One of the keys behind the success of the modern semiconductor technology has been the ion implantation of silicon, which allows its electronic properties to be tailored. For similar purposes, heteroatoms have been introduced into carbon nanomaterials both during growth and using post-growth methods. However, due to the nature of the samples, it has been challenging to determine whether the heteroatoms have been incorporated into the lattice as intended, with direct observations so far being limited

A combination of scanning transmission electron microscopy, electron energy loss spectroscopy, and ab initio calculations is used to describe the electronic structure modifications incurred by free6standing graphene through two types of single6atom doping. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 dopant atom shows an unusual broad asymmetric peak which is the result of delocalised π * states away from the B dopant. The asymmetry of the B K towards higher energies is attributed to highly6localised σ* anti6bonding states. These experimental observations are then interpreted as direct fingerprints of the expected p6 and n6type behaviour of graphene doped in this fashion, through careful comparison with density functional theory calculations. graphene, doping, electronic structure, STEM, EELS, ab5initio calculations, DFT

The plane-wave density functional theory code CASTEP was used with the Tkatchenko-Scheffler van der Waals correction scheme and the GGA PBE functional to calculate the binding energy of Au, Cr and Al atoms on the armchair and zigzag edge binding sites of monolayer graphene, and at the high-symmetry adsorption sites of single layer, bilayer and trilayer graphene. All edge site binding energies were found to be substantially higher than the adsorption energies for all metals. The adatom migration activation barriers for the lowest energy migration paths on pristine monolayer, bilayer and trilayer graphene were then calculated and found to be smaller than or within an order of magnitude of at room temperature, implying very high mobility for all adatoms studied. This suggests that metal atoms evaporated onto graphene samples quickly migrate across the lattice and bind to the energetically favourable edge sites before being characterised in the microscope. We then prove this notion for Al and Au on graphene with scanning transmission electron microscopy (STEM) images showing that these atoms are observed exclusively at edge sites, and also hydrocarbon-contaminated regions, where the pristine regions of the lattice are completely devoid of adatoms. Additionally, we review the issue of fixing selected atomic positions during geometry optimisation calculations for graphene/adatom systems and suggest a guiding principle for future studies.

We present a universal synthesis method for mixed phase TiO2(B)/anatase thin films on any substrate.