Correlative microscopy using 3-dimensional atom probe (3DAP) and transmission electron microscopy for microanalysis of impurity atoms segregating at grain boundaries

Abstract

  Principle of three-dimensional atom probe (3DAP) is summarized, and an analysis of 3D distribution of oxygen atoms segregated at Σ9{114} grain boundaries (GBs) in silicon ingots, within a high spatial resolution of less than 0.5 nm by a correlative microscopy using 3DAP assisted by scanning transmission electron microscopy and a focused ion beam (FIB) processing operated at −150 °C, is demonstrated. The analysis reveals a segregation of oxygen atoms within a range of 2.5 nm across the GB plane, which is much narrower in comparison with the previous reports obtained using the conventional FIB processing operated at room temperature. The oxygen concentration profile accurately reflects the distribution of the segregation sites, which exist at bond-centered sites under tensile stresses above 2 GPa, as calculated by ab initio local stress calculations. The results strongly support the usefulness of this correlative technique to analyze the interactions between GBs and impurity atoms at an atomistic level.