(220d) Quantum Confinement In Core-Shell Particles Via Atomic Layer Deposited Zinc Oxide Films

ZnO films were coated onto silica nanospheres using atomic layer deposition (ALD) in a fluidized bed reactor. The temperature-dependent difficulties of ZnO ALD on a large quantity of particles are discussed, specifically when an aqueous-based oxidizer is used. An optimal deposition temperature was observed to balance the propensity toward liquid bridging and particle agglomeration at low temperatures and precursor deposition leading to Zn-rich films at high temperatures. Using the optimal deposition temperature, a statistical experimental plan was carried out to quantify the thickness-dependent bandgap shift of ZnO semiconductor films deposited using ALD. Thermal annealing steps were also used to modulate crystallite size for further investigation of quantum confinement. Finally, similar studies were carried out using a non-aqueous oxidizing precursor for the low-temperature ALD of ZnO on particles.