Tin oxide (SnO2) nanotubes have been synthesized using carbon nanotubes (CNTs) as removable templates. The entire synthesis takes place on the microscale on a micromachined hotplate, without the use of photolithography, taking advantage of the device’s built-in heater. Well-aligned multiwalled CNT forests were grown directly on microhotplates at 600 °C using a bimetallic iron/alumina composite catalyst and acetylene as precursor. Thin films of anhydrous SnO2 were then deposited onto the CNT forests through chemical vapor deposition of tin nitrate at 375 °C. The CNTs were then removed through a simple anneal process in air at temperatures above 450 °C, resulting in SnO2 nanotubes. Gas sensing measurements indicated a substantial improvement in sensitivity to trace concentrations of methanol from the SnO2 nanotubes in comparison with a SnO2 thin film. The synthesis technique is generic and may be used to create any metal oxide nanotube structure directly on microscale substrates.
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