HIGH-RATE GROWTH OF PURELY A-AXIS ORIENTED YBCO HIGH-T-C THIN-FILMS BY PHOTO-ASSISTED MOCVD

The growth of purely a-axis oriented YBCO thin films on LaAlO3 (100) substrates with no template layer addition has been accomplished by photo-assisted MOCVD. In addition to the requirement of lattice-matched substrates, the difficulty of growth of purely a-axis oriented YBCO films with this processing technique has been overcome by utilizing three appropriate processing/growth factors: substrate temperature (T-s), total partial pressure of oxidizing gases O-2 and N2O (P(O-2 + N2O)), as well as high film growth rate. A high growth rate (up to 7000 Angstrom/min) has been accomplished through MOCVD growth assisted by photo-irradiation with tungsten-halogen lamps. Variance of the three factors leads to tailored growth of either a-axis, c-axis or [110] oriented growth for YBCO. The growth of a-axis YBCO thin films under different precursor flow rates also affects the film morphology.