PLD of thin WO₃ films for solid-state electrochromic cells

The thin WO₃ films have been produced on the c-sapphire and melted quartz substrates by the droplet-free pulsed laser deposition method at the oxygen pressure from 20 to 60 mTorr. The oxygen pressure influence on the optical properties and morphology of the WO₃ films has been investigated in the spectral range from 200 to 2000 nm. The surface roughness of the films poorly depended on the oxygen pressure during the film deposition and was 4-5 nm. The transmission of the WO₃ films increased from 40% to 75% in the visible and UV regions, and from 10% to 70% in the IR region as the oxygen pressure was varied from 20 to 60 mTorr during the film growth. The energy gap width of the WO₃ films produced at the room temperature changed from 3.01 to 3.34 eV for the films on the sapphire substrates and from 2.95 to 3.42 eV for the films on the quartz substrates with increasing the oxygen pressure from 20 to 60 mTorr during the film deposition. The maximum transparency of the c-Al₂O₃/SnO₂:Sb/WO₃ structure was reached at the oxygen pressure of 60 mTorr during the WO₃ film growth, and the thermal annealing of this structure expanded the range of its transparency in the UV region from 3.5 to 3.6 eV and raised the maximum transparency by 10% in the IR region. (paper)