The cross-linking of carbosilane polymers is part of the process used to produce silicon carbide fibers. AFM observations of the photo-induced reactions occurring on the surface of the materials during the cross-linking process reveal substantial material transport during the phase transformations. It is also reported that the cross-linking occurs through the ethynyl and hydrosilyl moieties of the title materials. The AFM also allows the study of the details of the reactions as the information obtained is not averaged out as in other surface analytical techniques.