Hydrogen retention induced by ion implantation in tungsten trioxide films

Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Yoshikawa, Masahito; Shikama, Tatsuo*

We quantitatively studied the relation between hydrogen retention and optical properties induced by hydrogen ion implantation in tungsten trioxide (WO) films. Films of WO (300 nm) covered with tungsten metal layers (200 nm) were prepared on transparent SiO substrates by a reactive sputtering in Ar and O mixture. When H ions were implanted into the samples at an acceleration voltage of 10 kV, the concentration of hydrogen retaining in the WO films increased up to 0.4 H/W in proportion to the fluence of H ions. The optical absorption coefficient at 750 nm of samples increased linearly by 3 m with increasing the concentration of hydrogen implanted up to 0.1 H/W. And then, increased and saturated at 4 m with the increase of hydrogen concentration higher than 0.1 H/W. It was found that the hydrogen retention up to 0.1 H/W in tungsten trioxide layers can be monitored by measuring the optical absorbance.