The scanning tunnelling microscope (STM) relies on the phenomenon of quantum tunnelling.
Explain what is meant by quantum tunnelling of an electron across the potential barrier in an STM.
An STM can be operated in constant-current mode to map the vertical features of a sample surface.
Describe how the STM creates a map of the surface in this mode.
The smallest features that an STM can resolve are approximately equal in size to the de Broglie wavelength of the tunnelling electrons.
Deduce whether electrons with kinetic energies of 80 eV80\text{ eV}80 eV are suitable to resolve individual silicon atoms on a reconstructed Si(111)-7×7\text{Si}(111)\text{-}7\times7Si(111)-7×7 surface where the atomic spacing between features is 0.15 nm0.15\text{ nm}0.15 nm.
26 exam-style questions on AQA A Level Physics Wave-particle duality (A-level only), covering Newton's corpuscular theory of light (A-level only), Significance of Young's double slits experiment (A-level only), Electromagnetic waves (A-level only), The discovery of photoelectricity (A-level only), Wave-particle duality (A-level only), and Electron microscopes (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.