Field-induced structural control of CO<i>x</i> molecules adsorbed on graphene

Matsubara, Manaho; Okada, Susumu

doi:10.1063/1.5029510

Cited by 1 publication

(1 citation statement)

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“…In many cases, the substrates underneath graphene can electrically dope the graphene. − Doping induces additional charges in graphene that can strongly affect the growth of ad-molecules on top of the graphene. Indeed, the adsorption of several molecules, including water, oxygen, carbon monoxide, and carbon dioxide, on graphene exhibits a dependence on the graphene’s doping state. − Such results strongly indicate the feasibility of modulating the assembly of OSC molecules on graphene by controlling the graphene’s electronic states.…”

Section: Controlled Growth Of Organic Semiconductor Molecules On Grap...mentioning

confidence: 99%

van der Waals Epitaxy of Organic Semiconductor Thin Films on Atomically Thin Graphene Templates for Optoelectronic Applications

Nguyen

Lee

et al. 2022

Acc. Chem. Res.

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Conspectus Organic semiconductors (OSCs) offer unique advantages with respect to mechanical flexibility, low-cost processing, and tunable properties. The optical and electrical properties of devices based on OSCs can be greatly improved when an OSC is coupled with graphene in a certain manner. Our research group has focused on using graphene as a growth template for OSCs and incorporating such high-quality heterostructures into optoelectronic devices. The idea is that graphene’s atomically flat surface with a uniform sp2 carbon network can serve as a perfect quasi-epitaxial template for the growth of OSCs. In addition, OSC–graphene heterostructures benefit from graphene’s unique characteristics, such as its high charge-carrier mobility, excellent optical transparency, and fascinating mechanical durability and flexibility. However, we have often found that OSC molecules assemble on graphene in unpredictable manners that vary from batch to batch. From observations of numerous research systems, we elucidated the mechanism underlying such poor repeatability and set out a framework to actually control the template effect of graphene on OSCs. In this Account, we not only present our scientific findings in this spectrum of areas but also convey our research scheme to the readers so that similar heterostructure complexes can be systematically studied. We began with experiments showing that the growth of OSCs on a graphene surface was driven by van der Waals interactions and is therefore sensitive to the cleanliness of the graphene surface. Nonetheless, we noted that, even on similarly clean graphene surfaces, the OSC thin film still varied with the underlying substrate. Thanks to the graphene-transfer method and in situ gating methods that we developed, we discovered that the decisive parameter for molecule–graphene interaction (and, hence, for the growth of OSCs on graphene) is the charge density in the graphene. Thus, to prepare a graphene template for high-quality graphene–OSC heterostructures, we controlled the charge density in the graphene to minimize the molecule–graphene interaction. Moreover, the possible charge transfer between OSC molecules and graphene, which induces additional molecule–graphene interactions, should also be taken into account. Eventually, we demonstrated a wide range of optoelectronic applications that benefitted from high-quality OSC–graphene heterostructures fabricated using our proof-of-concept systems.

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