Bottom-up realization of a type-II organic-TMD heterointerface: Pentacene on monolayer WS2

TL;DR

This study demonstrates the bottom-up synthesis and characterization of a high-quality pentacene/WS2 heterostructure with type-II band alignment, enabling advanced interfacial studies for optoelectronic applications.

Contribution

It introduces a reliable MBE growth method for atomically flat WS2 and explores the electronic properties of the hybrid interface using advanced spectroscopy and calculations.

Findings

Successful epitaxial growth of ordered pentacene on monolayer WS2.

Observation of type-II band alignment in the heterostructure.

High-quality heterostructure suitable for interfacial charge transfer studies.

Abstract

Stacked van der Waals heterostructures based on transition metal dichalcogenides (TMDs) exhibit a rich variety of exotic interfacial phenomena. Substituting one component with an organic semiconductor (OSC) enables the design of hybrid heterostructures with tunable functionalities for optoelectronic, photovoltaic, and spintronic applications. In this work, exploiting scanning tunneling spectroscopy (STS), photoemission orbital tomography (POT) and G0W0 electronic structure calculations, we experimentally and theoretically demonstrate the self-assembly of an ordered single layer of pentacene (5A) above monolayer WS2, exhibiting a type-II (staggered) band alignment in the hybrid 5A/WS2 interface. Central to this result is the synthesis of extended, atomically flat WS2 - an essential prerequisite for a highly ordered and electronically homogeneous OSC/TMD interface - which can only be reliably achieved via bottom-up growth, most notably molecular beam epitaxy (MBE). We realize this by leveraging Au(111) as an atomically clean and conductive sample for epitaxial growth - a necessary requirement for reliable and comparable STS/POT characterizations. The high quality of the synthesized heterostructure, together with its type-II band alignment, establishes pentacene/WS2 as a model system for orbital-resolved studies of charge transfer, energy-level renormalization, and non-equilibrium interfacial processes in hybrid organic-inorganic-2D heterostructures.