THE GROWTH OF (001)YBA2CU3O(7-DELTA) THIN-FILMS ON (001)MGO BY PULSEDORGANOMETALLIC-BEAM-EPITAXY WITH CONTROLLED INPLANE ORIENTATION

Thin films of (001) YBCO are grown on epitaxially polished (001) MgO b y pulsed organo-metallic beam epitaxy. The in-plane orientation of the film is controlled by the thickness of a BaO layer, grown in situ, Fr ier to the YBCO growth, For thin BaO layers (<approximate to 0.7x10(15 ) Ba cm(-2)) the films grow [110]YBCO parallel to[100]MgO. For thick B aO layers (>approximate to 1.1x10(15) Ba cm(-2)) the films grow. [100] YBCO parallel to[100]MgO. For YBCO films grown with thin BaO layers (> approximate to 0.7 times 10(15) Ba cm(-2)), ex situ, low energy Ar+ io n sputtering of the MgO surface prior to film growth will also induce a change of in-plane orientation from [110]YBCO parallel to[100]MgO on epitaxial polished MgO to [100]YBCO parallel to[100]MgO on Ar+ sputte red MgO, A mechanism that relates the change in YBCO in-plane orientat ion to a change in the structure of the initial BaO layers with BaO th ickness is described.