ELSEVIER Surface Science 352-354 (1996) 383-386 surface science ~ ~ ~ ~ . ......... ~ i~ Reactive and unreactive interfaces studied by means of metastable deexcitation spectroscopy L. Pasquali ~'*, P. Fantini a, S. Nannarone a, M. Canepa h, L. Mattera b a INFM, unit?t di Modena and D ipartimento di Fisica, University di Modena, Via G. Campi 213 / a, 1-411O0 Modena, Italy b INFM, unit~ di Genova andDipartimento di Fisica, University di Genova, Via Dodecanneso 33, 1-16146 Genova, Italy Received 5 September 1995; acceptedfor publication31 October 1995 Abstract The present paper is devoted to the application of metastable deexcitation spectroscopy (MDS) for studying interface formation with reference to Yb/GaAs(ll0) and Sb/GaAs(110). These systems are prototypical examples of intermixed disordered and ordered interfaces. In the discussion, emphasis is given to the potentiality offered by MDS in interface formation studies. A comparison with photoemission is discussed. Keywords: Angle resolved photoemission;Antimony; Atom-solid scattering and diffraction- inelastic; Crystalline-amorphousinterfaces; Gallium arsenide; Metal-semiconductorinterfaces; Ytterbium 1. Introduction Thanks to its characteristics of extreme surface sensitivity, metastable deexcitation spectroscopy (MDS) has demonstrated during the years to be particularly suitable for studying the electronic struc- ture of low dimensional systems [1]. The technique is based on the use of neutral metastable atoms which undergo interatomic Auger type deexcitation in consequence of the overlap be- tween atom and surface wave functions [2]. Since the interaction involves the orbitals of the first atomic layer, and in particular the charge density which is oriented towards vacuum, MDS can perform surface * Corresponding author. Fax: +39 59 367488; e-mail: pasquali@imoax 1.unimo.it. valence band (VB) spectroscopy with extreme sur- face sensitivity. The present paper deals with the MDS study of the formation of Yb/GaAs(110) and Sb/GaAs(110) interfaces. The discussion is centered on the poten- tiality of the MDS technique in the investigation of the early stages of interface growth. In this respect, the two systems chosen were prototypical examples of disordered and ordered metal-semiconductor in- terfaces, respectively. The interface between Yb and GaAs(ll0) is formed upon the strong reaction between the rare- earth and the semiconductor giving rise to a non- crystalline inhomogeneous and intermixed layer [3]. Sb forms on GaAs(110) an epitaxial 1 × 1 over- layer which saturates the dangling bonds and repre- sents an ideal termination of the substrate lattice (atomic geometry and electronic structure) [4,5]. 0039-6028/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved SSDI 0039-6028(95)01165-X