Photo-induced C-C reactions on insulators towards photolithography of graphene nanoarchitectures

Journal Of The American Chemical Society 136, 4651 - 4658 (2014)

Photo-induced C-C reactions on insulators towards photolithography of graphene nanoarchitectures

Carlos-Andres Palma, Katharina Diller, Reinhard Berger, Alexander Welle, Jonas Björk, Jose Luis Cabellos, Duncan J. Mowbray, Anthoula C. Papageorgiou, Natalia P. Ivleva, Sonja Matich, Emanuela Margapoti, Reinhard Niessner, Bernhard Menges, Joachim Reichert, XinLiang Feng, Hans Joachim Räder, Florian Klappenberger, Angel Rubio, Klaus Müllen, Johannes V. Barth

On-surface chemistry for atomically precise sp2 macromolecules requires top-down lithographic methods on insulating surfaces in order to pattern the long-range complex architectures needed by the semiconductor industry. Here, we fabricate sp2-carbon nm-thin films on insulators and under ultra-high vacuum (UHV) conditions from photo-coupled brominated precursors. We reveal that covalent coupling is initiated by C–Br bond cleavage through photon energies exceeding 4.4 eV, as monitored by laser desorption ionization (LDI) mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) gives insight into the mechanisms of C–Br scission and C-C coupling processes. Further, unreacted material can be sublimed and the coupled sp2-carbon precursors can be graphitized by e-beam treatment at 500 °C, demonstrating promising applications in photolithography of graphene nanoarchitectures. Our results present UV-induced reactions on insulators for the formation of all sp2-carbon architectures, thereby converging top-down lithography and bottom-up on-surface chemistry into technology.

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The authors are especially grateful to Karl Eberle for XPS measurements and Thomas Schuster for additional LDI measurements. We gratefully acknowledge silicon wafers from Jose Antonio Garrido and preliminary Raman measurements from Max Seifert, Stefan Funk, Stefan Niedermayer, and Hai Bi. C.-A.P. thanks Hristo Iglev for continuous help, Christian Lütke-Eversloh for additional UV data and Achim Hartschuh for support. We acknowledge financial support from the European Research Council Advanced Grant DYNamo (ERC- 2010-AdG-267374) Spanish Grants (FIS2010-21282-C02-01 and PIB2010US-00652), Grupos Consolidados UPV/EHU del Gobierno Vasco (IT578-13), Ikerbasque and the European Commission projects CRONOS (Grant 280879-2 CRONOS CP-FP7). C.-A.P. and K.D. were funded through the ERC Advanced Grant MolArt (no. 247299). D.J.M. acknowledges funding through the Spanish “Juan de la Cireva” program (JCI- 2010-08156). J.L.C acknowledges funding through the Mexican CONACyT program. J.B. acknowledges the National Supercomputer Centre, Sweden, for computational resources.

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