Er-doped ZnO Thin Films Research Articles

Influence of Annealing on the 1.5 μm Light Emission of Er-doped ZnO Thin Films and its Crystal Quality

Intensity variation of 1.5 μm light emission at room temperature from Er-doped epitaxial and polycrystal ZnO films depending on annealing temperature (773–1373 K) was studied. As-grown Er-doped epitaxial ZnO film emitted 1.5 μm photoluminescence(PL) higher than as-grown Er-doped polycrystal ZnO. It was found that the annealing in air increases PL intensity and the maximum PL intensity was obtained by annealing at optimal temperature (1073 K). Spectrum shape and intensity of 1.5 μm PL of Er-doped epitaxial ZnO after annealing at 1073 K resembled those of Er-doped polycrystal ZnO after annealing at 1073 K. X-ray diffraction measurement demonstrated that annealing improves crystal quality of Er-doped ZnO film. We assumed that the process of 1.5 μm light emission is dependent on local area placement of Zn and O atoms around Er as well as crystal quality of ZnO.

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.

1.54 μm emission dynamics of erbium-doped zinc-oxide thin films

Erbium-related 1.54 μm emission dynamics of Er-doped ZnO thin films has been investigated for the different excitation conditions. The excitation was achieved either by exciting indirectly Er3+ ions due to an electron–hole-mediated process or exciting directly discrete energy levels of Er3+ ions. There is no change in the 1.54 μm emission spectrum feature in spite of the different excitation conditions, whereas dramatic change can be seen in the rise time of 1.54 μm emission. The shorter rise time of 1.54 μm emission observed for indirect excitation implies an excitation efficiency superior to direct excitation of Er3+ ions.

Fabrication and optical transition dynamics of Er-doped ZnO thin films formed on Si substrates

Er-doped ZnO (ZnO : Er) thin films fabricated on Si substrates were investigated by photoluminescence (PL) and PL excitation (PLE) spectroscopy. The ZnO : Er thin films emit sharp and intense 1.54 μm luminescence. It is shown that the Er-related PL gives rise to different features under direct and indirect excitations. An over band-gap excitation leads to a faster lifetime of the 1.54 μm PL indicating a strong interaction of electron–hole pairs in the host with 4f electrons in the Er 3+ ions. The ZnO : Er is a promising candidate for optoelectronic devices excited by carrier injection because of its high electrical conductivity.