Influences of annealing temperature on anti-reflective performance of amorphous Ta2O5 thin films

Abstract Influences of thermal annealing on structural, optical and morphological properties of the tantalum pentoxide (Ta2O5) thin films were investigated and anti-reflective performances were discussed in detail. The Ta2O5 thin films were deposited onto Corning Glass (CG), Si, GaAs and Ge substrates by radio-frequency (RF) magnetron sputtering technique using Ta2O5 ceramic target. The obtained secondary ion mass spectroscopy (SIMS) analysis results showed that uniform Ta and O distribution have formed throughout depth of the films deposited on substrates. The X-Ray diffraction (XRD) results indicated that the annealed Ta2O5 thin films at 100, 200, 300 and 500 °C have exhibited amorphous (a-Ta2O5) characteristic. The increased temperature has resulted in increasing the surface roughness from 0.67 to 1.60 nm. The optical transmittance of the annealed thin films has increased from 70.85 to 80.32% with increasing temperature. Spectroscopic ellipsometer (SE) measurement results demonstrated that the increased temperature has increased the refractive index of the Ta2O5 thin film from 2.11 to 2.18. The Ta2O5 thin film has reduced the average optical reflectivity of the Si, GaAs and Ge substrates by 78, 55 and 70%, respectively. In addition, thermal annealing process has decreased the optical reflectivity of the film. The obtained experimental results showed that single-layer Ta2O5 thin films can be used as anti-reflective layer in optical and optoelectronic applications. The best optical transmittance and anti-reflective performance were obtained at the annealing temperature of 500 °C.