Low‐angle twist grain boundary in SrTiO₃ fabricated by spark plasma sintering techniques

Abstract

A SrTiO 3 bicrystal with a low-angle twist grain boundary was fabricated using the spark plasma sintering (SPS) instrument. The atomic and electronic structure of the grain-boundary core was characterized using scanning transmission electron microscopy techniques. It was determined that the boundary is comprised of 2 types of defects with distinct electronic structures: screw dislocations and dislocations with an [001] edge component. The dislocations with an [001] edge component dissociated into 2 partial dislocations, separated by a stacking fault consisting of 2 Ti-O layers. The screw dislocations are attributed to the twist component of the grain boundary, while dislocations with an [001] edge component are attributed to surface steps on the original (100) SrTiO 3 surfaces prior to diffusion bonding. The observed repeat distances between the dislocations with edge components along the grain-boundary plane are smaller than those discovered during traditional diffusion bonding experiments. The higher planar defect density observed in this study results partly from higher heating rates, lower processing temperatures, and shorter holding times during SPS processing. K E Y W O R D S electron microscopy, grain boundaries, oxides, spark plasma sintering

Stacking and Twisting of Freestanding Complex Oxide Thin Films

“…The observations of bright regions interspaced by darker regions at the interface of STO/STO stack (Figure 5a,b and Figure S7d, Supporting Information) are in excellent agreement with what has been reported earlier in artificially assembled 4° twisted STO bicrystals, in which the bonding between layers was achieved at a temperature of 800 °C for 20 min with an applied pressure of 120-140 MPa. [36] The dark regions observed at the interfaces in our stack are similar to those seen previously in STO bicrystals, which correspond to dislocation cores. [36] The possibility of tuning the dislocation network at the interface by twisting can, e. tune the ionic conductivity at interfaces, which is crucial for a wide range of energy technologies, [37] ranging from fuel cells to batteries and catalysis, to name a few.…”

“…[36] The dark regions observed at the interfaces in our stack are similar to those seen previously in STO bicrystals, which correspond to dislocation cores. [36] The possibility of tuning the dislocation network at the interface by twisting can, e. tune the ionic conductivity at interfaces, which is crucial for a wide range of energy technologies, [37] ranging from fuel cells to batteries and catalysis, to name a few. Carbon residues from the transfer process were found at the interface similar to what is often observed in stacks of 2D materials (Supporting Information, Figure S8).…”