Chemical states and electronic structure of a HfO2/Ge(001) interface -: art. no. 042902

We report the chemical bonding structure and valence band alignment at the HfO2/Ge(001) interface by systematically probing various core level spectra as well as valence band spectra using soft x rays at the Stanford Synchrotron Radiation Laboratory. We investigated the chemical bonding changes as a function of depth through the dielectric stack by taking a series of synchrotron photoemission spectra as we etched through the HfO2 film using a dilute hydrogen fluoride solution. We found that a very nonstoichiometric GeOx layer exists at the HfO2/Ge interface. The valence band spectra near the Fermi level in each different film structure were carefully analyzed, and as a result, the valence band offset between Ge and GeOx was determined to be Delta E-v (Ge-GeOx)=2.2 +/- 0.15 eV, and that between Ge and HfO2, Delta E-v (Ge-HfO2)=2.7 +/- 0.15 eV. (c) 2005 American Institute of Physics.