  Van der Waals heterostructure based on layered two-dimensional (2D) materials
offers unprecedented opportunities to create materials with atomic precision by
design. By combining superior properties of each component, such
heterostructure also provides possible solutions to address various challenges
of the electronic devices, especially those with vertical multilayered
structures. Here, we report the realization of robust memristors for the first
time based on van der Waals heterostructure of fully layered 2D materials
(graphene/MoS2-xOx/graphene) and demonstrate a good thermal stability lacking
in traditional memristors. Such devices have shown excellent switching
performance with endurance up to 107 and a record-high operating temperature up
to 340oC. By combining in situ high-resolution TEM and STEM studies, we have
shown that the MoS2-xOx switching layer, together with the graphene electrodes
and their atomically sharp interfaces, are responsible for the observed thermal
stability at elevated temperatures. A well-defined conduction channel and a
switching mechanism based on the migration of oxygen ions were also revealed.
In addition, the fully layered 2D materials offer a good mechanical flexibility
for flexible electronic applications, manifested by our experimental
demonstration of a good endurance against over 1000 bending cycles. Our results
showcase a general and encouraging pathway toward engineering desired device
properties by using 2D van der Waals heterostructures.
