First-principles study of orthorhombic CdTiO3 perovskite

In this work we perform an ab-initio study of CdTiO3 perovskite in its orthorhombic phase using FLAPW method. Our calculations help to decide between the different cristallographic structures proposed for this perovskite from X-Ray measurements. We compute the electric field gradient tensor (EFG) at Cd site and obtain excellent agreement with available experimental information from a perturbed angular correlation (PAC) experiment. We study EFG under an isotropic change of volume and show that in this case the widely used "point charge model approximation" to determine EFG works quite well.Comment: 4 pages, 1 figure. Accepted in Physical Review

Thermal stability and diffusion in gadolinium silicate gate dielectric films

Gadolinium silicate films on Si(100) annealed in oxygen and vacuum at temperatures up to 800\u200a\ub0C were analyzed by Rutherford backscattering and narrow resonance nuclear profiling. Oxygen diffused into the film eliminating oxygen vacancies, but Si diffusion, previously observed in Al and Y oxides and in La and Zr silicate films, was absent. Higher-temperature annealing in oxygen resulted in the formation of an interfacial layer observable in high-resolution electron micrographs. Gd0.23Si0.14O0.63 films crystallize at temperatures between 1000 and 1050\u200a\ub0C. These observations combined with recent electrical measurements show that gadolinium silicate films may be a good candidate for the replacement of SiO2 in deep submicron metal\u2013oxide\u2013semiconductor gates.NRC publication: Ye

Thermochemical behavior of hydrogen in hafnium silicate films on Si

HfSiO films on Si were sequentially annealed in vacuum, oxygen, hydrogen, or deuterium atmospheres followed by quantification of H and D by nuclear reaction analysis. The observed H D incorporation and desorption behaviors are discussed in terms of two H bonding states in the films. Si–H bonds are easier to break thermally and formation of these bonds can be suppressed by annealing in O2 to fully oxidize Si atoms. O–H bonds are harder to break thermally. However, hydrogen atmospheres ease desorption of H in O–H species. The results indicate possible paths to achieve low H content in HfSiO gate dielectrics

Thermal growth of silicon oxynitride films on Si: A reaction-diffusion approach

We present some experimental results and propose a reaction-diffusion model to describe thermal growth of silicon oxynitride films on Si in NO and N2O, as well as annealing in NO of thermally grown silicon oxide films on Si. We obtain growth kinetics and N and O depth distributions for the different growth routes by changing only initial and boundary conditions of a set of nonlinear differential equations. The results suggest that the puzzling differences in film growth rate and N incorporation originate from dynamical effects, rather than in differences in chemical reactions

Structure and composition of amorphous Ge1−xSnxthin films

The composition and bonding configuration of amorphous germanium-tin (a-Gel 1--xSnx ) thin films are reported (O≤x < 0.3). Mössbauer spectroscopy analyses show that under the reported deposition conditions all tin atoms enter the a-Ge network in a perfect substitutional way, i.e., in a covalent tetrahedral configuration. The absence of defect structures in the tin sites is discussed and compared with results on films prepared under different conditions

The influence of tin implantation on the oxidation of iron

The high-temperature oxidation of metallic iron implanted with Sn ions at doses between 5 X 10 15 and 5 X 10 16 Sn ions cm-² is studied in the temperature range from 300 to 500 °c. Ion implantation of Sn reduces the oxidation rate constant of iron up to a factor of 10 at all experimental temperatures. The mechanisms that underlie this process are investigated using physical techniques such as Rutherford backscattering of 4He particles, conversion electron Mössbauer scattering of 57Fe and 119Sn and scanning electron microscopy to analyze the surface of the implanted and oxidized samples. The FeSn2 intermetallic phase was formed in the sample implanted at room temperature. This compound is partially decomposed to the FeSn intermetallic and free Sn in solution in iron when the implanted sample is oxidized at 500 °C. Ion implantation produces a surface composition very similar to that obtained with the more conventional methods oftinplating. The observed inhibition of the corrosion is discussed on the basis of this similarity