  Atomically flat, epitaxial, and stoichiometric thin films of the
electronically phase separated compound
(La$_{0.5}$Pr$_{0.5}$)$_{0.67}$Ca$_{0.33}$MnO$_{3}$ were grown on as-received
and treated NdGaO$_{3}$ substrates by fine tuning of oxygen pressure during
deposition. Optimal thin films with step flow growth mode show superior
physical properties compared to thin films grown in off-optimal oxygen
pressures, {\em viz.} the highest maximum temperature coefficient of
resistance, the highest peak-resistivity temperature, and reduced coercive
fields. Transport, magnetization, and x-ray diffraction measurements indicate
that the oxygen pressure during growth plays a critical role in the formation
of oxygen vacancies, cation vacancies, and grain boundaries.
