Atomic Force Microscopy Of Micron Size Silicalite Crystals

Abstract

ABSTRACTWe have imaged micron sized silicalite crystals with an atomic force microscope (AFM). High resolution images taken in the repulsive mode show a periodic pattern that locally has a symmetry and periodicity which can be mapped onto the expected image looking along the [010] direction. Extra spots, however, appear in the image in regions which should correspond to channels exposed at the surface. These extra spots are attributed to multiple tip effects which should not affect the ability to detect long range ordering. On a scale length of ˜ 3 – 5 unit cells, the ordering in images deviates from that expected for a perfect crystal. This may be due to imperfections in the ordering at crystal surfaces. One other important aspect of the surface crystallography is revealed in low resolution scans where definite steps / grooves in the exposed surface are seen. The results are discussed in terms of the potential of AFM as a probe of surface crystallography.