p-Type Doping of Epitaxial Graphene by p-tert-Butylcalix[4]arene

Abstract

The Chemical Doping of epitaxial graphene (EG) due to p-tert-butylcalix [4]arene was investigated using high resolution photoemission spectroscopy (HRPES). The measured work function changes verified that increased adsorption of the p-tert-butylcalix [4]arene on EG showed p-type doping characteristics due to charge transfer from the graphene to the p-tert-butylcalix [4]arene through the hydroxyl group. A single oxygen bonding feature associated with the O 1s peak was clearly observed in the core-level spectra, indicating the presence of one equivalent adsorption state.

Evidence of Chemical Functionalized Molecules Adsorbed on the Interface Region of Epitaxial Graphene: Interface Roughness and Modification of the Electronic Properties

“…24À29 Recently, we characterized the properties of a variety of compounds as chemical dopants on EG, such as the 4-amino-2,2,6,6-tetramethyl-1-piperridinyloxy (TEMPO), azidotrimethylsilane, and p-tert-butylcalix [4]arene, to identify functionalized molecules with interesting dopant properties for enhancing the electronic properties of EG. 11,12,30 Usually, significant results were obtained by using radical-containing dopants which prefer to bind to defect sites, such as point defects or interface layers below the EG layer. These compounds may modulate the band gap and electronic structure of EG.…”

“…The two-dimensional (2D) EG structures, which include sp 2 orbitals, and the chemical inertness of EG require unique approaches to chemical doping for the purposes of modulating and enhancing the electronic properties of EG. In general, weak interactions between a dopant and EG lead to charge transfer ( n -type , or p -type, ,, depending on the direction), which preserves the conical band structure of EG. Hence, an in-depth understanding of the interactions between dopants and EG is important for tuning the desired properties of EG and improving graphene doping methods.…”