Hang Ji

Surface reconstruction and faceting of group IIIIV(113) systems — common characteristics of the stable surface structures

In the present paper we report on studies of the group IIIIV(113) systems of Al, Ga and In on Si(113) and Ge(113) with LEED and AES. LEED shows that after being annealed the surfaces of the AlSi, GaSi and InGe systems facet to (103), (013), (112) and (115) facets while those of the InSi, AlGe and GaGe systems reconstruct to (113)-(1 × 2). In the entire tested range of coverage and annealing temperature none of the six systems form (113)-(1 × 1). Combining this observation with the results of previous work on group IIIIV(001) and group IIIIV(111) we suggest that the common characteristics of all stable surface structures of the IIIIV systems are: (i) the group 13 atoms form sp2-like back bonds, and (ii) the surface contains some group IV atoms with a dangling bond. The former is an intrinsic requirement of group III atoms, while the latter facilitates relief of the strain induced by the former, and is thus probably more general.

Atomic structure of the Si(103)1 × 1-In surface

Abstract To test the model that was originally proposed for the Si(103)1 × 1-Al facets and was later on tested with STM to be correct for the Ge(103)1 × 1-In facets, in the present paper we have studied the Si(103)1 × 1-In surface by means of the QKLEED/CMTA technique. A unit cell of the model consists of an indium atom, which sits in an adatom position and forms three sp 2 -like bonds with bulk silicon atoms, and a surface silicon atom with a dangling bond. The model has passed the QKLEED/CMTA test and the best parameters of it have been obtained. It has been noticed in the experiment that the clean Si(103) surface has a surprisingly high thermal stability.

A comparative study of the thermal stability of the (103) surface of group-III-metal/group-IV-semiconductor systems

Abstract To investigate and understand the thermal stability of the (103) surface of the Al Si , Ga Si , In Si , Al Ge , Ga Ge , and In Ge systems, in the present article we study well-annealed surfaces of the systems as well as those of the Ga Si , Al Ge , and Ga Ge (001) systems by means of LEED and AES. The results show that the (103) surfaces of the Al Ge and Ga Ge systems are unstable while those of the other four III IV (103) systems are very stable. On the basis of the atomic structure of the III IV (103) 1 × 1 surface and the covalent bond length of the involved elements, we suggest that this is because group-III atoms would induce significant tensile stresses to the surface of the Al Ge and Ga Ge systems, while tensile stresses around group-III atoms are not favored by the III IV systems.

{310} faceting of the Ge(001) 2 × 1 surface induced by indium

Abstract In the present paper, by means of scanning tunneling microscopy, low-energy electron diffraction, and Auger electron spectroscopy, we have found and studied the {310} faceting induced by In on the Ge(001)2 × 1 surface. On the basis of the dual bias STM images a model, which contains one In atom and only one dangling bond in a unit cell, has been proposed for the atomic structure of the {310} facets. We suppose that the faceting process proceeds through expansion of many mini-{310}-facets in the cost of the original (001) surface, instead of via any other transient surface structures.

Effect of the convergence of Cu cap on the structure of Co/Cu(111) film

Annealing Cu(111) covered with more than 10 ML Co film results in substrate Cu atoms diffusing through the Co film, and forming a Cu overlayer capping the Co him. Through AES and LEED experiments and QKLEED calculation, we found that the coverage of the Cu cap has an important effect on the top layers of the Co film. When the coverage of the Cu cap is less than 0.7 ML, the stacking sequence of the top layers is hcp, the same as that of Co film. When the coverage of the Cu cap is more than 1 ML, the top layers become fee and present twinned fee because of stacking on hcp Co him. This tends to explain the results of Co/Cu(111) superlattice studies in which Co show a fee stacking sequence

Surface reconstructions and faceting of the GaGe(113) system

Abstract Surfaces of the Ga Ge (113) system have been studied by means of low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). It has been found that the only two reconstructions of the system, i.e., ( 8 −1 5 1 ) and “1 × 2”, consist of the same (1 × 2)-like building blocks and, hence have only slightly different coverages. Coexisting with the reconstructions are small (112) and (115) facets, which develop through bunching of steps. On the basis of LEED patterns and STM images and under the guidance of the common characteristics of surface structures of III IV systems, structural models have been proposed for these reconstructions and the (112) facets for further investigation. It has been noticed that only small percentages of a monolayer of Ga can make the Ge(113) surface entirely 3 × 1; otherwise it contains a great many small 3 × 2 patches scattered inside large 3 × 1 domains.

Atomic Structure of the Domain Walls of the Discommensurate Phases in Ge(111)/Ga

We have studied the γ and β discommensurate phases of the Ge(111)/Ga system with scanning tunneling microscopy (STM). On the basis of the features of these phases known from our STM images as well as from previous papers, models of domain-wall structure of both phases have been proposed for further investigations.