212
7 Structuring Possibilities
Fig. 7.2 Sketch of the CVD-growth process for controlled monolayer TMDC deposition in a hot
furnace. The method described in [6] has been further refined to date and enables different growth
modes, such as large area single-crystal growth, full monolayer polycrystalline coverage, selective
or even site-controlled growth. The interested reader is referred to the growth-specific TMDC
literature. Reproduced under the terms of the CC-BY 4.0 Licence (http://creativecommons.org/
licenses/by/4.0/). [6] Copyright 2015 The Author(s) and Springer Nature. Right inset: CVD-grown
WSe 2 monolayer flake obtained from this method (also see caption of Fig. 1.1). Adapted under
the terms of the CC-BY 3.0 Licence (http://creativecommons.org/licenses/by/3.0/) from Lippert et
al., 2D Mater., “Influence of the substrate material on the optical properties of tungsten diselenide
monolayers”, https://doi.org/10.1088/2053-1583/aa5b21 [7] Copyright 2017 IOP Publishing Ltd
the combination of different evapourated or gaseous precursor materials under atmospheric pressures and high temperatures (usually hundreds of degrees more than in
the case of MBE) in a growth reactor.
Chemical reactions taking place on the surface then lead to material-specific
growth on the rotated and heated substrate. In contrast to MBE, the chamber is
full of material vapour and very high amounts of growth materials end up in an
exhaust. However, the major advantage of CVD lies in the large-scale production
possibilities in comparison to MBE.
Particularly, metal-organic CVD (MOCVD
2 ) is very prominent in the domain
of semiconductor devices growth. In fact, operation costs and quality issues are
comparable to that of MBE according to textbooks, although it can be said that
interface sharpness might not match those of MBE-grown heterostructures. However,
it should be noted as a clear advantage that deterministic and repeatable production
output can become scalable when using industry-scale shower head reactors. Still,
as examples from the field of semiconductor-disk-laser research show [5], MOCVD
is a very attractive production method for lab-scale activities and is known to deliver
high-performance photonic devices.
In recent times, the need for large-area production in the field of monolayer 2Dmaterials synthesis has also grown. In this context, CVD techniques have provided
access to large-scale pattern growth of graphene and TMDC films, for instance for
stretchable transparent electrodes [8] or fundamental studies, such as on the growth
scale and kinetics [6, 9]. A typical growth setup is schematically shown in Fig. 7.2a
together with polycrystalline CVD-grown monolayer WSe 2 flakes of intermediate
size (b) from the generation of samples studied in [7] in comparison with mechanically exfoliated monolayers.
2 Also known as metal-organic vapor-phase epitaxy, MOVPE.
7 Structuring Possibilities
Fig. 7.2 Sketch of the CVD-growth process for controlled monolayer TMDC deposition in a hot
furnace. The method described in [6] has been further refined to date and enables different growth
modes, such as large area single-crystal growth, full monolayer polycrystalline coverage, selective
or even site-controlled growth. The interested reader is referred to the growth-specific TMDC
literature. Reproduced under the terms of the CC-BY 4.0 Licence (http://creativecommons.org/
licenses/by/4.0/). [6] Copyright 2015 The Author(s) and Springer Nature. Right inset: CVD-grown
WSe 2 monolayer flake obtained from this method (also see caption of Fig. 1.1). Adapted under
the terms of the CC-BY 3.0 Licence (http://creativecommons.org/licenses/by/3.0/) from Lippert et
al., 2D Mater., “Influence of the substrate material on the optical properties of tungsten diselenide
monolayers”, https://doi.org/10.1088/2053-1583/aa5b21 [7] Copyright 2017 IOP Publishing Ltd
the combination of different evapourated or gaseous precursor materials under atmospheric pressures and high temperatures (usually hundreds of degrees more than in
the case of MBE) in a growth reactor.
Chemical reactions taking place on the surface then lead to material-specific
growth on the rotated and heated substrate. In contrast to MBE, the chamber is
full of material vapour and very high amounts of growth materials end up in an
exhaust. However, the major advantage of CVD lies in the large-scale production
possibilities in comparison to MBE.
Particularly, metal-organic CVD (MOCVD
2 ) is very prominent in the domain
of semiconductor devices growth. In fact, operation costs and quality issues are
comparable to that of MBE according to textbooks, although it can be said that
interface sharpness might not match those of MBE-grown heterostructures. However,
it should be noted as a clear advantage that deterministic and repeatable production
output can become scalable when using industry-scale shower head reactors. Still,
as examples from the field of semiconductor-disk-laser research show [5], MOCVD
is a very attractive production method for lab-scale activities and is known to deliver
high-performance photonic devices.
In recent times, the need for large-area production in the field of monolayer 2Dmaterials synthesis has also grown. In this context, CVD techniques have provided
access to large-scale pattern growth of graphene and TMDC films, for instance for
stretchable transparent electrodes [8] or fundamental studies, such as on the growth
scale and kinetics [6, 9]. A typical growth setup is schematically shown in Fig. 7.2a
together with polycrystalline CVD-grown monolayer WSe 2 flakes of intermediate
size (b) from the generation of samples studied in [7] in comparison with mechanically exfoliated monolayers.
2 Also known as metal-organic vapor-phase epitaxy, MOVPE.