Browsing by Author "Michalak, D. J."
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Item Cobalt and Iron Segregation and Nitride Formation from Nitrogen Plasma Treatment of CoFeB Surfaces(American Institute of Physics Inc) Mattson, Eric C.; Michalak, D. J.; Veyan, Jean Francois; Chabal, Yves J.; 0000-0002-3743-5521 (Veyan, JF); 0000-0002-6435-0347 (Chabal, YJ); Mattson, Eric C.; Veyan, Jean Francois; Chabal, Yves J.Cobalt-iron-boron (CoFeB) thin films are the industry standard for ferromagnetic layers in magnetic tunnel junction devices and are closely related to the relevant surfaces of CoFe-based catalysts. Identifying and understanding the composition of their surfaces under relevant processing conditions is therefore critical. Here we report fundamental studies on the interaction of nitrogen plasma with CoFeB surfaces using infrared spectroscopy, x-ray photoemission spectroscopy, and low energy ion scattering. We find that, upon exposure to nitrogen plasma, clean CoFeB surfaces spontaneously reorganize to form an overlayer comprised of Fe2N3 and BN, with the Co atoms moved well below the surface through a chemically driven process. Subsequent annealing to 400 °C removes nitrogen, resulting in a Fe-rich termination of the surface region. © 2016 Author(s).Item Morphology and Chemical Termination of HF-Etched Si₃N₄ Surfaces(American Institute of Physics Inc.) Liu, Li-Hong; Debenedetti, William J. I.; Peixoto, Tatiana; Gokalp, Sumeyra; Shafiq, Natis; Veyan, Jean-François; Michalak, D. J.; Hourani, R.; Chabal, Yves J.Several reports on the chemical termination of silicon nitride films after HF etching, an important process in the microelectronics industry, are inconsistent claiming N-Hx, Si-H, or fluorine termination. An investigation combining infrared and x-ray photoelectron spectroscopies with atomic force and scanning electron microscopy imaging reveals that under some processing conditions, salt microcrystals are formed and stabilized on the surface, resulting from products of Si₃N₄ etching. Rinsing in deionized water immediately after HF etching for at least 30s avoids such deposition and yields a smooth surface without evidence of Si-H termination. Instead, fluorine and oxygen are found to terminate a sizeable fraction of the surface in the form of Si-F and possibly Si-OH bonds. The fluorine termination is remarkably stable in air and water vapor in ambient conditions, with clear implications on further surface chemical functionalization.