Ultra-small rare-earth oxide nanocrystals: development, film assembly, optical and dielectric studies

Abstract

The oxides of rare-earth elements (rare-earth sesquioxide: RE2O3) are known for their optical and dielectric properties. Europium oxide is known for characteristic red luminescence and gadolinium oxide has excellent insulating properties (band gap: 5.5 eV). Development of ultra-small nanocrystals (sub-3 nm diameter) of these rare-earth oxides and investigation of their optical and dielectric properties are explored in this dissertation. A new synthesis process was developed successfully to produce ultra-small colloidal nanocrystals, which were capped with oleic acid. Europium oxide nanocrystals exhibited a new luminescence peak because of the occupation of Eu3+ ions in a surface site. The nanocrystals were assembled into films from their suspensions in hexane by electrophoretic deposition. Films of europium oxide were highly transparent in visible spectral region because of minimal scattering losses within the films and exhibited characteristic red luminescence. Gadolinium oxide nanocrystals exhibited charge-storage properties when integrated in a metal-insulator-semiconductor structure. Layered heterostructures of carbon nanotubes and nanocrystals were fabricated and their charge-storage properties were studied.