Surface-Directed Molecular Assembly of Pentacene on Monolayer Graphene for High-Performance Organic Transistors

Abstract

Organic electronic devices that use graphene electrodes have received considerable attention because graphene is regarded as an ideal candidate electrode material. Transfer and lithographic processes during fabrication of patterned graphene electrodes typically leave polymer residues on the graphene surfaces. However, the impact of these residues on the organic semiconductor growth mechanism on graphene surface has not been reported yet. Here, we demonstrate that polymer residues remaining on graphene surfaces induce a stand-up orientation of pentacene, thereby controlling pentacene growth such that the molecular assembly is optimal for charge transport. Thus, pentacene field-effect transistors (FETs) using source/drain monolayer graphene electrodes with polymer residues show a high field-effect mobility of 1.2 cm(2)/V s. In contrast, epitaxial growth of pentacene having molecular assembly of lying-down structure is facilitated by π-π interaction between pentacene and the clean graphene electrode without polymer residues, which adversely affects lateral charge transport at the interface between electrode and channel. Our studies provide that the obtained high field-effect mobility in pentacene FETs using monolayer graphene electrodes arises from the extrinsic effects of polymer residues as well as the intrinsic characteristics of the highly conductive, ultrathin two-dimensional monolayer graphene electrodes.

Two-dimensional quasi-freestanding molecular crystals for high-performance organic field-effect transistors

“…Compared with the previous efforts to grow organic crystals on 2D materials 26,40,42 , our results truly demonstrate the advantage of this concept by proving the high quality of the interface.…”

Giant enhancement in vertical conductivity of stacked CVD graphene sheets by self-assembled molecular layers

“…2c-f) show that these SAMs saturate at a thickness of 0.7±0.1 nm due to its self-terminating ability. This is different from the self-assembly behaviour of aromatic organic molecules where longer assembly time leads to multilayer formation 24 . As can be seen in Fig.…”

Van Der Waals Heterostructures between Small Organic Molecules and Layered Substrates

“…Conductive and transparent monolayer G can be used as a template to tune pentacene molecular orientation from standing-up to lying-down in well-defined films [15,36]. The AFM image in Figure 3a shows that the morphology of 50 nm thick pentacene films on CVD-G-covered and bare SiO 2 has an abrupt change cross the boundary, which revealed remarkable differences in growth and the modulation effect of substrates.…”

“…For example, pentacene possesses a relatively higher mobility in its b-c plane than a-b plane, as shown in Figure 1e [6,7]. Thus, various substrates, metals [8][9][10], native oxide silica [11][12][13][14], and layered materials [6,7,[15][16][17][18], have been chosen for the growth of high quality thin films. In order to optimize the devices performance, it is essential to clarify how the interactions between molecules and substrates affect the growth of organic thin films.…”