BaSi 2 formation mechanism in thermally evaporated films and its application to reducing oxygen impurity concentration
Year: 2018
Type: article
Abstract: Thermal evaporation is a simple and rapid method to fabricate semiconducting BaSi 2 films. In this study, to elucidate the BaSi 2 formation mechanism, the microstructure of a BaSi 2 epitaxial film fabricated by thermal evaporation has been investigated by transmission electron microscopy. The BaSi 2 film is found to consist of three layers with different microstructural characteristics, which is well explained by assuming two stages of film deposition. In the first stage, BaSi 2 forms through the diffusion of Ba atoms from the deposited Ba-rich film to the Si substrate while in the second stage, the mutual diffusion of Ba and Si atoms in the film leads to BaSi 2 formation. On the basis of the BaSi 2 formation mechanism, two issues are addressed. One is the as-yet unclarified reason for epitaxial growth. It is found important to quickly form BaSi 2 in the first stage for the epitaxial growth of upper layers. The other issue is the high oxygen concentration in BaSi 2 films around the BaSi 2 –Si interface. Two routes of oxygen incorporation, i.e., oxidation of the Si substrate surface and initially deposited Ba-rich layer by the residual gas, are identified. On the basis of this knowledge, oxygen concentration is decreased by reducing the holding time of the substrate at high temperatures and by premelting of the source. In addition, X-ray diffraction results show that the decrease in oxygen concentration can lead to an increased proportion of a -axis-oriented grains.
Institutions: University of Yamanashi, Nagoya University
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2791486576