Lanthanum lutetium oxide thin films were grown on ͑100͒ Si by pulsed laser deposition. Rutherford backscattering spectrometry, atomic force microscopy, x-ray diffraction, and x-ray reflectometry were employed to investigate the samples. The results indicate the growth of stoichiometric and smooth LaLuO 3 films that remain amorphous up to 1000°C. Internal photoemission and photoconductivity measurements show a band gap width of 5.2± 0.1 eV and symmetrical conduction and valence band offsets of 2.1 eV. Capacitance and leakage current measurements reveal C-V curves with a small hysteresis, a dielectric constant of Ϸ32, and low leakage current density levels. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2393156͔The study of ultrathin gate dielectrics has recently gained great attention due to the technological need to replace SiO 2 films in metal-oxide-semiconductor field-effect transistors ͑MOSFETs͒. 1 The scaling has led to MOSFETs with ultrashort physical gate lengths ͑Ͻ50 nm͒ and insulating SiO 2 -based films with thickness less than 1 nm. At such a thickness, these films suffer from excessively high leakage of charge carriers and poor reliability with respect to dielectric breakdown. Therefore, to overcome these limitations new gate dielectric materials with a higher dielectric constant must be developed to replace the SiO 2 . According to the International Technology Roadmap for Semiconductors, 2 the implementation of high-gate dielectrics with a dielectric constant between 10 and 20 will be required by 2008, which will later be replaced by materials having a larger than 20, in order to meet both low leakage current density and performance requirements.Ternary rare earth oxides ͑e.g., DyScO 3 and GdScO 3 ͒ are emerging as promising candidates for high-applications. As shown by Schlom and Haeni, 3 single crystals of these oxides show values of 20-35 which were also observed for amorphous LaScO 3 , GdScO 3 , and DyScO 3 films deposited on silicon ͑ =22-23͒. 4,5 In addition, these materials fulfill the requirements for large optical band gaps ͑5.6 eV͒ and band offsets ͑2 -2.5 eV͒, 6 while their amorphous phase is stable up to 1000°C ͑for GdScO 3 and DyScO 3 ͒. 4,5 Lanthanum lutetium oxide ͑LaLuO 3 ͒, as a member of this class of ternary oxides, is predicted to have similar properties. 3,7 Experimental data related to high-gate applications of amorphous LaLuO 3 films are, however, still not available. In this letter, we present the results of a systematic study on the microstructural and electrical properties of amorphous LaLuO 3 thin films, deposited on silicon substrates by means of pulsed laser deposition ͑PLD͒.LaLuO 3 films were deposited by PLD using a stoichiometric ceramic target. The target was made by milling a stoichiometric mixture of Lu 2 O 3 ͑Alfa Aesar, 99.99%͒ and La 2 O 3 ͑Alfa Aesar, 99.999%͒ powders with a molar ratio of 1:1. The ground powder was dried and then fired at 1300°C in air for 12 h. After regrinding, the powder was pressed with a uniaxial press ͑3 tons͒. The pellets were the...

The incorporation of chemical species during annealing at the interface between the Ru gate electrode and the dielectric perturbs the electrostatic potential, thus affecting the effective work function of the metal. For both SiO2 and HfO2 gate dielectrics, O2 anneal at 550°C leads to Ru oxidation (i.e., to RuOx formation) at the Ru∕dielectric interface, resulting in a higher effective work function than that of metallic Ru. In turn, when RuOx is exposed to hydrogen, a work function reduction occurs, caused by either a reduction of RuOx into Ru or hydroxyl incorporation at the interface.

Internal photoemission, photoconductivity, and spectroscopic ellipsometry experiments were carried out to characterize the electronic structure of interfaces of (001) and (111)-oriented Si with crystalline (epitaxially grown) and amorphous Gd2O3 insulators. The energy barriers for electrons and holes (3.2 and 3.9eV, respectively) appear to be sensitive neither to the orientation of the Si crystal surface nor to the oxide phase (crystalline or amorphous). This result indicates that despite the difference in Si–O bond density in going from (001) to (111)Si, the interface dipoles do not ensue any measurable effect on the electronic structure of the interface and the associated band offsets.

Energy diagrams of interfaces between (100)Ge and several rare-earth oxide insulators deposited from a molecular beam are determined using a combination of internal photoemission and photoconductivity measurements. For the wide band gap (5.9eV) oxides Gd2O3 and LaHfOx, the band alignment at the interface is found to be close to that of HfO2 and is characterized by conduction/valence band offsets of ∼2∕∼3eV. In contrast, CeO2 which has a much narrower band gap (3.3eV) does not provide a band alignment diagram corresponding to sufficient insulation.

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