  In this work, an optimized method was implemented for attaining stable
multibit operation with low energy consumption in a two-terminal memory element
made from the following layers: Ag/Pt nanoparticles (NPs)/SiO2/TiN in a
1-Transistor-1-Memristor configuration. Compared to the reference sample where
no NPs were embedded, an enlarged memory window was recorded in conjunction
with reduced variability for both switching states. A comprehensive numerical
model was also applied to shed light on this enhanced performance, which was
attributed to the spatial confinement effect induced by the presence of the Pt
NPs and its impact on the properties of the percolating conducting filaments
(CFs). Although 5-bit precision was demonstrated with the application of the
incremental-step-pulse-programming (ISPP) algorithm, the reset process was
unreliable and the output current increased abnormally when exceeded the value
of 150 uA. As a result, the multibit operation was limited. To address this
issue, a modified scheme was developed to accurately control the distance
between the various resistance levels and achieve highly reliable 6-bit
precision. Our work provides valuable insights for the development of
energy-efficient memories for applications where a high density of conductance
levels is required.
