Inelastic electron tunnelling spectroscopy

Experiments have used inelastic electron tunnelling spectroscopy as a method of measuring the phonon density of states of the tunnelling barrier. The magnitude of the measured d2I/dV2 characteristic is proportional to the density of phonon states multiplied by a weighting factor, which depends on the strength of the interaction between the electron and the phonon. Without a knowledge of this weighting factor the experiments can only yield qualitative results. The authors present a study of the tunnelling process and derive a weighting factor which allows the phonon density of states to be deduced from the experimental data.