Rare earth functionalization effect in optical response of ZnO nano clusters Manasi S. Mahabal, Mrinalini D. Deshpande, Sudip Chakraborty, Tae Won Kang and Rajeev Ahuja Eur. Phys. J. D, 70 3 (2016) 63 Published online: 22 March 2016 DOI: 10.1140/epjd/e2016-60314-8