Formation of antimony 1D-nanostructures on Si (5 5 12) surface
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Formation of antimony 1D-nanostructures on Si (5 5 12) surface S. M. Shivaprasad1, Mahesh Kumar1, Amish G. Joshi1, Vinod Kumar Paliwal1,2 1 Surface Physics & Nanostructures Group, National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi-110 012. 2 Department of Physics, Dyal Singh College, University of Delhi, Lodhi Road, New Delhi, 110003, India. ABSTRACT Of late, high index Si surfaces like, (5 5 12) are being explored for the formation of 1D nanostructures in the form of nanowires or chains. The surface topography of Si (5 5 12) presents an unique template for the growth of 1D nanostructures. In this paper we report the adsorption-desorption studies of Sb onto (2×1) reconstructed surface of Si (5 5 12). Motivated by our earlier studies of adsorption/desorption of Sb on low index surfaces (001) and (111), studying the interaction on high index surface like (5 5 12) is found to be interesting. The experiments have been performed in UHV with in-situ growth and probed by using AES, LEED and EELS techniques. The uptake curve shows initially a simultaneous multilayer growth of Sb up to 4 ML and then at 20 ML the entire Si surface is covered by Sb. The LEED patterns show a disorder during growth at RT above 1 ML. EELS studies at 250 eV, primary beam energy show that as the adsorption proceeds the features of bulk Sb start appearing above 4ML coverage. However, the bulk Sb features are not complete until a high enough coverage of Sb (~20ML) which suggests the existence of the primary rows up to a higher coverage. Annealing studies have also been performed on the RT adsorbed system, to study the residual thermal desorption characteristics. Annealing the system to about 7900C results in Si (337) facets at a low coverage of 0.2 ML. The anisotropy in the LEED spots suggests an ordered Sb adsorption along ( 1 10) and a local disorder in the (66 5 ) direction. Thus we provide evidence for the formation of a zig-zag 1D-nanowire of Sb grown on the (5 5 12). The new phase is also accompanied by forming a dangling bond state at 3 eV in EELS. INTRODUCTION
Silicon surfaces of different orientations have always been the center of interest to surface scientists because of their various surface reconstructions, induced by various kinetic and thermodynamic pathways. Vicinally cut low index surfaces like in case of Si (111) and Si (001) have been studied extensively in the formation of nano-sized structures which have potential applications as quantum lasers, delta-doped structures etc [1,2]. Oflate, interest has grown in forming 1-D structures on reconstructed surfaces that have natural channels like the Si (100)-(2x1) and the Si (5 5 12)-(2x1)[3-5]. Si (5 5 12) is an energetically stable high index surface with its plane oriented 30.5o away from the (001) towards the (111) plane and is composed of (111) like chains and (001) like tetramer rows [3,6]. The unit cell is one of the largest ever-observed (5.35 nm x 0.768 nm) where the primary rows divide the large unit cell into row like trenches of Si (337) and Si (225) su
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