SU8 Derived Glassy Carbon for Lithium Ion Batteries

We have fabricated single carbon nanowires (CNWs) suspended between carbon MEMS (CMEMS) structures with good Ohmic contacts employing photolithography, electrospinning and pyrolysis of SU8. By applying a current between the underlying CMEMS electrodes the CNW alone are Joule-heated, which initiate a chemical vapor deposition (CVD) process. We have successfully deposited a granular tungsten oxide (WO₃) film by decomposing tungsten hexacarbonyl [W(CO)₆] selectively onto these heated CNWs using this technique. WO₃ is a well known metal oxide semiconductor material extensively researched for its highly selective nitrogen oxide NO_x sensing ability. It is a wide band-gap (~2.7 eV) n-type semiconductor material, which exhibits high sensitivity, quick response and an enhanced selectivity to detect NO_x gases at low concentrations. The CNWs coated with WO₃ nanoparticles could become an invaluable addition to the nanosensor options as they might allow for NO_x gas sensor fabrication with at an affordable cost. The W(CO)₆ to WO₃ conversion reaction  takes place at 400-700^oC,[30] which is likely the actual temperature of the CNW. In other words the CVD deposition temperature is a good indicator of the actual temperature and the temperature profile along the length of the CNW. In addition, this fabrication technique can be utilized for a wide variety of applications by depositing any desired material from a volatile precursor at elevated temperatures selectively on to CNWs.