This article reviews a recent study on atomic-scale Turing patterns observed in monolayer bismuth. The article highlights how the researchers proved the observed strange patterns are the Turing patterns and arrived at this conclusion, including the arguments on the Grinfeld instability. The article also explains the concept of Turing patterns, non-equilibrium relaxation processes, and a possible way to create various Turing patterns．

  Colloidal particles at an interface exhibit a wide range of self-assembly and compaction dynamics, depending on their shape. In a recent article (A. N. Kato et al., Journal of Colloid And Interface Science 641, 492–498 (2023)), we clarified how the surface roughness of particles affects interparticle interactions at interfaces. Sufficiently rough particles exhibit an intermediate state between a gas-like state and a solid-like state, which is featured by percolating network formation due to roughness-induced capillary attraction. Moreover, roughness lowers the jamming point and finally drives the gradual collapse due to the asperities of particles. In this article, we first review the interfacial properties of anisotropic colloids at interfaces and then focus on the results of our paper on rough colloids.

  Optical second harmonic generation (SHG) and sum frequency generation (SFG) are second-order nonlinear optical responses of matter. When two intense light pulses with photon energies ℏω₁ and ℏω₂ enter a solid, a new light pulses with photon energy ℏω₁+ℏω₂ can be generated. This phenomenon is called SHG when ω₁=ω₂, and SFG when ω₁≠ω₂. Within the electric dipole approximation, SHG and SFG have a unique property of being allowed for media without spatial inversion symmetry. In this paper, I describe examples of analyses of a photocatalyst material titanium dioxide (TiO₂), metal nanowire arrays, hydrogen-terminated Si(111) surfaces, and chiral biomaterials, by SHG/SFG spectroscopic or microscopic observation. I will pay special attention to a viewpoint of inversion symmetry breaking causing SHG or SFG in each material.

  Two types of the linear optical spectroscopic methods, that is, surface differential reflectance spectroscopy (SDRS) and reflectance difference spectroscopy (RDS) are described. These methods can be used as a non-destructive optical probe of surfaces, and can be applied not only in vacuum condition but also in atmospheric and liquid conditions. We summarize our studies of the surface reaction, growth process of organic molecules, and interface structure on silicon surfaces using these methods. Second harmonic generation (SHG) is a powerful means to investigate nonlinear optical processes of nanoscale materials. We here introduce an example of the combinative use of both linear and nonlinear optical methods to investigate transition metal dichalcogenides.

  We propose and demonstrate one-dimensional doping with using a one-dimensional surface structure such as Bi nanolines/Si(001) as a dopant, where the process is mainly based on autosurfactant. Surfactants in heteroepitaxy are catalytic elements that float up to the surface during growth to control the energetics/kinetics of adatoms. “Autosurfactants” are exceptional in that the surfactant action is self-contained without foreign species. Here, autosurfactants play a role of surface-segregation quenchers: Bi, a dopant with a strong surface-segregation tendency in Si, is utilized to lock otherwise elusive Bi adatoms themselves to the Si lattice underneath during molecular beam epitaxy. We realize another one dimensional doping of Mn into Si/Ge interfaces using Mn atomic chains on Si(001) as a dopant. Doping methods based on the burial of surface nanostructures in epitaxial layers allow the realization of systems for where conventional doping methods fail.