408
14 Nanostructures
Fig. 14.13 a Atomic
arrangement of a 1 nm
wide ZnO nanowire. b
Theoretical band structure
and charge density of the c
lowest conduction band
and d highest valence band
state. Adapted from
[1362], reprinted with
permission, ©2006 AIP
the wire diameter. It is mainly composed by surface oxygen 2p like dangling bonds (Fig. 14.13d).
The LUMO (Fig. 14.13c) is delocalized in the whole nanowire, indicating that it is a bulk state. The
delocalized distribution is also responsible for the large dispersion of the LUMO from to A. The
energy of the LUMO increases substantially with decreasing diameter due to the radial confinement.
14.3 Carbon Nanotubes
14.3.1 Structure
A carbon nanotube (CNT) is a part of a graphene sheet (cf. Sect. 13.1) rolled up to form a cylinder.
CNTs were first described as multi-walled nanotubes by Iijima [1363] in 1991 (Fig. 14.14b) and in
their single-walled form (Fig. 14.14a) in 1993 [1364]. Reviews can be found in [1247, 1365].
The chirality and diameter of a nanotube are uniquely described by the chiral vector
Fig. 14.14 a TEM image of single-walled carbon nanotubes (SWNT). b TEM images of various multi-walled carbon
nanotubes (MWNT). Adapted from [1363], reprinted with permission, ©1991, SpringerNature
14 Nanostructures
Fig. 14.13 a Atomic
arrangement of a 1 nm
wide ZnO nanowire. b
Theoretical band structure
and charge density of the c
lowest conduction band
and d highest valence band
state. Adapted from
[1362], reprinted with
permission, ©2006 AIP
the wire diameter. It is mainly composed by surface oxygen 2p like dangling bonds (Fig. 14.13d).
The LUMO (Fig. 14.13c) is delocalized in the whole nanowire, indicating that it is a bulk state. The
delocalized distribution is also responsible for the large dispersion of the LUMO from to A. The
energy of the LUMO increases substantially with decreasing diameter due to the radial confinement.
14.3 Carbon Nanotubes
14.3.1 Structure
A carbon nanotube (CNT) is a part of a graphene sheet (cf. Sect. 13.1) rolled up to form a cylinder.
CNTs were first described as multi-walled nanotubes by Iijima [1363] in 1991 (Fig. 14.14b) and in
their single-walled form (Fig. 14.14a) in 1993 [1364]. Reviews can be found in [1247, 1365].
The chirality and diameter of a nanotube are uniquely described by the chiral vector
Fig. 14.14 a TEM image of single-walled carbon nanotubes (SWNT). b TEM images of various multi-walled carbon
nanotubes (MWNT). Adapted from [1363], reprinted with permission, ©1991, SpringerNature