Air-Stable Atomically Encapsulated Crystalline-Crystalline Phase Transitions in In2Se3

Abstract

The layered semiconductor In2Se3 has a low temperature crystalline–crystalline (α → β) phase transformation with distinct electrical properties that make it a promising candidate for phase change memory. Here, using scanning tunneling microscopy, correlative in situ micro-Raman, and electrical measurements, it is shown that the β phase can persist in bulk crystals at room temperature in non-oxidative environments. Of particular note, the stability of β phase crystals in ambient conditions under encapsulation of graphene and similar passivation layers, is reported for the first time. The strategy of encapsulation to ensure the persistence of β phase overlaps with efforts to passivate switching materials. It is further demonstrated that degradation from the elevated temperatures required for the phase change is slowed through examination of Raman signatures. These results demonstrate an alternative method of phase manipulation with a new stabilization of β-In2Se3 in ambient conditions potentially extendable to other polymorphic materials, and the importance of passivation in In2Se3 memory devices.