Dual-crossed-beam pulsed laser deposition of complex stoichiometry optical materials

Pulsed laser ablation appears as a promising technique for depositing thin films. A large variety of successful experimental results were obtained in this field, including the growth of high- temperature superconducting films, ferroelectric films, oxides, semiconductors, diamonds, etc. One of the main advantages of this technology is the relative simplicity of the experimental set-up and the possibility to get good homogeneity, complex stoichiometry materials and well adhesive dense layers. The main drawback seems to be the production of macroparticles, their transfer to the growing film inducing inhomogeneity and roughness onto the surface, lowering the properties of the thin films. In a common configuration, the laser-generated flux is collected on a planar substrate positioned parallel to the irradiated surface. In order to improve the stoichiometry and the quality of the films (particle free) several modifications were proposed like simultaneous generation of two plumes from different targets (double ablation) with different laser beams. In this paper, we present some results concerning the production of cryolite thin films using the conventional pulsed laser deposition technique (C-PLD) and the dual crossed beam pulsed laser deposition technique DCB-PLD). Plasma plumes expanding in vacuum and interacting together are visualized. The different species ejected in the plumes are detected through narrow-band filters in order to determine their kinetic energies. The morphology and the composition of the films are compared with the thermal evaporation technique.