Pulsed laser deposition of mesoporous niobium oxide thin films and application as chemical sensors

The pulsed laser deposition (PLD) of a mesoporous niobium oxide, Nb-TMS1, and post-hydrothermal treatment result in mesoporous thin films (90 nm-3 mu m thick) having what appears to be a three-dimensional disordered hexagonal or 'wormhole' structure. These films were characterized by FT-IR spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The mesoporous Nb-TMS1 thin films were employed as the dielectric phase in capacitive-type chemical sensors. These sensors produce a capacitance change upon the reversible absorption of volatile compounds into the molecular sieve pores. The molecular sieve based sensors were exposed to a variety of analytes, including N-2, CO2, H2O, NH3, methanol and acetone. The mesoporous niobium oxide based sensors were found to be particularly good humidity sensors, exhibiting capacitance changes at least 10 times greater than that for N-2, ammonia, methanol and acetone. The Nb-TMS1 based sensors also showed responses to H2O that were 1000 times greater than for dense Nb2O5 based sensors prepared by PLD. (C) 1999 Elsevier Science B.V. All rights reserved.