Dissimilar Decoupling Behavior of Two-Dimensional Materials on Metal Surfaces

Abstract

The efficiency of hexagonal boron nitride and graphene to separate the hydrocarbon molecule C64H36 from Ru(0001) and Pt(111) surfaces is explored in low-temperature scanning tunneling microscopy and spectroscopy experiments. Both 2D materials enable the observation of the Franck–Condon effect in both frontier orbitals. On hexagonal boron nitride, vibronic progression with two vibrational energies gives rise to sharp orbital sidebands that are clearly visible up to the second order of the vibrational quantum number with different Huang–Rhys factors. In contrast, on graphene, orbital and vibronic spectroscopic signatures exhibit broad line shapes, with the second-order progression being hardly discriminable. Only a single vibrational quantum energy leaves its fingerprint in the Franck–Condon spectrum.

Second Floor of Flatland: Epitaxial Growth of Graphene on Hexagonal Boron Nitride

“…Most likely, these structures are due to residual intercalated Pt atoms or clusters. Importantly, in agreement with previous reports [ 30,39,41,46 ] a moiré pattern is absent from the lower right part of the STM image, which strongly hints at graphene rather than h‐BN as the imaged 2D material because h‐BN‐covered Pt(111) gives rise to a clearly discernible moiré lattice (see Figure , Supporting Information). Indeed, the absence of a moiré pattern is consistent with the weak graphene–Pt(111) hybridization [ 47 ] and large twist angles enclosed by the close‐packed lattice direction of graphene, , and Pt(111), , [ 39,46 ] as inferred from the atomically resolved graphene (Figure 2) and Pt(111) (see Figure , Supporting Information) lattices.…”

“…The fabrication of h‐BN on Pt(111) from molecular precursor BNH 6 leads to a closed sheet that extends over several terraces (Figure 1a), in agreement with previous works. [ 31,40,41 ] The subsequent deposition of the Pt film gives rise to a strongly corrugated surface, which is due to Pt clusters residing on a closed Pt film (Figure 1b). At the film–h‐BN interface an epitaxial relationship between the Pt film and h‐BN likely applies, as observed for Au deposition on h‐BN [ 42 ] or for Pt on graphene.…”

“…Furthermore, hydrocarbon molecules adsorbed on these surface regions exhibit signatures of Franck–Condon vibrons that are characteristic for graphene (see Figure , Supporting Information) and clearly deviate from the situation on h‐BN. [ 41 ] Therefore, the presence of MLG on Pt(111) after the subsequent growth of h‐BN and graphene can reasonably be assumed.…”

Local stiffness and work function variations of hexagonal boron nitride on Cu(111)

“…For example, thin films of h-BN have been used as a passivating layer for graphene and MoS 2 -based electronics utilising the small lattice mismatch, the large optical phonon modes, and particularly the large bandgap [3][4][5][6][7][8][9][10]. Furthermore, when grown on metal substrates h-BN can be used as a nanoscale template for atoms, molecules, and nanostructures with well-controlled adsorption and electronic properties [11][12][13][14][15][16][17][18]. In such systems, h-BN shows a rich structural and electronic morphology, which depends on the lattice mismatch and the interaction strength with the substrate: Large and flat lattice-matched terraces for h-BN/Ni(111) [19,20], strain-induced highly corrugated layers for h-BN/Rh(111) [21][22][23], and template layers for molecules with strong local variations of the work function for h-BN/Ir(111) [24] are representative of such morphological diversity.…”

Local stiffness and work-function variations of hexagonal boron nitride on Cu(111)

“…For example, thin films of h-BN have been used as a passivating layer for graphene and MoS 2 -based electronics utilising the small lattice mismatch, the large optical phonon modes, and particularly the large bandgap [3][4][5][6][7][8][9][10]. Furthermore, when grown on metal substrates h-BN can be used as a nanotemplate for atoms, molecules, and nanostructures with well controlled adsorption and electronic properties [11][12][13][14][15][16][17][18]. In such systems, h-BN shows a rich structural and electronic morphology which depends on the lattice mismatch and the interaction strength with the substrate: Large and flat lattice-matched terraces for h- BN/Ni(111) [19,20], strain-induced highly-corrugated layers for h-BN/Rh(111) [21][22][23], and template layers for molecules with strong local variations of the workfunction for h-BN/Ir(111) [24] are representative of such morphological diversity.…”