Maskless Synthesis of van der Waals Heterostructure Arrays Engineered for Light Harvesting on Large Area Templates.

Large area stacking of van der Waals heterostructure arrays, based on 2D Transition Metal Dichalcogenide semiconductors (TMDs), is achieved by an original physical deposition process utilizing Ion Beam Sputtering. Silica substrates endowed with periodically faceted nanoridges are fabricated using interference lithography and serve as templates for maskless deposition of TMD at glancing angles. This approach enables the creation of laterally confined few-layer WS nanostripe arrays coated by MoS films. The subwavelength periodicity of the high refractive index WS nanostripes facilitates the excitation of photonic anomalies at the onset of the evanescence condition. As a consequence, light flow is effectively steered and trapped within the 2D-TMDs heterostructures and the supporting dielectric slab. Photon harvesting is engineered in the flat optics regime by optimizing the thickness of the WS nanostripes, which serve as optical sensitizers. This innovative design achieves a resonant enhancement of optical absorption, up to a remarkable factor of 450%, when compared to a reference flat MoS/WS heterostructure of equivalent thickness. This result highlights the promising potential of the novel 2D-TMD platforms for scalable real-world applications of van der Waals heterostructures, targeting photoconversion, photocatalysis, and energy storage.