  Heterostructures composed of two-dimensional (2D) materials are already
opening many new possibilities in such fields of technology as electronics and
magnonics, but far more could be achieved if the number and diversity of 2D
materials is increased. So far, only a few dozen 2D crystals have been
extracted from materials that exhibit a layered phase in ambient conditions,
omitting entirely the large number of layered materials that may exist in other
temperatures and pressures. Here, we demonstrate how these structures can be
stabilized in 2D van der Waals stacks under room temperature via growing them
directly in graphene encapsulation by using graphene oxide as the template
material. Specifically, we produce an ambient stable 2D structure of copper and
iodine, a material that normally only occurs in layered form at elevated
temperatures between 645 and 675 K. Our results establish a route to the
production of more exotic phases of materials that would otherwise be difficult
or impossible to stabilize for experiments in ambient.
