Deposition of MgF2 Thin Films by Pulsed Laser Ablation Technique

In this paper, we report the successful growth of MgF2 thin films on Si and sapphire (Al2O3) substrates at room temperature by direct laser ablation of a pure MgF2 target. The irradiations were performed in high vacuum (10-5 Pa) using the fourth harmonic of a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (λ= 266 nm, τFWHM = 7 ns) with energy density of about 10 J/cm2. Uniform films, with a good adhesion on the substrate were obtained. The average ablation and deposition rates resulted to be 1.1 µg/pulse and 0.03 Å/pulse, respectively. Different diagnostic techniques were used to study the morphology and chemical composition of deposited films. Time-resolved mass spectrometry studies of the laser ablated material indicate a strong correlation between the chemical species present in the plume and the residual gas. Present interest in the deposition of MgF2 thin films by laser ablation technique is related to their potential application as protecting coating in photocathodes.