Reliable doping and carrier concentration control in graphene by aerosol-derived metal nanoparticles
Reliable doping and carrier concentration control in graphene have been realized by depositing aerosol-derived metal nanoparticles (NPs) with consistent size and configuration on the channel of a graphene field-effect transistor. Here, the spherically shaped Ag or Pt NPs with a fairly narrow size distribution of 7.5 ± 1.5 or 6.4 ± 1.4 nm, respectively, have been produced through the spark discharge process. The transfer characteristics show that Ag NPs deposited on graphene induce n-type conduction with an electron concentration of 0.3–1.9 × 1012 cm−2 at a NP surface coverage of 12–21%, while Pt NPs lead p-type doping with a hole concentration of 3.9–5.2 × 1012 cm−2 at 24–32% surface coverage. The observed electrical transport properties are interpreted as the metal NP doping-induced Fermi level shift of initially p-type doped graphene by the adsorbed oxygen molecules under ambient conditions. Also, the minimum conductance at the Dirac point before and after the deposition of metal NPs shows no appreciable change, implying the absence of noticeable sp3 hybridization of the graphene surface due to aerosol-derived NPs.