Understanding Thin Film Formation Through Molecular Beam Epitaxy Studies of Atomiclevel Interactions in Order to Link Deposition Process Conditions to Device Performance in 2 Materials: MgO and Cs3s

The understanding and control of initial states of film formation acquired by building correlations between deposition parameters (e.g. substrate temperature, relative fluxes) and film metrics (e.g. chemistry, structure, quantum efficiency) can open up new possibilities in the development of engineered thin film materials that can meet the evolving and necessary performance requirements of next-generation two-dimensional electronic materials. Robust correlations between deposition parameters and film metrics are also necessary to engineer scalable manufacturing processes that produce consistent material quality results. The work of this dissertation builds the case for dynamic, real time characterization of film formation and explores next-generation X-ray light source materials needed to achieve this probing of bond formation.;Studies of the chemistry and structure evolution of the MgO films grown on SiC suggest that the starting substrate surface chemistry and structure is critical to effective integration, and the etching mechanism using hydrogen seems to be key in controlling the starting surface. We have investigated the effect of two different cleaning mechanisms on the chemistry and structure of 6H-SiC (0001). The hydrogen furnace cleaning at 1600 °C of 6H-SiC (0001) substrates surfaces proved to produce a smooth, uniformly stepped surface and a √√3x√3R30º surface reconstruction, with less than 10 at% residual oxygen contamination. Whereas, the atomic hydrogen cleaning of 6H-SiC (0001) substrates was observed to produce a (1x1) surface structure with less than 7 at% residual oxygen contamination at relatively low temperature of 700 °C. In addition the structure and initial layers of crystalline MgO (111) films deposited on SiC (0001) by MBE are greatly affected by the resulting chemistry of the MgO films. The MgO deposited by MBE on SiC prepared by the hydrogen furnace was found to have both two dimensional and three dimensional features even at thickness of around 2nm. Although the MgO template is seen to be effective and necessary to promote the pseudo-hexagonal, heteroepitaxy of BTO(111), The chemistry and structure of high quality BTO films are highly dependent on that of the under-layer MgO films. Therefore, it is necessary to understand atomic level mechanisms involved in the nucleation and growth of thin films on solid surfaces, in order to develop consistent processing strategies capable of producing high-quality MgO thin film in a reproducible way. However, the challenge of reproducing desired film properties is generally highly impeded by the limitations of static characterization techniques that are available and used in the MgO film study. Dynamically observing how bonds are formed in real-time at surfaces and interfaces is needed in order to have a more consistent process for enable films through a variety of techniques.;The challenges and limitations of using static characterization techniques to develop a consistent process for enable high quality MgO and BTO films led to the study of Cs3Sb systems for next-generation X-ray light sources capable of probing atomic bonding in a dynamic way. Through the use of MBE techniques, a new growth method capable of growing atomically smooth Cs3Sb thin films was explored. The co-deposition of Cs3Sb yielded stoichiometric thin films with high quantum efficiency (20% at 405 nm, 8% at 532 nm) which is one step toward the overarching goal of developing nano-engineered materials that favor electron transport in the direction normal to the surface, while maintaining high quantum efficiency and minimizing the energy spread of the electrons. Detailed investigations performed suggested that the successful growth of photoactive Cs3Sb thin films is highly dependent on a careful balance between the initial stoichiometric flux ratio, substrate temperature and growth rate.;Although, many other important properties (surface roughness, intrinsic emittance, response time) were not investigated in this study, the successful demonstration of the co-deposition of high quantum efficiency Cs3Sb thin films is an important contribution toward exploring novel mechanisms capable of improving desired fundamental material properties. The full implementation of next-generation X-ray light sources remains a goal which goes beyond the current status of this study: toward showing atom-to atom detail of the time evolution of electronic charge in bonds. This can be beneficial for all applications, including MBE where viable and reproducible processes for commercially manufacturing 2-D materials are still being developed.