Long-Term Aging Effects in Electrical Devices Based on High-Quality Chemical Vapor Deposition-Grown Single-Domain WSe ₂

The long-term stability and scalability of layered two-dimensional (2D) materials are crucial for their practical integration into the electronic industry. While transition metal dichalcogenides, such as tungsten diselenide (WSe 2 ), have demonstrated promising performance in electronic and optoelectronic applications, their long-term ambient-condition stability remains poorly understood, particularly for chemical vapor deposition (CVD) synthesized materials. In this study, we investigate the electrical and morphological aging of CVD-grown, single-domain, multilayer WSe 2 -based field-effect transistors over 28 months. Devices fabricated with Ni/Au contacts were analyzed using the transmission line method and Y-function method, demonstrating p-type behavior with an average mobility of ∼35 cm 2 /V·s and a maximum on-state current of 80.5 μA/μm. Electrical measurements at six months of air exposure showed clear aging effects, including increased p-doping and substantial reductions in current levels ranging from 34 to 80%, along with a 49% mobility reduction. Over the following 22 months, the electrical performance degraded only slightly (further average reduction of 11 and 29%, for current levels and mobility, respectively), with an average mobility remaining relatively large (16.1 cm 2 /V·s, even after 28 months of ambient exposure. Furthermore, material degradation mechanisms were assessed using Raman spectroscopy, XPS, and photoluminescence, revealing intensity reductions and blue shifts, attributed to oxygen chemisorption at selenium vacancies. These findings highlight the necessity of combining structural and electrical measurements for a deeper understanding of aging in 2D-based devices to mitigate degradation and ensure performance reliability.