Symmetric thickness modulation in MoS₂/WSe₂heterostructures: tuning mobility and PVCR for next-generation electronics

Two-dimensional transition metal dichalcogenide heterostructures, such as MoS₂/WSe₂, offer unique electronic properties and atomic-scale thickness, making them promising candidates for next-generation electronic devices. However, optimizing their performance requires a deeper understanding of how layer thickness influences key electrical parameters. This study systematically examines how symmetric layer-number variations influence key electrical properties, including mobility, threshold voltage (V_th), and peak-to-valley current ratio (PVCR), in MoS₂/WSe₂field-effect transistors (FETs) across a broad thickness range (3/3-137/137 layers). The 12/12-layer configuration achieves a maximum PVCR of 10⁵, attributed to efficient band-to-band tunneling, while the 19/19-layer configuration demonstrates peak mobility of 25.41 cm²V·s^-1, highlighting the role of interlayer coupling in enhancing device performance. The 12-40-layer range emerges as a versatile thickness range for balancing these properties, suitable for various device applications. The study also investigates pristine MoS₂and WSe₂layers, revealing their individual optimal thicknesses, with peak mobilities of 59.01 cm²V·s^-1at 11 layers and 96.3 cm²V·s^-1at 12 layers, respectively. A 24 h acetone exposure test on single-layer WSe₂FETs underscores the environmental vulnerability of ultra-thin configurations, revealing extended depletion voltage ranges (up to 80 V) and insulator-like behavior. These findings demonstrate the critical importance of symmetric thickness control in enhancing the multifunctionality and robustness of MoS₂/WSe₂heterostructures. They pave the way for scalable, high-performance electronic and optoelectronic applications, including multi-functional transistors and environmentally resilient devices.