In adsorption on Si(112) and its impact on Ge growth M. Speckmann Th. Schmidt J. I. Flege J. Falta The change of the Si(112) surface morphology and structure induced by In adsorption, as well as the impact of In preadsorption on the growth kinetics and island morphology in Ge/Si(112) epitaxy, has been investigated by means of low-energy electron microscopy and diffraction. The intrinsically faceted Si(112) surface is smoothed upon In saturation. In contrast to a previously reported (7  1) reconstruction (reported in a recent work of Gai et al.), we observe a ½ð3 þ xÞ 1 superstructure, with x  1=2. This is attributed to the coexistence of (3  1) and (4  1) building blocks with In vacancies. The presence of such vacancy rows is confirmed by the saturation of the ½ð3 þ xÞ 1 structure at about 0.8 monolayers. Ge growth on In-saturated Si(112) leads to the formation of 3-D islands, the morphology of which depends on the growth temperature. At 450  C, isotropic and dashlike islands are observed, whereas at 500  C, larger islands with a triangular outline are found. The orientation of the side facets of these triangular islands have been identified to be (111), (013), and (103). The dependence of the island density on the growth temperature indicates an enhanced Ge surface diffusion, as compared with growth on bare Si(112). Introduction The adsorption of group-III metals on Si and Ge surfaces has been intensively studied for (001) and (111) surfaces. The technological potential for this class of material systems is mainly based on the surface passivation that is achieved by the adsorption of the trivalent metals on the group-IV semiconductors. Such a passivation can play an important role in surface functionalization, for example, for inorganic/organic material interfaces, where the interaction between the inorganic substrate and organic adlayers is modified by the group-III substrate termination. Another field of application is Ge/Si heteroepitaxy, where the growth mode has been shown to be drastically influenced if the surface is passivated prior to growth [1–9]. As Ge/Si growth is usually performed at elevated temperatures that provide sufficient activation energy for site-exchange processes [10], and since it is energetically favorable to keep the surface passivated, the group-III metals will, in general, segregate to the surface during Ge/Si growth [5, 11]. In contrast to low-index surfaces like Si(111) and Si(001), vicinal surface orientations like Si(112) or Si(113) provide less symmetry, which can be exploited for the growth of anisotropic nanostructures such as quantum wires. For instance, Ge nanowires can be grown on bare Si(113) in a narrow temperature window [12, 13]. In the case of Ga preadsorption on Si(113), the surface is completely decomposed into (112) and (115) facets, which can be employed to increase the density and to change the orientation of the Ge wires [14]. Hence, for a better understanding of the influence of metal preadsorption on subsequent Ge growth, the investigation of the adsorbate-induced change in substrate surface reconstruction and morphology is an important issue [15, 16]. For indium on silicon, many studies can be found for (111) and (001) surface orientations. In the case of In/Si(112), the only report is by Gai et al. [17], who found that the intrinsically faceted [18, 19] Si(112) surface is smoothed upon In adsorption and exhibits a (7  1) reconstruction. In this paper, we revisit the In/Si(112) surface structure and show that the surface reconstruction does not have a (7  1) but rather a ½ð3 þ xÞ 1 periodicity, with x close to 1/2. The impact of group-III metals on Ge growth on Si(112) has been already studied for Ga. Ga adsorption also leads to smoothing of the Si(112) surface [20, 21], and a ½ð5 þ xÞ 1 reconstruction is found [22]. Subsequent Ge deposition on Ga-terminated Si(112) enables the growth ÓCopyright 2011 by International Business Machines Corporation. Copying in printed form for private use is permitted without payment of royalty provided that (1) each reproduction is done without alteration and (2) the Journal reference and IBM copyright notice are included on the first page. The title and abstract, but no other portions, of this paper may be copied by any means or distributed royalty free without further permission by computer-based and other information-service systems. Permission to republish any other portion of this paper must be obtained from the Editor. Digital Object Identifier: 10.1147/JRD.2011.2158763 M. SPECKMANN ET AL. 11: 1 IBM J. RES. & DEV. VOL. 55 NO. 4 PAPER 11 JULY/AUGUST 2011 0018-8646/11/$5.00 B 2011 IBM