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 (Ta 2 O 5 ) thin films were investigated and anti-reflective performances were discussed in detail. The Ta 2 O 5 thin films were deposited onto Corning Glass (CG), Si, GaAs and Ge substrates by radio-frequency (RF) magnetron sputtering technique using Ta 2 O 5 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 Ta 2 O 5 thin films at 100, 200, 300 and 500 °C have exhibited amorphous ( a -Ta 2 O 5 ) 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 Ta 2 O 5 thin film from 2.11 to 2.18 . The Ta 2 O 5 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 Ta 2 O 5 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.