Optical Properties of ZnCoO Films and Nanopowders

E. Wolskaa, b, M. Łukasiewicza, J.D. Fidelusb, W. Łojkowskib, E. Guziewicza and M. Godlewskia, c a Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland b Institute of High Pressure Physics, Polish Academy of Sciences, "Unipress", Sokołowska 29/37, 01-142 Warsaw, Poland c Dept. of Mathematics and Natural Sciences, College of Science, Cardinal S. Wyszyński University, Dewajtis 5, 01-815 Warsaw, Poland

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ZnCoO is one of the most studied and promising semiconductor materials for spintronics applications. In this work we discuss optical and electrical properties of ZnCoO films and nanoparticles grown at low temperature by either atomic layer deposition or by a microwave driven hydrothermal method. We report that doping with cobalt quenches a visible photoluminescence of ZnO. We could observe a visible photoluminescence of ZnO only for samples with very low Co fractions (up to 1%). Mechanisms of photoluminescence quenching in ZnCoO are discussed. We also found that ZnO films remained n-type conductive after doping with Co, indicating that a high electron concentration and cobalt 2+ charge state can coexist.

DOI: 10.12693/APhysPolA.116.918 PACS numbers: 68.55.Ln, 78.55.Et, 81.07.Wx, 61.72.uf, 78.66.Hf