The surfaces of pure and Mn doped TiSe2 were etched using a scanning tunneling microscope. Roth types of samples were found to etch easily when scanning was performed in ambient conditions. This process was enhanced at step edges or other surface defects. In pure samples, material was removed in a layer-by-layer fashion with a strong dependence on the scanning direction of the tip. Doped samples etched far more rapidly, to the point that stable scanning conditions were difficult to establish. Doped samples also showed a greater number of pits and other defects on their surface. A relatively small percentage of dopants was necessary to strongly impact the surface topography and stability. These results show that impurities can play a dominant role when using scanning tunneling microscopy to create surface nanostructures.