of high sensitive gas sensor units

Highly sensitive single wall carbon nanotube (CNT)-embedded gas sensor units were fabricated by the mass production scheme. The wafer-scale produced sensor units provide repeatable sensing performances to 10 ppb level of NO2 and the distinctive response to CO. Inkjet approach was applied to deposit CNTs to be arrayed on a 4 in. wafer at designated positions and controlled the density of CNT arrays with reliable accuracy. Metal deposition above the CNT arrays forms the metal-sitting structure providing a good Ohmic contact formation, which also ensures the active CNT responses to gas molecules with less effect from the metal contacts.We discuss the reaction mechanism of CNTs to gas species and mass production schemes of sensor units on a wafer-scale.