Effect of physisorption of inert organic molecules on Au(111) surface electronic states

Abstract

The modification of the Au(111) Shockley surface state (SS) by an n-alkane molecule (n-tetratetracontane) monolayer was observed by angle-resolved ultraviolet photoemission spectroscopy. Although there is little chance of chemical interaction in this ideal physisorption system, the volume of the Fermi surface of the SS was significantly reduced accompanied by the formation of large interface electric dipoles. Moreover, Rashba splitting of the SS by spin-orbit interactions was slightly increased upon n-tetratetracontane adsorption, which arose from the decrease in the symmetry of the wave function around the Au nuclei at the surface. The detailed information about the simple physisorption system presented in this paper provides basic knowledge for understanding the electronic structure at the interface between other organic molecules and metal substrates.

The Impact of Dipolar Layers on the Electronic Properties of Organic/Inorganic Hybrid Interfaces

“…Using n-tetratetracontane on Au(111) as a prototypical physisorbed system, Mizushima et al observed a work-function reduction due to pushback in excess of 1 eV. [215] They also provided a more detailed description of the interaction, involving, e.g., an adsorbate-induced modification of the Shockley surface state of the metal in combination with system-specific interfacial charge rearrangements. [215] These are rationalized through electron sharing between substrate and adsorbate involving bonding and antibonding CH states in the metal-molecule bond [216] and by including the hybridization between metal d-bands and unoccupied molecular orbitals.…”

“…[215] They also provided a more detailed description of the interaction, involving, e.g., an adsorbate-induced modification of the Shockley surface state of the metal in combination with system-specific interfacial charge rearrangements. [215] These are rationalized through electron sharing between substrate and adsorbate involving bonding and antibonding CH states in the metal-molecule bond [216] and by including the hybridization between metal d-bands and unoccupied molecular orbitals. [217] In the context of Pauli pushback, one also has to keep in mind that it is massively reduced, when the metal substrate is not clean (e.g., covered by a thin hydrocarbon layer) or when it is intentionally or unintentionally covered with a thin nonmetallic layer (e.g., an oxide).…”

Electronic Properties of Tetraazaperopyrene Derivatives on Au(111): Energy-Level Alignment and Interfacial Band Formation

“…They are smaller than the work function reductions usually found for systems that interact only via Pauli pushback, which for inert organic molecules on gold often amounts to up to 1 eV. 76 , 77 An almost zero net interface dipole has been observed for the low-coverage phase of hexaazatriphenylene-hexanitrile (HATCN) on Ag(111). 78 However, in contrast to HATCN/Ag(111), for TAPP-CF 3 /Au(111), we find that the molecule is ≈0.2 e positively charged (when applying the Mulliken charge partitioning scheme, see the Supporting Information ), while the LUMO remains empty (see Figure 6 a).…”

Electronic Properties of Tetraazaperopyrene Derivatives on Au(111): Energy Level Alignment and Interfacial Band Formation

“…They are smaller than the work function reductions usually found for systems that interact only via Pauli pushback, which for inert organic molecules on gold often amounts to up to 1 eV. 76,77 An almost zero net interface dipole has been observed for the low-coverage phase of hexaazatriphenylene-hexanitrile (HATCN) on Ag(111). 78 However, in contrast to HATCN/Ag(111), for TAPP-CF 3 /Au(111) we find that the molecule is ≈ 0.2e positively charged (when applying the Mulliken charge partitioning scheme, see supporting informa-tion), while the LUMO remains empty (see Figure 6a).…”