Hot-electron effects in thin silicon dioxide films studied with ballistic electron emission microscopy

Ultra-high vacuum (UHV) ballistic electron emission microscopy (BEEM) is used to study the phenomena associated with the presence of hot electrons in silicon dioxide (SiO{dollar}sb2{dollar}) films. Our contribution to a parallel project studying silicon carbide (SiC) with BEEM is also presented.; We show that BEEM can be used to induce microscopic (tens of nanometers wide) build-up of trapped charge in SiO{dollar}sb2{dollar} film sandwiched into a metal/oxide/silicon (MOS) structure. We devise a method based on BEEM, which allows us to estimate the local magnitude and depth of the trapped charge. Our measurements indicate that BEEM could be sensitive to very small numbers (of the order of ten or less) of electrons trapped in buried SiO{dollar}sb2{dollar} films. Image-force lowering of the oxide barrier is also observed.; We further expand the ability of BEEM to explore trapped charge by combining the depth-profiling method with the measurement of the lateral oxide potential profile. From this combined measurement and through numerical electrostatic calculations we effectively obtain microscopic three-dimensional profile of the trapped charge in buried SiO{dollar}sb2{dollar} films. We use this approach to measure the distribution of oxide trapped charge following injection of hot electrons into the MOS structure at a single point. Based on our Monte Carlo (MC) simulations of ballistic-electron scattering in the metal overlayer we propose a model explaining the relatively large width of the trapped charge by a combination of scattering of hot electrons in the oxide and saturation of trapping efficiency.; On MOS structures made with ultra thin SiO{dollar}sb2{dollar} films we observe quantum-mechanical resonance of hot electrons in the oxide film. We assume a certain effective electron mass in the oxide as a function of energy and fit the oscillations observed in the BEEM spectra.; We also describe some of the results obtained on metal/SiC heterostructures. From our analysis of the BEEM spectra obtained on different polytypes of SiC we determine Schottky barrier heights, extract the energy separations of the second conduction band minima in 4H-SiC and 15R-SiC and match them with the theoretical band structure calculations.