Abstract
ABSTRACT For realization of new informative systems, the memristor working like synapse has drawn much attention. We developed isolated high-density Fe3O4 nanocrystals on Ge nuclei/Si with uniform and high resistive switching performance using low-temperature growth. The Fe3O4 nanocrystals on Ge nuclei had a well-controlled interface (Fe3O4/GeOx/Ge) composed of high-crystallinity Fe3O4 and high-quality GeOx layers. The nanocrystals showed uniform resistive switching characteristics (high switching probability of ~90%) and relatively high Off/On resistance ratio (~58). The high-quality interface enables electric field application to Fe3O4 and GeOx near the interface, which leads to effective positively charged oxygen vacancy movement, resulting in high-performance resistive switching. Furthermore, we successfully observed memory effect in nanocrystals with well-controlled interface. The experimental confirmation of the memory effect existence even in ultrasmall nanocrystals is significant for realizing non-volatile nanocrystal memory leading to neuromorphic devices.
Highlights
New informative systems toward next-generation human society such as artificial intelligence and internet of things have been extensively studied
The experimental confirmation of the memory effect existence even in ultrasmall NCs is significant for realizing non-volatile NC memory leading to neuromorphic device
From Reflection high energy electron diffraction (RHEED) observations, it was confirmed that Fe3O4 NCs were epitaxially grown on Ge nuclei/Si (Figure 2(b)), which detailed RHEED analyses are reported in our previous studies [17,26]
Summary
New informative systems toward next-generation human society such as artificial intelligence and internet of things have been extensively studied. It has been revealed that the resistive switching is originated from the thickness change of high resistance layer (HRL) near Fe3O4/ GeOx/Ge interface caused by electric-field-induced oxygen vacancy movement (Figure 1(b)). The identity of HRL, a key of this nanoionics-based resistive switching, has not been clarified: in the interface layer, existence or non-existence of Fe-Ge mixing, and oxidation degree, etc. In this study, aiming at forming well-controlled Fe3O4/GeOx/Ge interface in the NC system, we perform low-temperature growth of epitaxial Fe3O4 NCs without the interface reaction degrading the performance by depositing Fe on Ge nuclei at room temperature (RT) under a low-pressure oxygen atmosphere and subsequently post-annealing. It is found that HRL related to resistive switching mechanism is composed of Fe3O4 near the interface and GeO. The experimental confirmation of the memory effect existence even in ultrasmall NCs is significant for realizing non-volatile NC memory leading to neuromorphic device
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