Control of the dipole layer of polar organic molecules adsorbed on metal surfaces via different charge-transfer channels

Abstract

Abstract:Organic molecules with a permanent electric dipole moment have been widely

Using irradiation effect to study the disparate anchoring stabilities of polar-organic molecules adsorbed on bulk and thin-film metal surfaces

“…Chloroaluminium Phthalocyanine (ClAlPc), have received much attention due to its applications in electronic devices [8,9], especially as its two different adsorption configurations, Cl-up and Cl-down (see Figure 1), allow the tuning of the energy level alignment (ELA) that is crucial for charge-transport performance [10]. Manipulation of the dipole-up and dipole-down configurations of polar MPcs has shown to be possible by choosing different growing conditions or experimental techniques [11][12][13].…”

“…Lin et al [13] successfully correlated the MES obtained by photoemission spectroscopy to the density of states (DOS) for the Cl-up and Cl-down configurations of ClAlPc. It was also demonstrated that the dipole orientation of the first ClAlPc layer can be controlled by adjusting the deposition rate and post annealing conditions with the ELA of the two adsorption modes of ClAlPc differing by ∼0.4 eV.…”

“…1, for the Cl-down configuration, the VL shift is influenced by the Al-Cl molecular dipole as well as the Cl-Ag interfacial dipole that in view of the large differences in electronegativity [15,16] between Cl (3.16) and Ag (1.93) is expected to be strong. For the Cl-up configuration, the VL shift is mainly influenced by the Al-Cl molecular dipole and the push-back effect [13] originating from the large interaction area of the phthalocyanine (Pc) plane and the Ag(111) surface [11,17]. Another important aspect for both configurations is the adsorption stability.…”

“…Another important aspect for both configurations is the adsorption stability. According to DFT calculations [13], ClAlPc has an adsorption energy of −3.56 eV in Cl-down configuration and of −5.22 eV in Cl-up configuration. While the latter can be attributed to the stabilizing interaction of the Pc molecule with the substrates surface, it is still possible to form a monolayer (ML) mainly consisting of Cl-down configuration on Ag(111) via a very slow deposition rate [13].…”

“…According to DFT calculations [13], ClAlPc has an adsorption energy of −3.56 eV in Cl-down configuration and of −5.22 eV in Cl-up configuration. While the latter can be attributed to the stabilizing interaction of the Pc molecule with the substrates surface, it is still possible to form a monolayer (ML) mainly consisting of Cl-down configuration on Ag(111) via a very slow deposition rate [13]. Hollow sites among Ag(111) atoms were considered important for the formation of the metastable Cl-down ClAlPc layer [13].…”