STRUCTURAL AND ELECTRICAL-PROPERTIES OF LA0.5SR0.5COO3 EPITAXIAL-FILMS

Epitaxial La0.5Sr0.5CoO3 films with very smooth surface morphology wer e grown on (100) SrTiO3 and (100) MgO substrates by pulsed laser depos ition. Scanning tunneling microscopy reveals that the thin film is for med by the coalescence of many aligned square mesas. The growth procee ds from the edges of terraces which are stacked on the mesa. Spiral gr owth is never observed. Films display an crystallographically isotropi c metallic-like electrical conductivity but become semiconductor-like after vacuum annealing. The energy for carrier activation is 0.3 eV. T he change of the electrical resistivity of La0.5Sr0.5CoO3 with oxygen pressure at high temperature is much less sensitive than that of YBa2C u3O7-x.