Surface structure investigations using noncontact atomic force microscopy J.J. Kolodziej * , B. Such, M. Goryl, F. Krok, P. Piatkowski, M. Szymonski Research Centre for Nanometer-Scale Science and Advanced Materials (NANOSAM), Faculty of Physics, Astronomy and Computer Science, Jagiellonian University, ul. Reymonta 4, 30-059 Krako ´w, Poland Available online 9 May 2006 Abstract Surfaces of several A III B V compound semiconductors (InSb, GaAs, InP, InAs) of the (0 0 1) orientation have been studied with noncontact atomic force microscopy (NC-AFM). Obtained atomically resolved patterns have been compared with structural models available in the literature. It is shown that NC-AFM is an efficient tool for imaging complex surface structures in real space. It is also demonstrated that the recent structural models of III–V compound surfaces provide a sound base for interpretation of majority of features present in recorded patterns. However, there are also many new findings revealed by the NC-AFM method that is still new experimental technique in the context of surface structure determination. # 2006 Elsevier B.V. All rights reserved. PACS: 68.35.Bs; 68.37.Ps; 68.47.Fg Keywords: Surface structure; III–V semiconductors; Atomic force microscopy 1. Introduction Complex surface reconstructions occur on many semicon- ductor surfaces including A III B V compound (0 0 1) polar surfaces. Moreover, depending on the surface stoichiometry, many different reconstructions are possible on these surfaces. Solving of such complex surface structures is a very difficult task that often takes tens of years. For example, the c(8  2) GaAs(0 0 1) surface were first studied by Jona in 1965 [1] and by many authors since then [2–15] but its detailed structure is still not fully understood. Interestingly, while in the case of comparably complex and long studied (7  7) Si(1 1 1) surface, the quick success was enabled by the invention of a scanning–tunneling microscope (STM), the GaAs c(8  2) surface stood not resolved despite over 10 years of studies with the use of STM. This indicates that STM technique alone may be not sufficient for real-space imaging with atomic resolution and for testing of surface structural models. Today, many research and innovation activities aim at gaining control over processes at atomic scale, e.g. those concerning site sensitive chemical reactions, molecular self- assembly, nano-patterning, construction of ultrathin magnetic layers. Surface reconstruction is thus, in obvious way, becoming a major issue. Since the number of possible different surface structures is in principle indefinite (since they depend on crystal face, surface composition, adsorbates, and so on) efficient tools that could be used for fast determination/ verification of complex surface structures are necessary. Majority of known surface atomic structures have been derived with trial and error techniques, such as dynamic LEED [16,17]. However, direct methods combined with X-ray diffraction and theoretical ab initio studies are now becoming of increasing significance. Although the general impression may be different, very few structures have been derived basing solely on the STM technique, and probably none using the NC- AFM, as discussed by M.A van Hove in his ‘Comparison of different atomic-scale surface structure techniques’ [16]. In an experimental practice, STM is widely used for studying complex surface structures of alloys or compounds, but usually only the first hypothesis for the structure is suggested, far from being a proof. In contrast, as one may judge from the yearly NC-AFM Conference abstracts [18], NC-AFM is still tested as a new technique, on well known, surfaces such as: (7  7) Si(1 1 1), CaF 2 (1 1 0), MgO(0 0 1), InAs(1 1 0) and alkali www.elsevier.com/locate/apsusc Applied Surface Science 252 (2006) 7614–7623 * Corresponding author. Tel.: +48 12 6635541; fax: +48 12 6337086. E-mail address: jkolodz@if.uj.edu.pl (J.J. Kolodziej). 0169-4332/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2006.03.054