Surface Modification Of ZnO Nanocrystals And Their UV-Photoconductive Properties

ZnO is a direct wide band-gap semiconductor material. It is expected to become a new generation of optoelectronic materials because of its appealing properties. In this thesis, we synthesized well-dispersed ZnO nanocrystals by a hot-injection method, and carried out surface modication by different methods. We prepared ZnO nanocrystal films and measured their UV-photoconductive properties, investigating the effects of surface modification. The main contents are as follows:1. We used n-butylamine to repalce the original stearate ligands. FTIR spectra showed that n-butylamine could effectively replace stearate ligands. UV spectra showed the ZnO nanocrystals, both before and after ligand exchange, exhibited excellent colloidal solubility. XRD spectra showed that the ZnO nanocrystals, both before and after ligand exchange, were hexagonal wurtzite structure. TEM images showed that the morphology of the ZnO nanocrystals was converted from nanopyramids to spherical nanoparticles after ligand exchange. The pristine ZnO nanocrystal thin films exhibited no UV-photoresponse, while the Ion/Ioff of the thin films based on ZnO nanocrystals after ligand exchange reached107. These results demonstrated that the ligand exchange of using n-butylamine to replace stearate ligands was successful.2. TMAH solution could effectively remove the original stearate ligands. TMAH solutions with different concentrations (10mg/mL and20mg/mL) and solvents (methanol and ethanol) were used. FTIR spectra showed that increasing the concentration of TMAH solution could accelerate the removal of the stearate ligands. UV spectra showed that the TMAH-treatment could weaken the scattering of ZnO nanocryst films, improving the quality of the film. The ZnO nanocrystal films without TMAH-treatment exhibited no UV-photoresponse, while the Ion/Ioff of the ZnO nanocrystal films with TMAH-treatment was as high as106.