An experiment was conducted to demonstrate that epitaxially self-assembled alkane layers on graphene influence its structural, electrical and optical properties of grapheme. Graphene were mechanically exfoliated on a Si chip with 280 nm SiO2 capping layer using mechanical exfoliation method.] The SiO2 substrate was cleaned with piranha and oxygen plasma, resulting in hydrophilic surface. All the electrodes for FETs were patterned with e-beam lithography, followed by deposition of metal and lift-off process. Before HTC deposition, graphene surface was cleaned in chloroform at 60°C several times for 30 min to remove poly(methyl methacrylate) (PMMA) residue. Well-ordered HTC on grapheme remarkably reduces the effects of charge density inhomogeneity, resulting in enhancement of carrier mobility and reduction of doping in GFETs. We emphasize that the similar performance enhancement was also obtained for molybdenum disulfide FETs, which verifies that the applicability of our facile HTC self-assembly approach can be extended to large-scale FET arrays based on various high-quality 2D materials. Concerning the mechanism of the observed mobility improvement, atomistic multiscale simulations show that molecular assemblies induce grapheme flattening and locally lift up graphene away from the SiO2 surface, resulting in the dramatic recovery of the intrinsic electronic properties of graphene. This indicates that the reduction in nanometer-scale strain variations is closely correlated with that of charged-impurity effects, thus providing a reconciling viewpoint for the long-standing controversy over the dominant source of electron-hole puddles.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering