Surface-interface exploration of Mg deposited on Si(100) and oxidation effect on interfacial layer

Abstract

International audienceUsing scanning tunneling microscopy and spectroscopy, Auger electron spectroscopy, and low energy electron diffraction, we have studied the growth of Mg deposited on Si(100)-(2 x 1). Coverage from 0.05 monolayer (ML) to 3 ML was investigated at room temperature. The growth mode of the magnesium is a two steps process. At very low coverage, there is formation of an amorphous ultrathin silicide layer with a band gap of 0.74 eV, followed by a layer-by-layer growth of Mg on top of this silicide layer. Topographic images reveal that each metallic Mg layer is formed by 2D islands coalescence process on top of the silicide interfacial layer. During oxidation of the Mg monolayer, the interfacial silicide layer acts as diffusion barrier for the oxygen atoms with a decomposition of the silicide film to a magnesium oxide as function of O2 exposure

Growth, stability and decomposition of Mg2Si ultra-thin films on Si (100)

“…It has been stated as corresponding to Mg atoms in a Mg2Si binding environment [18] and reveals the formation of a Mg2Si silicide thin film with high chemical purity. Note that an accurate calibration of the Mg deposition was stated by AES and STM in a previous work, together with a Frank van der Merwe growth mode for Mg on Si(100) at RT [1]. One can firstly observe for each AES plot that the silicon Auger peak exhibits stronger intensity after silicide film formation, while it is slightly, partially or almost completely attenuated as a result of Mg deposition at RT in Figs.…”

“…magnesium silicide formation. As previously shown in the early stages of deposition at RT, magnesium reacts to form a selflimited ultra-thin layer of Mg2Si on Si(100) up to 0.25 Mg deposited ML [1]. Upon further deposition, this silicide behaves as a reaction barrier preventing the reactants from coming into contact, so that Mg metal starts growing on top of the interfacial silicide [19].…”

“…The Mg2Si thin films were then obtained by silicidation, through a solid-phase reaction between Mg and Si that was thermally enhanced under UHV by annealing the samples at 200°C for a few minutes. Note that the magnesium deposition rate was defined using coupled AES and STM calibrations stated in a previous work [1]. The AES plots were obtained in the derivative mode by monitoring the Auger intensities or peak-to-peak intensities of the following lowenergy transitions: Si(LMM)_92eV, O(KLL)_511eV, Mg(LVV)_45eV, oxidized Mg(LVV)_35eV and silicide Mg(LVV)_43.5eV [17].…”

“…Addressing the challenge of metal silicides integration into micro and nanoelectronics devices overlaps with several important and pressing requirements relying on exquisite control of their synthesis process. Therefore, epitaxial growth of metal silicides [1] has been extensively studied over the past few years, the main goals being to reach low contact resistances, a high thermal stability and a thickness control for films at a nanometric scale [2][3][4][5][6][7]. Magnesium silicide thin films, among others, have attracted much interest as promising indirect-gap semiconductors to be used in various electronic, mechanical and infrared optoelectronics applications.…”

“…In a previous work, our group has studied the spontaneous and self-limited formation of an ultra-thin Mg2Si layer (70 pm thick) in the early stages of Mg deposition (0.25 ML) on Ag(111) [15] and Si(100) at RT [1]. Used as a growth template for MgO atomic films, we have then reported the RT crystallization of this interfacial Mg2Si driven by its partial decomposition under oxygen exposure [16].…”