The emphasis is on forming thin-film perovskite structures below 500°C since, for the applications intended, it is desirable to avoid excessive heating of the underlying semiconductor substrate3. Such low temperatures may be a disadvantage for alternate fabrication processes because of the sluggishness of various reactions. This may be overcome for gas phase reactions using plasmas induced by radio-frequency coupling (13.56 MHz). Compared to thermal decomposition processes, a 10 to 40 fold increase in deposition rates can result due to the plasma. This effect is equivalent to raising the temperature of the reaction without substantially raising the temperature of the substrate. In addition, the interaction of a plasma with solid interfaces will likely stimulate surface relaxation processes. We observe that the perovskite content of the thin films is greatly influenced by the plasma power which is probably related to structural rearrangements on the solid surface. Thus, plasma power density becomes an important experimental control in achieving 100% perovskite at low temperatures.