In this thesis, I present the results of three studies on thin films and metal oxide nanostructures: (1) as investigation of the surface chemistry of tert-butanol on silicon, towards the eventual goal of understanding the interfacial properties of ZrO2 thin films grown on Si by atomic layer deposition, (2) integration of HfO2 on an exfoliated LiNbO 3 substrate using atomic layer deposition, (3) epitaxial growth and characterization of one-dimensional ZnO nanostructures.
In Chapter 4, I study the surface reaction of tert-butanol, an important byproduct of zirconium tetra-tert-butoxide during atomic layer deposition of ZrO2, with a Si(100) surface. I have investigated the role of tert-butanol in the initial stage of ALD growth by using UHV probes including temperature programmed desorption (TPD) and Auger electron spectroscopy (AES). This UHV study showed isobutene and hydrogen are the main desorption species, and also showed saturation of surface hydrogen at low coverage, which suggests full dissociative chemisorption of the tert-butanol. In addition, the surface reactions in the presence of hydrogen-terminated surface are also studied for understanding how H-termination affects tert-butanol reactions. Based on these results, I provided insight into the released organic groups contributing to the formation of surface carbon during the ALD growth process.
Second, in Chapter 5, I demonstrated the integration of a thin layer of HfO2 on a 10-μm-thick crystal ion sliced (CIS) He-implanted lithium niobium sample using atomic layer deposition (ALD), followed by exfoliation. The surface, thickness, growth rates and optical properties of the low-temperature-grown HfO2 film are investigated using various characterization tools, and the measurements show that the quality of both the HfO2 films before and after exfoliation are comparable, indicating that the exfoliation process does not damage the film. Patterned growth of the HfO2 has also been achieved on a pre-implanted LiNbO3 substrate, providing a platform for tuning or even fabricating a multilevel oxide integrated structure for future applications. Further, I proposed a strip-loaded HfO2/LiNbO 3 waveguide structure, which shows tuning of the near-surface optical index can be achieved by the HfO2 layer on the LiNbO3 surface.
Finally, in Chapter 6, I have investigated metal-surface-catalyzed growth of ZnO nanowires using four different metal catalysts and using substrates of differing materials and crystal orientation. Multiple materials diagnostics were employed to compare the material, structural, and optical properties of the nanowires grown using these different surface systems. Further, the study revealed that these differences in growth modes are also closely related to the differences in materials properties of these wires including the degree of nanowire alignment on the substrates, and the atomic composition ratio of Zn/O, as well as the relative intensity of the oxygen vacancy-related emission in photoluminescence spectra.