Growth of GdCa4O(BO3)(3) thin films by pulsed-laser deposition for nonlinear optical applications

This paper reports the first results obtained on calcium gadolinium oxobora te GdCa4O(BO3)(3) (GdCOB) thin films grown on silicon coated with amorphous silica at high temperature by pulsed-laser deposition (PLD). It was found that the chemical composition (i.e. Ca/Gd ratio) depends critically on the oxygen pressure used during pulsed-laser deposition (PLD) experiments. The crystallization of thin films about 500 nm thick required a high temperatur e substrate (750 degreesC) during the PLD process followed by a post anneal ing treatment at 800 degreesC in an oxygen atmosphere. Under these conditio ns, the layers are polycrystalline and no texturation features have been fo und. The surfaces of the films are smooth (average roughness: 5-6 nm) with only a few particles or droplets. The refractive index of the films is esti mated to be 1.746 at 633 nm, in agreement with the bulk GdCOB value.