Oxidation-driven structural, chemical and electrical transformation in ZrSe2

The intrinsic air sensitivity of two-dimensional (2D) transition metal dichalcogenides (TMDs) poses a major challenge for their deployment in nanoelectronics devices. In this work, we present a comprehensive study of the oxidation-driven degradation of ZrSe2, revealing the time-dependent evolution of surface morphology, chemical composition, and device performance. Using a suite of experimental techniques including AFM, SEM, STM, EDX, XPS, and Raman spectroscopy, complemented by density functional theory (DFT) simulations, we track the spontaneous formation of Se-rich protrusions and nanowires resulting from oxidation. Our findings demonstrate that oxidation initiates both at defect sites and edges, leading to the formation of a native Zr oxide that promotes selenium segregation. EDX confirms Se-rich blisters and nanowires, while Raman spectroscopy reveals the loss of ZrSe2 vibrational modes and the emergence of Se peaks over time. DFT results further explain this behaviour by showing that oxygen adsorption weakens Zr-Se bonds and facilitates Se clustering. Encapsulation with a thin e-beam evaporated ZrO2 layer limits degradation and offers a path toward improved field-effect transistor performance under optimized conditions. This work provides new insights into the degradation pathways of ZrSe2 and underscores the critical importance of interface engineering and environmental control for reliable 2D semiconductor devices.