Detection of Dielectric Trap States in Hafnium Oxide By Single Electron Tunneling Force Spectroscopy

Atomic scale detection and imaging of electronic trap states in dielectric films has recently been demonstrated.\footnote{J.P. Johnson et al, Nanotechnology \textbf{20} (2009) 055701} Standard methods typically provide characterization over a much larger scale. Single Electron Tunneling Force Spectroscopy has been employed to measure the energy levels of trap states in HfO$_{2}$ with sub-nanometer spatial resolution. Analysis of individual spectra obtained at different locations shows variation in the density of defect states. When multiple spectra taken from 40 different locations are averaged, a broad peak 0.3 eV below the conduction band is observed, which agrees with data obtained over large areas by standard measurements.\footnote{G. Ribes et al, IEEE Trans. Dev. Mat. Reliability \textbf{6}, 132 (2006).} Additional peaks, not seen by the standard methods, are also observed. The method will be described and the data discussed.