We have recently reported a new two-dimensional material of boron monosulfide (BS) nanosheet. It was produced by the mechanical exfoliation of rhombohedral boron monosulfide (r-BS) synthesized by heating the mixture of amorphous boron and sulfur at 1873 K and 5.5 GPa. Experimental characterizations and density functional theory calculations revealed tunable band-gap of BS nanosheets as much as approximately 1.0 eV. These results are introduced in detail.

We have investigated the electronic states of active and inactive dopant sites in Si-doped GaN using the X-ray absorption near-edge structure (XANES), Auger electron spectroscopy (AES), and photoelectron spectroscopy (PES). From AES and PES, it was found that Si-doped GaN contains Si₃N₄ and SiN_x dopant states. According to Si K-edge XANES, the Si₃N₄ state does not exhibit electronic states in the GaN bandgap, indicating that these dopant sites in Si-doped GaN are inactive, whereas SiN_x exhibited bandgap states. Thus, the SiN_x state should act as an active dopant site in Si-doped GaN. The simulated XANES spectra accurately reproduce the electronic state in the GaN-bandgap where a Ga atom is replaced by a Si atom, suggesting that these are the active dopant sites. Inactive dopant sites (Si₃N₄) in Si-doped GaN are formed predominantly close to the surface. Since Ga vacancies are formed largely at sites close to the surface, it is apparent that the quantity of Ga atoms or its vapor should be optimized to prevent formation of Ga vacancies thus avoiding population of the inactive sites.

Aqueous lubrication has received considerable attention not only due to the benefits for energy efficiency and low environmental burden but also due to the importance in designing low-friction surfaces of biomaterials. The excellent fluidity of water is obtained even in molecular scale confinement between surfaces (this is not the case for oil lubricants), which is the major origin of low friction in boundary lubrication. However, this high fluidity may result in the easily squeezed out of water from the sliding interface that leads to surface damage. Selecting suitable chemicals as additives is one of the solutions for this problem ; the impact of using water-soluble polymers as additives for aqueous lubrication was investigated. We found that some silicone-type amphiphilic polymer formed an adsorbed layer on surface and exhibited excellent lubricity (friction coefficient of the order of 10^－5), due to the easy slippage of monomolecular layer of water between the adsorbed layers.

Nano-structuring technique can be an ultimate technique for realizing material development and device functionality because the nano meter is the same scale of the specific length relating to the collective systems for electrons, spins, charge, and so on, which determines physical properties. On the basis of the creation techniques originated from surface science, we have developed the original nanofabrication techniques, which enable the creation of the Fe₃O₄ epitaxial ultra-thin films and nanowires at a 10 nm length scale. Despite the high density of inevitable nanoscale defects, the ultrasmall Fe₃O₄ samples exhibit a prominent Verwey transition.