Probing the Properties of Quasi‐Isolated ClAlPc by Using Polycrystalline h‐BN on Pt(111) as a Testbed

Abstract

The structural and electronic properties of chloro‐aluminum phthalocyanine (ClAlPc) molecules on insulating hexagonal boron nitride (h‐BN) monolayers (MLs) grown on Pt(111) surfaces are studied via scanning tunneling microscopy and spectroscopy (STM/STS) along with low energy electron diffraction in ultra‐high vacuum conditions. As a reference, the structural properties of the h‐BN/Pt(111) surface are studied, where various moiré patterns associated to different orientations of the h‐BN lattice with respect to the Pt(111) surface below are characterized, for the first time, at the atomic scale. Room temperature deposition of ClAlPc molecules on h‐BN/Pt(111) gives rise to the formation of mainly bilayer molecular structures, where the ClAlPc molecules adopt an alternating Cl‐up and Cl‐down stacking configuration. Upon annealing, bilayer molecular structures become islands comprising only a single layer of molecules adsorbed in a Cl‐up configuration. In the ML regime, the possible influence of the moiré pattern superstructure and the h‐BN lattice on the molecular ordering is also studied. Finally, the electronic properties of ClAlPc on h‐BN/Pt(111) are investigated through high‐resolution STM imaging of the frontier molecular orbitals and differential conductance plots. The results point toward a weak molecule–substrate interaction.

Growth of 1D ClAlPc molecular chains mediated by graphene moiré patterns

“…38 On the other hand, extended regions of the ClAlPc monolayer have never been found in the experiments when molecules are deposited on the substrate held at RT. A similar sample morphology was also reported for ClAlPc grown on graphene, 39,40 graphite, 35,38,39,41 and h-BN 42 at RT. However, it differs from that of noble metals, [43][44][45][46][47] in which the interaction with ClAlPc is expected to be stronger, where molecules always form monolayers, adopting a mixture of Cl-up and Cl-down configurations at the same time.…”

“…Analogous bilayer–monolayer transition of the ClAlPc molecules caused by mild temperature annealing was observed for ClAlPc on graphite, 38 graphene 40 and h-BN. 42 On Au(111) 43 and Ag(111), 46 thermal annealing only triggers a change in the molecular orientation, forcing all the ClAlPc molecules to adopt a Cl-up configuration.…”

Mesoscopic 2D molecular self-assembly on an insulator

“…transition metal dichalcogenides, hexagonal boron nitride [hBN]), with their relatively weak outof-plane chemical reactivity [22], are promising platforms as support for electronically functional low-dimensional molecular nanosystems. Despite these advantages, examples of self-assembly of organic nanostructures (in particular, large-area monocrystalline 2D systems) on these substrates remain limited [23][24][25][26][27][28][29][30][31][32][33][34]. Here, we present low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) results on the mesoscale 2D self-assembly of a flat aromatic molecule-9,10-dicyanoanthracene (DCA)-on a 2D atomically thin insulator, hBN grown on Cu(111).…”

Moiré Pattern Dislocation in Continuous Atomic Lattice of Monolayer h-BN

“…The moiré superlattice, formed due to the lattice mismatch between 2D materials and their substrates, can offer an outstanding platform for constructing and investigating moiré pattern dislocations. As a representative material, the hexagonal boron nitride (h-BN), a 2D semiconductor having a wide direct band gap, can be fabricated on several metal substrates, − with different moiré patterns, due to the lattice mismatch and rotations. − With the relatively weak interfacial interaction, the h-BN on Pt(111) can have multiple moiré pattern phases with different rotations. Moreover, the step edges of Pt(111), where a stacking translation between the atom layers of the adjacent terraces exists, offer an opportunity to investigate the moiré pattern dislocations of the h-BN film.…”