Miki Nakamura

Mechanically activated switching of Si-based single-molecule junction as imaged with three-dimensional dynamic probe

Understanding and extracting the full functions of single-molecule characteristics are key factors in the development of future device technologies, as well as in basic research on molecular electronics. Here we report a new methodology for realizing a three-dimensional (3D) dynamic probe of single-molecule conductance, which enables the elaborate 3D analysis of the conformational effect on molecular electronics, by the formation of a Si/single molecule/Si structure using scanning tunnelling microscopy (STM). The formation of robust covalent bonds between a molecule and Si electrodes, together with STM-related techniques, enables the stable and repeated control of the conformational modulation of the molecule. By 3D imaging of the conformational effect on a 1,4-diethynylbenzene molecule, a binary change in conductance with hysteresis is observed for the first time, which is considered to originate from a mechanically activated conformational change.

Formation of homochiral glycine/Cu(111) quantum corral array realized using alanine nuclei

Glycine has enantiomeric isomers on a Cu(111) surface through the dissociation of hydrogen from the carboxyl group and forms an array of quantum corrals of ~1.3 nm diameter. Stable homo-chiral glycinate trimers are formed in the first step, which subsequently form a network with a hexagonal arrangement. However, domains with R- or S-chirality coexist with the same probability. On the other hand, α-alanine has D- and L-chirality in nature and forms a similar quantum corral array on Cu(111) with R- and S-chirality, respectively. Here, by using α-alanine molecules as nuclei, the chirality of glycine molecules was controlled and a homochiral quantum corral array was successfully formed, which indicates the possibility that the optical isomers can be separated through a method such as preferential crystallization.

Rapid measurement of ultrahigh viscosity using an electro-magnetically spinning system

The electro-magnetically spinning (EMS) viscometer we recently developed enables non-contact viscosity measurement. The measurement sample is confined in an isolated sample cell, and the viscosity, which is one of the most important mechanical parameters to determine ultrasonic propagation in fluids, is easily obtained in a few minutes for lower-viscosity liquids. In this paper, we report an improved system for the measurement of highly viscous liquids: laser light is incident on a probe metal sphere, and the speckle pattern generated by the scattered light is observed using detectors aligned along a circle around the center of the speckle rotation. We successfully measured a viscosity of 103 Pas within only 0.1 s, demonstrating the systems ability to measure rapid changes of viscosity, for example, in a material undergoing the glass transition.