Thin films of YBa2Cu3O7-δ were deposited on (100) SrTiO3 substrates held at 600 and 700°C in N2O and O2 ambients using 355 nm Nd-YAG laser pulses for ablation of the target. The experiments were done either in the presence or absence of 193 nm excimer laser irradiation of the ambient gas between the target and the substrate. Results without the excimer irradiation show that in 0.2 Torr of both N2O and O2, at 700°C substrate surface temperature, excellent smooth films with Tc (R=0) of 93 K and Jc (88 K) of 1.3×106 A/cm2 were obtained. At 600°C, semiconducting films with no superconducting transition were obtained in O2 ambient, whereas in N2O, semiconducting normal state behavior with broad superconducting transition was found. With the 193 nm irradiation, no change was observed in the electrical properties of the films deposited in O2 at 600°C, whereas in N2O reasonably good superconducting films with normal metallic behavior and Tc (R=0) of 84 K were found. Since the 193 nm photons hardly dissociate O2 molecules, but very efficiently photodissociate the N2O molecules to form N2 and O(1D), it is concluded that the atomic oxygen produced by photodissociation of N2O is responsible for the superconducting film deposition at 600°C.