GROWTH OF BETA-BARIUM BORATE (BETA-BAB2O4) THIN-FILMS FOR NONLINEAR-OPTICAL APPLICATIONS

We have prepared crystalline beta barium berate, beta-BaB2O4 (the so-c alled BBO), thin films on several kinds of substrates using pulsed las er deposition (PLD) and opposed-targets magnetron sputtering (OTMS) te chniques. From the measurement of X-ray diffraction, we have found tha t the crystallinity of the BBO film grown by both techniques is highly dependent on the deposition temperature and the choice of the substra tes. There is a different phase transition temperature for the BBO fil ms grown on different substrates and by different deposition technique s. The best films obtained were the ones grown on a sapphire (0001) su bstrate at a deposition temperature of 800 degrees C by PLD and 700 de grees C by OTMS, which show a single X-ray diffraction (006) peak norm al to the surface of the film. The second harmonic generation (SHG) si gnal of these films reveals a 6-fold symmetry with a large magnitude c ontrast between its maximum (1.2 pm/V) and minimum (0.2 pm/V).