Synthesis of silicon quantum dots showing high quantum efficiency.

ABSTRACT

Quantum efficiencies of Si quantum dots (QDs) have been investigated from the reaction of magnesium silicide and ammonium chloride. The change of quantum yield and optical characterization of Si QDs are measured depending on the reaction time. Highly luminescent Si QDs were obtained as the reaction time increased. Absorption measurement indicated that the Si QDs consisted of only silicon and hydrogen atom. Optical characterizations of Si QDs were measured by UV-Vis and PL spectroscopy. The size distribution and orientation of Si QDs were measured by TEM and XRD. TEM image displays the spherical Si QDs with the size of 3-4 nm. As the reaction time increased, Si QDs grew and their emission wavelength shifted to the longer wavelength. The monotonic shift of the PL as a function of excitation wavelength resulted in the excitation of different sizes of QDs that had different optical transition energies. Photoluminescence quantum yields exceeding 60% have been achieved.