Electron spin resonance of defects in single crystal and thin films of tungsten trioxide

The ESR spectra of single crystals and amorphous thin films of WO₃ have been measured in the temperature range 77-300^∘{}K. In the case of single crystal the observed resonance lines were identified as due to Mo⁵⁺ ions. The observed values are: gI=1.776, gII=1.796, and gIII=1.833 and the hyperfine splitting constants are AI=0.0029, AII=0.0026, and AIII=0.0074. In the case of thin-film broad resonance absorption at $g=2.012$ and $g=1.918$ was observed for colorless film which on electrocoloration showed an additional resonance at $g=1.75$. The temperature dependence of the electrical conductivity and spin density gave activation energies of 0.21 and 0.04 eV, respectively.