Water‐Induced Bandgap Engineering in Nanoribbons of Hexagonal Boron Nitride

• Published in: Advanced materials (Weinheim) 2023-09, Vol.35 (36), p.e2303198-n/a
• Main Authors: Chen, Chen, Hang, Yang, Wang, Hui Shan, Wang, Yang, Wang, Xiujun, Jiang, Chengxin, Feng, Yu, Liu, Chenxi, Janzen, Eli, Edgar, James H., Wei, Zhipeng, Guo, Wanlin, Hu, Weida, Zhang, Zhuhua, Wang, Haomin, Xie, Xiaoming
• Format: Article
• Language: English
• Subjects: Adsorbed water; Adsorption; bandgap engineering; Boron; Boron nitride; boron nitride nanoribbons; edge modification; Electric fields; Energy gap; Equivalence; hexagonal boron nitride; Ice formation; Materials science; Nanoribbons; Optoelectronic devices; Photoelectric effect; Room temperature; Silicones; transverse potential; water adsorption; Water chemistry
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202303198

Different from hexagonal boron nitride (hBN) sheets, the bandgap of hBN nanoribbons (BNNRs) can be changed by spatial/electrostatic confinement. It is predicted that a transverse electric field can narrow the bandgap and even cause an insulator–metal transition in BNNRs. However, experimentally introducing an overhigh electric field across the BNNR remains challenging. Here, it is theoretically and experimentally demonstrated that water adsorption greatly reduces the bandgap of zigzag‐oriented BNNRs (zBNNRs). Ab initio calculations show that water molecules can be favorably assembled within the trench between two adjacent BNNRs to form a polar ice layer, which induces a transverse equivalent electric field of over 2 V nm−1 accounting for the bandgap reduction. Field‐effect transistors are successfully fabricated from zBNNRs with different widths. The conductance of water‐adsorbed zBNNRs can be tuned over 3 orders in magnitude via modulation of the equivalent electrical field at room temperature. Furthermore, photocurrent response measurements are taken to determine the optical bandgaps of zBNNRs with water adsorption. The zBNNR with increased width can exhibit a bandgap down to 1.17 eV. This study offers fundamental insights into new routes toward realizing electronic/optoelectronic devices and circuits based on hexagonal boron nitride. The effective bandgap modulation of water‐adsorbed zigzag‐oriented hexagonal boron nitride nanoribbons (zBNNRs) is reported. A water layer adsorbed at the edges creates a huge transverse potential and then greatly reduces its bandgap. The conductance of ≈8 nm‐wide zBNNRs with adsorbates of water can be tuned over 3 orders in magnitude via electrical field modulation at room temperature.