Student bursaries—XII international vacuum congress

Vacuum News is a mine of information on the construction and handling of capillary and needle sources in which molten metal, such as gallium, gold, uranium etc. has to be persuaded to flow smoothly through a capillary or over the surface of a needle; a locally applied electric field literally pulls the molten metal out in the form of a Taylor cone, from whose tip, of only a few nanometres in radius of curvature, a stream of ions is emitted by field evaporation. The brightness (current density per steradian) of this source is, in principle and to a large extent in practice, orders of magnitude higher than that of a Duoplasmatron source, the previous work-horse in the field. This may be judged, for example, by the considerably larger current that can now be focused into a 20 nanometre spot in state-of-the-art scanning ion microscopes. Other parts of the book deal with the electrical characteristics of LMIS and the energy distributions of the emitted particles, not all of which are, in fact, charged. Intense ion beams, of course, give rise to strong mutual Coulomb interaction, resulting in large energy spreads, typically 10 eV or more, compared with 1 eV with field emission electron sources. Moreover, these Coulomb effects cause defocusing of the beam and additional aberrations; these can now be calculated by Monte Carlo methods and relevant computer programs have recently become available. Unfortunately, the high aberration electrostatic lens rather than the low aberration magnetic lens must be used with ions, because of their larger masses compared with those of electrons. Another section of the book deals with LMIS columns which serve as ion beam microscopes and secondary ion microanalysers (SIMS), mask repair instruments and ion microbeam lithography columns, particularly for

writing specialized parts of the circuit calling for higher definition than can be achieved with electrons. This must be traded off against the fact that ion beam lithography is a relatively slow process. Finally an overview is given of the role of LMIS in materials science. Copious references are supplied at the end of each chapter, so the book is a most useful stepping stone to a deeper study of the world literature for those who want to go more deeply into the subject. The weakest chapter is probably the one dealing with the focusing of ion beams from LMIS. The authors adopt an empirical approach, but this is understandable as the present theories do not adequately explain the fundamental ion optical characteristics of the liquid metal source itself or the effect of Coulomb interactions within the beam. The experimental evidence presented suggests that the basic source size is not too different from that of field emission electron guns, around a few nanometres in diameter. However, it has not yet been possible to image such a source directly in an ion microscope to determine its actual size and hence the true ion-optical brightness of the source. One reason for this could be that the source is in fact subject to high frequency transverse oscillations; these would smear out the source and prevent its full potential being realized. These are tasks for the future. This is a stimulating and informative book. It can be recommended to all who already know about LMIS or wish to familiarize themselves with this intriguing subject. Professor T Mulvey Aston University

Announcements, prizes and awards The Max Auwiirter Stiftung

Student Bursaries-XII

The Max Auwarter Stiftung in Balzers, Liechtenstein, offers every two years the Max Auwlrter-preis to a promising student or young university scientist working in the fields of surface science, vacuum science techniques or inorganic and organic thin films, who has published an outstanding work in the respective field either in German or English.

The British Vacuum Council will provide Bursaries (up to f250.00) for postgraduate students (in the UK and Republic of Ireland only) attending the XII International Vacuum Congress to be held in The Hague, The Netherlands, 12-l 6 October 1992.

Further information from

:

Michael J Higatsberger lnstitut fur Experimentalphysik der Universitat Wien Boltzmaangasse 5 A-l 090 Wien Austria Tel 0222 34 52 32 Fax 0222 316 26 83

international Vacuum Congress

Application must be made on the appropriate form which can be obtained from the Secretary at the address given below. The deadline for receipt of completed application forms is 1 May 1992. Preference will be given to those presenting papers at the congress. The Secretary The British Vacuum Council 47 Belgrave Square London SW1 X 8QX Tel 071 235 6111

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