Raman scattering in ZnO thin films doped with Fe, Sb, Al, Ga, and Li Available to Purchase

Polarized micro-Raman measurements were performed to study the phonon modes of Fe, Sb, Al, Ga, and Li doped ZnO thin films, grown by pulsed-laser deposition on $c$-plane sapphire substrates. Additional modes at about 277, 511, 583, and $644 cm−1,$ recently assigned to N incorporation [A. Kaschner et al., Appl. Phys. Lett. 80, 1909 (2002)], were observed for Fe, Sb, and Al doped films, intentionally grown without N. The mode at $277 cm−1$ occurs also for Ga doped films. These modes thus cannot be related directly to N incorporation. Instead, we suggest host lattice defects as their origin. Further additional modes at 531, 631, and $720 cm−1$ seem specific for the Sb, Ga, and Fe dopants, respectively. Li doped ZnO did not reveal additional modes.