Hydrogen retention induced by ion implantation in tungsten trioxide films

The relation between hydrogen retention and optical properties of an amorphous tungsten trioxide (WO3) film was investigated using 10 keV H2+ ion implantation. WO3 films (350 nm) covered by W layers (200 nm) were deposited on SiO2 glass substrates by sputtering in a mixture of Ar and O2 gases. The hydrogen concentration in the WO3 film was characterized by elastic recoil detection analysis (ERDA). The hydrogen concentration in the WO3 film increased by 0.4 H/W in proportion to the fluence of the H2+ ions implanted into the W layer. The optical absorption coefficient of the film at 750 nm increased linearly by 3 μm−1 with an increase in the concentration of the implanted hydrogen up to 0.1 H/W, and saturated at 4 μm−1 with the concentration higher than 0.1 H/W. These results indicate that the introduced hydrogen up to a hydrogen concentration of 0.1 H/W can be monitored by measuring the optical absorbance in the WO3 films.