Growth and characterization of ultrathin TiO2-Cr2O3 nanocomposite films

This paper presents growth of TiO2-Cr2O3 nanocomposite ultrathin films (∼30 nm thick) by sputtering technique for gas sensor applications. The deposited films were annealed to grow rutile TiO2 and eskolaite Cr2O3 phases. Grain sizes of the pristine Cr2O3 and TiO2 films (45-50 nm) were found to be larger compared to the nano-composite (7.1-69.5% Cr2O3 in TiO2) films (15-40 nm). The Raman spectra of the pristine TiO2 film showed peaks at 220 cm−1(B1g), 435 cm−1 (Eg) and 610 cm−1 (A1g) are attributed to the rutile phase of TiO2. The pristine eskolaite Cr2O3 layer exhibited four Eg peaks at 300 cm−1, 350 cm−1, 520 cm−1 and 620 cm−1 along with the characteristic intense peak at 551 cm−1 (A1g mode). The peak positions of the A1g mode (Cr2O3) and Eg mode (TiO2) are found to be red shifted from its characteristic peak positions; but no shift is detected due to the intermixing of Cr2O3 and TiO2 phases. However, the FWHM of the A1g mode is found to be increased from 9 cm−1 (pristine Cr2O3) to 13 cm−1 (26.1% Cr2O3); while the Eg mode is found to be increased from 48 cm−1 (pristine TiO2) to 80 cm−1 (46.9% Cr2O3) due nanocomposite formation between the rutile and eskolaite phases.