  Atomically thin layered two-dimensional materials, including transition-metal
dichacolgenide (TMDC) and black phosphorus (BP), (1) have been receiving much
attention, because of their promising physical properties and potential
applications in flexible and transparent electronic devices . Here, for the
first time we show non-volatile chargetrap memory devices, based on
field-effect transistors with large hysteresis, consisting of a few-layer black
phosphorus channel and a three dimensional (3D) Al2O3 /HfO2 /Al2O3 charge-trap
gate stack. An unprecedented memory window exceeding 12 V is observed, due to
the extraordinary trapping ability of HfO2. The device shows a high endurance
and a stable retention of ?25% charge loss after 10 years, even drastically
lower than reported MoS2 flash memory. The high program/erase current ratio,
large memory window, stable retention and high on/off current ratio, provide a
promising route towards the flexible and transparent memory devices utilising
atomically thin two-dimensional materials. The combination of 2D materials with
traditional high-k charge-trap gate stacks opens up an exciting field of
nonvolatile memory devices.
