J. Eur. Opt. Society-Rapid Publ. 21, 6( 2025) 49
Figure
4. SEM micrographs of( a)( b) the pure V 2 O 5 / FTO film and( c)( d) the TiO 2-doped V 2 O 5 / FTO film.
Figure 5. XRD image of( a) the pure V 2 O 5 / FTO film and( b) the TiO 2-doped V 2 O 5 / FTO film.
the TiO 2-doped V 2 O 5 / FTO film is 18.282 % at 700 nm and the average optical modulation amplitude in 400 – 1600 nm band is 7.423 %. Comparing with the pure V 2 O 5 / FTO film. the maximum optical modulation of the film increases by 9.663 % after TiO 2-doping, and the average optical modulation from visible light to near-infrared band increases by 2.973 %. It shows that the doping of TiO 2 powder has improved the optical properties of the film under the changing of temperature. The increases of the transmittance are probably due to the bandgap broadening of the composite film and the blueshifting of optical absorption boundary caused by TiO 2-doping.
To further investigate the electrical performance of TiO 2-doping effect to V 2 O 5 films, the MSM structures were fabricated based on the 12 % TiO 2-doped V 2 O 5 / FTO film and the pure V 2 O 5 / FTO film as shown in Figure 2, yielding to the FTO / V 2 O 5-TiO 2 / FTO device and the FTO / V 2 O 5 / FTO device. The resistance of the devices was measured at temperatures from 20 – 360 ° C under heating / cooling conditions. According to Figure 8( a), the resistance of the FTO / V 2 O 5 / FTO device is 177.60 kX at 20 ° C, while 149.35 X of the FTO / V 2 O 5-TiO 2 / FTO device, as shown in Figure 8( b). Comparing with the former device, the resistance of the latter reduces by 3 – 4 orders of magnitude, which may due to the change of the band structure of the material caused by TiO 2-doping, or the amount of the oxygen vacancies corresponds to Figure 6( e). During the heating process, the resistance-temperature curve displays a downward trend in three stages: slowly decreases from 20 ° Cto220 ° C, significantly drops from 220 ° Cto 290 ° C, and slowly decreases again from 290 ° C to 360 ° C. The minimum resistance reaches 84.08 X at