Annihilation and Generation of Dislocations by Irradiation by Ions and Electrons in Strontium Titanate Single Crystal

Abstract

The physical and chemical properties of many oxide materials depend strongly on their defect concentration, which gives rise to unique electronic, optical, and dielectric properties. One such promising material for various applications, including energy storage, photocatalysis, and electronics, is SrTiO3 (STO). It exhibits several interesting phenomena, including a metal-to-insulator transition that can be induced by reduction. By extension, 1-D defects, such as dislocations, play a significant role in its electronic properties. Thus, we investigate the process of dislocation movement, its creation, and annihilation under two stimuli: ion thinning and electron irradiation. First, we designed and produced a lamella from a mechanically modified sample with variable thickness in the form of a wedge using a focused ion beam (FIB/Ga+) to investigate thickness-dependent dislocation movement. The lamella was investigated by transmission electron microscopy, allowing for the measurements of dislocation concentration as a function of its thickness. We have noticed a sharp decrease in the defect concentration with respect to the starting sample, showing a process of annihilation of dislocations. Second, we used an electron beam to drive a relatively large current into the STO surface. This experiment produced an electrical breakdown-like pattern. Optical and atomic force microscopy revealed that this pattern evolved due to the removal of material from the surface and local metal-insulator-transition along the dislocations network. Thus, we observe the dislocations generation and movement.

Keywords

• strontium titanate
• extended defects
• dislocation concentration