Si(100):H and Ge(100):H Dimer Rows Contrast Inversion in Low-temperature Scanning Tunneling Microscope Images

Detailed low-temperature scanning tunneling microscope images of the Si(100)-2$\times$ 1-H and the Ge(100)-2$\times$ 1-H surfaces show a remarkable contrast inversion between filled- and empty-state images where the hydrogen dimer rows appear bright for filled-state images and dark for empty-state images. This contrast inversion originates from the change in the dominant surface states and their coupling to the tip apex and the bulk channels as a function of the bias voltage.