Plasma-enhanced growth techniques have emerged as a critical method for synthesizing high-quality 2D nitrides such as hexagonal boron nitride (hBN) and gallium nitride (GaN). These techniques leverage the unique properties of plasma to enable precise control over nucleation, layer uniformity, and defect density, often at lower temperatures than conventional thermal chemical vapor deposition (CVD). The approach is particularly advantageous for 2D materials, where maintaining atomic-scale precision while minimizing thermal stress is essential for achieving desired electronic and structural properties.

Plasma chemistry plays a central role in the growth of 2D nitrides. In plasma-enhanced CVD (PECVD), a gas mixture containing nitrogen and precursor species (e.g., ammonia for nitrogen, trimethylgallium for GaN, or borane for hBN) is ionized using radiofrequency (RF) or microwave power. The plasma dissociates these precursors into highly reactive radicals, ions, and atomic species, which then adsorb onto the substrate surface. For instance, nitrogen plasma generates active N radicals that readily bond with metal or boron atoms, facilitating nitride formation even at reduced temperatures. The ionization process also enhances surface diffusion, promoting lateral growth of 2D layers rather than 3D island formation. Unlike thermal CVD, where high temperatures are required to break precursor bonds, PECVD enables efficient precursor decomposition at lower energies due to electron-impact dissociation in the plasma.

One of the most significant advantages of plasma-enhanced growth is the ability to synthesize 2D nitrides at low temperatures, typically between 300°C and 800°C, compared to thermal CVD, which often exceeds 1000°C. This is particularly beneficial for integrating nitrides with temperature-sensitive substrates such as polymers or pre-fabricated electronic devices. Lower growth temperatures also reduce thermal stress-induced defects, such as cracks or dislocations, which are common in high-temperature processes. Additionally, the reduced thermal budget minimizes unwanted interdiffusion between layers in heterostructures, preserving sharp interfaces critical for 2D device performance.

Defect mitigation is another key benefit of plasma-enhanced techniques. The reactive species generated in the plasma can passivate dangling bonds and vacancies during growth, improving crystallinity. For example, in hBN growth, nitrogen plasma can compensate for boron vacancies, reducing charge traps that degrade electronic properties. Similarly, in GaN, the enhanced reactivity of nitrogen species suppresses the formation of nitrogen vacancies, a common defect in thermal CVD. Plasma parameters such as power density, pressure, and gas flow ratios can be finely tuned to optimize stoichiometry and minimize point defects. Studies have shown that PECVD-grown hBN exhibits fewer defects and higher uniformity compared to thermally grown counterparts, as evidenced by photoluminescence spectroscopy and atomic force microscopy.

The differences between plasma-enhanced growth and thermal CVD are substantial. Thermal CVD relies solely on temperature-driven reactions, which often result in slower nucleation kinetics and less control over layer thickness. In contrast, PECVD provides independent control over precursor activation and substrate temperature, enabling faster growth rates and better thickness uniformity. The plasma environment also allows for the use of less stable precursors that would decompose unpredictably in thermal CVD. For instance, ammonia decomposition in thermal CVD requires high temperatures and often leads to incomplete nitridation, whereas plasma activation ensures efficient nitrogen incorporation even at lower temperatures.

However, plasma-enhanced growth is not without challenges. The high-energy environment can introduce ion bombardment-related defects if not carefully controlled. Optimizing plasma power and substrate bias is crucial to minimize damage while maintaining sufficient reactivity. Another consideration is the uniformity of plasma distribution, which can affect large-area growth. Advanced reactor designs, such as remote plasma configurations, mitigate these issues by spatially separating the plasma generation zone from the substrate, reducing direct ion exposure.

In summary, plasma-enhanced growth techniques offer a versatile and efficient pathway for synthesizing 2D nitrides with superior control over crystallinity, stoichiometry, and defect density. The ability to operate at lower temperatures expands compatibility with diverse substrates and integration schemes, while the unique plasma chemistry enables precise tuning of material properties. These advantages position PECVD as a promising alternative to thermal CVD for applications requiring high-quality 2D nitrides in electronics, optoelectronics, and quantum technologies. Future advancements in plasma source design and process optimization will further enhance the scalability and reproducibility of these growth methods.