Quenching surface states with the tip: STM scans on Fe(1 0 0)

STM topographies and spectroscopies are compared with first principles simulations using the transfer-Hamiltonian method. We show that simulations agree with measurements in the range above 400 pm tip–sample separation, provided the tungsten tip is terminated by a (1 0 0) or (1 1 1) face. Measurements disagree with experiments for the (1 1 0) face. The approach fails to describe tunneling topographies in the range below 400 pm. It is argued that this failure is due to interactions, and it is demonstrated how quenching of surface states by the approaching tip accounts for the experimental features in this range.