Reconstruction of the local density of states in Ag(111) surfaces using scanning tunneling potentiometry

We present scanning tunneling microscopy data on clean Ag(111) surfaces in UHV. Standing-wave patterns of the surface state are investigated to study the influence of a thermal step across the tunnel junction on constant current topographies. When constant current topographies are measured at bias voltages below 10 mV with temperature differences of more than a few kelvins between tip and sample, the apparent corrugation is drastically increased. Constant current topographies at low bias voltages and finite temperature differences do not reveal the true local density of states of the surface. The apparent corrugation is caused by a spatial varying thermovoltage superimposed to the bias voltage while scanning the sample's local density of states. With the help of scanning tunneling potentiometry, the correct local density of states of the sample can be reconstructed.