Impact of directional walk on atom probe microanalysis

TL;DR

This paper investigates how directional walk of solutes driven by field gradients and thermal activation affects atom probe microanalysis of steels, explaining compositional inconsistencies and molecular ion appearances.

Contribution

It introduces the concept of surface migration of solutes as a key factor influencing atom probe analysis results, supported by field-ion microscopy observations.

Findings

Surface migration causes compositional inconsistencies.

Directional walk affects solute detection and molecular ion formation.

Field gradients and thermal activation drive solute migration.

Abstract

In the atom probe microanalysis of steels, inconsistencies in the measured compositions of solutes (C, N) have often been reported, as well as their appearance as molecular ions. Here we propose that these issues might arise from surface migration of solute atoms over the specimen surface. Surface migration of solutes is evidenced by field-ion microscopy observations, and its consequences on atom probe microanalysis are detailed for a wide range of solute (P, Si, Mn, B, C, N). It is proposed that directional walk driven by field gradients over the specimen surface and thermally activated is the prominent effect.