Emission Spectroscopic and Mass Spectrometric Characterization of Laser-Ablated Species from a Ferroelectric SrBi 2 Ta 2 O 9 Target

Abstract

The ablation of a SrBi₂Ta₂O₉ (SBT) target under 355 nm laser irradiation has been investigated with an angle- and time-resolved quadrupole mass spectrometric technique. Mass and angular distributions of ionic and neutral ablated species are measured. The observed major ablated species include metal atoms and ions as well as binary metal oxides. The time-of-flight (TOF) spectra of ablated species such as Bi and SrO are measured and can be well fitted by a Maxwell–Boltzmann distribution with a stream velocity. The estimated kinetic energies of metal ions are found to be much higher than those of neutral species. The angular distributions of ablated species show that ionic and neutral species ejected within a coneshaped plume can be simulated by cos ⁿ θ and acosθ + bcos ⁿ θ functions, respectively. The optical emission spectroscopic technique is also employed in order to examine the electronically excited SrO, TaO, and BiO, in which BiO is not observed in mass spectroscopy. The dependence of the concentrations of metal oxides on the pressure of ambient oxygen provides helpful information for the growth of SBT thin films.