Study of vertical Si/SiO2 interface using laser-assisted atom probe tomography and transmission electron microscopy

• The interface reaction can be activated by laser-assisted field evaporation and affects the quantification of the interfacial composition.
• The features of the reaction depend on the direction of the laser illumination and the inner structure of tip.
• At the vertical interface of Si/SiO2, SiO2 tends to combine and evaporate with Si when Si atoms are atomically close to the evaporation site.
• This was explained using transmission electron microscopy observations before and after atom probe experiments.
• Therefore, in compositional analysis of heterogeneous structures using an AP, the laser–matter interaction must be prudently considered to reduce erroneous analyses.

Laser-assisted atom probe tomography has opened the way to three-dimensional visualization of nanostructures. However, many questions related to the laser–matter interaction remain unresolved. We demonstrate that the interface reaction can be activated by laser-assisted field evaporation and affects the quantification of the interfacial composition. At a vertical interface between Si and SiO2, a SiO2 molecule tends to combine with a Si atom and evaporate as a SiO molecule, reducing the evaporation field. The features of the reaction depend on the direction of the laser illumination and the inner structure of tip. A high concentration of SiO is observed at a vertical interface between Si and SiO2 when the Si column is positioned at the center of the tip, whereas no significant SiO is detected when the SiO2 layer is at the center. The difference in the interfacial compositions of two samples was due to preferential evaporation of the Si layer. This was explained using transmission electron microscopy observations before and after atom probe experiments.