Highly Oriented Hexacene Molecules Grown in Thin Films on Cu(110)–(2 × 1)O

Abstract

Larger acenes, such as hexacene, are increasingly considered as promising materials for applications in optoelectronic devices. We studied electronic interface properties and the molecular orientation of hexacene on Cu(110)−(2 × 1)O using X-ray absorption spectroscopy (XAS) and photoelectron spectroscopy. Interactions between hexacene and the substrate are weak. The detailed investigation of the orientation greatly benefits from a combination of polarization-dependent XAS and angle-resolved photoemission. The angular dependence of valence band features indicates that the molecules grow highly oriented with their long axes parallel to the oxygen rows of the Cu(110)−(2 × 1)O substrate, whereas XAS reveals that the short axis of the molecule is distinctly tilted with respect to the substrate surface. This orientation is maintained up to a film thickness of at least 16 nm, indicating that Cu(110)−(2 × 1)O acts as a template for the hexacene film growth.

Pushing the Limits of Acene Chemistry: The Recent Surge of Large Acenes

“…The electronic interface properties and molecular orientation of 6ac on oxygen‐terminated copper, Cu(110)–(2×1)O, was also investigated by using XAS and XPS, respectively [67] . The molecules align with their long axis parallel to the oxygen row, while the short axis is tilted with respect to the substrate (Figure 4).…”

“… The orientation of 6ac on a Cu(110)–(2×1)O surface. Reproduced with permission [67] . Copyright 2018, American Chemical Society.…”

“…[66] The electronic interface properties and molecular orientation of 6ac on oxygen-terminated copper, Cu(110)-(2 1)O, was also investigated by using XAS and XPS, respectively. [67] The molecules align with their long axis parallel to the oxygen row, while the short axis is tiltedw ith respectt ot he substrate ( Figure 4). [67] This shows that the Cu(110)-(2 1)O surfacec an be used as at emplate for film growth of 6ac up to at hickness of at least 16 nm.…”

“…[67] The molecules align with their long axis parallel to the oxygen row, while the short axis is tiltedw ith respectt ot he substrate (Figure 4). [67] This shows that the Cu( 110)-(2 1)O surfacec an be used as at emplate for film growth of 6ac up to at hickness of at least 16 nm. [67] The first attempts at the synthesis of heptacene (7ac)d ate back to 1942.…”

Going beyond Pentacene: Photoemission Tomography of a Heptacene Monolayer on Ag(110)

“…The largest acene, for which film formation on crystalline surfaces was achieved and adequately characterized, is hexacene. 27 , 28 Its next higher neighbor heptacene 3 can be obtained from thermally induced cycloreversion of a D 2h symmetrical 1 and a C s symmetrical 2 diheptacene isomer mixture ( Scheme 1 ), which can be synthesized via a modified Meerwein–Ponndorf–Verley (MPV) reduction 29 (cf. Supporting Information ( SI )).…”