Tuning luminescence properties of silicon nanocrystals by lithium doping

Doping silicon nanocrystals (SiNCs) provides a new way to modify their luminescence properties and tailor them for a particular application. We prepared Li-doped SiNCs and characterized them by neutron depth profiling and x-ray diffraction. Our SiNC samples are doped with around 10-100 Li atoms per one nanocrystal and their lattice slightly expands after lithium insertion. We show that the photoluminescence (PL) properties of Li-doped SiNCs are distinctly modified compared to the undoped case. The PL maximum shifts to shorter wavelengths and the PL decay time decreases, both these features being favorable for applications in photonics. The spectral blue-shift is attributed to the tensile strain in SiNCs induced by doping with lithium. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4754518]