ELECTRON-TUNNELING THROUGH A DIELECTRIC BARRIER

Electron tunneling through a dielectric barrier is considered with spe cial attention given to questions relevant for STM experiments in diel ectric liquids. The effect of the barrier dielectric response on the t unneling probability is studied using the effective Hamiltonian formal ism for the polarization dynamics in the barrier, and two different th eoretical approaches for the calculation of the tunneling probability: A generalization of the Bardeen's formalism to inelastic tunneling an d the quasiclassical of Brink, Nemes, and Vautherin as expanded by Sum etskii. Although based on different approximations, both approaches yi eld similar results in the slow barrier limit, where their ranges of v alidity coincide. The approach based on the Bardeen's formalism relies on the adiabatic approximation and fails for fast barrier dynamics. T he overall effect of the barrier dielectric response is to enhance the tunneling probability relative to the rigid barrier case. The enhance ment factor is larger for thicker barrier, higher temperature and fast er barrier dynamics. Both the elastic and inelastic components of the tunneling current show these trends in the relevant range of parameter s.