Systematic study of adsorption of single atoms on a carbon nanotube

Abstract

We studied the adsorption of single atoms on a semiconducting and metallic single-wall carbon nanotube from first principles for a large number of foreign atoms. The stable adsorption sites, binding energy, and the resulting electronic properties are analyzed. The character of the bonding and associated physical properties exhibit dramatic variations depending on the type of the adsorbed atom. While the atoms of good conducting metals, such as Cu and Au, form very weak bonding, atoms such as Ti, Sc, Nb, and Ta are adsorbed with relatively high binding energy. Most of the adsorbed transition-metal atoms excluding Ni, Pd, and Pt have a magnetic ground state with a significant magnetic moment. Our results suggest that carbon nanotubes can be functionalized in different ways by their coverage with different atoms, showing interesting applications such as one-dimensional nanomagnets or nanoconductors and conducting connects, etc. DOI: 10.1103/PhysRevB.67.201401 PACS number͑s͒: 73.22.Ϫf, 68.43.Bc, 73.20.Hb, 68.43.Fg Single-wall carbon nanotubes ͑SWNT's͒ can serve as templates to produce reproducible, very thin metallic wires with controllable sizes.1 These metallic nanowires can be used as conducting connects and hence are important in nanodevices based on molecular electronics. Recently, Zhang et al.2 have shown that a continuous Ti coating of varying thickness and a quasicontinuous coating of Ni and Pd can be obtained by using electron-beam evaporation techniques. Metal atoms such as Au, Al, Fe, Pb were able to form only isolated discrete particles or clusters instead of a continuous coating of SWNT's. Low-resistance contacts to metallic and semiconducting SWNT's were achieved by Ti and Ni ohmic contacts.3 Most recently, ab initio density-functional calculations 4 have indicated that stable rings and tubes of Al atoms can form around a semiconducting SWNT. It is argued that either persistent currents through these conducting nanorings, or conversely very high magnetic fields can be induced at their center. 4 It is expected that novel molecular nanomagnets and electromagnetic devices can be generated from these metallic nanostructures formed by adatom adsorption on SWNT's. As an example, one can contemplate to generate a nanodevice by the modulating adsorption of adatoms on a bare ͑8,0͒ SWNT, which is a semiconductor 5 with an energy gap of ϳ0.64 eV. This band gap can increase to 2 eV by the adsorption of a hydrogen atom.6 Then, a quantum well ͑or dot͒ can form between two barriers at the hydrogen covered sections of the ͑8,0͒ tube. This structure is connected to the metallic reservoirs through metal coated ends of SWNT's. This way a resonant tunneling device with metal reservoirs and connects at both ends can be fabricated on a single SWNT.Clearly, the study of adsorption of atoms on nanotube surfaces is essential to achieve low-resistance ohmic contacts to nanotubes, to produce nanowires with controllable size, and to fabricate functional nanodevices. In particular, it is important to know the following: ͑i͒ Ho...

Silicon and III-V compound nanotubes: Structural and electronic properties

“…The energy increase with n is small. According to our results E b 's of (n, n) armchair SWSiNTs are ∼ 0.05 eV larger than those of (n, 0) zigzag ones because of their relatively larger radius at a given n. Corresponding E b for SWCNTs is calculated to be 9.1 eV [51] theoretically.…”

“…Earlier, TM atoms are shown to form rather strong bonds with the carbon atoms on the surface of SWCNTs. [51] Motivated by the work of Singh et al [15], we investigated whether (3,0) SWSiNT can be stabilized in the same manner. The (3,0) tube has radius R ∼ 2.4Å in which interaction between the atoms located at the opposite walls of the tube as well as excess strain on the Si-Si bonds are the prime causes of structural instability even at T=0 K. On the other hand, the radius of (3,0) is comparable with the sum of ionic radii of V and Si, i.e R V + R Si = 2.27Å, and hence V atoms can easily be accommodated inside the tube.…”

A facile method for the selective decoration of graphene defects based on a galvanic displacement reaction

“…Wrinkles have higher chemical reactivity than pristine regions because of their enhanced sp 3 characteristic arising from high local curvatures. 30 Therefore, Pd NPs are deposited along wrinkles with polygonal shapes, leading to the formation of polygonal Pd lines. In addition, if the height of a wrinkle is sufficient, the wrinkle collapses, leading to the formation of two curved sides (see Supplementary Figure S3).…”

The role of the catalytic particle temperature gradient for SWNT growth from small particles

“…These are the bond-saturated carbon atoms (C S ) that are bonded to three other C atoms (and that form part of a graphitic island or SWNT) and bond-unsaturated carbon atoms (C Uns ) that are bonded to at most two other C atoms (and are found, for example, at the edge/end of a graphitic island or SWNT). The C S -Fe and C Uns -Fe interaction energies were fit to results of DFT calculations, which show that the C S -Fe bond energy (0.14 eV [14]) is about an order of magnitude weaker than the C Uns -Fe bond energy (1.5 eV [15]). …”