Observation of curious spiral-like features on spray pyrolysed Pb doped Hg-based HTSC films Original Research Article

The surface morphology of spray pyrolysed Hg(Pb)Ba2Ca2Cu3O8+δ films is investigated by scanning electron microscopy (SEM). By imaging the as-grown surfaces of the films, we have directly observed spiral-shaped growth terraces that emanate from screw dislocations. The high density of screw dislocations (∼106 cm−2) observed by SEM micrographs of the films is expected to nucleate during the initial stages of growth due to the bi-phasic nature of the material, providing a continual supply of ledge incorporation sites for the depositing species. A possible mechanism, for the generation of these screw dislocations in terms of incoherent coalescence of growth fronts formed from Hg(Pb):1223 and Hg(Pb):1234 nuclei, is described.