Low-Power 2D CMOS and Optoelectronic Devices via Oxidation Treatment of Tungsten Diselenide

Luke Smith^1*

¹Physics Department, National Cheng Kung University, Tainan, Taiwan

* Presenter:Luke Smith, email:lukesmith@phys.ncku.edu.tw

As silicon technology nodes advance toward angstrom dimensions, two-dimensional (2D) transition metal dichalcogenides (TMDs) have significant potential to complement existing technologies. Their absence of surface dangling bonds and atomic thickness efficiently overcome short-channel effects enabling device miniaturization, where such issues degrade silicon transistor performance. However, doping strategies for 2D materials remains a key challenge. Doping is essential to form low-resistance ohmic contacts and define n- and p-type regions from a single 2D material for scalable CMOS technologies. The polarity of 2D TMDs is typically controlled by material selection (e.g., MoS₂ for n-type, WSe₂ for p-type), or in the case of single material devices separate integration schemes or different contact metals can control n- and p-polarity. However, we show that fabrication can be simplified by selective-area oxidation of WSe₂ to create n- and p-type polarity within a single flake using the metal type for all contact electrodes, offering substantial benefits for scalability by streamlining processes. We fabricate n- and p-regions in few layer WSe₂ using oxygen plasma treatment and selective-area removal, providing a comprehensive assessment for both CMOS and optoelectronic applications. Photodetector measurements display ultra-high sensitivity with very low dark current, self-powered operation, minimal charge trapping, and short rise/fall times in the hundred-microsecond range. For CMOS logic, the device achieves unity gain with ultra-low power consumption of ~1.6 pW at 0.5 V_D. Having verified n- and p-regions through electrical and optical methods, we use Kelvin probe microscopy and broadband electrostatic force microscopy techniques to characterize oxidized and pristine WSe₂ lateral junctions for the first time, revealing a work function difference of ~120 meV and confirming majority carrier types through bias dependent measurement. By achieving homogenous TMD n- and p-type functionality for single contact metal type, we demonstrate simplified process attractive for CMOS scaling.

Keywords: Two-dimensional materials, Transition metal dichalcogenides , Tungsten diselenide , Native oxide