Atom probe tomography (APT) has been used to study InxGa1−xAs quantum dots buried in GaAs. The dots have an average base width of 16.1±1.1nm and height of 3.5±0.3nm, but a wide range of sizes. APT composition profiles across the dots are similar to a previous study by cross-sectional scanning transmission electron microscopy, but show significant gallium incorporation (average x=0.22±0.01). The direct three-dimensional nature of the APT data also reveals the complex spatial distribution of indium within the dots. Data such as these are vital for optimizing the performance of quantum dot materials and devices.

This study addresses the ongoing debate concerning the distribution of indium in InxGa1−xN quantum wells (QWs) using a combination of atom probe tomography (APT) and transmission electron microscopy (TEM). APT analysis of InxGa1−xN QWs, which had been exposed to the electron beam in a TEM, revealed an inhomogeneous indium distribution which was not observed in a control sample which had not been exposed to the electron beam. These data validate the effectiveness of APT in detecting subtle compositional inhomogeneities in the nitrides.

Pulsed laser atom probe tomography was employed to study the interfacial chemistry in an InAs/GaSb superlattice nanostructure. The InAs-on-GaSb anion sublattice interface was found to be wider than the GaSb-on-InAs interface, in good agreement with previous electron microscopy studies. Hetero-nuclear group-V cluster ions at the InAs-on-GaSb interface as detected by atom probe are indicative of a strong As for Sb exchange reaction when InAs is grown onto GaSb.

Afield ion atom probe study has been made of a low carbon steel after furnace cooling and rapid quenchingfrom 700°C. Marked segregation of carbon to the boundaries was observed after furnace cooling, but not after rapid quenching. From comparison of previous and present results, it is concluded that the ky value of a steel can be related to the interstitial impurity content (mainly carbon) at the grain boundaries. Heat treatments that, encourage grain boundary segregation of interstitials will result in steels having a high ky value.MSTj1569