Passivation of Layered Gallium Telluride by Double Encapsulation with Graphene

Layered semiconductor gallium telluride (GaTe) undergoes a rapid structural transition to a degraded phase in ambient conditions, limiting its utility in devices such as optical switches. In this work, we demonstrate that the degradation process in GaTe flakes can be slowed down dramatically via encapsulation with graphene. Through examining Raman signatures of degradation, we show that the choice of substrate significantly impacts the degradation rate and that the process is accelerated by the transfer of GaTe to hydrophilic substrates such as SiO₂/Si. We find that double encapsulation with both top and bottom graphene layers can extend the lifetime of the material for several weeks. The photoresponse of flakes encapsulated in this way is only reduced by 17.6 ± 0.4% after 2 weeks, whereas unencapsulated flakes display no response after this time. Our results demonstrate the potential for alternative, van der Waals material-based passivation strategies in unstable layered materials and highlight the need for careful selection of substrates for 2D electronic devices.