Comparative Studies on the Laser Damage Resistance of Ta₂O₅ and Nb₂O₅ Films Performed under Different Electron Beam Currents

Ta₂O₅ and Nb₂O₅ films are deposited by conventional e−beam method under different electron beam currents. The optical transmittance, chemical composition, absorption, scattering, surface topography and laser-induced damage threshold (LIDT) of the films are comparatively studied. It is shown that the increase of electron beam current results in a decrease of the optical transmittance and stoichiometry, whereas it increases the absorption, scattering and rms roughness for both Ta₂O₅ and Nb₂O₅ films. However, the LIDT increases first and then decreases with the increase of electron beam current. In addition, the annealing improves the optical transmittance, stoichiometry and LIDT for the two kinds of films. Both the effects of electron beam current and annealing on the LIDT can be mainly attributed to three factors: substoichiometric defects, structural defects and adhesive force. Furthermore, the comparative results indicate that the laser damage resistance of Ta₂O₅ is lower than that of Nb₂O₅.