In Situ Transmission Electron Microscopy for Electronics

Electronic devices are strongly influenced by their microstructures. In situ transmission electron microscopy (in situ TEM) with capability to measure electrical properties is an effective method to dynamically correlate electric properties with microstructures. We have developed tools and in situ TEM experimental procedures for measuring electronic devices, including TEM sample holders and sample preparation methods. The method was used to study metallic nanowire by electromigration, magnetoresistance of a ferromagnetic device, conductance quantization of a metallic nanowire, single electron tunnelling, and operation details of resistive random access memories (ReRAM)

A pH sensor based on electric properties of nanotubes on a glass substrate

We fabricated a pH-sensitive device on a glass substrate based on properties of carbon nanotubes. Nanotubes were immobilized specifically on chemically modified areas on a substrate followed by deposition of metallic source and drain electrodes on the area. Some nanotubes connected the source and drain electrodes. A top gate electrode was fabricated on an insulating layer of silane coupling agent on the nanotube. The device showed properties of ann-type field effect transistor when a potential was applied to the nanotube from the top gate electrode. Before fabrication of the insulating layer, the device showed that thep-type field effect transistor and the current through the source and drain electrodes depend on the buffer pH. The current increases with decreasing pH of the CNT solution. This device, which can detect pH, is applicable for use as a biosensor through modification of the CNT surface

Measurement of the Casimir force between a spherical gold tip and Si(111)-(7 x 7) surfaces

We have performed the measurement of Casimir force between a spherical Au tip and an atomically flat Si(111)-(7 x 7) surface at tip-sample distances ranging from 15 to 50nm in an ultrahigh vacuum of 1.5 x 10(-8)Pa by frequency-modulation atomic force microscopy. Atomically flat Si(111) surfaces provided by the ultrahigh-vacuum condition and a degassed Au tip reduce the contact potential difference that must be compensated. These experimental conditions led to the elucidation of the distance dependence of the Casimir force down to the distance of 15 nm. The observed distance dependence still follows a theory provided by Chen et al. [Phys. Rev. A 74, 022103 (2006)] within these distances. (C) 2016 The Japan Society of Applied Physic

Spin-polarized scanning tunneling microscopy and spectroscopy study of c(2x2) reconstructed Cr(001) thin film surfaces

Spin dependent electronic properties of c(2x2) Cr(001) thin film surfaces grown on MgO(001) substrates are investigated by means of spin-polarized scanning tunneling microscopy and spectroscopy. An averaged dI/dV spectrum obtained on the c(2x2) Cr(001) thin film surfaces exhibits a surface state around +0.1 eV above the Fermi level. The intensity of the surface state peak in the spectra measured on (001) terraces is alternately varied whenever a monatomic step is crossed. Therefore, the shifted surface state as well as an original one on (1x1) Cr(001) surfaces has spin-polarized feature. (C) 2006 American Institute of Physics

Electron-transfer-induced metallic electronic states in a H/Fe3O4(001) film subsurface

We investigate the local electronic properties of Fe atoms in a H/Fe3O4(001) film subsurface using scanning tunneling microscopy/spectroscopy (STS). Local barrier height measurements show a H-adsorption-induced reduction of the local work function, indicating electron transfer from H to surface atoms. The STS results and high-resolution spatial mapping of the occupied density of states near the Fermi level reveal that subsurface Fe atoms located beneath a OH group exhibit a metallic electronic state, different from the semiconducting state for intrinsic subsurface Fe atoms. These results can be explained by considering the extension of electron transfer to the subsurface layer. (c) 2019 The Japan Society of Applied Physic

Calculation method of reflectance distributions for computer-generated holograms using the finite-difference time-domain method

The research on reflectance distributions in computer-generated holograms (CGHs) is particularly sparse, and the textures of materials are not expressed. Thus, we propose a method for calculating reflectance distributions in CGHs that uses the finite-difference time-domain method. In this method, reflected light from an uneven surface made on a computer is analyzed by finite-difference time-domain simulation, and the reflected light distribution is applied to the CGH as an object light. We report the relations between the surface roughness of the objects and the reflectance distributions, and show that the reflectance distributions are given to CGHs by imaging simulation. (C) 2011 Optical Society of Americ