Time-resolved quadrupole mass spectrometric studies on pulsed laser ablation of TiO2

Pulsed laser ablation of TiO2 at 355 nm and 532 nm has been investigated using an angle-and time-resolved quadrupole mass spectrometric technique. The major ablated species include O (m/e = 16), O-2 (m/e = 32), Ti (m/e = 48), TiO (m/e = 64) and TiO2 (m/e = 80). The time-of-flight (TOF) spectra of ablated species are measured for the ionic and neutral ablated species, and they can be fitted by a Maxwell- Boltzmann (M-B) distribution with a center-of-mass velocity. The measured angular distributions of the ionic species (O+ and Ti+) and the neutral species (O and Ti) can be fitted with cos(n) theta and acos theta + (1 - a)cos(n) theta, respectively. In addition, a continuous wave oxygen molecular beam is introduced into the ablated plume, and the enhancement of the signal intensities of TiO is observed. It implies that the ablated Ti atoms/ions species can react with ambient oxygen molecules in the gas phase. In the meanwhile, the physicochemical mechanism of pulsed laser ablation of TiO2 is discussed.