Field Emission From Tetra-Needle Like ZnO Whiskers

Zinc oxides have been widely used in sophisticated ceramics, piezoelectric and photoelectric products, catalysts for their comprehensive and peculiar behaviors such as semiconducting property, photoluminescence and chemical stability. Recently, ZnO has become one of the most promising cathode materials for field emission.The field emission properties of tetra-needle like zinc oxide whiskers (T-ZnOw) were studied in this dissertation. For its tetra-needle like structure, the productive T-ZnOw showed a relative low turn-on field of 3.7V/μm and threshold field of 6.9V/μm, and the field enhancement factorβvalue was 2315.The Al-doped T-ZnOw samples were prepared by solid solution treatment with different loadings of Al³⁺. SEM images and X-ray diffraction patterns indicated that the dopant of Al³⁺ didn't change the tetra-needle like morphology and wurtzite structure of T-ZnOw. Al³⁺ substituted Zn2+ in ZnO crystal and the lattice constant decreased with the increasing of loaded Al³⁺. Photoluminescence spectra indicated that 0.5mol% Al³⁺-doped T-ZnOw showed the best crystal quality and the dopant of Al³⁺ changed the carrier concentration, which were confirmed by Raman spectra. Ultraviolet-visible spectroscopies indicated that Al³⁺ doping made the absorption edge blue-shift and broadened the banding energy of T-ZnOw.T-ZnOw films were fabricated using screen-printing technique. It was found that the field emission properties of T-ZnOw were improved by heat treatment and the turn-on field and threshold field were 2.6V/μm and 5.2 V/μm, respectively, while the field enhancement factorβvalue was 4129. Furthermore, the field emission properties of T-ZnOw were greatly improved by the Al³⁺ doping. For the samples of 0.5mol% Al³⁺-doped T-ZnOw, the values of turn-on field, threshold field,βand emission dots density were 0.74V/μm, 2.6V/μm, 30249, and 10³/cm², respectively, and the emission current was no degradation in 8h, which demonstrated that Al³⁺-doped tetra-needlelike ZnO whiskers might have potential application in the field of vacuum electron devices.