Quantum dots, semiconductor nanocrystals and semiconductor particles used as fluorescent coding elements

A system for obtaining information about an object, comprising:

• a plurality of regions associated with the object, each region emitting a predetermined wavelength of light;
• a detector for detecting the light;
• and
• a decoder for decoding information from the detected light, wherein
• at least one region is comprised of semiconductor particles having a radius larger than a quantum dot radius for a corresponding semiconductor material, and a chemical composition selected to provide the predetermined wavelength of light, wherein the semiconductor material is comprised of one of a Group II-VI alloy, or a Group III-V alloy, or a compound comprised of an indirect bandgap material, and wherein the concentrations of the alloy or compound constituent elements are preselected to provide the predetermined emission wavelength.

A system for obtaining information about a substrate comprising:

• a substrate having a plurality of discrete regions thereon, at least one of the discrete regions containing particles, each of the particles having a surface dimension greater than a quantum dot dimension for a corresponding semiconductor material, wherein the particles are preselected to emit an associated predetermined emission wavelength;
• an excitation source, adapted to provide radiation that causes the particles of a particular region to emit the associated predetermined emission wavelength of the particular region;
• a detection unit adapted to detect the associated predetermined emission wavelength from the particles of each region and the detection unit adapted to generate electrical signals as a function of the detected associated predetermined emission wavelength;
• and
• a processing unit adapted to receive the electrical signals from the detection unit and process the electrical signals to establish a characteristic of the substrate.