Investigation of Metal Free Naphthalocyanine Vapor Deposited on Au(111)

Abstract

Naphthalocyanines (Ncs) are promising candidates for future components in electronic devices and applications. To maximize the efficiency of Nc devices, it is critical to understand their structural and electronic properties and how these are impacted by deposition methods. The formation of a metal free naphthalocyanine (H 2 Nc) self-assembled monolayer on a Au(111) crystal was investigated by scanning tunneling microscopy under ultra-high-vacuum conditions at room temperature. A rigorous purification and processing procedure was developed to produce high purity, low defect, and well-ordered monolayers. High-resolution STM images reveal epitaxial growth of H 2 Nc on Au(111) with the observed structure having a molecular spacing of 1.6 ± 0.05 nm, with molecules orientated slightly off (roughly 2.5°) the low density packing direction of Au(111). A commensurate structure having 4 molecules per unit cell and unit cell parameters of A = 3.25 ± 0.05 nm, B = 3.17 ± 0.05 nm, and α = 87.5 ± 2°is proposed. Orbital-mediated tunneling spectroscopy was used to examine the electronic properties of individual molecules within the thin film. The first ionization potential and electron affinity of H 2 Nc adsorbed on Au(111) were measured to be −0.68 ± 0.03 and 1.12 ± 0.02 eV, relative to the Fermi energy.

Surface chemistry of porphyrins and phthalocyanines

“…The rhombic unit cell (17 Â 55 Å 2 , 951) observed for the stable island structure contained three molecules [292]. A well-ordered 2HNc structure with even higher packing density was observed on Au (1 1 1) [293]. The rhombic (near-square) unit cell (32.5 Â 31.7 Å 2 , 92.51) contained four molecules.…”

“…Adsorption of 2HNc (see Fig. 9) was studied on Au(1 0 0) [292] and Au(1 1 1) [293,294]. On the hexagonally reconstructed Au(1 0 0) surface, a submonolayer coverage (0.5 ML) of 2HNc deposited at room temperature formed clusters, stripes, and densely packed islands, which were aligned along the two high-symmetry directions of the substrate.…”

“…Ref. [293] provides a detailed comparison of the different structures and packing densities of 2HNc on Au(1 0 0) [292], Au (1 1 1) [293] and graphite (HOPG) [295][296][297]. 4 1.…”

Naphthalocyanine Thin Films and Field Effect Transistors

“…However, there have so far been very few studies of the properties of sublimed Nc thin films 11,14,15 ; in fact it has been suggested that Nc cannot be sublimed 13 , although the deposition of monolayer coverages have been reported by a number of groups [16][17][18][19][20][21][22] .…”

A new variable temperature solution-solid interface scanning tunneling microscope

“…[1][2][3][4][5] The technique can be used in various environments such as vacuum, 6 air, 7 solution, 8 and even under gel. 9 Among these environments, ultrahigh vacuum (UHV)-solid and solution-solid (SS) interfaces get the most attention.…”