Research Interests

Overview of Past Research My principal research interests have focussed on an understanding of the fundamental properties of the family of 17 rare-earth metals. The rare-earth metals have many unusual and exotic physical, chemical, electronic and magnetic properties. It is the behaviour of the electrons that dictates most of these properties, and so there is a need to understand what the electrons are doing. There are two obstacles to achieving this goal; one experimental and one theoretical. Probing the behaviour of the electrons necessarily employs experimental techniques that are sensitive to any contamination at the surface of the sample being studied. The rare earths are very reactive, and so preparing and maintaining a clean surface to study is a non-trivial task. Simulating theoretically the electron states in the rare earths is complicated by the coexistence of electrons that are localised to their parent atoms and electrons that wander freely through the metal. These factors combined to produce a situation where few theoretical models existed, and those that did were largely untested by experiment. This was the motivation for my undertaking an extensive series of synchrotron radiation photoemission experiments at Daresbury Laboratory in the late 1980s.

As well as the electrons in the rare earths, I have studied the geometric arrangement of the atoms at the surfaces of the metals using low-energy electron diffraction (LEED). In the course of these studies I discovered that the atoms at the surface of some of the rare-earth metals undergo a dramatic rearrangement, or reconstruction (Barrett 1991). Unlike the very shallow surface reconstructions observed on many other metals and semiconductors, this recrystallisation of rare-earth surfaces extends many atomic layers into the surface region, beyond the depth to which we can probe with conventional surface sensitive techniques. (This early work developed into a programme of structural studies of the surfaces of various elemental and compound surfaces.) In addition to LEED, structural information can be obtained from scanning tunnelling microscopy (STM). My research group published the first STM images of the surface of a bulk single-crystal rare-earth metal (Dhesi 1995).

My experience in researching in the field of rare-earth metal surfaces resulted in an invitation to write a book on The Structure of Rare-Earth Metal Surfaces, which was published by World Scientific in 2001. I co-authored the book with Sarnjeet Dhesi, previously a PhD student and then a postdoctoral research assistant in the Rare Earth Group at Liverpool. The contents pages and the first chapter of the book can be viewed as pdf files by clicking on the links below. For a copy of the book, click on the cover picture on the right.

Contents and Preface Chapter 1 Introduction to the Rare Earths

Image Analysis and Processing Software I have written software for the analysis and processing of images produced by scanning probe microscope (SPM) and scanning electron microscope (SEM) systems. This program is called Image SXM and is being used by university academics, research scientists and commercial organisations throughout the world. The current user base comprises users in ~ 2000 institutes in ~ 90 countries. A description of how public domain software can be customised for scanning microscopy and examples of some of the features of Image SXM are given in the article Software For Scanning Microscopy. I have found that Image SXM is an excellent platform on which to develop specialist image analysis solutions for the specific needs of users, including those who obtain images from light microscopes. MIASMA is the result of a number of these specialist applications having some common ground and so benefiting from being considered as part of a larger, overarching project. PrinCIPia is a customised version of Image SXM that handles the calculation, display, analysis and manipulation of images representing the crystallographic orientation of grains in rock samples imaged by a polarising microscope. It was developed in collaboration with Professor Renée Heilbronner at the University of Basel.

Collaborators, Past and Present

Dr Enitan Carrol, Institute of Child Health, UoL Professor Carlos de Carvalho, University of Vicosa, Brazil Professor Alister Craig, School of Tropical Medicine, UoL Dr Rod Dillon, School of Tropical Medicine, UoL Professor Peter Dowben, University of Nebraska, USA Professor Paul Durham, Daresbury Laboratory, UK Dr Duncan Fullerton, School of Tropical Medicine, UoL Dr Stephen Gordon, School of Tropical Medicine, UoL Professor Simon Harding, Ophthalmology Research Unit, UoL

Professor Renée Heilbronner, University of Basel, Switzerland Professor John Inglesfield, Cardiff University, UK Dr Fauzia Paize, Liverpool Women's Hospital Dr Richard Sarginson, Alder Hey Children's Hospital, Liverpool Dr Derek Sloan, Clinical Sciences, UoL Dr Walter Temmerman, Daresbury Laboratory, UK Professor Gerrit van der Laan, Daresbury Laboratory, UK Dr Yalin Zheng, Ophthalmology Research Unit, UoL

Steve Barrett    February 2018 S.D.Barrett@liv.ac.uk

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