The subject of surface modification due to van der Waals forces on adatoms by a nearby tip is being addressed. Since it has been found that electric fields can modify the surface under a charged tip creating a mound on the substrate [1-3], and van der Waals forces may be of the same magnitude, it is reasonable that van der Waals induced surface modification also might be present [4].
Here, the magnitude of the electrical and van der Waals forces under a tip is being calculated and compared with experiments. We used an in-situ transmission electron microscopy probing method [5,6] to directly image the surface modification, the tip and sample distance and radius. We observe surface modification due to van der Waals forces at short distances (below 3 nm).
[1] H. J. Mamin, P. H. Guethner, and D. Rugar, Phys. Rev. Lett. 65, 2418 (1990)
[2] J. Mendez, J. Gomez-Herrero, J. I. Pascual, J. J. Saenz, J. M. Soler, and A. M. Baro
J. Vac. Sci. Technol. B 14, 1145 (1996)
[3] T. M. Mayer, J. E. Houston, G. E. Franklin, A. A. Erchak, and T. A. Michalske. Electric field induced surface modification of Au. J. Appl. Phys. 85, 8170 (1999)
[4] D. Erts, A. Lohmus, R. Lohmus, H. Olin, A. V. Pokropivny, L. Ryen, and K. Svensson. Force interactions and adhesion of gold contacts using a combined atomic force microscope and transmission electron microscope. Appl. Surf. Sci.188, 460 (2002)
[5] K. Svensson, Y. Jompol, H. Olin, and E. Olsson, A compact design of a TEM-STM holder with 3-dimensional coarse motion
Rev. Sci. Instr. 74, 4945 (2003)
[6] Nanofactory Instruments (www.nanofactory.com)
|