Atomic layer deposition of quantum confined nanostructures on particles

Atomic layer deposition (ALD) was used here to experimentally demonstrate the ability to deposit films that exhibit quantum confinement on spherical particle surfaces. Polycrystalline ZnO films ranging from ∼1.5 to 15 nm in thickness were deposited via ALD using diethylzinc and hydrogen peroxide at 100°C. Conformai, pinhole-free films were deposited on Si wafers and on nano-sized spherical SiO₂ particles using an augmented central composite design strategy. A statistical design of experiments was performed to quantify the crystallite size of the primary peaks associated with polycrystalline ZnO, as well as the change in bandgap associated with the small crystal domains based on the number of ALD cycles and thermal annealing post-treatments. The shift in the optical bandgap of ZnO nanoshells was correlated to the domain size within the films at each point in the experimental matrix. The blue shift of 0.3 eV dissipated beyond crystallite sizes exceeding ∼10nm, which was indicative of quantum confinement.