216
7 Structuring Possibilities
Fig. 7.3 a Graphene field-effect transistor (FET) achieved from processing steps involving laser
cutting. In this example, the graphene channel was defined by laser cutting/ablation, resulting in
an approximately 100 μm channel width. The source and drain contacts were achieved by laser
cutting of an aluminum mask for physical-vapour deposition of metals on the target substrate.
Remarkably, this yielded good enough phototransistor structures to perform the experiments with
homemade cQD-decorated graphene FETs [23], sketched in (b). Reproduced under the terms of
the CC-BY 4.0 Licence (http://creativecommons.org/licenses/by/4.0/). [23] Copyright 2016 The
Author(s), published by Springer Nature
It shall be also briefly mentioned that etching is naturally not only used in connection with lithography but also independently. For instance, when a laser chip’s
top capping layer needs to be thinned down from half-wavelength to nearly quarterwavelength thickness to enable an anti-resonant chip design based on a resonant
chip structure, wet chemical etching with known etching rates for the target material is applied (see for instance works on mode-locked VECSELs [24]). Another
example used selective etching to carve out a concave cavity from a fibre tip, removing predominantly the core and not the cladding, as successfully demonstrated for
microcavity experiments by the author’s partner group of W. Fang at the Zhejiang
University [25] (see below and Fig. 7.7 at the end of this section).
7.2.2 Synthesis of Nanoparticles
The use of nanoparticles in the form of colloidal quantum dots (cQDs) or plasmonic
nanoparticles in science is huge, and even industry has been eyeing them for different
purposes [26]. A prominent example how cQDs can improve industrial products is
given by the developments in high-quality display technology [27]. Quantum dots
had become particularly attractive because of their size-tunable emission wavelength,
saturated emission colours and near-unity luminance efficiency. Moreover, they are
7 Structuring Possibilities
Fig. 7.3 a Graphene field-effect transistor (FET) achieved from processing steps involving laser
cutting. In this example, the graphene channel was defined by laser cutting/ablation, resulting in
an approximately 100 μm channel width. The source and drain contacts were achieved by laser
cutting of an aluminum mask for physical-vapour deposition of metals on the target substrate.
Remarkably, this yielded good enough phototransistor structures to perform the experiments with
homemade cQD-decorated graphene FETs [23], sketched in (b). Reproduced under the terms of
the CC-BY 4.0 Licence (http://creativecommons.org/licenses/by/4.0/). [23] Copyright 2016 The
Author(s), published by Springer Nature
It shall be also briefly mentioned that etching is naturally not only used in connection with lithography but also independently. For instance, when a laser chip’s
top capping layer needs to be thinned down from half-wavelength to nearly quarterwavelength thickness to enable an anti-resonant chip design based on a resonant
chip structure, wet chemical etching with known etching rates for the target material is applied (see for instance works on mode-locked VECSELs [24]). Another
example used selective etching to carve out a concave cavity from a fibre tip, removing predominantly the core and not the cladding, as successfully demonstrated for
microcavity experiments by the author’s partner group of W. Fang at the Zhejiang
University [25] (see below and Fig. 7.7 at the end of this section).
7.2.2 Synthesis of Nanoparticles
The use of nanoparticles in the form of colloidal quantum dots (cQDs) or plasmonic
nanoparticles in science is huge, and even industry has been eyeing them for different
purposes [26]. A prominent example how cQDs can improve industrial products is
given by the developments in high-quality display technology [27]. Quantum dots
had become particularly attractive because of their size-tunable emission wavelength,
saturated emission colours and near-unity luminance efficiency. Moreover, they are