High-resolution electron microscopy and microanalysis of ZnSe quantum dots in glass matrices

Quantum dots of ZnSe, an interesting optical material for blue light lasers, have been prepared by nucleation and growth from a supersaturated glass solution. The average nanoparticle diameter of as-cast ZnSe-in-glass samples was 5.5 +/- 1.7 nm, and an average diameter of 3.7 +/- 1.1 nm was obtained with rapid quenching. The experimentally observed quantum dot sizes are less than the Bohr exciton diameter of 11.4 nm, consistent with an observed blue shift in the absorption edge of about 0.52 eV. HRTEM revealed the ZnSe quantum dots to be single crystal in nature, with a few larger internally twinned particles observed in the larger crystals present in the as-cast sample. EDXS data indicated the majority of particles to be ZnSe, with SAED confirming the cubic structure. A minority of the quantum dots were found to be composed of selenium or selenium oxide, and were redissolvable in the glass matrix under conditions of strong convergence of the electron beam during TEM analysis.