Surface Science Letters Atomic-resolution images of radiation damage in KBr R. Bennewitz a, * , S. Sch ar a , V. Barwich a , O. Pfeier a , E. Meyer a , F. Krok b , B. Such c , J. Kolodzej c , M. Szymonski c a Department of Physics and Astronomy, Institute of Physics, University of Basel, Klingelbergstr. 82, CH-4056 Basel, Switzerland b Regional Laboratory of Physicochemical Analyses and Structural Research, Jagellonian University, Ingardena 3, 30-060 Krakow, Poland c Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Krakow, Poland Received 24 July 2000; accepted for publication 11 November 2000 Abstract The ®rst steps of electron irradiation induced modi®cation of a KBr10 0) surface have been studied by dynamic force microscopy with atomic resolution. Rectangular pits of monatomic depth with not more than one kink site per pit have been found. The atomic structure of KBr10 0) is preserved at the bottom of the pits. Possible deexcitation and desorption mechanisms are discussed based on these results. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Atomic force microscopy; Electron stimulated desorption ESD); Alkali halides; Surface defects The surface topography of alkali halide crystals that have been exposed to ionizing irradiation can exhibit structures, which re¯ect the high symmetry of the lattice structure [1±5]. The development of such structures may help to understand the un- derlying deexcitation and desorption processes, as it for example turns out that there is a close con- nection between surface topography and desorp- tion yield [6]. Furthermore, the radiation-induced structures form a high density of well-de®ned steps at the surface, which play an important role for the growth of overlayers. Well-de®ned defect struc- tures at surfaces of insulators on a nanometer scale would allow a controlled nucleation of metal clusters. With the development of dynamic force microscopy DFM), the study of surfaces of in- sulators became feasible even in atomic resolution [7,8]. In this paper, we report on a DFM study of electron-irradiated KBr100) surfaces, where im- ages of the ®rst steps of radiation damage in atomic resolution could be obtained. After a short introduction into the experimental procedures we present the results together with a discussion of the peculiarities of imaging small structures by DFM. In the ®nal discussion we compare the results to models of the desorption process. Single crystals of pure KBr were purchased from Kelpin, Neuhausen Germany). Two spring- like tungsten wires, which are pulled through two pits in the crystal, clamp it to a sample holder plate. Crystals cleaved in air were transferred to thevacuumchamberwithin30saftercleavage,and Surface Science 474 2001) L197±L202 www.elsevier.nl/locate/susc * Corresponding author. Tel.: +41-61-267-3725; fax: +41-61- 267-3784. E-mail address: roland.bennewitz@unibas.ch R. Benne- witz). 0039-6028/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0039-602800)01053-0