Vacuum emission of hot electrons from silicon dioxide at low temperatures

Abstract

Low temperature (to 83 K) vacuum emission of hot electrons from silicon dioxide films is reported. This technique is specifically used to study the temperature dependence of the electronic distributions emerging into vacuum from very thin (50-60 Å) oxide layers where a significant number of the electrons have traveled through the insulator ballistically. The measured energy distributions of the emerging carriers are shown to reflect the temperature-dependence of the distribution of the electron source in the silicon substrate at the abrupt interface with the silicon dioxide layer, particularly the Fermi tail, and possibly quantized levels in the silicon accumulation layer. The other features in the electron distributions are shown to be due to single phonon scattering of ballistic electrons in the silicon dioxide layer. Additionally, it is shown that as the oxide thickness is increased, the distribution broadens into its steady-state characteristic, showing very little temperature dependence. All data are shown to be in good agreement with a temperature-dependent, Monte Carlo simulation that includes the details of the electron source function at the interface of the silicon substrate and the oxide layer.