Question:

What are some easy samples to image with the STM?

Graphite or more specifically Highly oriented pyrolitic Graphite (HOPG) is often used as a sample or substrate in air. Because the top few layers can be cleaved off with a piece of adhesive tape leaving a clean, atomically flat surface to work on. I can only recall two papers imaging natural graphite. I have tried it once without success. A geologic sample often used Galena also known as lead sulfide. Is relatively easy to cleave off crystals it has relatively interesting features at almost all size scales, including atomic resolution.