Frontier induced semi-infinite-medium (FISIM) states at semiconductor surfaces and interfaces D. Olguín, J. A. Rodríguez and R. Baquero Eur. Phys. J. B, 32 1 (2003) 119-126 Published online: 14 March 2003 DOI: 10.1140/epjb/e2003-00080-0