Direct structural and spectroscopic investigation of ultrathin films of tetragonal CuO: Six-fold coordinated copperD. Samal, Haiyan Tan, Y. Takamura, W. Siemons, Jo Verbeeck, G. Van Tendeloo, E. Arenholz, C. A. Jenkins, G. Rijnders and Gertjan KosterEPL, 105 1 (2014) 17003DOI: https://doi.org/10.1209/0295-5075/105/17003