| 초록 |
The extraordinary electronic properties of graphene, including massless Dirac fermion behavior of charge carriers, ambipolar electric field effect, and quantum Hall effect, offer new opportunities for next-generation electronics. For the ultimate realization of graphene-based electronics, a robust and controllable p- and n-type doping method is a crucial prerequisite. To date, a few doping methods have been exploited for graphene, including substitutional doping, electrostatic doping by external field, and charge transfer doping. Unfortunately, these approaches reveal intrinsic drawbacks, such as undesired defect formation, complex processing steps, and subtle sensitivity to environment. More significantly, ambient stable complementary p- and n-type doping with conventional device fabrication has hardly been demonstrated yet. In this work, we report ambient stable p- and n-type polymer doping of graphene and its application to graphene devices. Highly stable graphene doping is achieved by simply coating different dipolar polymers onto a pristine graphene surface. While conventional polymers with different dipolar characteristics enable the precise tunability of doping level, poly(4-vinylpyridine) (P4VP) imposes a strong dipole field to yield an n-type doping, highly stable at ambient conditions. Moreover, the dipole field can dramatically improve and balance the carrier mobility by screening the impurity charge effect from the bottom SiO2 substrate. Taking advantage of complementary p- and n-doping with different polymers, ambient stable inverters are fabricated by area-selective doping in conjunction with conventional photolithography. The inverter devices employing a back gate regime demonstrated robust inverting performance with clear voltage inversion and a voltage gain of 0.17 at a 3.3 V input voltage under ambient condition. Furthermore, along with our current research effort for semiconducting graphene preparation, this straightforward polymer doping can be exploited for various graphene-based electronics with improved switching and rectifying performances, particularly in mechanically flexible form. |
