Direct bandgap silicon quantum dots achieved via electronegative capping
  We propose a novel concept of achieving silicon quantum dots with radiative rates enhanced by more than two orders of magnitude up to the values characteristic for direct band gap semiconductors. Our tight-binding simulations show how the surface engineering can dramatically change the density of confined electrons in real- and $k$-space and give rise to the new conduction band levels in $\Gamma$-valley, thus promoting the direct radiative transitions. The effect may be realized by covering the silicon dots with covalently bonded electronegative ligands, such as alkyl or teflon chains and/or by embedding in highly electronegative medium. 
A. N. Poddubny, K. Dohnalov\'a
cond-mat.mes-hall cond-mat.mtrl-sci