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In order to study the possible advantage of photo-assisted MOCVD compared with thermal MOCVD during the annealing process after film growth, a piece of c-axis oriented YBa2Cu3O7−δ film on Φ1″ LaAlO3 (1 0 0) substrate was prepared by photo-assisted MOCVD. It has well in-plane alignment and high critical current density (Jc > 2.5 MA/cm2, @ 0 T, 77 K, thickness ≈ 430 nm). Small pieces cut from it were annealed by photo-assisted or thermal annealing process to realize deoxidization or oxidization respectively. By monitoring the c-axis lattice constant, it was found that oxidization rate of photo-assisted annealing is obviously higher than that of thermal annealing. Inversely, the deoxidization rate of photo-assisted annealing is lower than that of thermal annealing. And a phenomenon that the long-time stable c-axis lattice constant is related to the temperature, unrelated to annealing process has been observed. It conforms to the thermodynamic equilibrium which is relative to annealing temperature and oxygen partial pressure, irrespective to whether photo activation or thermal activation.

Pure GdBa 2 Cu 3 O 7− δ (GdBCO) films were deposited on (1 0 0)-oriented LaAlO 3 (LAO) substrates by photo-assisted metal organic chemical vapor deposition (PhA-MOCVD) technique. The effects of substrate temperature ( T s ) and oxygen partial pressure (Po 2 ) on microstructure, growth rate and superconducting critical current density ( J c ) were investigated. A dense and no grain boundary visible, single-crystal-like cross-sectional morphology was observed. For the GdBCO film sample obtained at T s of 810 °C and Po 2 of 4 Torr, the full width at half-maximum were 0.08° and 0.41° for out-of-plane and in-plane orientations, respectively. Such low values were similar to that of single crystal GdBCO. Optimally processed GdBCO samples exhibited J c of 2.5 MA/cm 2 at 77 K in self-field. A relatively high growth rate of 0.104 μm/min for the GdBCO film is realized by the PhA-MOCVD technique.

Y 2 O 3 nanodots were fabricated on vicinal substrate (1 0 0)-oriented LaAlO 3 (LAO) by photo-assisted metalorganic chemical vapor deposition (PhA-MOCVD). Nucleation and growth processes of Y 2 O 3 nanodots self-assembled as rows along the terraces of LAO were investigated with various growth parameters. It is found that density and size of Y 2 O 3 nanodots can be tuned and well controlled by varying substrate temperature ( T s ), oxygen partial pressure and growth time. At lower T s , the morphologies of Y 2 O 3 nanodots are characterized by small and dense solid cones. With elevating T s , the dots gradually grow larger and sparser. This phenomenon could be illustrated by two competitive kinetic processes, i.e. surface diffusion of adatoms and yttrium desorption. Morphologies of these nanodots were also influenced by variation of oxygen partial pressure. To further discuss the growth kinetics, a more clearly quasi-linear distribution was obtained and the coarsening effect is modified by varying growth time.

The growth of purely a -axis oriented YBCO thin films on LaAlO 3 (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 N 2 O ( P (O 2 + N 2 O)), as well as high film growth rate. A high growth rate (up to 7000 a/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.

ZrO2 nanodots are successfully prepared on LaAlO3 (LAO) (100) substrates by photo-assisted metal-organic chemical vapor deposition (MOCVD). It is indicated that the sizes and densities of ZrO2 nanodots are controllable by modulating the growth temperature, oxygen partial pressure, and growth time. Meanwhile, the microwires are observed on the surfaces of substrates. It is found that there is an obvious competitive relationship between the nanodots and the microwires. In a growth temperature range from 500 ?C to 660 ?C, the microwires turn longest and widest at 600 ?C, but in contrast, the nanodots grow into the smallest diameter at 600 ?C. This phenomenon could be illustrated by the energy barrier, decomposition rate of Zr(tmhd)4, and mobility of atoms. In addition, growth time or oxygen partial pressure also affects the competitive relationship between the nanodots and the microwires. With increasing oxygen partial pressure from 451 Pa to 752 Pa, the microwires gradually grow larger while the nanodots become smaller. To further achieve the controllable growth, the coarsening effect of ZrO2 is modified by varying the growth time, and the experimental results show that the coarsening effect of microwires is higher than that of nanodots by increasing the growth time to quickly minimize ZrO2 energy density.