Han WangFollow

Date of Completion


Embargo Period


Major Advisor

Brian Willis

Associate Advisor

Barrett Wells

Associate Advisor

George Rossetti, Jr.

Field of Study

Materials Science and Engineering


Doctor of Philosophy

Open Access

Open Access


Strontium Oxide (SrO) is of interest for the growth of epitaxial perovskite oxides on semiconductors where it acts as a buffer layer between the reactive semiconductor and metal oxide layers. Magnesium oxide (MgO) is widely used as the intervening tunnel barrier to enable efficient spin injection in the magnetic tunnel junctions (MTJs). Due to the strong basicity, MgO and SrO are chemically unstable once exposed to the air, and ex situ chemical and structural analysis tools may not reveal the true properties of MgO and SrO films. Moreover, ex situ optimization of atomic layer deposition (ALD) process parameters, such as saturation curves and deposition temperature windows, becomes a laborious task when multiple films of different thicknesses have to be deposited. Thus, in order to better understand and control ALD processes, in situ thin film analysis techniques are highly desirable. Spectroscopic ellipsometry is an alloptical, non-destructive method, and in situ real time spectroscopic ellipsometry (RTSE) provides a fast and simple way to acquire thickness and optical property data during ALD growth. The objective of this work is to provide insight into the mechanisms of SrO and MgO ALD by using RTSE to study ALD half-cycles, and to learn about nucleation surface chemistry for Sr and Mg precursors reactions with oxide, hydroxide, and metal surfaces. We emphasize the importance of substrate effects in metal oxide ALD processes and establish correlations between the composition and crystallinity of substrates and thin film material properties.