We have investigated the effect of the saturation of surface dangling bonds of Si(lll) surfaces with atomic hydrogen upon Ag thin-film growth. By using time-of-flight-type low-energy ion-scatteringrecoil analysis techniques, we find that the growth mode of Ag thin films is drastically changed by the hydrogen termination of Si(l 1 0-7x7 surfaces and that the epitaxial growth of ^4-type Ag(l 11) films is promoted by the hydrogen atoms residing at the film/substrate interface. PACS numbers: 68.55Jk, 61.16.Fk, 85.40.Ls The growth of a metal thin film on a semiconductor substrate has attracted much attention from both fundamental scientific and practical viewpoints. A primary concern in obtaining good crystal growth is the growth mode or the crystallographic orientation of the film. There are three known modes of thin-film growth: 1 layer-by-layer growth [Frank-Van der Merwe (FM) mode], island growth [Volmer-Weber (VW) mode], and layer-plus-island growth [Stranski-Krastanov (SK) mode]. Which growth mode will be adopted in a given system will depend upon the surface free-energy terms and on the lattice mismatch. Modification of the substrate surface by the introduction of a foreign atomic layer that alters the surface free energy can change the growth mode of a film. Copel et al. 2 have proposed the use of a segregating As monolayer in the heteroepitaxial layer-by-layer growth of Si/Ge/Si(100). In the present paper, we will demonstrate growth-mode control of Ag thin films on Si(ll 0-7x7 surfaces by hydrogen termination of the Si substrate prior to the film growth. In comparison with the clean surface, the hydrogenterminated surface reveals a different "substrate surface energy," and hence a different contact angle between the deposit and substrate, leading to the modification of the growth mode. Thus, hydrogen-terminated Si surfaces, which have been reported 3 ' 4 to not only have a very low defect density but also be stable even in air, have been found here for the first time to also alter the growth process of metal thin films drastically.The system of Ag thin films grown on a clean Si(l 1 0-7x7 substrate is one of the most thoroughly studied systems so far. 5 It is widely accepted that at room temperature (RT) the growth proceeds basically in a layer-bylayer fashion (FM mode) and that at high temperature, beyond about 200 °C, the growth process turns to a SK mode with 3D island formation after completion of a 2D overlayer which displays a y/3x^/3-R30° periodicity. In this paper, on the basis of impact-collision ion-scattering spectroscopy (ICISS) with time-of-flight (TOF) detection, we report that (1) the above-described growth mode can be drastically changed by the atomic hydrogen termination of the Si substrate and (2) the epitaxial growth of single-domain Ag(lll) planes is significantly promoted by the hydrogen termination. We call these phenomena hydrogen-mediated epitaxy (HME).In usual ICISS, 6 ions scattered into the direction of the scattering angle range of 140°-170° are analyzed by electrostatic analyzer...

Inflation symmetry is one of the peculiar features of the diffraction pattern of a quasicrystal. However, it is not an exclusive property of quasicrystalline structures and it may be present in incommensurately modulated structures, as shown recently in the Al-Mg system (Donnadieu P et al 1996 J. Physique I 6 1153-64). The conditions that a single modulation parameter of an incommensurate structure must fulfil in order to have inflation symmetry are determined. Although the number of possible distinct inflation-symmetric quasilattices is infinite, from physical/experimental arguments it can be concluded that, in practice, only a few of them can be experimentally observed, the reported phase of the Al-Mg system being one of these particular cases. A quantitative criterion to classify the modulation parameters that give rise to quasilattices with observable inflation symmetry is proposed. The generalization of the analysis of incommensurate structures with more than one single modulation parameter is also discussed. Finally, the inflation parameters of diffraction patterns with rotational point groups of finite order, C N , are compared with the parameters of the one-dimensional case.

No abstract

No abstract

Effects of excess oxygen introduced during sputter deposition on carrier mobility in as-deposited and postannealed indium-tin-oxide films