Mesoscopic scanning tunneling and atomic force microscopy study of the misfit-layer compounds (LaSe)(x)NbSe2 and (PbSe)(x)NbSe2

The surface of the misfit-layer compounds (LaSe)(x)NbSe2 and (PbSe)(x)NbSe2 is studied by means of scanning tunneling microscopy (STM) and atomic forc e microscopy (AFM), in air and nitrogen, in the range of 0.5 to 10 mu m(2). The cleaved surface of (LaSe)(x)NbSe2 presents flat non-stepped surfaces w hich crack and react. Inner layers do not appear to crack. The dynamic proc ess taking place in the superficial layers produces pieces which arrange in a self-similar way and eventually gives rise to discrete islands which sel f-organize periodically in one direction. On the other hand, the cleaved su rface of (PbSe)(x)NbSe2 is stepped and shows no reactivity. The influence o f the cleavage, the strain, the strength of the interlayer and intralayer b onding, and the misfit of the compounds are discussed as reasons for the me soscopic behaviour of these materials, (C) 1999 Elsevier Science B.V. All r ights reserved.