Growth and characterization of ultrathin TiO2-Cr2O3 nanocomposite films

Abstract

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.