(705e) Atomic Layer Deposition of Quantum-Confined Nanostructured Materials

semiconductor material, is a useful ability that can be achieved by few techniques. Atomic layer

deposition (ALD) was used to experimentally demonstrate the ability to deposit films that

exhibit quantum confinement on 2D and 3D surfaces. Amorphous TiO₂ and polycrystalline ZnO films ranging from 1.5 to 15 nm in thickness were deposited via ALD using TiCl₄-H₂O₂ and diethylzinc-H₂O₂ at 100°C, respectively. Conformal, pinhole-free films were deposited on Si wafers and on nanosized spherical SiO₂ particles of varying diameter. Powder XRD was used to measure the crystallite size of the films and monitor size evolution on the basis of the number of ALD cycles and thermal annealing post-treatments. The crystallite size of each peak increased almost linearly with the number of cycles, and was further increased via thermal annealing steps. The absorbance of the ZnO films on Si wafers and SiO₂ particles was measured using spectroscopic ellipsometry and diffuse transmittance techniques, respectively. The bandgap shift with respect to crystallite size and/or ALD film thickness followed the Brus model quite well. The blue shift of +0.3 eV dissipated beyond dimensions exceeding ~10 nm, and was indicative of the successful deposition of quantum confined nanostructures. The precision control afforded by ALD can be used to deposit quantum confined materials on substrates, independent of geometry and morphology.