American University
thesesdissertations_2713_OBJ.pdf (1.33 MB)

Epitaxial deposition mechanism of barium fluoride on single crystal silicon substrate using molecular beam epitaxy

Download (1.33 MB)
posted on 2023-08-04, 15:14 authored by Francisco Santiago

The deposition of films made of fluoride compounds has been a goal for researchers because of their application as insulators in integrated microelectronics and as substrates. Films of barium fluoride (BaF$\sb2)$ have been grown directly on both (111), and (100) oriented silicon (Si) crystals. BaF$\sb2$ films of excellent quality grow oriented along the (111) direction regardless of the substrate orientation. The Si crystal has a lattice constant of 5.45 A in contrast with BaF$\sb2$ with a lattice constant of 6.20 A. It is difficult to explain how BaF$\sb2$ can be grown on Si using a simple atomic stacking mechanism. Strains at the interface due to differences in lattice constants should not allow the hetero-epitaxy system to exist. This work deals with the first attempt to explain how BaF$\sb2$ can be grown on Si by investigating the chemistry at the interface. X-ray photoelectron spectroscopy was used to analyze the interface between BaF$\sb2$ and Si. Results show that fluorine is not present at the interface but rather a barium-silicon compound is formed at the interface. X-ray diffraction measurements confirm the formation of a new compound at the interface. Further evidence of the chemical reaction at the interface is that by heating the BaF$\sb2$ films on Si, all of the film can be converted to the barium-silicon compound. This new Ba-Si film was used as a substrate for deposition of PbTe with excellent results. PbTe like BaF$\sb2$ has a lattice constant considerable larger that silicon (6.49 A). The PbTe films grew (100) oriented and had very little strain according to X-ray diffraction results. The results reported here suggest that a new procedure for making silicide films can be developed. Also the results can be used to explain the chemistry in other fluorides on Si.



American University




Ph.D. American University 1992.


Media type


Access statement


Usage metrics

    Theses and Dissertations


    No categories selected