Frequently, fundamental scientific and technological issues are related to the chemical structure of a material at the nanometer or even atomistic length scales. This includes, but is not limited to, internal interfaces of complex topology as they appear, for example, in current energy-harvesting applications or advanced microelectronics. Scientific understanding of the underlying physics and chemistry requires advanced characterization tools that provide critical three-dimensional information at the subnanometer length scale. Atom probe tomography (APT) meets such requirements. Today, with remarkable progress in instrumentation and sample preparation, APT has become a very versatile tool to address fundamental questions of materials science. In this issue of MRS Bulletin, the APT technique is introduced, with a particular focus on recent developments and the broadening range of studied material classes and applications.

This article focuses on four topics that demonstrate the importance of atom probe tomography for obtaining nanostructural information that provides deep insights into the structures of metallic alloys, leading to a better understanding of their properties. First, we discuss the microstructure–coercivity relationship of Nd-Fe-B permanent magnets, essential for developing a higher coercivity magnet. Second, we address equilibrium segregation at grain boundaries with the aim of manipulating their interfacial structure, energies, compositions, and properties, thereby enabling beneficial material behavior. Third, recent progress in the search to extend the performance and practicality of the next generation of advanced high-strength steels is discussed. Finally, a study of the temporal evolution of a Ni-Al-Cr alloy through the stages of nucleation, growth, and coarsening (Ostwald ripening) and its relationship with the predictions of a model for quasi-stationary coarsening is described. This information is critical for understanding high-temperature mechanical properties of the material.

As the characteristic length scale of electronic devices shrinks, so does the required scale for measurement techniques to provide useful feedback during development and fabrication. The current capabilities of atom probe tomography (APT), such as detecting a low number of dopant atoms in nanoscale devices or studying diffusion effects in a nanowire (NW), make this technique important for metrology on the nanoscale. Here we review recent APT investigations applied to transistors (including regions such as gate oxide, channel, source, drain, contacts, etc.), heterogeneous dopant incorporation in NWs, and Pt-based nanoparticles.

Atomic-scale characterization of interfaces in ceramic materials is needed in order to fully understand their electronic, ionic, mechanical, magnetic, and optical properties. The latest development of laser-assisted atom probe tomography (APT), as well as new specimen preparation methods, have opened the realm of ceramics for structural and chemical characterization with high sensitivity and nearly atomic spatial resolution. This article reviews recent APT investigations of interfaces in thin nitride films and thermally grown oxides: TiAlN layers and oxide scales on alumina- and chromia-formers and Zr alloys. The selected examples highlight the role of interfaces in the decomposition of films and in transport processes.

A series of recent instrumental advances have facilitated the application of atom probe tomography (APT) to the characterization of an increasingly wide range of materials and devices. Whereas APT was previously mostly limited to the analysis of alloys, advances in areas such as laser pulsing and detectors have enabled characterization of semiconductors and brittle materials. Most recently, ultraviolet laser pulsing has facilitated the analysis of materials previously considered not viable for the atom probe, such as minerals and large bandgap insulator materials. The development of in situ gas reaction cells fully integrated in atom probe instruments has enabled the characterization of surface reactions of materials exposed to highly controlled environments. Finally, current work toward an integrated cryo-transfer system is anticipated to create new directions for APT research.

This article reviews post-analysis processing methods for data acquired using atom probe tomography (APT). Field-induced aberrations of APT images arise from distorted ion flight trajectories and differences in ion evaporation rates. Addressing this issue requires the development of image processing tools that yield three-dimensionally reconstructed images that reliably reflect the original specimens. One of the biggest advantages of the APT technique is its ability to collect information about millions of individual atoms. Understanding these data requires the development of mathematical and statistical data mining tools, involving disciplines beyond the basic physics of APT. The above issues have important implications for addressing materials science-related questions.

This article provides a brief introduction to third-order nonlinear optical materials, including both the real and imaginary components, and is intended to be a personal perspective of the field. It describes applications that can be enabled by molecules with large two-photon absorption (2PA) cross sections and how symmetrical donor–(π-bridge)–donor molecules exhibit large cross sections associated with significant changes in quadrupole moment between the ground- and first-excited electronic states. The application of such materials for 2PA three-dimensional microfabrication is described. The article then turns its focus to materials for all-optical switching applications and explains how cyanine-like molecules can be developed to have both very large real third-order nonlinear coefficients and small 2PA cross sections, both of which are necessary for efficient all-optical switching materials.