Laser-induced structural transitions in YBa2Cu3Oy amorphous films with nanocrystalline clusters

We investigated the influence of UV (KrF, (h) over bar omega=5.01 eV) pulse d laser irradiation on the atomic order and optical properties of amorphous YBaCuO films containing crystalline clusters of nanometer (up to 25 nm) si ze and characterized by high mobility of structural elements due to the lac k of sharp interphase boundaries. The presence of crystalline clusters in a morphous medium leads to higher disorder of the latter, while electronic st ates in relatively narrow (approximate to 2 eV) Cu 3d(10) band become local ized and practically do not participate in optical transitions. We found th at UV radiation destroys the crystalline clusters, increases order in the a morphous medium and initializes the processes of (11l)+(10l)double right ar row(00l) orientational transition. Increase of atomic order results in part ial delocalization of electron states in the Cu 3d(10) band and the conduct ion band switches over from Cu 4s(1) to Cu 3d(10).