Thomas Koprucki, Karsten Tabelow
Anieza Maltsi (WIAS)
01.01.2019 – 31.12.2021
Semiconductor quantum dots are nanostructures that form a technological path to innovative optoelectronic and photonic devices (Bimberg 2006). Among them single quantum dots are promising candidates for single and entangled photon sources which are of importance for future quantum technologies such as quantum information processing, quantum cryptography, and quantum metrology (Santori et al. 2010; Buckley et al. 2012).
Quantum dots (QDs) are composed of two materials: the quantum dot material, e.g., InAs, and the surrounding crystal (GaAs). The lattice mismatch between both materials causes a mechanical strain field that strongly influences the QD electronic states (Schliwa 2007). QDs can be produced by a self-organized epitaxial growth process (Stranski-Krastanow growth), where shape, size and density of the QDs can be controlled by process parameters (Bimberg et al. 1999). With the buried stressor approach it is even possible to nucleate single QDs in prescribed spatial regions (Strittmatter et al. 2012).
The growth of QDs with desired electronic properties would highly benefit from the assessment of QD geometry, distribution, and strain profile in a feedback loop between growth and analysis of their properties. One approach to assist the optimization of QDs consists in imaging bulk-like samples (thickness 100-300 nm) by transmission electron microscopy (TEM) instead of high resolution (HR) TEM of capped samples (thickness 10 nm). The sample preparation for HRTEM is much more time-consuming, strongly modifies the strain field and potentially destroys the QDs. However, a direct 3D geometry reconstruction from TEM of bulk-like samples by solving the tomography problem is not feasible due to its limited resolution (0.5-1 nm) and strong stochastic influences, e.g., detector noise, spatially correlated events on the detector array.
In this project, we will therefore develop a novel 3D model-based geometry reconstruction (MBGR) of QDs. This will include
The MBGR approach will enable a high-throughput characterization of QD samples by TEM via QD geometry, distribution and strain field. Furthermore, it will provide a guiding example for mathematically enhanced microscopy for the reconstruction of other nanoscale objects in different applications.
The WIAS-pdelib software is used to find the displacement and the pyTEM software, from TU Berlin, to simulate the corresponding TEM image.
Please insert any kind of pictures (photos, diagramms, simulations, graphics) related to the project in the above right field (Image with Text), by choosing the green plus image on top of the text editor. (You will be directed to the media library where you can add new files.)
(We need pictures for a lot of purposes in different contexts, like posters, scientific reports, flyers, website,…
Please upload pictures that might be just nice to look at, illustrate, explain or summarize your work.)
As Title in the above form please add a copyright.
And please give a short description of the picture and the context in the above textbox.
Don’t forget to press the “Save changes” button at the bottom of the box.
If you want to add more pictures, please use the “clone”-button at the right top of the above grey box.