Identification of luminance-suppressing interface defects at SiC quantum dots embedded in SiO2, using multiscale QM/MM simulations

• Applicant: Dr. Jan M. Knaup, from 11/2008 until 10/2009
• Subject Area: Materials Science
• Term: from 2008 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 99202591

A new experimental method allows easy and cost-effective manufacture of 3C-SiC quantum dots embedded in SiO2 on a Si substrate. However, contrary to expectations, these QD do not yet exhibit electro- or photoluminiescence. It is assumed that, similar to the situation with Si nanoparticles in SiO2, this is caused by SiC/SiO2 interface defects, which allow non-radiative recombination of carrier pairs. The goal of this project is to explore the structure of this specific SiC/SiO2 interface and to identify the defects which suppress luminescence in this system, using atomically resolved simulation methods. To achieve this, formation enthalpies of the interface point-defects and their electronic structures will be examined. A direct simulation using ab-initio methods is impossible since the size of the quantum dots is in the range of several nm. Recently, advances in the embedding of quantum mechanically treated clusters, using the density-functional based tight-binding method, into solid state surroundings modeled by molecular mechanics, were achieved. They allow to examine interface defects quantum mechanically, taking into account influences from the quantum dot and the matrix. Using this new method, models of embedded quantum dots with their possible interface defects shall be constructed. Based on this, the suitability of the method to identify luminescence suppressing interface defects shall be evaluated and the search for such defects begun.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Efthimios Kaxiras