*Ufuk Kilic¹, Daniel Schmidt¹, Mathew Hilfiker¹, Giselle Melendez², Rafal Korlacki¹, Eva Schubert¹, Mathias Schubert^1
1University of Nebraska Lincoln, Lincoln, NE; ² Polytechnic University of Puerto Rico, San Juan, Puerto Rico
A wide range of interesting electrical, optical, and photocatalytic properties make zinc-oxide (ZnO) ultra-thin films attractive for photovoltaic, electroluminescent, and optoelectronic device applications. In this work, we successfully fabricated ZnO ultra-thin films by means of plasma enhanced atomic layer deposition (PE-ALD) technique. We utilized in-situ spectroscopic ellipsometry (SE) technique to monitor precursor-surface interactions and accurate control of deposition conditions. By applying recently proposed SE data based dynamic dual box model, we achieved resolving the evolution of layer thickness and surface roughness during separate steps of individual cycles. We extracted the ZnO dielectric function from in-situ SE data based multiple-sample-analysis which is performed retroactively after the growth by analyzing selected data sets acquired during the growth. We further present and discuss the optical properties of ultra-thin ZnO films fabricated at different substrate temperatures. Additionally, for complete material characterization, the chemical composition, surface morphology, and crystalline structure of these ultra-thin films were also investigated by using X-ray photo-electron spectroscopy, atomic force microscopy, and X-ray diffraction techniques, respectively.