A method has been presented for determining a local atomic structure in an amorphous thin film of sub-micron thickness grown on a substrate by the grazing incidence x-ray scattering (GIXS) method. The capability of this method was demonstrated by analyzing amorphous SiO2 and Si3N4 films 200 and 70 nm thick, respectively. A network structure in the amorphous SiO2 film consists of SiO4 tetrahedra connecting each other by oxygen atoms at their vertices. This resembles that in a bulk amorphous SiO2. The local ordering unit structure in the amorphous Si3N4 film was found to be a SiN4 tetrahedron. A significant feature in the present amorphous Si3N4 film is the presence of two types of Si-Si pairs in the near neighbor region while only one type is present in the α-Si3N4 crystal. This indicates that a part of the network structure formed by the SiN4 tetrahedra is quite different from that in its crystalline state. According to the coordination number of 3.8 for Si-N pairs, some nitrogen vacancies are quite likely involved in the film. Such nitrogen vacancies, then, are responsible for the modified network structure in the present amorphous Si3N4 film.
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Physical and Theoretical Chemistry