Ion-Induced Phase Changes in 2D MoTe2 Films for Neuromorphic Synaptic Device Applications.

Two-dimensional molybdenum ditelluride (2D MoTe2) is an interesting material for artificial synapses due to its unique electronic properties and phase tunability in different polymorphs 2H/1T'. However, the growth of stable and large-scale 2D MoTe2 on a CMOS-compatible Si/SiO2 substrate remains challenging because of the high growth temperature and impurity-involved transfer process. We developed a large-scale MoTe2 film on a Si/SiO2 wafer by simple sputtering followed by lithium-ion intercalation and applied it to artificial synaptic devices. The Al2O3 passivation layer allows us to develop a stable 1T'-MoTe2 phase by preventing Te segregation caused by the weak bonding between Mo and Te atoms during lithiation. The lithiated MoTe2 film exhibits excellent synaptic behavior such as long-term potentiation/depression, a high Ion/Ioff ratio (≈103) at lower sweep voltage, and long-term retention. The in situ Raman analysis along with a systematic microstructural analysis reveals that the intercalated Li ion can provide an efficient pathway for conducting filament formation.