Sergio Pineda edited Alloying_can_be_complex_to__.tex  about 9 years ago

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Alloying can be complex to understand because at least three different elements are involved Au, As, Ga. Therefore a ternary phase diagram must once again be studied in order to decide temperatures that would allow for eutectic stable liquid (eutectic point is the lowest melting point achieved by a mixture of metals) or solid alloys. \cite{Joyce_2011}   Although VLS and MOVPE are techniques that have been commonly used for decades there is doubt about the mechanism of growth mentioned earlier. \cite{Persson_2004} \cite{Dick_2005} In particular a solid phase diffusion mechanism instead of liquid phase for GaAs nanowire growth has been proposed. \cite{Persson_2004} An experiment growing two types of GaAs nanowires, differing only in method growth termination, was conducted. Method one included switching off the Ga pressure while maintaining As pressure, and method two involved switching off the gas supply of both at the same time. X-ray energy dispersive spectrometry reveal the ratio of Ga and As in the nanowire body and seed particle, results conclude that the concentration of Ga for eutectic melt is never reached, suggesting a solid phase mechanism. \cite{Persson_2004} Another Gas Source Molecular Beam Epitaxy (GS-MBE) coupled with self assembled Au particles has been successfully used to grow GaAs nanowires.\cite{Plante_2006}. Briefly, GS-MBE works as follows...Samples are carfully prepared and so that a clean single crystal face is oriented towards the beam source. The beam source is placed at a sufficient distance t oalow uniform deposition onto the surface. Growth rates depend on the flux of gas usedand formation rate of clusters.\cite{9780199544219}  Axial and radial growth are the two directions of growth taking place during nanowire growth for MOVPE and VLS. Radial growth occurs when species are absorbed on the sidewalls of the nanowire. It is possible for these species to be further absorbed towards the Au catalyst causing the toe be incorporated into the axial growth.