Band gap and band offsets for ultrathin (HfO2)x(SiO2)1-x dielectric films on Si(100)

Energy band profile of ultrathin Hf silicate dielectrics, grown by atomic layer deposition, was studied by using x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The band gap energy only slightly increases from 5.52 eV for (HfO2)(0.75)(SiO2)(0.25) to 6.10 eV for (HfO2)(0.25)(SiO2)(0.75), which is much smaller than 8.90 eV for SiO2. For ultrathin Hf silicate dielectrics, the band gap is mainly determined by the Hf 5d conduction band state and the O 2p valence band state. The corresponding conduction band offsets are in the vicinity of 1 eV, which satisfies the minimum requirement for the carrier barrier heights. (c) 2006 American Institute of Physics.