Manipulation of the graphene surface potential by ion irradiation

Abstract

We show that the work function of exfoliated single layer graphene can be modified by irradiation with swift (E kin = 92 MeV) heavy ions under glancing angles of incidence. Upon ion impact individual surface tracks are created in graphene on SiC. Due to the very localized energy deposition characteristic for ions in this energy range, the surface area which is structurally altered is limited to ≈ 0.01 µm 2 per track. Kelvin probe force microscopy reveals that those surface tracks consist of electronically modified material and that a few tracks suffice to shift the surface potential of the whole single layer flake by ≈ 400 meV. Thus, the irradiation turns the initially n-doped graphene into p-doped graphene with a hole density of 8.5 × 10 12 holes/cm 2 . This doping effect persists even after heating the irradiated samples to 500 • C. Therefore, this charge transfer is not due to adsorbates but must instead be attributed to implanted atoms. The method presented here opens up a new way to efficiently manipulate the charge carrier concentration of graphene.

Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation

“…In addition, we have identified the surface as the origin of a new prolonged and anisotropic thermal heating process, which we could correctly describe with a 3D TTM model. The novel defect creation mechanism presented in our paper can be applied for defect engineering of SiC surfaces, as it has been recently demonstrated for SiC/graphene heterostructures, for example 28 . The nanostripes could also easily be used for techniques such as template-directed adsorption.…”

“…On these graphite and graphene flakes, we measure a local contact potential that we attribute to the work function of graphite and graphene 29,30 , namely, 4.65 and 4.5 eV (ref. 28), respectively. The ion-induced grooves can be clearly seen in the KPFM image (see Fig.…”

“…The measured depth of the grooves is fully compatible with a region of atoms missing from the topmost layer. To determine what kind of atoms are at the bottom of the grooves, we performed quantitative Kelvin probe force microscopy (KPFM) to measure the local work function 27,28 . We used ultra-thin layers of graphite that were mechanically exfoliated onto the SiC sample to calibrate the unknown work function of the tip.…”

Double-resonant LA phonon scattering in defective graphene and carbon nanotubes

“…The graphene samples were then transferred to a vacuum chamber and irradiated with swift heavy ions (Xe 26+ , 91 MeV) using a fluence of 65.000 ions/µm 2 at normal angle to the graphene plane. Under grazing-incidence irradiation these projectiles cause extended modifications in graphene 30,31 , while at normal incidence point-like defects are created 32 . Due to their high energy, the interaction of swift heavy ions with matter is exclusively by inelastic scattering.…”

Thin-film barristor: A gate-tunable vertical graphene-pentacene device

“…The modulation of current through the graphene/organic interface may be of interest in the fabrication of organic transistors, organic light-emitting diodes, and organic solar cells. With modest increases in the range of tunability of graphene's Fermi energy, for example by more efficient electrochemical gates 3 or by chemical doping 12 , 13 , we envision that the interfacial barrier could be reduced to zero, providing highly transparent interfaces for increased efficiency in organic devices.…”