You would probably not consider a hair to be inconceivably thin compared to the lecture room's width. By the same token molecules are not inconceivably small, just very small - 100,000 times smaller in width than a hair. It is certainly a point of pride for science that by using SPM we can "feel" individual molecules (or even atoms), but it is not inconceivable. Before SPM came along chemists tended to think of a molecule as inconceivably small, so it came as quite a surprise that a rather simple machine could feel one.

(I) For a simple description of STM and AFM click this University of Colorado web site.

Follow the links to see both types of images.

Think about the horizontal and vertical scales in comparison to atomic and molecular dimensions.

Under the STM link follow "More STM images" or click here to see the MDS74 on graphite image shown in class.

For more details see a booklet describing scanning probe microscopy.

(II) The spectacular "Quantum Corral" of 48 iron atoms is shown at this IBM Almaden site.

For the specific image shown in class click here.

(III) Click Digital Instruments, to see actual tips used in AFM (they manufacture SPMs)

The standard silicon nitride tips shown early on this page are typical. Note the size of the tips especially their radius of curvature (how wide the bottom of the tip is).