5.1 Advanced Optical Tools
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additional information about the dynamics. Thus, time-resolved photoluminescence
(commonly μ-PL) and transient absorption have become typical tools for the investigation of nanomaterials and quantum structures.
Conveniently, combining microscopy with spectroscopy allows one to obtain
spectral—if time-resolved methods used, then even temporal—information about
various microscopic samples and structures with even sub-micrometer lateral resolutions. The major difference of the techniques lies in the underlying measurement
principles, and the spatial, momentum, spectral, and temporal resolution. Combined
with scanning-probe techniques, spectroscopic methods can even reach resolutions
on the nanoscale.
In the following, a selection of useful methods for the characterisation of typical
quantum structures and functional nanomaterials is summarised (also see [4] for
methods explained in the context of polariton research). Where appropriate, examples
related to the research presented in this work are provided. A more complete picture
regarding these subjects can be acquired through the vast literature and a thorough
discussion of these topics remains out of the scope here.
5.2 Microscopy and Spectroscopy
To perform imaging and spectroscopy with microscopic resolution, an optical microscope extended with a spectroscopy apparatus is required. Optical microscopy itself
remains very attractive for sample monitoring and surface imaging. Remarkably, 2D
materials as thin as one monolayer usually still provide enough optical contrast to
be recognised visually due to their pronounced light–matter interactions. With an
excitation source directed into the microscope and a monochromator attached on the
diagnostics side, various spectroscopy modes can be used to characterise such materials (see for instance [5]) even during processes such as van-der-Waals-mediated
layer stacking (e.g., shown in the Supporting Information section of [6]).
5.2.1 Monitoring and Imaging
Spectroscopy of samples first of all requires knowledge about the sample location,
its spatial properties and its environment. In the first place, microscopy is used to
investigate microscopic samples with features which can be still resolved optically.
In addition, it can be also used to monitor and analyse samples comprising smaller
structures not visible under the microscope, but accessible (while invisible) under
the microscope for spectroscopic studies through the knowledge of the environment
and position markers, for instance when dealing with buried quantum-dot structures
in planar or patterned substrates.
Nevertheless, microscopy can also serve in conjunction with spectroscopy as a
means of strong spatial selection of a seemingly homogeneous sample area. For
135
additional information about the dynamics. Thus, time-resolved photoluminescence
(commonly μ-PL) and transient absorption have become typical tools for the investigation of nanomaterials and quantum structures.
Conveniently, combining microscopy with spectroscopy allows one to obtain
spectral—if time-resolved methods used, then even temporal—information about
various microscopic samples and structures with even sub-micrometer lateral resolutions. The major difference of the techniques lies in the underlying measurement
principles, and the spatial, momentum, spectral, and temporal resolution. Combined
with scanning-probe techniques, spectroscopic methods can even reach resolutions
on the nanoscale.
In the following, a selection of useful methods for the characterisation of typical
quantum structures and functional nanomaterials is summarised (also see [4] for
methods explained in the context of polariton research). Where appropriate, examples
related to the research presented in this work are provided. A more complete picture
regarding these subjects can be acquired through the vast literature and a thorough
discussion of these topics remains out of the scope here.
5.2 Microscopy and Spectroscopy
To perform imaging and spectroscopy with microscopic resolution, an optical microscope extended with a spectroscopy apparatus is required. Optical microscopy itself
remains very attractive for sample monitoring and surface imaging. Remarkably, 2D
materials as thin as one monolayer usually still provide enough optical contrast to
be recognised visually due to their pronounced light–matter interactions. With an
excitation source directed into the microscope and a monochromator attached on the
diagnostics side, various spectroscopy modes can be used to characterise such materials (see for instance [5]) even during processes such as van-der-Waals-mediated
layer stacking (e.g., shown in the Supporting Information section of [6]).
5.2.1 Monitoring and Imaging
Spectroscopy of samples first of all requires knowledge about the sample location,
its spatial properties and its environment. In the first place, microscopy is used to
investigate microscopic samples with features which can be still resolved optically.
In addition, it can be also used to monitor and analyse samples comprising smaller
structures not visible under the microscope, but accessible (while invisible) under
the microscope for spectroscopic studies through the knowledge of the environment
and position markers, for instance when dealing with buried quantum-dot structures
in planar or patterned substrates.
Nevertheless, microscopy can also serve in conjunction with spectroscopy as a
means of strong spatial selection of a seemingly homogeneous sample area. For