A time-of-flight mass spectrometric study of laser fluence dependencies in SnO₂ ablation: Implications for pulsed laser deposited tin oxide thin films

We report on a time-of-flight mass spectrometric study of laser fluence dependencies in the 532nm ablation of SnO₂ targets. At all fluences investigated, SnO and Sn₂O₂ are the primary neutral gas-phase species. The relative yield of neutral tin-containing species increases exponentially up to a fluence of ∼1.9×10⁸Wcm ^-2, and saturates at higher fluences. The yield of metal oxide clusters (primarily Sn₂O₂, Sn₄O₄) increases in the saturated region, while the yield of bare metal species (primarily Sn, Sn₂) decreases. In contrast, the peak kinetic energy of the primary neutral ablated species is insensitive to laser fluence in this range. These results support the hypothesis that the initial Sn:O stoichiometry of amorphous SnO_x films grown in vacuum using pulsed laser deposition (PLD) plays an important role in the formation of α-SnO during post-deposition annealing.