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

Abstract

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.

Flexible Zinc Oxide Nanowire Array/Graphene Nanohybrid for High-Sensitivity Strain Detection

“…Under no bending, the Dirac point (minimum I DS ) which is depicted by black dotted line located on the positive voltage side (above V G = 0) since CVD Gr is typically p-doped in ambient, 48 which has been confirmed in our recent works on similar CVD Gr. 49 − 51 When the ZnO-VANWs/Gr/PET nanohybrid sensor is subjected to downward bending ( Figure 6 b), a compressive strain is applied to the ZnO-VANWs, resulting in positive charges generated at the ZnO-VANWs/Gr interface. This is equivalent to applying a fixed positive top-gate voltage in the double-gate graphene field-effect transistor.…”

Pure Graphene Oxide Vertical p–n Junction with Remarkable Rectification Effect

“…The current increasing under forward bias is much stronger than that under reverse bias, showing nonlinear characteristics and asymmetry of GO-GO film with voltage variation. The current is close to zero at a reverse bias while reaches up to mA level at forward bias, showing a superior rectification performance compared to other lateral graphene p-n junctions, as their µA level of current at the same forward bias [25][26][27]. Moreover, the rectification characteristics of pGO vertical junctions are greater than that of the previous graphene vertical p-n junctions, as summarized in Table 1.…”

“…Recently, we have reported the direct observation of Na-Cl crystals/Graphene heterojunction [17] and Ca-Cl crystals/Graphene heterojunction [18] with rectification effect in rGO films. However, these graphene p-n junctions and heterojunctions reported are fabricated via chemical doping [19][20][21] or electrostatic doping [22][23][24], and most of them are lateral p-n junction [25][26][27] and heterojunctions [17,18]. Chemical doping is a method wherein nitrogen [28], potassium [29], and other elements are doped into graphene to control the semiconductor type of graphene.…”

“…Therefore, these traditional doping methods for p-n junctions greatly limit the practical application of graphene p-n junctions in electronics and sensors. Moreover, the lateral graphene p-n junction shows a limited rectification effect [25][26][27] due to the Klein tunnel effect [30], in which the transmission probability for a single square barrier could reach 100% in a certain range of energies [31]. In addition, the area of the depletion layer depends on the contact area between the GO and rGO films, which can be large-scale preparation for vertical structure, superior to lateral ones.…”

Probing performance limiting factors in uncooled quantum dots/graphene SWIR-MWIR detectors

“…Considering such a control must be at an atomic resolution, several post interface-cleaning processes have been explored including light-assisted vacuum annealing, 81,82 ligand exchange, 83,84 and ultrafast thermal annealing (UTA) 85 .…”