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ABSTRACT: Understanding energy-level alignment and molecular growth characteristics of an organic semiconductor on the graphene surface is crucial for graphene-related device performance. Here we demonstrate that tunable interface properties and molecular orientation can be achieved by modifying graphene films on a SiC substrate with monolayer copper-hexadecafluorophthalocyanine (F16CuPc) molecules. On clean graphene, pentacene molecules form a tilted configuration even at very low coverage (one or two monolayers) rather than flat-lying as on the graphite surface. Pentacene molecules prefer to grow with a (022) plane parallel to the clean graphene surface. With increasing coverage, X-ray adsorption data indicate there is no obvious change of molecular stacking orientation. The corresponding hole injection barrier is about 0.7 eV. On the modified graphene where thin (one or two monolayers) F16CuPc molecules are flat-lying on graphene, an almost perfect up-standing molecular stacking of pentacene film was formed on the modified surface. A low hole injection barrier of 0.3 eV was observed. Furthermore, the interface of dirty graphene upon pentacene was also discussed.
The Journal of Physical Chemistry C. 01/2013; 117(8):3969-3975.
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D Usachov, O Vilkov,
A Grüneis,
D Haberer,
A Fedorov,
V K Adamchuk,
A B Preobrajenski,
P Dudin,
A Barinov,
M Oehzelt,
C Laubschat,
D V Vyalikh
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ABSTRACT: A novel strategy for efficient growth of nitrogen-doped graphene (N-graphene) on a large scale from s-triazine molecules is presented. The growth process has been unveiled in situ using time-dependent photoemission. It has been established that a postannealing of N-graphene after gold intercalation causes a conversion of the N environment from pyridinic to graphitic, allowing to obtain more than 80% of all embedded nitrogen in graphitic form, which is essential for the electron doping in graphene. A band gap, a doping level of 300 meV, and a charge-carrier concentration of ∼8×10(12) electrons per cm2, induced by 0.4 atom % of graphitic nitrogen, have been detected by angle-resolved photoemission spectroscopy, which offers great promise for implementation of this system in next generation electronic devices.
Nano Letters 11/2011; 11(12):5401-7. · 13.20 Impact Factor
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Danny Haberer,
Cristina E Giusca,
Ying Wang,
Hermann Sachdev,
Alexander V Fedorov,
Mani Farjam,
S Akbar Jafari,
Denis V Vyalikh,
Dmitry Usachov,
Xianjie Liu,
Uwe Treske,
Mandy Grobosch, Oleg Vilkov,
Vera K Adamchuk,
Stephan Irle,
S Ravi P Silva,
Martin Knupfer,
Bernd Büchner,
Alexander Grüneis
Advanced Materials 10/2011; 23(39):4497-503. · 13.88 Impact Factor
