Surface science studies of metal hexaborides

• Published in: Science and technology of advanced materials Vol. 13; no. 2; p. 23002
• Main Author: Trenary, Michael
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 01.04.2012; Taylor & Francis Ltd; Taylor & Francis Group
• Subjects: Adsorbates; Electronic structure; Emitters; Emitters (electron); Evaporation rate; Lanthanum; Lanthanum hexaboride; Single crystals; Surface science studies; Thermionic emission; Topical Review; Ultrahigh vacuum; Work function measurements; Work functions; Lanthanum hexaboride; Thermionic emission; Surface science studies; Work function measurements
• ISSN: 1468-6996; 1878-5514
• DOI: 10.1088/1468-6996/13/2/023002

Over 30 years of surface science research on metal hexaborides are reviewed. Of this class of compounds, lanthanum hexaboride has been the subject of the majority of the studies because of its outstanding properties as a thermionic emitter. The use of LaB 6 cathodes as an electron source stems from the unusually low work function of ∼2.5 eV for the (100) surface combined with a low evaporation rate at high temperatures. Of particular interest has been the determination of the surface geometric and electronic structure responsible for the low work function and how the work function is affected by various adsorbates. The low-index faces of single crystals of LaB 6 and other hexaborides have been studied with a variety of ultrahigh vacuum surface science methods to gain a better understanding of the structure and properties of the clean surfaces as well as their interactions with gases such as O 2 , H 2 O and CO.