In situ analysis of the conductance of SnO2 crystalline nanoparticles in the presence of oxidizing or reducing atmosphere by scanning tunneling microscopy

SnO2 crystalline semiconductor nanoparticles have been studied by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) in ord er to analyze the change of conductance spectra in an oxidizing or reducing atmosphere. We measured tunneling current versus bias voltage and obtained STM images in different bias voltage conditions for SnO2 nanoparticles pla ced on the surface of different gas sensor layers. There was a reduction of surface bandgap and a displacement of the gap to positive bias potentials in a reducing environment, but we observed an increase of surface bandgap a nd a displacement to negative bias potentials in an oxidizing atmosphere. The presented methodology of study becomes an innovative powerful tool for the development and understanding of semiconductor gas sensors. (C) 2001 El sevier Science B.V. All rights reserved.