STM

1. STM Scanning Tunneling Microscope Indirect Observation (Activity) Developed by Malory M. Peterson, Summer 2006 Nanotechnology Grant National Science Foundation #0532516

2. Indirect Observation • The AFM and STM use a method called indirect observation. • This is when the researcher relies on reported observation. • For the STM and AFM the researcher doesn’t exactly “see” the atoms, but they can decide what they look like from current read by the microscope.

3. What to do… • You will need markers, colored pencils, or crayons. • Use the wooden dowel to “probe” into the holes on the top of the wooden box. You will need to scan each row of holes in order to determine what the bottom of the box looks like. You will do this with two different boxes. • You will create a topographic map using the graph paper. Be prepared to explain what the bottom of your box looks like. • Color the highest regions one color. • Color the lower regions another color. • Color the in between regions another color. • DON’T forget to draw a key for your map.

4. Questions • Imagine your dowel is not touching the bottom of the box, it is an STM tip. Also, imagine the bottom of the box is a conductive sample. • In this case, what color would you use where the current between the tip and sample is the greatest? • What color would you use if the current was the weakest? • How do you know?