The advent of two-dimensional (2D) materials has revolutionized the field of photonics, offering unprecedented control over light-matter interactions at the atomic scale. Among the most promising avenues for optimizing these materials is atomic precision defect engineering, a technique that involves the deliberate introduction of defects to tailor photonic properties. Unlike traditional bulk materials, where defects often degrade performance, 2D materials allow defects to be engineered with precision, enabling new functionalities for photonic circuits.
Defects in 2D materials—such as vacancies, substitutions, and grain boundaries—can drastically alter electronic and optical behavior. These modifications include:
Precision defect engineering requires advanced fabrication and characterization techniques. Key methods include:
Focused ion beams (FIB) or helium ion microscopy (HIM) enable selective defect creation with sub-nanometer resolution. By adjusting beam energy and dose, researchers can introduce vacancies or interstitial defects in specific lattice sites.
Controlled exposure to reactive gases (e.g., oxygen, hydrogen) can functionalize 2D materials, creating stable defect configurations. For example, hydrogenation of graphene introduces sp3 hybridized carbon atoms, altering its optical conductivity.
Mechanical strain can induce defect formation or reconfiguration in 2D materials. Techniques such as atomic force microscopy (AFM) nanoindentation allow localized strain application to create defects at predefined locations.
High-resolution electron beams can selectively remove atoms from 2D materials, creating well-defined vacancy defects. This method is particularly useful for patterning photonic crystal cavities in transition metal dichalcogenides (TMDs).
Defects in hBN have been engineered to act as room-temperature single-photon emitters (SPEs). By introducing boron or nitrogen vacancies via plasma treatment, researchers have demonstrated bright, stable SPEs suitable for quantum photonic circuits.
Graphene’s plasmonic properties can be enhanced by introducing atomic-scale defects. Nitrogen-doped graphene exhibits tunable plasmon resonances in the mid-infrared range, enabling compact plasmonic waveguides for integrated photonics.
Sulfur vacancies in monolayer MoS2 have been exploited to achieve optically pumped lasing at room temperature. The defects act as gain centers, facilitating population inversion and stimulated emission.
Despite progress, several challenges remain:
First-principles calculations and machine learning models play a critical role in predicting defect properties. Density functional theory (DFT) simulations can identify stable defect configurations and their optical signatures, guiding experimental efforts.
The future of defect engineering in 2D photonics lies in:
Atomic precision defect engineering represents a paradigm shift in 2D photonics, offering unparalleled control over material properties. By leveraging advanced fabrication and characterization techniques, researchers can design next-generation photonic circuits with tailored functionalities. However, addressing reproducibility and stability challenges will be crucial for real-world applications.