Near-surface compositional oscillations of Co diffused into Si(100) at -60 °C: a study by high-resolution Rutherford backscattering

Abstract

Highly resolved Co depth profiles have been obtained during the initial stages of Co growth on Si(100) at low temperature (−60 • C) by in situ high-resolution Rutherford backscattering spectrometry. We found extensive Co in-diffusion in the submonolayer growth regime even at this low temperature, besides Co on top of the Si surface. The amount of diffused-in Co is larger than the amount of Co at the Si surface. Every second Si layer is depleted of Co, starting at the Si surface, thus giving rise to compositional oscillations of Co in the Si(100) lattice. At this low temperature the growth of metallic Co on the Si surface is observed at 0.1 ML of deposited Co, which continues for higher coverages. At much higher coverage (5.93 ML of Co) almost exclusively low Co content silicides are formed at the Co/Si interface. The data presented here are compared with previous room temperature deposition data and are different in several aspects.PACS 68.55.ag; 82.80.Yc

Initial stages of growth of iron on silicon for spin injection through Schottky barrier

“…This is similar to results on the diffusion microstructure of Ni in Si (100) and the distribution of metal atoms in metal alloys like Cu 3 Au close to the surface 21, 22. A similar behavior is also found for the deposition of Co on Si (100) at very initial stages at room temperature and even more pronouncedly at −60 °C 23, 24. In these systems such a configuration is stabilized by the minimization of the Gibbs free energy, consisting of atomic binding, strain, and surface energies, and the entropy of mixing.…”

Improvement of interface structure and magnetic properties of Co on Si (100) by surfactant (Sb) mediated growth

“…2b). We want to note that this amount of 4.7 ML of Co in silicide phases at the interface is also lower than the amount of Co in silicide phases (4.93 ML) when Co is deposited on Si at −60°C [21].…”

Tunnel Contacts for Spin Injection into Silicon: The Si-Co Interface with and without a MgO Tunnel Barrier—A Study by High-Resolution Rutherford Backscattering

“…For higher coverage various silicide phases start to grow at the surface, but no pure Co film, even at the highest coverage (2.93 ML of Co) is investigated in this study. In order to reduce the in-diffusion of Co and the outdiffusion of Si and to enhance the growth of layers of pure Co two ways were followed in two subsequent investigations: (a) Co deposition was done while keeping the substrate at lower temperature, -60 • C [17]; (b) a thin layer of surfactant (1 ML of Sb) was used to reduce the amount of out-diffusion of Si to the surface during Co deposition [18]. Both techniques were helpful to reduce the silicide formation to some extent but could not stop it in total.…”

“…In this way they give information about the sharpness of the interface and the homogeneity of the Co and MgO thin films and allow in particular identifying various types of cobalt silicides as a function of depth. The data on the Co-Si Schottky interface have been published before in three publications [16][17][18] and are here summarized in a comparative way. The data on the MgO tunnel barrier are new.…”

“…Introduction. As evident, for example, from the results presented in Section 2, Co-Si (100) interfaces are in no way sharp with an abrupt transition between Co and Si but show diffusion of Co and Si with spontaneous silicide formation at the interface at room temperature[16,20] and even below room temperature[17]. This structural disorder at the interface would drastically reduce the spin-polarizationAdvances in Materials Science and Engineering 7 Co and Si (and Sb) concentrations as derived by RUMP simulations from the HRBS data of Figures 3 and 4.…”