  Nonvolatile phase change random access memory (PCRAM) is regarded as one of
promising candidates for emerging mass storage in the era of Big Data. However,
relatively high programming energy hurdles the further reduction of power
consumption in PCRAM. Utilizing narrow edge-contact of graphene can effectively
reduce the active volume of phase change material in each cell, and therefore
realize low-power operation. Here, we demonstrate that a write energy can be
reduced to about ~53.7 fJ in a cell with ~3 nm-wide graphene nanoribbon (GNR)
as edge-contact, whose cross-sectional area is only ~1 nm2. It is found that
the cycle endurance exhibits an obvious dependence on the bias polarity in the
cell with structure asymmetry. If a positive bias was applied to graphene
electrode, the endurance can be extended at least one order longer than the
case with reversal of polarity. The work represents a great technological
advance for the low power PCRAM and could benefit for in-memory computing in
future.
