Direct integration of Carbon Nanotubes in Si microsystems — Towards truly integrated micro/nano systems

Nanomaterials such as Carbon Nanotubes (CNTs) show a long range of properties opening for new applications, but their integration into microsystems remains a challenge for widespread use as functional materials in electronics and smart systems. This paper presents our work towards a process for making complete, integrated CNT / CMOS / MEMS systems. We demonstrate the feasibility of the process, using room-temperature processing, low-cost equipment and consumables, and electrical control with automation possibilities. CNTs are directly integrated at the desired positions in the Si microsystem, forming closed Si / CNT / Si circuits. These circuits can show rectifying (Schottky-like) or near-ohmic behavior. A Si / CNT / Si circuit is shown to respond to CO₂ presence in Ar atmosphere, indicating the possible of monitoring aging/ fermenting of food packaged in inert atmosphere by a sensor fabricated by the method investigated in this paper. The possibility of functionalization of CNTs is demonstrated, using thermal evaporation of Pd. This opens for selective and sensitive sensors for various gases and analytes. Detailed microscopic characterization of the obtained CNTs are presented.