Imaging in scanning tunneling microscopy and its relationship with surface roughness

We study the texture of surfaces imaged by scanning tunneling microscopy (STM) under different; control conditions in the feedback loop of the STMs control unit. The surface texture parameters such as the rms-roughness, the average wavelength and the fractal character have a strong dependence on the values of the parameters used in the feedback: loop even when the visual quality of the images is the same. The reliability of the images can be described quantitatively by giving the values of two nondimensional parameters that described the measurement conditions.