Advanced Materials: TechConnect Briefs 2015Advanced Materials TechConnect Briefs 2015

Nanoparticle Synthesis & Applications Chapter 5

Low turn-on field of ZnO nanostructures grown with catalyst-free vapor-phase transport

S-H Yang, Y-M Hsu, M-W Tsai, L-L Chang, P-J Chiang
National Kaohsiung University of Applied Sciences, Taiwan

pp. 207 - 210

Keywords: pseudo-catalyst, seed layer, field emission

Low turn-on electric field of ZnO nanostructures were grown with pseudo-catalyst by vapor phase transport. A ZnO:Al (AZO) seed layer was deposited on a silicon substrate by RF magnetron sputtering, which formed nucleation sites and facilitated the growth of pure ZnO nanostructures on lattice-mismatched Si substrate. A ZnO seed layer deposited by sputtering was also used to grow nanostructures. When ZnO:Al/Si substrate was used, nanostructures with a hexagonal dipyramidal structure and a bead-chain-like shape were vertically grown; the wedged-thread shaped nanoemitters were also found. The estimated angle of the wedge was approximately 120°. Hexagonal-prismatic tapered nanostructures appeared while lateral surfaces were grown. The growth of cylindrical round-top nanostructures was observed as well. When the nanostructures were grown on ZnO/Si substrate in vacuum, the morphology of nanostructures was not changed by the addition of Ga atoms, however, optical energy gap of nanostructures was decreased, accordingly, red-shift in emission wavelength and decrease in emission intensity were resulted. Field emission analyses showed that the lowest turn-on field of 0.57 V/μm was measured when the current density was set at 10 μA/cm2. The highest field enhancement factor was 2563.