We have studied the particulates formed on single-phase copper oxide thin films obtained by laser deposition in a variable oxygen atmosphere. Two different targets have been used: a thick copper foil and a sintered copper powder. We conclude that there are two very different kinds of particulates. The first have very irregular morphology and very similar average size. They are due to solid debris coming from the surface target. The second kind of particulate observed has a round perimeter and is formed in the liquid phase. The morphology of the latter round particulates, which varies considerably, is dependent on the substrate and the oxygen content. Thus, we have been able to determine the conditions for growing particulate-free single-phase copper oxides. © 1992.