Structure and electronic properties of ionic nano-layers MBE-grown on III±V semiconductors M. Szymonski a, b, * , P. Korecki b , J. Kolodziej a , P. Czuba a , P. Piatkowski a a Institute of Physics, Jagiellonian University, Reymonta 4,30-059 Krakow, Poland b Regional Laboratory for Physicochemical Analyses and Structural Research, Jagiellonian University, Krakow, Poland Abstract Thin epitaxial NaCl and KBr layers of various thickness (from 3 to 100 monolayers) have been deposited on (100) surfaces of GaAs and InSb semiconductors by means of molecular beam epitaxy (MBE). Electronic and structural properties of the freshly prepared ®lms were subsequently investigated in the attached UHV analytical chamber by means of low energy electron diffraction, low electron energy loss spectroscopy, Auger electron spectroscopy and an electron holography. Alkali halide growth mode was found to be a two-dimensional layer-by-layer type (Franck van der Merve growth mode). It was possible to demonstrate that the ®rst monolayer of alkali halide on the A III B V semiconductor is arranged by the strong bond formed between the halogen ion and the A III metallic element. In case of NaCl/GaAs(100) system a local atomic con®guration was found for an early stage of epitaxy (three to ®ve monolayers) by means of the electron holography. A detailed analysis of the reconstructed diffraction patterns revealed that an initial formation of the Cl-Ga bond occurred in the system, and after deposition of ®ve monolayers NaCl, the substrate was uniformly covered by a layer at least three monolayers thick. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Semiconductor-insulator interface; Surface structure; Molecular beam epitaxy; III±V semiconductor compounds; Electron holography; Low energy electron diffraction 1. Introduction The growing interest in investigation of mezoscopic systems is caused by remarkable electronic, optical, and magnetic properties of such systems which are much differ- ent from those of macroscopic ones. Moreover, the possi- bility of modi®cation of those properties by varying their size, and/or limiting their dimensions to two-, one-, and even quasi-zero-dimension system causes that such systems could have broad applications in micro- and opto-electronics. One can produce nanostructures and control their unique properties simply by proper choice of their size [1]. One of the numerous methods in device fabrication for electronics is the deposition of thin insulat- ing layers on semiconductor substrate by means of chemi- cal vapour deposition (CVD) or molecular beam epitaxy (MBE). Recent developments in semiconductor-on-insula- tor (SOI) technology require the fundamental understand- ing of the electronic properties of these interfaces [2]. Early work has focused on the alkaline earth-¯uoride compounds because of their cubic structure, the good lattice match between the ¯uorides and several semicon- ductors, and the ease of evaporating stoichiometric ¯uoride ®lm. The CaF 2 /Si system has provided the most impressive demonstration of epitaxial growth in these systems [3,4]. This has been attributed to the small lattice mismatch (less than 1%) between the substrate and the overlayer. Later it has been found that thin epitaxial layers of several alkali halides could be successfully grown on single crystal semi- conductors such as Si, Ge, and GaAs. Alkali halides as overlayers on semiconductors probably would not be considered for the immediate technological applications, but they seem to be ideally suited for investigations of several aspects of fundamental interest, such as insulator- semiconductor interface formation, ionic compound deposition and epitaxial growth, alkali metal or halogen adsorption, thickness dependent preferential desorption and metallization processes in ionic epitaxial layers. In this review we report on experimental procedures for growth and characterisation of thin epitaxial layers of NaCl and KBr MBE-deposited on (100) surface of GaAs and InSb semiconductors, respectively. Thin Solid Films 367 (2000) 134±141 0040-6090/00/$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S0040-6090(00)00663-5 www.elsevier.com/locate/tsf * Corresponding author. Tel.: 148-12-632-4888 (5560), fax: 148-12- 633-7086. E-mail address: szymon@castor.if.uj.edu.pl (M. Szymonski)