EFFECTS OF SELF-MODIFYING MULTIPLE TIPS ON STM SURFACE PICTURES

During the study of a mechanically produced hole in a graphite of appr oximately 500 Angstrom diameter, the STM image showed two holes separa ted by a distance of about 560 Angstrom due to a double tip. In additi on, a continuous change in the contrast of the images of the hole, res ulting from a continuous change in the relative position of the tips i n the z-direction, was observed. This means the tip is modifying durin g the scan. When the two tips were at equal distances from the sample, the depth of the holes appeared to reduce by half since the total tun nelling current comprises contributions from both tips. Methods for re ducing the chance of formation of multiple tips by picking up particle s from the etching solution are also discussed.