International Journal of Electrical and Computer Engineering (IJECE) Vol. 7, No. 6, December 2017, pp. 2993~3001 ISSN: 2088-8708, DOI: 10.11591/ijece.v7i6.pp2993-3001  2993 Journal homepage: http://iaesjournal.com/online/index.php/IJECE STM Observation of the Si(111) - (7×7) Reconstructed Surface Modified by Excess Phosphorus Doping Hirulak D. Siriwardena 1 , Toru Yamashita 2 , Masaru Shimomura 3 1,3 Graduate School of Science and Technology, Shizuoka University, Japan 2,3 Graduate School of Integrated Science and Technology, Shizuoka University, Japan Article Info ABSTRACT Article history: Received Aug 23, 2017 Revised Nov 12, 2017 Accepted Nov 26, 2017 The electronic properties of semiconductor surfaces change readily upon changing the carrier densities by controlling the dopant concentration. Additionally, excess dopant atoms can exert electric field which would affect the molecular adsorption process and could be used to manipulate the dynamic movement of confined molecules. A mechanism can be developed to control the molecular dynamic movement on modified semiconductor surface by dopants thus changing the effect of the electric field on the active molecules. In this study, the Si(111) surface was doped with phosphorus excessively using thermal diffusion process. The surface was then reconstructed to the 7×7 configuration via heating under UHV conditions and then studied through STM and STS techniques. The protrusions due to surface and subsurface P atoms appear brighter due to the lone electron pair. The 7×7 reconstruction would be destabilized after a critical P substitution of Si-adatom concentration due to high surface strain result in P-terminated (6√3×6√3)R30º reconstruction. Keyword: Excess phosphorous doping Si(111)- (7×7) STM STS Copyright © 2017 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: Masaru Shimomura, Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Nakaku, Hamamatsu 432-8011, Japan. E-mail: shimomura.masaru@shizuoka.ac.jp 1. INTRODUCTION Dopant atoms are of extreme importance in semiconductor physics and applications since the dopant atoms determine the electronic properties [1]. The mostly affected electrical property component is the charge carrier concentration of the material. The electron and holes concentration of a semiconductor under thermal equilibrium is equal to each other. Introducing dopant atoms increase the conductivity of the substrate due to the increment in carrier concentrations. Very highly doped or degenerate semiconductor materials have conductivity property levels equivalent to metals and therefore show different properties when compared with typical semiconductors [2]. There are two basic methods which an impurity dopant atom may penetrate into a lattice. The dopant atom can substitute an atom of the host crystal which is known as the substitutional impurity. Otherwise, the dopant can remain in a position between the lattice site, which is known as the interstitial impurity. The best and well-recognized impurities are the atoms from group III and V of the periodic table for the group IV semiconductors. These atoms can enter the host lattice and can substitute by forming covalent bonds [3]. When phosphorus (P) atom enters the Si semiconductor, it occupied one of the lattice sites in the Si crystal. To form four stable bindings among the Si host atoms, P has to lose one electron, which is an element having five outer shell electrons, so four electrons can implement into the covalent structure. The impurity P atom becomes a positively charged ion after losing the election in the lattices and thus starts to exert a perturbing force on its nearby host atoms [2]. The perturbing potential acts similar to a Coulomb potential as a proton is placed at the impurity site.