Lateral Graphene p–n Junctions Realized by Nanoscale Bipolar Doping Using Surface Electric Dipoles and Self-Organized Molecular Anions

Lateral p–n junctions take the unique advantages of 2D materials, such as graphene, to enable single-atomic layer microelectronics. A major challenge in fabrication of the lateral p–n junctions is in the control of electronic properties on a 2D atomic sheet with nanometer precision. Herein, a facile approach that employs decoration of molecular anions of bis-(trifluoromethylsulfonyl)-imide (TFSI) to generate p-doping on the otherwise n-doped graphene by positively polarized surface electric dipoles (pointing toward the surface) formed on the surface oxygen-deficient layer “intrinsic” to an oxide ferroelectric back gate is reported. The characteristic double conductance minima V _Dirac− and V _{Dirac +} illustrated in the obtained lateral graphene p–n junctions can be tuned in the range of −1 to 0 V and 0 to +1 V, respectively, by controlling the TFSI anions and surface dipoles quantitatively. The unique advantage of this approach is in adoption of polarity-controlled molecular ion attachment on graphene, which could be further developed for various lateral electronics on 2D materials.