No abstract

Barrier-type anodic films 3-15 nm thick have been formed on electropolished 99.999% aluminium. Variable-angle XPS has been used to identify a significant proportion of hydroxyl ions at the surface of the relatively compact alumina films. The location of an oxygen-rich region at the outer surface of the oxide has been confirmed by medium-energy ion scattering (MEIS). Combining the information from these two techniques leads to the conclusion that a hydroxyl-containing surface region is responsible for this oxygen-rich surface layer, MEIS revealing an approximately linear relationship between the total oxide thickness and the thickness of the hydroxyl-rich surface region. From consideration of the mechanisms of amorphous alumina formation by ionic transport, with incorporation of electrolyte-derived species into the thickening film, the generation of the hydroxyl-rich outermost region is considered to result from the formation of gel-like material at the film/electrolyte interface.

Complementary but independent medium-energy and low-energy ion scattering studies of the (0001) surfaces of V 2 O 3 films grown on Pd(111), Au(111) and Cu 3 Au(100) reveal a reconstructed full O 3 -layer termination creating a VO 2 surface trilayer. This structure is fully consistent with previous calculations based on thermodynamic equilibrium at the surface during growth, but contrasts with previous suggestions that the surface termination comprises a complete monolayer of vanadyl (V=O) species.

No abstract

High dielectric constant hafnium oxide films were formed by electron beam ͑e-beam͒ evaporation on HF last terminated silicon ͑100͒ wafers. We report on the influence of low energy argon plasma ͑ϳ70 eV͒ and oxygen flow rate on the electrical, chemical, and structural properties of metal-insulator-silicon structures incorporating these e-beam deposited HfO 2 films. The use of the film-densifying low energy argon plasma during the deposition results in an increase in the equivalent oxide thickness ͑EOT͒ values. We employ high resolution transmission electron microscopy ͑HRTEM͒, x-ray photoelectron spectroscopy ͑XPS͒, and medium energy ion scattering experiments to investigate and understand the mechanisms leading to the EOT increase. We demonstrate very good agreement between the interfacial silicon oxide thicknesses derived independently from XPS and HRTEM measurements. We find that the e-beam evaporation technique enabled us to control the SiO x interfacial layer thickness down to ϳ6 Å. Very low leakage current density ͑Ͻ10 −4 A / cm 2 ͒ is measured at flatband voltage +1 V into accumulation for an estimated EOT of 10.9Ϯ 0.1 Å. Based on a combined HRTEM and capacitance-voltage ͑CV͒ analysis, employing a quantum-mechanical CV fitting procedure, we determine the dielectric constant ͑k͒ of HfO 2 films, and associated interfacial SiO x layers, formed under various processing conditions. The k values are found to be 21.2 for HfO 2 and 6.3 for the thinnest ͑ϳ6 Å͒ SiO x interfacial layer. The cross-wafer variations in the physical and electrical properties of the HfO 2 films are presented.