A state-of-the-art optical floating-zone furnace for crystal growth at high pressures

We are surrounded by man-made objects that perform a function for us - cell phones, computers, robots, cars, domestic appliances and so on, to name but a few. These devices are packed full of electronic, magnetic or optical components whose operation depends on the special properties of the constituent materials. For example, many of the electronic devices we use contain very highly purified silicon in single crystal form whose semiconductor characteristics makes it suitable to support integrated circuits.

More generally, new technologies depend on the development of materials which can perform different functions for us. The process which leads to new and better materials for applications is one of discovery, understanding, modelling and optimization. A key early step in this journey is the preparation of the material in single crystal form. Single crystals are a form of matter with a high degree of perfection at the atomic level, and are essential for the fundamental research that determines how materials behave under different conditions, and why. It is therefore important for the science and technology of materials that techniques exist to prepare single crystals.

This proposal seeks funding to install and operate a piece of equipment to prepare crystals called an optical floating-zone furnace. This type of furnace uses light as a heat source and mirrors to focus the light energy onto a bar of material in order to melt it. By slowing scanning the molten ("floating") zone along the bar one can grow a crystal as the liquid solidifies. The type of furnace we request is a new design of optical floating-zone furnace which allows the growth process to take place in a high pressure (up to 300 times atmospheric pressure) mixture of oxygen and argon gas. The use of a high gas pressure makes it possible to grow crystals of certain materials which cannot be grown under normal conditions.

The equipment we are requesting will be the first of its type in the UK, and will be used to grow a broad range of materials, ranging from metal oxides that exhibit desirable magnetic, electronic and superconducting properties, through systems with novel quantum phases to materials that offer considerable promise for use in energy, optoelectronic and information storage applications. Once installed and commissioned, we will operate a programme of crystal growth with the new equipment to provide samples which will ensure the success of quantum and functional materials research in Oxford and other UK universities, and at the national research facilities such as the Diamond Light Source and ISIS Facility on the Harwell campus.

Beyond the academic community, the research enabled by the equipment will have an impact on:

1) Existing and future industries, particularly those that exploit emerging functional materials, such as magnetic, spintronic, optical and superconducting materials. For example, we shall prepare and study materials with (i) metal-to-insulator transitions, which are used in fast-switching electronics, (ii) high temperature superconductors, used in medical imaging, transportation, and electrical power applications, (iii) correlated thermoelectrics and battery materials, important for energy efficiency and storage, (iv) magnetoelectric materials (hexaferrites, chromium oxide), for switching and sensor devices, (v) dielectric materials for optoelectronic applications. Oxides, which form the primary class of materials we shall prepare, are particularly attractive for applications because of their chemical stability under typical device operating conditions.

2) Intellectual culture in society. The general public is fascinated by science, especially younger members of society, as can be seen from the popularity of science communicators such as Jim Al-Khalili, Brian Cox and others. Effective communication of research is important for inspiring the next generation of scientists, and also for educating the wider public about the benefits and risks associated with science and technology, for example in the process of climate change. In addition to conventional academic dissemination routes we are committed to a wider spectrum of public awareness and outreach activities through our institutions which provide a vehicle to communicate to the public any important new discoveries arising from the research enabled by the equipment.

3) The national condensed matter facilities, such as the Diamond Light Source, the ISIS Neutron and Muon Facility, the European Synchrotron Radiation Facility, and the Institut Laue-Langevin neutron source. These facilities are of strategic national importance as they provide tools and infrastructure for the whole academic and industrial community across all disciplines, from physics, chemistry and biology to materials science and engineering. The success of these facilities depends upon the quality of the science performed on the instruments, which in turn depends on the quality of the samples that the users are able to obtain for their measurements. The requested equipment will provide users of the facilities with a new source of single crystal samples that are not currently available in the UK, which will enable better exploitation of the facilities.