Air sensitivity of GaSe 2D material and its potential implications on device reliability

This study demonstrates the oxidation-driven degradation of exfoliated GaSe highlighting the changes to not only the material's morphology but its chemical composition as well. We have employed a number of simulation and experimental techniques, including DFT calculations, SEM, EDX and Raman spectroscopy, to understand the atomic structure and vacancy effects between the β and ε polytypes, and to understand the degradation occurring. The combined results of the DFT and experimental results show that the crystal used was the β polytype with a bandgap value of ~ 1.92 eV. Further experimental analysis demonstrates that the oxidation occurs on the surface of the material producing Ga₂O₃ which is possibly due to defect sites or dangling bonds. This oxidation encourages the formation of hemispherical blisters on the material surface. EDX analysis indicates that these blisters are Se-rich while Raman spectroscopy confirms the presence of amorphous and crystalline Se in these regions while also showing the disappearance of the dominant vibrational modes of GaSe. This work emphasises the importance of the environment's role and developing encapsulation strategies in relation to interface engineering and material stability for fabricating air-stable nanoelectronic devices.