Abstract: A stratum or discontinuous monolayer of dielectric-coated semiconductor particles includes a high density of semiconductor nanoparticles with a tightly controlled range of particle sizes in the nanometer range. In an exemplary embodiment, the nanoparticles of the stratum are substantially the same size and include cores which are crystalline, preferably single crystalline, and include a density which is approximately the same as the bulk density of the semiconductor material of which the particle cores are formed. In an exemplary embodiment, the cores and particles are preferably spherical in shape. The stratum is characterized by a uniform particle density on the order of 1012 to 1013 particles/cm2. A plurality of adjacent particles contact each other, but the dielectric shells provide electrical isolation and prevent lateral conduction between the particles of the stratum. The stratum includes a density of foreign atom contamination of less than 1011 atoms/cm2.