Water induced bandgap engineering in nanoribbons of hexagonal boron nitride

TL;DR

This paper demonstrates that water adsorption can significantly reduce the bandgap of hexagonal boron nitride nanoribbons, enabling tunable electronic and optoelectronic properties through electric field modulation.

Contribution

It introduces a novel method of bandgap engineering in BNNRs via water adsorption, supported by both theoretical calculations and experimental device fabrication.

Findings

Water adsorption induces a transverse electric field over 2 V/nm.

Conductance of zBNNRs can be tuned over 3 orders of magnitude.

Wider zBNNRs exhibit a bandgap as low as 1.17 eV.

Abstract

Different from hexagonal boron nitride (hBN) sheets, the bandgap of hBN nanoribbons (BNNRs) can be changed by spatial/electrostatic confinement. It has been 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, we theoretically and experimentally demonstrate that water adsorption greatly reduces bandgap of zigzag oriented BNNRs (zBNNRs). Ab initio calculations show that water adsorbed beside the BNNR induces a transverse equivalent electric field of over 2 V/nm thereby reducing its bandgap. Field effect transistors were successfully fabricated from zBNNRs with different widths. The conductance of zBNNRs with adsorbates of water could be tuned over 3 orders in magnitude via electrical field modulation at room temperature. Furthermore, photocurrent response measurements were taken to determine the optical bandgap in zBNNR. Wider zBNNRs exhibit a bandgap down to 1.17 eV. This study yields fundamental insights in new routes toward realizing electronic/optoelectronic devices and circuits based on hexagonal boron nitride.