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 W${\mathrm{O}}_3$ 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 ${\mathrm{Mo}}^{5+}$ ions. The observed values are: $g_{\mathrm{I}}=1.776\mathrm{}$, $g_{\mathrm{II}}=1.796\mathrm{}$, and $g_{\mathrm{III}}=1.833\mathrm{}$ and the hyperfine splitting constants are $A_{\mathrm{I}}=0.0029\mathrm{}$, $A_{\mathrm{II}}=0.0026\mathrm{}$, and $A_{\mathrm{III}}=0.0074\mathrm{}$. In the case of thin-film broad resonance absorption at $g=2.012\mathrm{}$ and $g=1.918\mathrm{}$ was observed for colorless film which on electrocoloration showed an additional resonance at $g=1.75\mathrm{}$. The temperature dependence of the electrical conductivity and spin density gave activation energies of 0.21 and 0.04 eV, respectively.