Band alignment of vanadium oxide as an interlayer in a hafnium oxide-silicon gate stack structure

Vanadium oxide (VO2) is a narrow band gap material (Eg = 0.7 eV) with a thermally induced insulator-metal phase transition at similar to 343K and evidence of an electric field induced transition at T < 343 K. To explore the electronic properties of VO2, a sandwich structure was prepared with a 2nm VO2 layer embedded between an oxidized Si(100) surface and a 2 nm hafnium oxide (HfO2) layer. The layer structure was confirmed with high resolution transmission electron microscopy. The electronic properties were characterized with x-ray and ultraviolet photoemission spectroscopy, and the band alignment was deduced on both n-type and p-type Si substrates. The valence band offset between VO2 and SiO2 is measured to be 4.0 eV. The valence band offset between HfO2 and VO2 is measured to be similar to 3.4 eV. The band relation developed from these results demonstrates the potential for charge storage and switching for the embedded VO2 layer. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4761990]