Development of Synthetic Procedures for the Formation of Mn DOPED Semiconductor Quantum Dots

Physical and Analytical Chemistry Seminar

Lecturer: Inbal Hesseg

17 Apr 2016 @ 12:30

Location: Faculty Seminar Room

Semiconductor quantum dots (QDs) have been of special scientific and technological interest in the last three decades, due to their tunable electronic and optical properties, emanated from the “quantum size effect”. This effect is accounted by the three-dimensional confinement of carriers’ motion, which results in size-dependent quantization (discretization) of their energy levels. Since colloidal QDs can be easily prepared by wet chemistry methods, they are attractive materials for low-cost and scalable solution-processed optoelectronic devices. The most fundamental issue in development of technology based on QDs, is the achievement of high quality materials with control of their chemical and physical properties. This was achieved already by the use of colloidal chemistry, forming various QDs which are capped either by organic ligands or by inorganic epitaxial layers (the so-called – core/shell heterostructures), with reproducibility and optional scalability. The last show the most promising chemical and spectral stabilities, as well as allow additional physical properties’ tunability via change in the composition. Recent years also showed an interest in forming electrical or magnetic doping of the mentioned QDs. Doping of nanocrystals is a relatively new and attractive topic. It intentionally introduces impurities into semiconductor for the purpose of modulating its electronic, optical, and magnetic properties. We will show the incorporation of the Mn inside the different layers of the QDs.
The present work involved specific doping of Mn+2 ions into CdSe/CdS core/shell, when the Mn ions were controllably and selectively positioned either at the CdSe core or at the CdS shell. The specific dopant possesses high spin induces exchange interaction with photo-generated spins (e.g., electrons and holes) to produce giant magnetization which alter the magnetic and optical properties of the QDs. The new properties are of special interest for some spin-based applications. The positioning of the dopant will regulate the amount Mn-Lattice interactions and those render a control and tenability of the properties. The lecture will discuss mainly the development of the synthetic procedures for achievement of such unique structures.