Chapter 13
Two-Dimensional Semiconductors
Introducing a new experimental system is generally more rewarding than trying to
find new phenomena within crowded areas. [...] Of course, the fantastic results one
originally hopes for are unlikely to materialise, but, in the process of studying any
new system, something original inevitably shows up.
A.K. Geim, 2010 [1223]
Abstract 2D materials or atomic sheets are materials without a bulk. They offer unique physics and
properties, but also challenges in preparation and stability. Stacking of such 2D materials in van-derWaals heterostructures extends the possibilities.
2D materials are the ultimate thickness limit for semiconductors. While the thickness of quantum
wells can be controlled to the sub-atomic average thickness, they are still impacted by the roughness
or undulation of the underlying substrate. 2D materials are more like free two-dimensional molecules
with giant lateral extension and a vertical structure well defined by atomic bonding. Paper collections
and textbooks are available for this topic, e.g. [1224–1226].
13.1 Graphene and Related Materials
Graphene, its name proposed in [1227], is the ultimately thin material, a single sheet of carbon atoms
in honeycomb arrangement; this is not a hexagonal (cf. Fig. 3.3b) but a trigonal lattice with a two-atom
basis (Fig. 13.1). Graphene possesses unique physical properties such as a linear dispersion around the
Fermi energy, making it a solid-state analogue to ultra-relativistic physics [1228]. Graphene does not
possess a band gap in its ideal form. An account of the history of graphene research, starting in 1840,
is given in [1229].
Many applications for graphene and graphene-based composites have been envisioned in electronics such as superior conductor or transistor material [1230, 1231] as well as applications in energy,
biomedical, membranes and sensors [1232, 1233], but the current industrial use is still rather limited.
Here, we introduce ’flat’ graphene while quasi one-dimensional nanotubes based on graphene are
treated in Sect. 14.3.
© Springer Nature Switzerland AG 2021
M. Grundmann, The Physics of Semiconductors, Graduate Texts in Physics,
https://doi.org/10.1007/978-3-030-51569-0_13
383
Two-Dimensional Semiconductors
Introducing a new experimental system is generally more rewarding than trying to
find new phenomena within crowded areas. [...] Of course, the fantastic results one
originally hopes for are unlikely to materialise, but, in the process of studying any
new system, something original inevitably shows up.
A.K. Geim, 2010 [1223]
Abstract 2D materials or atomic sheets are materials without a bulk. They offer unique physics and
properties, but also challenges in preparation and stability. Stacking of such 2D materials in van-derWaals heterostructures extends the possibilities.
2D materials are the ultimate thickness limit for semiconductors. While the thickness of quantum
wells can be controlled to the sub-atomic average thickness, they are still impacted by the roughness
or undulation of the underlying substrate. 2D materials are more like free two-dimensional molecules
with giant lateral extension and a vertical structure well defined by atomic bonding. Paper collections
and textbooks are available for this topic, e.g. [1224–1226].
13.1 Graphene and Related Materials
Graphene, its name proposed in [1227], is the ultimately thin material, a single sheet of carbon atoms
in honeycomb arrangement; this is not a hexagonal (cf. Fig. 3.3b) but a trigonal lattice with a two-atom
basis (Fig. 13.1). Graphene possesses unique physical properties such as a linear dispersion around the
Fermi energy, making it a solid-state analogue to ultra-relativistic physics [1228]. Graphene does not
possess a band gap in its ideal form. An account of the history of graphene research, starting in 1840,
is given in [1229].
Many applications for graphene and graphene-based composites have been envisioned in electronics such as superior conductor or transistor material [1230, 1231] as well as applications in energy,
biomedical, membranes and sensors [1232, 1233], but the current industrial use is still rather limited.
Here, we introduce ’flat’ graphene while quasi one-dimensional nanotubes based on graphene are
treated in Sect. 14.3.
© Springer Nature Switzerland AG 2021
M. Grundmann, The Physics of Semiconductors, Graduate Texts in Physics,
https://doi.org/10.1007/978-3-030-51569-0_13
383