Optical characterisation of PbSe and CdSe 2D superstructures
Summary
Searching for new and interesting materials, nanoparticles really are a hot topic. Those nanoparticles have interesting properties that are mainly present because of their small size. A quantum dot is a special nanocrystal, namely a nanoparticle that is confined in all three spatial directions.
Fundamental and applied sciences are interested in these quantum dots. From the latter perspective, quantum dots are likely to be one of the new materials in all kind of applications, among them next-generation light detectors, emitting diodes (LED's) and even solar cells. From the fundamental perspective, the small nanoparticles might even be more interesting because they open up a complete new field of research.
This bachelor thesis is only one small link in the entire chain of applied and fundamental research. 2D superstructures of oriented attached PbSe and CdSe are investigated with optical experiments. Those 2D superstructures have remarkable properties. From a well-known 2D material, graphene, is reported that it absorbs light quanta per monolayer. It is unknown if the 2D superstructures of PbSe and CdSe also have this property. This brings us to the first research question: Does a PbSe 2D superstructure with a square geometry also absorb a light quantum of the theoretically predicted value of 2.3% per monolayer? As an answer to this question, a value of 1.5 +\- 0.4% is found. This is a value, corrected for the substrate quartz, is in agreement with the expected value.
The second part of this bachelor thesis is dedicated to the design of a new fluorescence microscope setup. The goal is to study the luminescent properties of the materials mentioned, mainly 2D CdSe superstructures, with this setup at room and low temperatures. These properties can provide interesting information of the studied material.