Optical and structural characterization of pulsed laser deposited ruby thin films for temperature sensing application

Highlights: ► Epitaxial ruby thin film is deposited on sapphire substrate. ► The PL spectra for R lines show highly crystalline stress free film with FWHM of 11.4 cm−1. ► PLD ruby thin film can be used as photonics based temperature sensor. - Abstract: The ruby thin films were deposited by pulsed laser deposition (PLD) technique in an atmosphere of oxygen using ruby pellet, indigenously prepared by mixing Al2O3 and Cr2O3 in appropriate proportion. The characteristics R1 and R2 lines at 694.2 nm and 692.7 nm in the photoluminescence spectra of target pellet as well as that of PLD thin films, confirmed the ruby phase in both. The XRD and Raman spectra confirmed deposition of c-axis oriented crystalline ruby thin film on sapphire substrate. Effect of deposition time, substrate and deposition temperature on PLD grown thin films of ruby are reported. The intensity of R1 and R2 lines of PLD ruby thin films increased enormously after annealing the film at 1000 °C for 2 h. The film deposited on sapphire substrate for 2 h was 260 nm thick and the corresponding deposition rate was 2.16 nm/min. This film was subjected to temperature dependent photoluminescence studies. The peak positions of R1 and R2 lines and corresponding line width of PLD ruby thin film were observed to be blue shifted with decrease in temperature. R1 line position sensitivity, dν¯/dT, cm−1/K in the range 138–368 K was very well fitted to linear fit and hence can be used as temperature sensor in this range.