Detection of N-Te bonds in the as-deposited amorphous nitrogen-doped GeTe-based phase change alloys using N K-edge XANES spectroscopy and their impact on crystallization

Abstract Using N K-edge XANES studies, we demonstrate a noticeable difference in local structure around the nitrogen atoms in as-deposited amorphous and annealed N-doped GeTe-based phase change alloys. The pronounced changes appear as a ≈ 2 eV shift in the absorption edge to higher photon energies and the overall shape of the XANES spectrum. Comparison of the experimental XANES spectrum of the as-deposited amorphous phase with ab-initio XANES simulations discloses that the as-deposited phase mainly consists of the NGe 3 and the NTe 3 pyramidal units in approximately equal concentration. When annealed, NTe 3 units gradually rebond to the NGe 3 units and at the same time N atoms diffuse through the amorphous phase to form the Ge x N y aggregates. Upon long-standing annealing at 400 ∘ C a compact interlayer of Ge 3 N 4 is formed in the crystalline phase.