Coordination and Bond Character of Silicon and Aluminum Ions in Amorphous Thin Films in the System SiO ₂ ‐Al ₂ O ₃

The coordination and bond character of the cations in amorphous SiO 2 ‐Al 2 O 3 films prepared by rf sputtering were examined by studying chemical shifts in the SiK and AlK X‐ray emission spectra. The coordination number of Si ions in these films was always 4, regardless of composition, whereas the average coordination number of Al ions changed from 4 to 5, depending onAl 2 O 3 content. TheSi‐O‐Al bond type seemed to appear as Al 2 O 3 was introduced into amorphous SiO 2 films or vice versa.