Takahiko Ban

Memristive nanoparticles formed using a biotemplate

We demonstrated a novel biological process based on the use of a supramolecular protein as a reaction cage, in which a memristive element is formed. We showed that ferritin can be used to generate memristive nanoparticles by biomineralization. Magnetite (Fe3O4) nanoparticles with a size of 6 nm were prepared using a biotemplate. After a fine monolayer of NPs was formed on the electrode, the protein shells were removed in order to improve the electrical contact between NP and electrode. The synthesized nanoparticles exhibit clear bipolar resistive switching behaviors in metal/oxide/metal structure. From c-AFM measurements, even a single NP exhibits the memory behavior, leading to their promising potential application in nanoscale resistive memory.

Ultra-short channel junctionless transistor with a one-dimensional nanodot array floating gate

The electrical properties of a junctionless field-effect transistor with a sub-10-nm scale channel and FeOx nanoparticles (NPs) were studied. The anisotropic wet etching of a silicon-on-insulator substrate was used to form V-grooves and define the nanometer-scale channel. The NPs were selectively placed on the bottom of the V-groove using the bio-nano process. Low-voltage operation and a wide threshold voltage (Vth) shift as memory behavior were confirmed in a device with a 3.6-nm channel length. These results indicate that the Vth is controlled by the single-nanodot floating gate along the channel length direction.

Charge effects of ultrafine FET with nanodot type floating gate

Metal nanoparticles (NPs) embedded in junctionless field-effect transistors (JL-FETs) with a length of 3.6 nm are fabricated and demonstrated. The anisotropic wet etching of a silicon-on-insulator (SOI) substrate was utilized to form V-grooves and to define nanometer-scale channel. Metal NPs are selectively placed onto bottom of V-groove using the Bio nano process (BNP). The JL-FET is applied to floating gate memory and used to investigate an impact on the short channel by charge trap of NPs. Low-voltage operation and broad threshold voltage shift as memory behavior are appeared in 3.6 nm channel length. It is expected that the JL-FETs can overcome the scaling limitations in floating gate memory, while the charge trap cause major problems in the sub 10 nm region.

Evaluation of TaOx nanoparitcles for resistive random access memory

We demonstrated a resistive memory using TaOx nanoparticles (NPs) utilizing Bio Nano Process (BNP). TaOx NPs were produced by ferritin proteins. The ReRAM with TaOx NPs exhibits resistive switching behavior evaluated by conductive atomic force microscopy. This result indicates that TaOx nano-ReRAM utilizing BNP can be a high-density non-volatile memory.