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We find that a five-phase (substrate, mixed native oxide and roughness interface layer, metal oxide thin film layer, surface ligand layer, ambient) model with two-dynamic (metal oxide thin film layer thickness and surface ligand layer void fraction) parameters (dynamic dual box model) is sufficient to explain in-situ spectroscopic ellipsometry data measured within and across multiple cycles during plasma-enhanced atomic layer deposition of metal oxide thin films. We demonstrate our dynamic dual box model for analysis of in-situ spectroscopic ellipsometry data in the photon energy range of 0.7-3.4eV measured with time resolution of few seconds over large numbers of cycles during the growth of titanium oxide (TiO2) and tungsten oxide (WO3) thin films, as examples. We observe cyclic surface roughening with fast kinetics and subsequent roughness reduction with slow kinetics, upon cyclic exposure to precursor materials, leading to oscillations of the metal thin film thickness with small but positive growth per cycle. We explain the cyclic surface roughening by precursor-surface interactions leading to defect creation, and subsequent surface restructuring. Atomic force microscopic images before and after growth, x-ray photoelectron spectroscopy, and x-ray diffraction investigations confirm structural and chemical properties of our thin films. Our proposed dynamic dual box model may be generally applicable to monitor and control metal oxide growth in atomic layer deposition, and we include data for SiO2 and Al2O3 as further examples. Funding Agencies|National Science Foundation (NSF) through the Nebraska Materials Research Science and Engineering Center (MRSEC)National Science Foundation (NSF) [DMR-1420645, CMMI 1337856, DMR 1808715]; Air Force Research Office [FA9550-18-1-0360]; American Chemical SocietyAmerican Chemical Society [ACS PRF 59374-ND5]; University of Nebraska-Lincoln; J. A. Woollam Co., Inc.; J. A. Woollam Foundation

We report on fabrication of spatially-coherent columnar plasmonic nanostructure superlattice-type thin films with high porosity and strong optical anisotropy using glancing angle deposition. Subsequent and repeated depositions of silicon and gold lead to nanometer-dimension subcolumns with controlled lengths. We perform generalized spectroscopic ellipsometry measurements and finite element method computations to elucidate the strongly anisotropic optical properties of the highly-porous Si-Au slanted columnar heterostructures. The occurrence of a strongly localized plasmonic mode with displacement pattern reminiscent of a dark quadrupole mode is observed in the vicinity of the gold subcolumns. We demonstrate tuning of this quadrupole-like mode frequency within the near-infrared spectral range by varying the geometry of Si-Au slanted columnar heterostructures. In addition, coupled-plasmon-like and inter-band transition-like modes occur in the visible and ultra-violet spectral regions, respectively. We elucidate an example for the potential use of Si-Au slanted columnar heterostructures as a highly porous plasmonic sensor with optical read out sensitivity to few parts-per-million solvent levels in water. Funding Agencies|National Science Foundation (NSF) through the Nebraska Materials Research Science and Engineering Center (MRSEC) [DMR-1420645, CMMI 1337856, EAR 1521428, DMR 1808715]; German Research Foundation [FE 1532/1-1]; Air Force Research Office [FA9550-18-1-0360]; American Chemical Society [ACS PRF 59374-ND5]; University of Nebraska-Lincoln; J.A. Woollam Co., Inc.; J.A. Woollam Foundation

We find that a five-phase (substrate, mixed native oxide and roughness interface layer, metal oxide thin film layer, surface ligand layer, ambient) model with two-dynamic (metal oxide thin film layer thickness and surface ligand layer void fraction) parameters (dynamic dual box model) is sufficient to explain in-situ spectroscopic ellipsometry data measured within and across multiple cycles during plasma-enhanced atomic layer deposition of metal oxide thin films. We demonstrate our dynamic dual box model for analysis of in-situ spectroscopic ellipsometry data in the photon energy range of 0.7-3.4 eV measured with time resolution of few seconds over large numbers of cycles during the growth of titanium oxide (TiO