Unexpected change in the electron affinity of diamond caused by the ultra-thin transition metal oxide filmsAmit K. Tiwari, J. P. Goss, P. R. Briddon, A. B. Horsfall, N. G. Wright, R. Jones and M. J. RaysonEPL, 108 4 (2014) 46005DOI: https://doi.org/10.1209/0295-5075/108/46005