Er-doped ZnO thin films grown by pulsed-laser deposition

Crystalline erbium(Er)-doped zinc oxide thin films have been grown by pulsed-laser deposition and were analyzed by the complementary use of Rutherford backscattering spectroscopy, x-ray diffraction analysis, atomic force microscopy, and photoluminescence. The composition, structure, and surface morphology of films were studied, as a function of the growth conditions (temperature from 300 °C to 750 °C and oxygen pressure from ${10}^{-6}$ to 0.5 mbar) and Er-doping rate, and were correlated to the emission spectroscopy of Er in the infrared domain. While these studies lead to the determination of optimal conditions for the growth of high crystalline quality films, results of photoluminescence experiments show that the insertion of Er ions in the ZnO matrix does not follow a simple pattern. The Er ions are incorporated from two pathways, one population is found inside the crystallites and another one at the grain boundaries, as a consequence of the differences in valence and ionic radius of Zn and Er.