Bi-12(GaxBi1-x)O-19.5 optical waveguides grown by pulsed laser deposition

Bi-12(GaxBi1-x)O-19.5 (BGaO) films with thickness in the range 100-1000 nm have been deposited on (100) Y-stabilized zirconia (YSZ) and (100) Bi12GeO20 (BGO) substrates using a KrF excimer pulsed laser and polycrystalline targets with composition x=0.63-0.72. The laser power density threshold for ablation of the targets has been determined to be J(0)=4.8 J/cm(2). A deposition rate of 0.03 Angstrom/pulse was found for the substrate-target distance (6 cm) and laser fluence (J=7 J/cm(2)) used. Transparent and crystalline films were obtained heating the substrate in the 450-550 degrees C range under 1.5X10(-1) mbar of oxygen pressure. Films deposited on hot substrates have a Ga stoichiometry x=0.5 but a Bi content slightly lower than that corresponding to sillenite. Films deposited on YSZ show preferential orientation. From the x-ray diffraction results and the comparison of the ionic distributions, it has been concluded that the most likely orientation between both lattices is [310]{130}BGaO parallel to[011]{100}YSZ. A {100}BGaO parallel to{100}BGO epitaxy has been inferred from Rutherford backscattering analysis. On both substrates the films behave as step waveguides with refractive index close to the value determined in bulk BGaO. (C) 1996 American Institute of Physics.