Structure and electrical conduction of WO3 nanorods epitaxially grown on mica

Tunsten oxide nanorods are grown on mica substrate in air from WO₃ vapor at 590 °C. They are epitaxially oriented on the substrate in three directions according to the hexagonal symmetry of the mica. Their morphology was investigated by Atomic Force Microscopy (AFM), their structure by Electron Diffraction (ED) and High Resolution Electron Microscopy (HRTEM). The energy dispersive X-ray analysis (EDX) associated with the TEM revealed the presence of potassium in the first step of the nanostructures growth suggesting the formation of a tungsten bronze. According to their thickness the nanorods have a structure either hexagonal or monoclinic. The structural investigations showed that numerous kinds of planar defects parallel to the growth direction are formed. The electrical conduction was analyzed with a Conductive Atomic Force Microscopy (CAFM) method which allows to obtain either an image of the resistance variations along the nanorods or a current-voltage response. The result demonstrates that the WO₃ nanorods form electrically networks suitable for gas sensing experiments.