Journal of Nanomedicine & Nanotechnology

Semiconductor quantum cones: Unique source of photons and electrons

9^th Nano Congress for Next Generation

August 01-02, 2016 Manchester, UK

Arturs Medvids

Riga Technical University, Latvia

Posters & Accepted Abstracts: J Nanomed Nanotechnol

Abstract:

Nanostructures are one of the most investigated objects in semiconductor physics, especially due to quantum confinement effect in quantum dots (0D), quantum wires (1D) and quantum wells (2D). A new laser technology elaborated for quantum cone formation in semiconductors is reported. A cone possesses the following unique properties: A small cone with angle α=60o at the top of the cone is a quantum dot �?? 0D, when α=0o is transformed to a quantum well �?? 2D and when a long one with α<60o is transformed to a quantum wire �?? 1D with the gradually decreasing diameter from the base till the top of the cone. Luminesce of such a quantum cone resembles rainbow. Where radii in cone are equal or less than Bohr�?? radius of electron, exciton or phonon Quantum Confinement Effect (QCE) takes place. Quantum cones on the surface of elementary semiconductors Si and Ge single crystals, and Si1-xGex (x=0.3 and x=0.4) solid solution were formed by fundamental frequency and second harmonic of Nd:YAG laser radiation. Strong change of the optical, mechanical and electrical properties of the semiconductors after irradiation by Nd:YAG laser are explained by the presence of QCE in quantum cones. �??Blue shift�?� of photoluminescence spectra and �??red shift�?� of phonon LO line in Raman spectrum are explained by exciton and phonon QCE in quantum cones, correspondently. Asymmetry of the photoluminescence band in the spectrum of Si quantum cones is explained by formation of graded band gap structure. Experimental data on quantum cones formation on a surface of Si, Ge crystals and their solid solution and their optical and electric properties are presented. Two-stage model of quantum cones�?? formation on the irradiated surface of the semiconductors is proposed. The first stage of the cones formation is characterized by the formation of a thin strained top layer, due to the redistribution of point defects in temperature-gradient field induced by strongly absorbed by laser radiation. As a result, p-n junction and hetero junction are formed in Ge crystal and SiGe solid solution, correspondently. The second stage is characterized by mechanical plastic deformation of the stained top layer leading to arising of quantum cones due to laser heating up of the top layer. Si quantum cone possesses the lowest work function of electron field emission due to graded band gap structure.

Biography :

Email: medvids@latnet.lv