Liquid phase epitaxy growth and structural characterization of highly-doped Er3+:LiYF4 thin films

Single-crystalline layers of LiYF4, singly doped with Er3+ ions and codoped with Er3+,Gd3+ ions are grown on (001) oriented undoped bulk LiYF4 substrates by Liquid Phase Epitaxy using LiF as a solvent. For the starting composition 73 LiF - 27 REF3 mol% (RE = Y, Er, Gd), the onset of crystallization is about 746 degrees C. The effect of apparent supercooling on the growth behavior is studied indicating an optimum value of 0.5 degrees C. Layers of 30-90 mu m in thickness are obtained corresponding to a growth rate of 0.8-1.6 +/- 0.5 mu m/min. The morphology, structure and composition of the layers are studied. The layers exhibit tetragonal structure (sp. gr . I4(1)/a) and small lattice mismatch with respect to the substrate. The segregation coefficient for Er 3+ ions is close to unity. Intense mid-infrared luminescence of Er3+ ions at similar to 2.8 mu m is observed from the layers, which, together with the waveguiding properties, indicates their suitability for waveguide lasers.