Nanocarbon materials, including graphene and carbon nanotubes (CNTs) have excellent electrical, thermal, and mechanical properties, and are expected to be used for various applications. Some of applications, such as the use of CNTs as conductive additives for lithium ion batteries, have already been realized. The application of nanocarbon materials to electronic devices, however, has not had great success as of yet. We have actually been working on such applications. Our targets include More Moore applications, such as a transistor and interconnect for large scale integrated circuits (LSIs), and More-than-Moore ones, such as a gas sensor and a detector diode for high-frequency waves. In this article, we briefly review More Moore and More-than-Moore applications of nanocarbon materials. Furthermore, we describe our recent efforts to develop novel functional devices.

In this article, I will show images of diamond defects using several estimation methods with the empirical information from estimation methods.

These defect images are useful for a discussion about the study of diamond power devices, and how defects affect power device performance. Because “where”, “how much” and “what kind” are important points for this topic, I focus on imaging methods to estimate the defects in a single crystal diamond.

Phonon engineering is expected to achieve a breakthrough in thermal management technology in solids. In macroscopic systems, thermal conduction is diffusive and difficult to control. However, in mesoscopic systems, the ballistic property of thermal phonons enables more advanced heat conduction control. In this article, we demonstrate a method to control the direction of heat flow using silicon membranes with arrays of holes. The arrays of holes form phonon fluxes oriented in the same direction. We also demonstrate “thermal lens” nanostructures, in which the emitted thermal phonons converge at the focal point. These demonstrations raise the idea of ray phononics because of some similarity to ray optics. Advanced technology in photonics may serve as a good model for phonon engineering.

Photonic crystal nanocavities with high quality factors (Q) have attracted quite a bit of attention from many researchers. Particularly, silicon high-Q nanocavities have increased the record for the highest Q for a photonic crystal cavity over these last 15 years. Currently, silicon nanocavities are studied in various areas for industrial applications. The current record for a Q exceeds 10 million and furthermore, an average value of 2 million has been recently achieved even in the nanocavities fabricated on a large diameter substrate using photolithography. Therefore, silicon nanocavities will be used in a wider range of fields. Here we describe the recent studies for these ultrahigh-Q silicon nanocavities.

We review recent studies of a new class of Fe-doped III-V ferromagnetic semiconductors (FMS). We first briefly summarize the history of FMS studies, and point out the unsolved problems of the most intensively studied Mn-doped III-V FMSs such as (GaMn)As. We then discuss the possibility and prospects of using Fe as a magnetic impurity in narrow-gap III-V semiconductors to realize a new family of FMSs that can solve all the problems of Mn-doped FMSs. We describe the crystal growth, detailed structural characterizations, and fundamental magnetic properties of n-type (InFe)As, p-type (GaFe)Sb, and n-type (InFe)Sb. We discuss possible applications of these Fe-doped FMSs to semiconductor spin devices.

Our research group is ultimately trying to establish a new academic field, “(bio)materials science based on anisotropy” focusing on living bone and the related biomaterials. The measurement of bone mineral density that has been conventionally used for bone diagnosis is insufficient to evaluate the function and/or strength in various bones such as pathological and regenerated bones. Because the apatite crystal in bones has an anisotropic hexagonal crystal structure, the orientation of the apatite c-axis in the bone matrix should be considered as a bone quality parameter that governs the bone mechanical function. In this manuscript, our latest knowledge of the anisotropic bone microstructure, its formation mechanism, and the development of artificial biomaterials for inducement of anisotropic bone microstructures are introduced.

The unoccupied states of solids can be directly examined by inverse photoelectron spectroscopy (IPES). The fundamental drawback of IPES is its low signal intensity. Although the intensity of the IPES signal may be enhanced by surface plasmon resonance (SPR), however, with conventional IPES this was impossible because the photon energy involved in this techinique is much higher than the SPR energy of existing materials. In 2012, we developed a low-energy IPES (LEIPS), in which the photon energy is lowered to less than 5 eV. Thus the photon energy of the IPES can be matched with the SPR energy. We demonstrate the enhancements of the LEIPS signal of Ag and organic semiconductors by the SPR of Ag nanoparticles.

Stimulated emission depletion (STED) microscopy is one of the fluorescence microscopy techniques, which enables sub-diffraction imaging of biological samples. The principle of the STED microscope and the role of optical components are explained. The alignment procedure and sample preparations are also discussed, and examples of STED images of fluorescent beads and actin filaments are demonstrated. Perspectives of the application of STED microscopy are also discussed.