Surface defects in carbon-doped hexagonal boron nitride for negative-contrast direct laser writing

TL;DR

This paper reports on the discovery and control of surface defects in carbon-doped hexagonal boron nitride, enabling negative-contrast direct laser writing of emissive patterns with potential applications in surface science and photonics.

Contribution

It introduces a new class of optically active surface defects in hBN that can be selectively quenched or activated, enabling precise patterning through laser writing techniques.

Findings

Surface defects exhibit distinct photophysical properties from bulk defects.

High-power laser can quench defect emission via structural reconfiguration.

Surface chemistry can permanently quench defects, enabling patterning.

Abstract

Radiative defects in hexagonal boron nitride (hBN) are active in a broad spectral range from deep ultraviolet to near-infrared wavelengths. Representatives of these defects act as bright single photon sources, spin-1 systems, and multiproperty atomic-scale sensors. They are predominantly investigated in bulk hBN films, where defects are decoupled from surface and interfacial effects. Here, we demonstrate a novel class of surface defects optically active in the green/yellow visible spectral range, which exhibit photophysical properties distinct from their bulk counterparts. High-power resonant laser illumination quenched the emission from the ensemble of such defects, which was attributed to a light-driven structural reconfiguration. The quenched defects were found to recover their emissive capabilities via a thermal cycling process, revealing an activation energy of 24.5 meV for the structural transition. Alternatively, permanent quenching of the defects was triggered by surface chemistry, involving lithiation-enabled attachment of functional groups. These mechanisms were utilized to realize negative-contrast direct laser writing, designing arbitrary geometric emissive patterns on demand in a microscopic configuration. The surface-active radiative centers in hBN appear particularly attractive for exploring environmental sensitivity, surface science, and coupling to photonic structures or electronic devices by taking unique advantage of the two-dimensional characteristics of the host lattice.