▎ 摘　　要

We report on the efficiency and thermal stability of p-doping by iodine on single and randomly stacked, weakly coupled bilayer polycrystalline graphene, as directly measured by photoelectron emission microscopy. The doping results in work function value increase of 0.4-0.5 eV, with a higher degree of iodine uptake by the bilayer (2%) as compared to the single layer (1%) suggesting iodine intercalation in the bilayer. The chemistry of iodine is identified accordingly as I-3(-) and I-5(-) poly iodide anionic complexes with slightly higher concentration of I-5(-) in bilayer than monolayer graphene, likely attributed to differences in doping mechanisms. Temperature dependent in-situ annealing of the doped films demonstrated that the doping remains efficient up to 200 degrees C. (C) 2014 AIP Publishing LLC.