Thermovoltage mapping of standing electron waves on Au(111) surfaces at low temperatures

Standing-wave patterns of Au(111) surface electrons in the vicinity of monatornic steps were studied by mapping the thermovoltage across the tunneling gap of a low-temperature scanning tunneling microscope (STM). In contrast to other STM spectroscopic methods, the amplitude of the standing-wave oscillations builds up with distance from the step, up to a maximum. When the temperature T is decreased, the position of this maximum shifts outwards proportional to 1/T. This behavior is explained with an analytical expression and also with numerical calculations of the thermovoltage in the framework of the model of Tersoff and Hamann.