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A systematic experimental evaluation of the thermal stability of Ru metal gate electrodes in direct contact with SiO2 and Hf-based dielectric layers was performed and correlated with electrical device measurements. The distinctly different interfacial reactions in the Ru/SiO2, Ru/HfO2, and Ru/HfSiOx film systems were observed through cross-sectional high-resolution transmission electron microscopy, high angle annular dark field scanning transmission electron microscopy with electron-energy-loss spectra, and energy dispersive x-ray spectra analysis. Ru interacted with SiO2, but remained stable on HfO2 at 1000 °C. The onset of Ru/SiO2 interfacial interactions is identified via silicon substrate pitting possibly from Ru diffusion into the dielectric in samples exposed to a 900 °C/10-s anneal. The dependence of capacitor device degradation with decreasing SiO2 thickness suggests Ru diffuses through SiO2, followed by an abrupt, rapid, nonuniform interaction of ruthenium silicide as Ru contacts the Si substrate. Local interdiffusion detected on Ru/HfSiOx samples may be due to phase separation of HfSiOx into HfO2 grains within a SiO2 matrix, suggesting that SiO2 provides a diffusion pathway for Ru. Detailed evidence consistent with a dual reaction mechanism for the Ru/SiO2 system at 1000 °C is presented. [ABSTRACT FROM AUTHOR]

Describes a substrate material for depositing high-temperature superconducting YBa[sub2]Cu[sub3]O[sub7-δ] (YBCO) thin films. Preparation of the films; Method used to examine the structure of the deposited YBCO thin films.

We investigate the scaling of Al2O3 dielectric on graphene by atomic layer deposition (ALD) using ultra-thin, oxidized Ti and Al films as nucleation layers. We show that the nucleation layer significantly impacts the dielectric constant (k) and morphology of the ALD Al2O3, yielding k = 5.5 and k = 12.7 for Al and Ti nucleation layers, respectively. Transmission electron microscopy shows that Al2O3 grown using the Ti interface is partially crystalline, while Al2O3 grown on Al is amorphous. Using a spatially uniform 0.6 nm-thick Ti nucleation layer, we demonstrate graphene field-effect transistors with top dielectric stacks as thin as 2.6 nm. [ABSTRACT FROM AUTHOR]

A study is reported on the growth mechanism of YBa[sub 2]Cu[sub 3]O[sub 7] with different growth speeds by high resolution transmission microscopy (HRTEM) and analysis of the interface and thin film microstructure. Two thin films were synthesized by pulse laser deposition on [100], miscut 5°, SrTiO[sub 3] substrate at 820°C, one with a pulse laser frequency of 1Hz and one with 6Hz. Cross-sections were studied by an H-9000 NAR HRTEM along the [010] direction. The growth process of the sample made at 1Hz was as follows. First, distorted step flow growth occurred on a step-mediated substrate surface of 3–4 cells thickness. Second, about a 15nm thickness of island shape growth becomes superimposed on the area of the step flow layer. Finally, thin film growth occurred but with growth fluctuation. The sample made at 6Hz showed the characteristics of island growth; the growth area of island or ball shape was of small size and dense distribution, and seemed to be a confused mosaic stack. The influence of growth speed on YBCO epitaxial film microstructure was studied explicitly by HRTEM. [ABSTRACT FROM AUTHOR]

Abstract: The effect of device fabrication temperature on the work function of ruthenium (Ru) metal gate and its bilayers was investigated. The work function shows strong temperature dependence when Ru electrodes are deposited on silicon oxide, SiO2, but not on hafnium silicates (HfSiO x ). Specifically, the work function of Ru on SiO2 increased from 4.5 eV at 500 °C to 5.0 eV at 700 °C. On further annealing to 900 °C or higher, the work function dropped to about 4.4 eV. In the case of HfSiO x , the work function of Ru changed by less than 100 mV over the same temperature range. Identical temperature dependence was observed using hafnium (Hf)/Ru and tantalum (Ta)/Ru bilayers. However, the peak values of the work function decreased with increasing Hf/Ru and Ta/Ru thickness ratios. Materials analysis suggests that these trends are driven by interactions at the Ru metal gate–dielectric interface. [Copyright &y& Elsevier]