The scanning tunnelling microscope (STM) relies on a quantum-mechanical phenomenon to image surfaces at the atomic level.
Explain what is meant by the quantum tunnelling of an electron across the gap between the sample and the tip of the STM.
An STM can be operated in constant-current mode to map the position of individual atoms on a crystalline surface.
Describe how the STM tip moves and how the surface map is generated when operating 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 54 eV54\text{ eV}54 eV are suitable to resolve individual atoms on a surface where the spacing between adjacent atoms is 0.18 nm0.18\text{ nm}0.18 nm.
