BSc in Chemistry Zhejiang University , China.
Structure and bonding in a bimettalic endohedral cage, [Co2@Ge16]z− X. Jin, G. Espinoza-Quintero, B. Below, V. Arcisauskaite, J. M. Goicoechea, J. E. McGrady, J. Organomet. Chem., 2015, in press
Modeling of defect structures in transition-metal doped Si/Ge
The properties and behaviours of transition metal atoms, both inside silicon/germanium clusters and bulk have attracted a great deal of attention in recent times, in part because they represent models of the defect structures found in transition-metal doped semiconductor materials which can lead to degradation of electronic devices. The process of gettering where isolated metal impurities migrate through a semiconductor lattice, ultimately forming islands of metal silicide is an effective method to control the problem but the mechanism of its process is not fully understood even until now. More recently, it has been suggested that some transition metals (such as Mn, Cr) have a potential of being used as dopant in Si/Ge to produce semiconductors with special properties such as room temperature magnetism.
We contribute to this field by looking at structures of bimetallic Si/Ge clusters (M2X16, where M= from Cr to Cu and from Mo to Ag in the 1st and 2nd transition metal rows and X=Si, Ge) which represent the simplest models of the defect structures. In collaboration with Dr. Jose M. Goicoechea (University of Oxford) we conducted a combined experimental and computational study on [Co2@Ge16]z- (z=0 - 4) clusters. Our DFT calculations suggested a 3-connected D2h structure for these clusters (see Fig below). We explained their stability using the 'jigsaw' model which we developed earlier, wherein the 'dual role' of electron pairs stabilizing both metal centres and the Ge cage is essential. We are also moving to more complex models of the defect structures found in transition-metal doped semiconductor materials, i.e., transition metal containing clusters on Si/Ge surface and inside bulk Si/Ge. We aim to examine trajectories of transition metals inside bulk Si and maybe even determine a possible mechanism for the early stage nucleation of metal and metal-silicide (gettering).