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.
The results from this pioneering work in one of the most substantial uncharted areas of solid state physics were compared to theoretical simulations carried out by my research group and collaborators at Daresbury Laboratory in an effort to establish whether the existing models describing the electronic structure of the rare earths were valid. The research of these early years was described in my review article on the surfaces of the rare-earth metals (Barrett 1992). Over the period 1988-1998 my research formed a part of the Interdisciplinary Research Centre (IRC) in Surface Science (now known as the Surface Science Research Centre).
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.
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
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,
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
Dr Enitan Carrol, Institute of Child
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