Dislocation injection in strontium titanate by femtosecond laser pulses

Femtosecond laser ablation is used in applications which require low damage surface treatments, such as serial sectioning, spectroscopy, and micromachining. However, dislocations are generated by femtosecond laser-induced shockwaves and consequently have been studied in strontium titanate (STO) using transmission electron microscopy (TEM) and electron backscatter diffraction analysis. The laser ablated surfaces in STO exhibit dislocation structures that are indicative of those produced by uniaxial compressive loading. TEM analyses of dislocations present just below the ablated surface confirm the presence of < 110 > dislocations that are of approximately 35 degrees mixed character. The penetration depth of the dislocations varied with grain orientation relative to the surface normal, with a maximum depth of 1.5 mu m. Based on the critical resolved shear stress of STO crystals, the approximate shockwave pressures experienced beneath the laser irradiated surface are reported.