Probing the interfacial chemistry in polycrystalline h-BN/Pt(1 1 1) surfaces through molecular adsorption

Abstract

One-atom-thick layers of polycrystalline h-BN comprising nanosized domains, associated to different rotational variants, have been grown under ultrahigh vacuum conditions on Pt(111) supports, and employed as substrates for molecular adsorption studies. The lowest growth temperature limit to obtain the highest rotational variety, without compromising the structural quality, is determined by low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The nanodomains exhibit different moiré patterns with distinct periodicities and corrugations, suggesting significant dissimilarities in their interfacial chemistries. Consequently, the junctions of these domains give rise to a rich variety of boundaries. Therefore, these h-BN/Pt(111) surfaces offer a wide spectrum of possibilities for molecular adsorption studies. As a probe molecule, the prototypical adsorbate perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA) has been employed. By a Fourier Transform analysis, it is possible to unveil the moiré pattern periodicity, and it is concluded that the molecular assembly and orientation is often the same in neighbour nanodomains, although the h-BN lattice underneath is rotated differently. This is consistent with a weak physisorption of PTCDA on h-BN/Pt(111). Additionally, the effect of the atomic steps of the underlying Pt(111) support on the molecular assembly has been analysed by STM measurements, having demonstrated a carpet-like growth of the PTCDA adlayer.