1 research outputs found
Local Environment of Sc and Y Dopant Ions in Aluminum Nitride Thin Films
The local environments of Sc and Y in predominantly ⟨002⟩
textured, Al1–xDoxN (Do = Sc, x = 0.25, 0.30 or Y, x = 0.25) sputtered thin films with wurtzite symmetry were investigated
using X-ray absorption (XAS) and photoelectron (XPS) spectroscopies.
We present evidence from the X-ray absorption fine structure (XAFS)
spectra that, when x = 0.25, both Sc3+ and Y3+ ions are able to substitute for Al3+, thereby acquiring four tetrahedrally coordinated nitrogen ligands,
i.e., coordination number (CN) of 4. On this basis, the crystal radius
of the dopant species in the wurtzite lattice, not available heretofore,
could be calculated. By modeling the scandium local environment, extended
XAFS (EXAFS) analysis suggests that when x increases
from 0.25 to 0.30, CN for a fraction of the Sc ions increases from
4 to 6, signaling octahedral coordination. This change occurs at a
dopant concentration significantly lower than the reported maximum
concentration of Sc (42 mol % Sc) in wurtzite (Al, Sc)N. XPS spectra
provide support for our observation that the local environment of
Sc in (Al, Sc)N may include more than one type of coordination