Reliable doping and carrier concentration control in graphene by aerosol-derived metal nanoparticles

Abstract

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 AE 1.5 or 6.4 AE 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 Â 10 12 cm À2 at a NP surface coverage of 12-21%, while Pt NPs lead p-type doping with a hole concentration of 3.9-5.2 Â 10 12 cm À2 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 sp 3 hybridization of the graphene surface due to aerosol-derived NPs. Fig. 7 Schematic energy band diagrams of graphenes before and after (a) Ag NPs doping with different surface coverage of 12, 16, 18, and 21%, and (b) Pt NPs doping with 24, 26, 29 and 32%. Journal of Materials Chemistry C Communication

Lowering the Schottky Barrier Height by Graphene/Ag Electrodes for High‐Mobility MoS2 Field‐Effect Transistors

“…However, the work function was reduced to 4.3 eV for the graphene on Ag (Figure f; Figure S11, Supporting Information). Considering that Ag has a relatively low work function, the presence of Ag underneath graphene leads to an n‐doping effect, resulting in an upshift in the Fermi level of graphene . This is supported by the XPS and Raman results for the MoS 2 /graphene/Ag (Figure S12, Supporting Information).…”

“…However, this problem can be solved by the work function modulation of graphene, in reference to its tunable Fermi level. It has been recently predicted theoretically and demonstrated experimentally that the work function of graphene can be controlled by the adsorption of metals . Thong and co‐workers achieved low contact resistance of MoS 2 FETs using a Ni‐catalyzed graphene interlayer .…”

“…However, thermal annealing treatment at 580 °C was required to create strong coupling between graphene and Ni, which necessitatedcareful investigation for side effects such as chemical impurities and thermal degradation of the underlying substrates and the channel. From previous studies, it is expected that there would be some synergistic advantages when a low work function metal and Fermi‐level‐tunable graphene are simultaneously employed as contacts for 2D TMDCs. Furthermore, most of the studies reported to date have used mechanically exfoliated TMDCs and/or graphene, which are not adapted for large‐area fabrication.…”

Probing the localization of charge and the extent of disorder through electronic transport on Au nanoparticle–copper phthalocyanine multijunction networks

“…Charge is transferred from the AuNP dopant to the CuPcSu layer, since the Fermi level of Au NPs in contact with the molecular film is spaced only 1.2 eV below the CB distribution maximum (in contrast to the 2.0 eV spacing from the VB maximum), which is equivalent to saying we have an extrinsic n‐type semiconductor. The concept of n‐type doping of originally p‐type semiconducting linkers through the utilization of metal NPs (metal NP doping‐induced Fermi level shift) has been reported before . The mixing of the π molecular orbitals with NP states is believed to be responsible for this electronic coupling.…”

Study on Graphene Based Next Generation Flexible Photodetector for Optical Communication

“…The nominal N + and P + region doping is taken of the order of 1 × 10 12 cm -2 , which is practically reliable value. [17]…”