Electronic, Optical and Magnetic Properties of Transition Metal Doped CdS Nanocrystals

Ghosh, Anirudha (2015) Electronic, Optical and Magnetic Properties of Transition Metal Doped CdS Nanocrystals. PhD thesis, Indian Institute of Science Education and Research (IISER) Kolkata.

PDF (PhD thesis of Anirudha Ghosh) Anirudha_Ghosh-Thesis.pdf - Submitted Version Restricted to Repository staff only Download (9MB)

Abstract

Through the decades of contagious investigations by various researchers across the world, it has been revealed that material properties are not only dependent solely on the electronic structure of atoms but also on the clustering of atoms. Evidently, this clustering of atoms directly modifies the electronic structure of the system as a whole. A very common example is when we bring large number of atoms together to form a solid, the electronic structure is no more implied by discrete energies, rather form a band of energy in solid. Thus, if we were able to control the number of atoms in a particular cluster, we could able to modify its electronic structure which subsequently has direct implications on various properties. This simple idea has led to the foundation of the present world of nanotechnology. In this research work, we have controlled the number of cadmium and sulfur atoms in a cluster to form CdS nanocrystals such that their sizes are smaller or of the order of the excitonic diameter; a phenomena called quantum confinement effect. The ultimate goal of this work is to understand the explicit role of the crystal structure of CdS nanocrystals in controlling the magnetic properties, when CdS nanoparticles are being doped with various transition metal elements like Mn and Fe. Here we have also investigated the role of capping molecules in providing structural stability to CdS nanoparticles and the solubility of transition metal ions in CdS lattice. In summary, we have investigated various structural, optical and magnetic properties of uncapped and thiol-capped CdS nanoparticles both in pristine and transition metal doped forms as a function of crystal structure of CdS nanoparticles.

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