Prof Richard Haverkamp, of Massey University, explains how a scanning tunnelling microscope works, accompanied by views of the device in use.
DR RICHARD HAVERKAMP
A scanning tunnelling microscope and an atomic force microscope are two related techniques.
I've got two of these machines and they can be either scanning tunnelling or atomic force. So the basic machinery is the same except for a little attachment you put on them. So the scanning tunnelling microscopy is where you are imaging using a little sharp needle, usually a platinum wire and you’re passing a current, between that wire and your sample. So the closer it is to the sample the more current will flow. And, so by measuring that current you can work out how close it is to the sample. This distance you can measure you can judge that distance down to incredibly small amounts so the fraction of the size of an atom.
With this machine you can't look through an eye piece, you have to see it through the computer, you’re doing it by touch, so the computer is poking with little needles and feeling the height and recording a number and it gives it to the computer and then you get the computer graphics to draw it up. So what you are seeing is generated by the computer from touch. So its a blind persons drawing really. And you can use colours to show heights, so you can make some beautiful looking pictures, but none of the colours relate to what you are looking at.