Improved Charge Transfer for NO<sub>2</sub> Gas Sensors by Using 0D SnS Quantum Dot/2D WSe<sub>2</sub> Heterostructures
Li-Hsin Cheng, Utkarsh Kumar, Zu-Yin Deng, Chiu‐Hsien Wu
Abstract
A highly sensitive array of two-dimensional (2D) WSe 2 nanosheets integrated with zero-dimensional (0D) SnS quantum dots was synthesized by combining liquid-phase exfoliation and wet chemical synthesis methods. The characterization results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) revealed the formation of WSe 2 /SnS heterostructures, which enable a cyclic and reproducible high gas sensing response. The role allocation of SnS on WSe 2 was verified by using density functional theory (DFT) calculations. The result indicates that the top alignment of SnS and the bottom layer of WSe 2 act as a gas adsorption layer and carrier conduction layer, respectively. The charge interactions of the heterostructures were systematically explored by monitoring changes in the transferred characteristics at room temperature (27 °C) after introducing 25–100 ppb NO 2 . The highest sensing response of WSe 2 /SnS heterostructures toward the NO 2 gas was found to be 1.08 at 25 ppb with a LOD of 10.6 ppb. The experimental and simulation results revealed that the charge transfer across the active sites increased after incorporating SnS in the WSe 2 . The sensing results showed an abrupt and reliable gas response under periodic NO 2 gas injection unambiguously achieved by such heterostructures. The sensor also exhibited satisfactory stability and accuracy in selectivity and is not affected by humidity at room temperature. DFT calculations were also used to explain the sensing mechanism and heterojunction for such nanocomposites.