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

Authors: 
King, D. M. - Presenter, University of Colorado, Boulder
Johnson, S. I. - Presenter, University of Colorado
Li, J. - Presenter, University of Colorado, Boulder
Du, X. - Presenter, University of Colorado
Liang, X. - Presenter, University of Colorado, Boulder
Weimer, A. W. - Presenter, University of Colorado at Boulder


The modulation of optoelectronic properties, such as the bandgap of a pure-component

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.