Electronic structure of noncrystalline transition metal silicate and aluminate alloys

A localized molecular orbital description (LMO) for the electronic states of transition metal (TM) noncrystalline silicate and aluminate alloys establishes that the lowest conduction band states are derived from d states of TM atoms. The relative energies of these states are in agreement with the LMO approach, and have been measured by x-ray absorption spectroscopy for ${\mathrm{ZrO}}_2–{\mathrm{SiO}}_{\mathrm{2}}$ alloys, and deduced from an interpretation of capacitance–voltage and current–voltage data for capacitors with ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_3–{\mathrm{Ta}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{5}}$ alloy dielectrics. The LMO model yields a scaling relationship for band offset energies providing a guideline for selection of gate dielectrics for advanced Si devices.