An Investigation of Nanocrystalline Semiconductor Assemblies as a Material Basis for Ionizing-Radiation Detectors

Nanocrystalline (NC) semiconductor materials have previously been studied as a means of increasing the exciton multiplicity upon the impingement of visible light, for applications such as solar cells. If the multi-exciton states have highly uniform multiplicities across macroscopic NC samples, then one can also potentially quench the statistical counting noise associated with charge-carrier creation in the bulk. We thus assess the viability of using NC semiconductor materials for the detection of ionizing radiation. Using CdTe and PbSe NC films, we report on the colloidal synthesis and deposition procedures for spherical NC particles with dimensions less than 10 nm. In particular, using a thioglycolic-acid (TGA)-stabilized CdTe NC solution adsorbed to polycations, CdTe nanocrystalline films were deposited on glass and metallic substrates using either the layer-by-layer (LBL) method or by using drop-casting techniques. A scanning electron microscope was used to study the surface morphology and impurity concentrations of the CdTe and PbSe-films, and by sandwiching the films between evaporated metallic electrodes, the junction properties of the material were studied, and rectifying characteristics were observed. The resulting depletion region and the material's response to alpha particle impingement were studied.