Phase transitions in epitaxial Ba0.5Sr0.5TiO3 thin films

Ba0.5Sr0.5TiO3 (BST) thin-film capacitor structures with various thicknesses, (50-1200 nm) and different strain conditions (on lanthanum strontium cobalt oxide La0.5Sr0.5CoO3 and strontium ruthenate SrRuO3 buffer layers) were made using pulsed laser deposition, and characterized by x-ray diffraction. The out-of-plane lattice parameter was followed as a function of temperature within the 100-300 K temperature interval. The phase sequence (cubic-tetragonal-orthorhombic-rhombohedral) known to exist in the bulk analog is shown to be strongly affected by both the stress conditions imposed by the buffer layer and the thickness of the BST film itself. Thus, no phase transition was found for the in-plane compressed BST films. On the stress-free BST films, on the contrary, more phase transitions were observed. It appeared that the complexity of structural phase transitions increased as the film thickness in this system was reduced.

A Blueprint for Democratic Policing Anywhere in the World? Police Reform, Political Transition and Conflict Resolution in Northern Ireland

This article provides an overview of the police reform process undertaken in Northern Ireland since 1999 as part of a broader program of conflict resolution. It considers the recommendations of the Independent Commission on Policing (ICP), which proposed a number of changes to policing structures and arrangements in Northern Ireland, and it assesses the degree to which these have been operationalized in the 8 years since the ICP published its report. It suggests that although the police reform process in Northern Ireland has been moderately successful and provides a number of international best practice lessons, the overall pace of change has been hindered by difficulties of implementation and, more fundamentally, by developments in the political sphere and civil society.