Spectra-orthogonal optical anisotropy in wafer-scale molecular crystal monolayers

TL;DR

This paper demonstrates wafer-scale 2D molecular crystal monolayers with independently tunable optical anisotropy and spectral response, enabling new ultra-thin optoelectronic functionalities.

Contribution

It introduces spectra-orthogonal optical anisotropy in 2D molecular crystals, allowing independent control of polarization and spectral properties at wafer scale.

Findings

Tunable optical polarization anisotropy in 2D molecular crystals.

Epitaxial relationship between 2DMC and TMD confirmed.

Scalable, molecule-based 2D platform with unique functionalities.

Abstract

Controlling the spectral and polarization responses of two-dimensional (2D) crystals is vital for developing ultra-thin platforms for compact optoelectronic devices. However, independently tuning optical anisotropy and spectral response remains challenging in conventional semiconductors due to the intertwined nature of their lattice and electronic structures. Here, we report spectra-orthogonal optical anisotropy, where polarization anisotropy is tuned independently of spectral response, in wafer-scale, one-atom-thick 2D molecular crystal (2DMC) monolayers synthesized on monolayer transition metal dichalcogenide (TMD) crystals. Utilizing the concomitant spectral consistency and structural tunability of perylene derivatives, we demonstrate tunable optical polarization anisotropy in 2DMCs with similar spectral profiles, as confirmed by room-temperature scanning tunneling microscopy and cross-polarized reflectance microscopy. Additional angle-dependent analysis of the single- and polycrystalline molecular domains reveals an epitaxial relationship between the 2DMC and the TMD. Our results establish a scalable, molecule-based 2D crystalline platform for unique and tunable functionalities unattainable in covalent 2D solids.