We have proposed, fabricated and tested a novel structure of Field-Effect Transistor (FET) combined with carbon nanotubes (CNT) to control the process of electrolysis. Our proposed device includes a conventional n-channel MOSFET, with a selective growth of carbon nanotubes in its drain region. MOSFET is made according to standard NMOS fabrication flow chart utilizing the advantage of a self-aligned process. The CNT growth is carried out in plasma and at a high temperature environment, so a thick layer of chromium (200nm) was deposited on the whole structure as a passivating layer to overcome MOSFET degradation caused by dopant escape. Afterward we deposited and patterned a thin layer of nickel (10nm) as the catalyst of CNT growth. The CNTs are grown in a DC-PECVD system. Following this step, we etched away the chromium layer completely. After the growth, the transistors needed an annealing treatment in Argon chamber at 500°C for 5 hours to retrieve their electrical behavior. We believe this happens because the atomic hydrogen can pass through the chromium layer and passivate the impurities and annealing in Argon chamber give them enough energy to leave the silicon.
In this structure, the CNT collection is used as one-side electrode of electrolysis and the MOSFET acts as the current controller. We tested the structure to electrolyze a one molar mixture of water and salt and observed well-controlled current-voltage characteristics.