Direct evidence of Cd vacancies in CdSe nanoparticles: positron annihilation studiesS. K. Sharma, K. Sudarshan, P. Maheshwari, D. Dutta, P. K. Pujari, C. P. Shah, M. Kumar and P. BajajEur. Phys. J. B, 82 3-4 (2011) 335-340DOI: https://doi.org/10.1140/epjb/e2011-20363-y