In this review, the physics and attractive applications of an NV center in diamonds are presented. The single electron spin in a nitrogen-vacancy (NV) center in a diamond has excellent properties such as single spin manipulation and a readout at room temperature. Thus the NV center has the potential to help achieve quantum sensing and quantum information devices. With quantum sensing, high-sensitivity nano-scale sensors of magnetic fields, electric fields, temperature and pressure are expected. With quantum information, devices for a quantum register, a single photon source, and a quantum repeater are expected.

Tunnel field-effect transistors (TFET) are one of the candidates for replacing conventional MOSFETs to realize an ultra-low power LSI. The most significant issue concerns their low ON current, for which one of the solutions is taking advantage of new channel materials such as Ge or III-V. Si is not favored for the channel because Si is an indirect-gap material having a low band-to-band tunneling probability. However, a new technology to enhance the ON current in Si-TFETs utilizing isoelectronic trap (IET) technology was recently proposed, which opens the door to enhanced ON current in Si-TFETs. This article outlines the ongoing TFET research and briefly discusses the IET technology.

This article introduces recent studies on the charge separation mechanism in organic solar cells. One of the important questions for organic solar cells is how free electrons and holes are generated, overcoming the Coulomb attraction at donor-acceptor interfaces. We carried out a combined electronic structure and quantum dynamical analysis that captures the elementary events from the exciton dissociation to the free carrier generation at polymer/fullerene donor-acceptor heterojunctions. Our calculations show that experimentally observed efficient charge separations can be explained by a combination of two effects: first, the delocalization of charges, which substantially reduces the Coulomb barrier, and second, the vibronically hot nature of the charge transfer state which promotes charge dissociation beyond the barrier.

The excited-state dynamics of organic molecules exhibiting thermally activated delayed fluorescence (TADF) was investigated by transient absorption spectroscopy aiming to reveal a mechanism leading to a highly efficient TADF. We found experimentally that both decreasing the ΔEST and increasing the spin-orbit coupling (SOC) between the singlet and triplet excited states were crucial for the efficiency. In particular, unexpected from the general assumption that the SOC of the purely organic TADF molecules is negligibly weak, the increase of the SOC is indeed the key for the TADF emission and is realized by closing a local excitonic triplet state to a charge-transfer singlet state. This situation is achieved by tuning the degree of the charge-transfer state. Some history of the TADF and its related recent research are also introduced.

In the present paper, we introduce the concept of reactions of insects to light and the utilization of LEDs in integrated pest management. In the presence of light, nine kinds of reactions take place; these include positive and negative phototaxis, light adaptation, and circadian rhythm disturbances. Via these reactions, LEDs enable us to develop integrated pest management techniques such as light traps with a monochromatic and bright light source with low electricity consumption and various wavelengths. LEDs thus contribute to promoting integrated pest management techniques.

Amorphous carbon nitride, a-CN_x, thin films are well known as a hard coating material with a low friction coefficient. But, there are still many findings concerning the electrical and optical properties of a-CN_x films, which are characterized by a wide variety of structures depending on the deposition techniques and conditions. In this study, we introduce one of the unique properties, a photoinduced deformation of a-CN_x film deposited by reactive radio frequency magnetron sputtering using a graphite target and pure nitrogen gas.

An alignment of an optical imaging system decides the quality of the experimental results. However, there are few books that describe the alignment. In this paper, some tips for the alignment in university laboratory experiments are given.