We deposit thin epitaxial YBaCu2O3 films on SrTiO3 (100) substrates by
pulsed laser deposition using a pursed molecular oxygen flow. We stud
y the oxygen pressure dependence of their growth and their surface mor
phology by means of reflection high energy electron diffraction (RHEED
) and atomic force microscope (AFM). A new method to improve the oxyge
n reactivity is also proposed.