Photoconductive Bi12MO20-type films prepared by pulsed laser deposition

Bi12TiO20 (BTO); Bi12GaxBi1-xO19.5 (BGaO); and Bi-12(M1/3P2/3)O-20, M = Cd, Zn, and Ni (BMPO) thin films were prepared by pulsed laser deposition usin g a KrF excimer laser on (100)Y-stabilized zirconia (YSZ), (100)Bi12GeO20 ( BGO), and (110)Bi12SiO20 (BSO) crystalline substrates. All these films have a sillenite structure. On (100)YSZ the silenite is oriented as {310} with the [130] direction parallel to the [021]YSZ directions ([130]{310}BTO\\[02 1]{100}YSZ). On (100)BGO and (110)BSO the sillenite film reproduces the sub strate orientation, and the films formed are able to channel He+ particles. The optimum deposition temperatures for BTO and BGaO are 600 and 550 degre es C, respectively. Higher temperatures must be avoided to minimize the nuc leation of Bi-deficient phases due to the diffusion of Bi into the YSZ subs trates. BMPO films are polycrystalline. The lattice parameters of these fil ms were determined. The crystalline films support guided optical modes. The refractive indices obtained for the films are close to those measured in b ulk crystals, being slightly larger for films deposited on isomorphous sill enite substrates. The crystalline films deposited on YSZ are photoconductor s when excited in the green and blue spectral regions.