Dipoloma Project in Theoretical Chemistry

Semiconductor nanotechnologies

Several diploma projects are available in this field

If you are interested in doing your diploma project at the Department of Theoretical Chemistry, or would like to have more information, you are welcome to contact us:

Dr. Ying Fu
Theoretical Chemistry, Biotechnology
Royal Institute of Technology
Tel: 08 55378417
Fax: 08 55378590
email: fyg@theochem.kth.se

1. Semiconductor quantum dots for multiphoton biophotonics applications

Optical properties of colloidal semiconductor quantum dots (QDs) are to be studied for multiphoton biophotonics applications. Due to the large number of energy states densely compacted in both the conduction and valence bands of the QDs, strong interband and intraband optical couplings are induced by the multiphoton excitation, implicating an efficient fluorescence of such QDs, and thus excellent candidates for biophotonics applications using fluorescence induced by multiphoton excitation.

2. Semiconductor quantum dots for ultradense optical circuit applications

Metal-dielectric-metal configurations of optical waveguides have a very high laterally packaging density at the cost of high optical loss. Photonic crystals based on refractive-index-modulation materials have been used in optics, e.g., two materials having different refractive indices form a well-defined Bragg refraction mirror. Such a waveguide has lower loss but also lower packaging density. From the outset of these two notions, we propose a photonic-crystal device based on the exciton-polariton effect in a three-dimensional array of semiconductor quantum dots (QDs) for ultradense optical planar circuit applications. Excitons are first photogenerated in the QDs by the incident electromagnetic field, the exciton-polariton effect in the QD photonic crystal then induces an extra optical dispersion in QDs. The high contrast ratio between the optical dispersions of the QDs and the background therefore creates clear photonic bandgaps. By carefully designing the QD size and the QD lattice structure, perfect electromagnetic field reflection can be obtained at a specific wavelength in the lossless case, thus providing the fundamental basis for ultradense optical waveguide applications.

3. Quantum dot infrared photodetector

Infrared photodetectors have gained a lot of attention during the past decades, due to the numerous applications in night vision, space, surveillance, search and rescue and medical diagnosis. Requirements on the detectors, such as higher operating temperature, create a demand for more advanced detector materials. Quantum dot infrared photodetectors (QDIPs) are strong candidates to face this demand, due to the prediction of decreased dark current and detection of normal incident radiation, caused by the 3D confinement of electrons in quantum dots (QDs). High temperature operation with high detectivity has been realised by means of QDIP structures by several research groups in the mid wavelength infrared (MWIR 3-5mu) region as well as in the long wavelength infrared (LWIR 8-12 mu) region, with intersubband transitions from the ground states to excited states of the QDs as the main detection mechanism.

(1) Strain field design
(2) Energy band tailoring
(3) Device/system designs

4. Colloidal quantum dots as wideband (UV, vis and IR) light sources and solar energy

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