Nobuatsu Watanabe

Bio: Nobuatsu Watanabe is an academic researcher from Kyoto University. The author has contributed to research in topics: Graphite & Fluoride. The author has an hindex of 25, co-authored 174 publications receiving 2098 citations.

Method for removing a film on a silicon layer surface

Abstract: A method for removing a film on a silicon layer formed on a surface of a substrate includes the steps of: (a) placing a substrate in a reaction chamber to be isolated hermetically from the outside air, and (b) feeding anhydrous hydrogen fluoride and alcohol simultaneously into the reaction chamber. Preferably, the method further includes the step of feeding only alcohol into the reaction chamber prior to and/or subsequent to the step (b). An alcohol layer is formed on the substrate surface, whereby the film can be removed uniformly by anhydrous hydrogen fluoride. A by-product of the reaction is taken out from the system of reaction by means of the alcohol on the substrate. No by-product remains on the substrate after the reaction. Since the silicon layer after the reaction is covered with alcohol, re-growth of a native oxide film thereon is also suppressed and on ionic contamination such as fluorine remains on the substrate surface.

Molecular dynamics with coupling to an external bath.

Abstract: In molecular dynamics (MD) simulations the need often arises to maintain such parameters as temperature or pressure rather than energy and volume, or to impose gradients for studying transport properties in nonequilibrium MD A method is described to realize coupling to an external bath with constant temperature or pressure with adjustable time constants for the coupling The method is easily extendable to other variables and to gradients, and can be applied also to polyatomic molecules involving internal constraints The influence of coupling time constants on dynamical variables is evaluated A leap‐frog algorithm is presented for the general case involving constraints with coupling to both a constant temperature and a constant pressure bath

A molecular dynamics method for simulations in the canonical ensemble

Abstract: A molecular dynamics simulation method which can generate configurations belonging to the canonical (T, V, N) ensemble or the constant temperature constant pressure (T, P, N) ensemble, is proposed. The physical system of interest consists of N particles (f degrees of freedom), to which an external, macroscopic variable and its conjugate momentum are added. This device allows the total energy of the physical system to fluctuate. The equilibrium distribution of the energy coincides with the canonical distribution both in momentum and in coordinate space. The method is tested for an atomic fluid (Ar) and works well.

Fluorographene: A Two‐Dimensional Counterpart of Teflon

Abstract: A stoichiometric derivative of graphene with a fluorine atom attached to each carbon is reported Raman, optical, structural, micromechanical, and transport studies show that the material is qualitatively different from the known graphene-based nonstoichiometric derivatives Fluorographene is a high-quality insulator (resistivity >10(12) Omega) with an optical gap of 3 eV It inherits the mechanical strength of graphene, exhibiting a Young's modulus of 100 N m(-1) and sustaining strains of 15% Fluorographene is inert and stable up to 400 degrees C even in air, similar to Teflon

Synthesis and Characterization

Abstract: As compared to bulk materials, magnetic nanoparticles possess distinct magnetic properties and attempts have been made to exploit their beneficial properties for technical and biomedical applications, e.g. for magnetic fluids, high-density magnetic recording, or biomedical diagnosis and therapy. Early magnetic fluids (MFs) were produced by grinding magnetite with heptane or long chain hydrocarbon and a grinding agent, e.g. oleic acid [152]. Later procedures for MFs precipitated Fe 3+/Fe 2+ of an aqueous solution with a base, coated the particles by oleic acid, and dispersed them in carrier liquid [161]. However, besides the elemental composition and crystal structure of the applied magnetic particles, particle size and particle size distribution determine the properties of the resulting MF. Many methods for nanoparticle synthesis including the preparation of metallic magnetic particles have been described in the literature. However, there still remain important questions, e.g. concerning control of particle size, shape, and monodispersity as well as their stability towards oxidation. Moreover, peptization by suitable surfactants or polymers into stable MFs is an important issue since each application in engineering or biomedicine needs special MFs with properties adjusted to the requirements of the system.