Effect of Substrate Chemistry on the Bottom-Up Fabrication of Graphene Nanoribbons: Combined Core-Level Spectroscopy and STM Study

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• 作者：Konstantin A. Simonov ; Nikolay A. Vinogradov ; Alexander S. Vinogradov ; Alexander V. Generalov ; Elena M. Zagrebina ; Nils M氓rtensson ; Attilio A. Cafolla ; Tomas Carpy ; John P. Cunniffe ; Alexei B. Preobrajenski
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：June 12, 2014
• 年：2014
• 卷：118
• 期：23
• 页码：12532-12540
• 全文大小：635K
• 年卷期：v.118,no.23(June 12, 2014)
• ISSN：1932-7455

文摘

Atomically precise graphene nanoribbons (GNRs) can be fabricated via thermally induced polymerization of halogen containing molecular precursors on metal surfaces. In this paper the effect of substrate reactivity on the growth and structure of armchair GNRs (AGNRs) grown on inert Au(111) and active Cu(111) surfaces has been systematically studied by a combination of core-level X-ray spectroscopies and scanning tunneling microscopy. It is demonstrated that the activation threshold for the dehalogenation process decreases with increasing catalytic activity of the substrate. At room temperature the 10,10鈥?dibromo-9,9鈥?bianthracene (DBBA) precursor molecules on Au(111) remain intact, while on Cu(111) a complete surface-assisted dehalogenation takes place. Dehalogenation of precursor molecules on Au(111) only starts at around 80 掳C and completes at 200 掳C, leading to the formation of linear polymer chains. On Cu(111) tilted polymer chains appear readily at room temperature or slightly elevated temperatures. Annealing of the DBBA/Cu(111) above 100 掳C leads to intramolecular cyclodehydrogenation and formation of flat AGNRs at 200 掳C, while on the Au(111) surface the formation of GNRs takes place only at around 400 掳C. In STM, nanoribbons have significantly reduced apparent height on Cu(111) as compared to Au(111), 70 卤 11 pm versus 172 卤 14 pm, independently of the bias voltage. Moreover, an alignment of GNRs along low-index crystallographic directions of the substrate is evident for Cu(111), while on Au(111) it is more random. Elevating the Cu(111) substrate temperature above 400 掳C results in a dehydrogenation and subsequent decomposition of GNRs; at 750 掳C the dehydrogenated carbon species self-organize in graphene islands. In general, our data provide evidence for a significant influence of substrate reactivity on the growth dynamics of GNRs.