Area-Selective Atomic/Molecular Layer Deposition of Europium-Organic Thin Films on Graphene and Other 2D Materials for Photoluminescent Heterostructures.

Abstract

Developing a controlled, defect-free, and spatially selective deposition of molecular and hybrid thin films on 2D materials remains a key challenge for their integration into multifunctional optoelectronic systems due to their surface inertness. Here, we demonstrate area-selective atomic/molecular layer deposition of europium-organic (Eu-BDC) thin films on graphene utilizing direct femtosecond laser two-photon oxidation. The laser dose defines the density of nucleation sites and precisely controls Eu-BDC film thickness and uniformity. By optimizing the deposition parameters and carefully choosing a transfer polymer, we achieve over 90% selectivity and high film homogeneity in the activated areas with submicron resolution. Upon 532 nm excitation, graphene/Eu-BDC exhibits strong emission at 612 nm with additional lines at 579, 592, and 652 nm. It also shows a green band at ∼566 nm, which is not observed on Si/SiO₂. Photoluminescence quenching on graphene shortens lifetimes due to energy and charge transfer at the graphene/Eu-organic interface. Moreover, the Eu-organic layer lowers the graphene work function and shifts the Dirac point, indicating a controllable n-type doping. The same laser modification strategy is also demonstrated on other 2D materials, as shown for MoS₂ and WS₂. This resist-free approach enables area-selective growth on 2D surfaces with tunable optical and electronic properties, providing compact integration of patterned emitters and photodetectors on a single chip.