Duncan Clifford Alan Smith

Hydrogen storage materials

Hydrogen storage materials including metal hydrides, carbon nanotubes, metal organic frameworks, and organic systems based on reversible hydrogenation–dehydrogenation cycles are compared in terms of the hydrogen storage capacity and the temperature required for storage and release of hydrogen.

High throughput methodology for synthesis, screening, and optimization of solid state Lithium ion electrolytes

A study of the lithium ion conductor Li(3x)La(2/3-x)TiO(3) solid solution and the surrounding composition space was carried out using a high throughput physical vapor deposition system. An optimum total ionic conductivity value of 5.45 × 10(-4) S cm(-1) was obtained for the composition Li(0.17)La(0.29)Ti(0.54) (Li(3x)La(2/3-x)TiO(3)x = 0.11). This optimum value was calculated using an artificial neural network model based on the empirical data. Due to the large scale of the data set produced and the complexity of synthesis, informatics tools were required to analyze the data. Partition analysis was carried out to determine the synthetic parameters of importance and their threshold values. Multivariate curve resolution and principal component analysis were applied to the diffraction data set. This analysis enabled the construction of phase distribution diagrams, illustrating both the phases obtained and the compositional zones in which they occur. The synthetic technique presented has significant advantages over other thin film and bulk methodologies, in terms of both the compositional range covered and the nature of the materials produced.

Novel metal gates for high κ applications

The development of gate systems suitable for high κ dielectrics is critical to the advancement of complementary metal-oxide-semiconductor (CMOS) devices. Both the effective work function and material stability are key parameters to these systems. A systematic study of metal gates of the composition HfxSi1-x (0.25 ≤ x ≤ 1) is demonstrated here, including XPS, XRD and four point probe measurements. The effective work function of each material is evaluated and it is shown that it can be tuned from 4.5 to less than 4.0 eV. Suitable work functions for n-channel metal-oxide-semiconductor applications (4.05 ± 0.2 eV) were achieved using hafnium rich compositions; however, XPS and diffraction measurements confirmed that these materials demonstrated a high propensity to oxidise, causing the reduction of the underlying oxides, making them unsuitable for commercial application.