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Updated: Sep 9, 2025

Ohmic Contact Fabrication Using a Focused-ion Beam Technique and Electrical Characterization for Layer Semiconductor Nanostructures
Published on: December 5, 2015
Superior NO2 sensing via semiconductor-metal transition in undoped Hf2CO2 MXene: doping-mediated trade-offs between
Renjie Zhu1, Zebang Cheng1, Wenjing Hu2
1College of Mathematics and Physics, Shanghai University of Electric Power, Shanghai 200090, China. plpeng@shiep.edu.cn.
Abstract:
In this paper, we employ density functional theory (DFT) and non-equilibrium Green's function (NEGF) calculations to investigate the gas-sensing properties of monolayer Hf2CO2 MXene, focusing on intrinsic vacancy defects and carbon-site substitutional doping. Among tested gases, NO2 exhibits exceptional sensitivity due to strong adsorption energy and significant charge transfer. Boron doping at carbon sites enhances charge transfer and adsorption strength through d-band center upshift (-0.349 eV → -0.076 eV) and induces metallic conductivity that diminishes current modulation sensitivity. By analyzing current-voltage (I-V) relationships for pristine and B-doped Hf2CO2 with/without NO2 adsorption, we demonstrate that the pristine Hf2CO2 monolayer exhibits superior gas-sensing performance, achieving a two-order-of-magnitude current surge upon NO2 adsorption compared to doped systems. This study reveals the critical trade-off between doping-induced adsorption enhancement and conductivity-driven sensitivity loss, providing a design framework for MXene-based sensors through strategic optimization of surface reactivity and electronic response.
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