Size Controlled Synthesis of Germanium Nanocrystals: Effect of Ge Precursor and Hydride Reducing Agent

Germanium nanocrystals (Ge NCs) have attracted increasing attention as a promising alternative to II–VI and IV–VI semiconductor materials as they are cheap, “green,” electrochemically stable, and compatible with existing CMOS processing methods. Germanium is a particularly attractive material for optoelectronic applications as it combines a narrow band gap with high carrier mobilities and a large exciton Bohr radius. Solution-phase synthesis and characterisation of size monodisperse alkyl-terminated Ge NCs are demonstrated. Ge NCs were synthesised under inert atmospheric conditions via the reduction of Ge halide salts (GeX4) by hydride reducing agents within inverse micelles. Regulation of NC size is achieved by variation of germanium precursor and the strength of hydride reducing agents used. UV-Visible absorbance and photoluminescence spectroscopy showed strong significant quantum confinement effects, with moderate absorption in the UV spectral range, and strong emission in the violet with a marked dependence on excitation wavelength.