2. Isolated molecules

2.1 High-resolution imaging

Images of isolated molecules require a molecule that is perfectly immobile and free from contamination. This is why these images are always obtained by STM or AFM under ultra-high vacuum (≈ 10 ^-10 mbar). Depending on the nature of the surfaces, observation temperatures are very different. On metals, as molecule diffusion is very important, we need to work at very low temperatures (< 77 K), whereas on semiconductors where surface atoms generally possess unsaturated dangling bonds that can interact with molecules, molecule diffusion is weaker and it's possible to observe isolated molecules even at room temperature. Images obtained with "standard" tips (i.e. without the adsorption of a single molecule at the...