Optical properties of self-assembled Cu2O nanocrystals embedded in a polyimide layer

Abstract

Self-assembled Cu2O nanoparticles embedded in a polyimide (PI) matrix were formed by curing Cu thin films with PI precursor layers. Transmission electron microscopy images and selected area electron diffraction patterns showed that Cu2O nanocrystals were created inside the PI layer. The excitonic peaks corresponding to the transitions from the electronic sublevel to the heavy-hole sublevel in the Cu2O nanocrystals embedded in the PI layer shifted to the lower energy side with increasing curing time, and this behavior is attributed to a decrease in the confinement effects because the size of the nanocrystals increases with the curing time. The activation energy of the electrons confined in the ground state of the Cu2O nanocrystals embedded in the PI layer, as obtained from the temperature-dependent photoluminescence spectra, was larger than that of those confined in the excited state. The present results can help us to improve understanding of the optical properties of Cu2O nanocrystals embedded in a PI layer.