Ion Implantation of Graphene—Toward IC Compatible Technologies

Abstract

Doping of graphene via low energy ion implantation could open possibilities for fabrication of nanometer-scale patterned graphene-based devices as well as for graphene functionalization compatible with large-scale integrated semiconductor technology. Using advanced electron microscopy/spectroscopy methods, we show for the first time directly that graphene can be doped with B and N via ion implantation and that the retention is in good agreement with predictions from calculation-based literature values. Atomic resolution high-angle dark field imaging (HAADF) combined with single-atom electron energy loss (EEL) spectroscopy reveals that for sufficiently low implantation energies ions are predominantly substitutionally incorporated into the graphene lattice with a very small fraction residing in defect-related sites.

Atomic Configuration of Nitrogen-Doped Single-Walled Carbon Nanotubes

“…The nitrogen 1s (N1s) ELNES, expanded in Figure 3E, show a strong peak at ~401 eV, with very little signal at energies above this. Comparing the spectra to density functional theory (DFT) ELNES calculations of possible single nitrogen defects, there is excellent agreement with the spectrum for substitutional nitrogen ( 2B) and with recent works on nitrogen doped graphene (19)(20)(21). The spectrum shows a number of signature features, which would be lost in a signal averaged with other nitrogen configurations.…”

Implantation and Atomic-Scale Investigation of Self-Interstitials in Graphene

“…Earlier theoretical predictions on B and N implantation 35 also suggest the possibility of implanting atoms into graphene, and in a recent experiment B and N atoms were, in fact, implanted in free-standing graphene 13 at a landing energy of 20 eV. Individual carbon adatoms are predicted to be mobile at room temperature, 23,25 and are thus not expected to be found after deposition, although, upon encountering another carbon adatom, a highly stable self-interstitial dimer can be formed.…”

Electronic Structure Modification of Ion Implanted Graphene: The Spectroscopic Signatures of p- and n-Type Doping

“…31 This ion6implantation technique, commonly used by the modern semiconductor industry for doping Si wafers, for instance, has the advantage of allowing the uniform incorporation over a large area of single dopants on a pre6screened, single6layer, suspended graphene sample, and of producing comparatively few defects or ad6atom configurations. 29 Recent progress in the application of Scanning Transmission Electron Microscopy (STEM) based spectroscopy to the study of 26dimensional materials has demonstrated the technique's ability to fingerprint single dopant atoms in graphene [32][33][34][35] and to differentiate between different electronic structure configurations, such as trivalent and tetravalent single atom Si impurities using subtle changes in the near edge fine structure of the Si L 2,3 ionisation edge in electron energy loss spectroscopy (EELS). 33,35 In this type of study ab initio calculations are essential tools in rationalising the experimental observations and in providing further insight into the nature of bonding around the foreign species; such a combined STEM6EELS and ab initio calculations approach was also used recently to probe the bonding of single nitrogen atoms in graphene 36,37 and N6doped single6walled carbon nanotubes.…”

“…The chosen experimental parameters provided enough EELS signal to be collected for unambiguous chemical fingerprinting of the single atom dopants spatially resolved within a C matrix, clearly identifying them as N and B atoms, respectively (see Figures 1c and 2c and Ref. 29 ). It was also possible to observe the near6edge fine structure with an excellent signal6to6noise ratio.…”