Surface morphology studies of Y-Ba-Cu-oxide thin films prepared by pulsed organometallic beam epitaxy

Pulsed organometallic beam epitaxy is a new technique for the deposition of complex metal oxide films. With this technique each metal precursor species is sequentially pulsed onto the substrate. The flux of the precursor is monitored and computer feedback control is used to adjust the size of each precursor pulse, allowing precise control of the metal stoichiometry. Smooth films of YBa₂Cu₃O_7-δ, as examined by SEM, can be made with this technique in a temperature range that includes 640-680 °C using the β-diketonate precursors, Y(dipivalolymethanate)₃, Ba(hexafluoroacetylacetonate)₂-tetraglyme, and Cu(acetylacetonate)₂. The morphology of the films is dependent on the ratio of the three precursors delivered to the substrate. The ratio of the three precursors must be held to better than +-10% in order to produce smooth films. The ratio between the three precursors needed to produce a smooth film changes with the deposition temperature. The relative amount of yttrium precursor delivered to the substrate must be decreased as the temperature is increased in order to maintain a smooth film. The metal composition of the smooth films is Y₁Ba₂Cu₃ (±4%).