Structure of Si(111) surfaces etched in 40% NH4F: Influence of the doping J.R. Roche, M. Ramonda, F. Thibaudau, Ph. Dumas, Ph. Mathiez, F. Salvan and P. Allongue Microsc. Microanal. Microstruct., 5 4-6 (1994) 291-299 DOI: 10.1051/mmm:0199400504-6029100