Shu Yamaguchi

Volatile/Nonvolatile Dual-Functional Atom Transistor

We demonstrate a conceptually new atom transistor operation by electric-field control of the nanoionic state. The new atom transistor possesses novel characteristics, such as dual functionality of selective volatile and nonvolatile operations, very small power consumption (pW), and a high ON/OFF ratio [106 (volatile operation) to 108 (nonvolatile operation)], in addition to complementary metal oxide semiconductor (CMOS) process compatibility enabling the development of future computing systems that fully utilize highly-integrated CMOS technology. Cyclic endurance of 104 times switching was achieved with the prototype.

Finite Size Effect of Proton-Conductivity of Amorphous Silicate Thin Films Based on Mesoscopic Fluctuation of Glass Network

The finite size effect of proton conductivity of amorphous silicate thin films, a-M(0.1)Si(0.9)O(x) (M = Al, Ga, Hf, Ti, Ta, and La), was investigated. The proton conductivity across films, σ, was measured in dry air by changing the thickness in the range of 10-1000 nm. σ of the films with M = Al, Ga, and Ta was elevated in a power law by decreasing thickness into less than a few hundred nanometers, and the increment was saturated at a thickness of several 10s of nanometers. On the other hand, σ of the films with M = Hf, Ti, and La was not related to the decrease of the thickness in the range of >10 nm. Thickness-dependent conductivity of the former could be numerically simulated by a percolative resistor network model that involves the randomly distributed array of two kinds of resistors R(1) and R(2) (R(1) > R(2)) in the form of a simple cubic-type lattice. High-resolution TEM clarified that a-M(0.1)Si(0.9)O(x) films involved heterogeneous microstructures made of the condensed domain and the surrounding uncondensed matrix due to the fluctuation of glass networks on the nanometer scale. The condensed domain had a wormlike shape with an average length of several 10s of nanometers and performed the role of the proton conduction pathway penetrating through the poorly conducting matrix. It was concluded that the thickness-dependent conductivity could be identical to finite-size scaling of the percolative network of the interconnected domains in the nanometer range.

Main group oxides: Making the transition

A chemically driven process turns the classic insulator, gallium oxide, into a metal by the formation of a heterogeneous mixture of crystalline and amorphous regions.