Formation of Air Stable Graphene p–n–p Junctions Using an Amine‐Containing Polymer Coating

Abstract

An ultrathin layer of a polymer containing simple aliphatic amine groups, polyethylenimine ethoxylated (PEIE), is deposited on a back‐gated field effect graphene device to form graphene p–n–p junctions. Characteristic I–V curves indicate the superposition of two separate Dirac points, which confirms an energy separation of neutrality points within the complementary regions. This is a simple approach for making graphene p–n–p junctions without a need for multiple lithography steps or electrostatic gates and, unlike, the destructive techniques such as substitutional doping or covalent functionalization, it induces a minor defect, if any, as there is no discernible D peak in the Raman spectra of the graphene films after creating junctions and degradation in the charge carrier mobilities of the graphene devices. This method can be easily processed from dilute solutions in environmentally‐friendly solvents such as water or methoxyethanol and does not suffer any change upon exposure to air or heating at temperatures below 100 °C.

Engineering high charge transfer n-doping of graphene electrodes and its application to organic electronics

“…. The G-band shift for PEIE doped graphene is also larger than reported in literature26,32 however, still significantly lower compared to Bphen:Cs 2 CO 3 . A clear systematic shift is observed in the G peak (~1600 cm -1 ) position where the energy of the G-band phonon of the doped graphene samples increases with respect to the unintentionally doped control sample.…”

“…[13][14][15] Numerous graphene doping schemes have been reported [16][17][18][19][20][21][22] including charge transfer from metal oxide, 7-9 molecular films and chemical doping via e.g. [13][14][15]21,[24][25][26] This challenge of n-doping is well-known in the field of organic electronics 27 and is compounded by the lack of a detailed understanding of doping mechanisms in complex interfaces. Whereas these strategies work well for p-type doping of graphene, efficient n-type doping is much more challenging as the latter requires materials/molecular species with a very low work function which are hence prone to oxidation.…”

“…4a shows the Raman spectra of monolayer CVD graphene directly after transfer, compared with Bphen:Cs 2 CO 3 and PEIE doped graphene, respectively, prepared using the technique described in Reference[26]. 4a shows the Raman spectra of monolayer CVD graphene directly after transfer, compared with Bphen:Cs 2 CO 3 and PEIE doped graphene, respectively, prepared using the technique described in Reference[26].…”

Surface Modification of Polymers: Methods and Applications

“…Increased hydrophilicity of polymers enables their application in oil–water separation and antifouling medium in oil and gas filtration units . In electronics, air stable p–n–p graphene junctions were fabricated with polymers containing aliphatic amine groups to control doping . P3HT thin films were surface treated with plasma for surface cleaning and greater adhesion of graphene for testing barrier performance in OPVs .…”

Raman and X-Ray photoelectron spectroscopic studies of graphene devices for identification of doping

“…Contact doping is similar, but in this case the electric field is formed due to differences in the work functions of graphene and contact materials [14,15]. Many others use chemical doping [6,8,16], which is generally relied on substitution of some of heteroatoms [17][18][19] to the carbon network or by surface transfer doping [20,21]. Although the substitutional doping results in doped and stable graphene, the sp 2 carbon network is irreversibly disrupted due to defect formation, which also leads to decrease in conductivity and mobility.…”