Structural study of crystalline and amorphous phases of Si0.65Ge0.35B (x = 0, 0.01, 0.05, 0.10) alloy prepared by long-time mechanical alloying

The atomic structure and configuration of Si _0.65Ge _0.35B _x ( x = 0, 0.01, 0.05, 0.10) powders prepared by long-time mechanical alloying are analyzed by X-ray total scattering measurement and transmission electron microscopy. The results show that the powders contain a large amount of the amorphous phase and a small amount of the crystalline phase. The structural parameters, including the fractions of the amorphous and crystalline phases, are obtained by pair distribution function (PDF) analysis applied to crystalline materials. There is a crystal growth mechanism attributable to small amounts of boron added, as a significant increase in crystalline phase fraction is only observed at x = 0.01. The angle of Bragg peaks does not shift monotonically with increasing amount of boron added. Furthermore, the lattice parameter shortening predicted from the peak shift exceeds that derived from boron substitution. This suggests the existence of another mechanism for lattice parameter change with boron doping. Crystal PDF analysis with a four-phase model consisting of three crystalline phases and one amorphous phase shows a decrease in the lattice constant of a B-doped Si–Ge crystal with increasing x, suggesting B substitution. Although not clear from this study, it is possible that boron doping or long-time mechanical alloying may have led to the formation of pure Si or a high-Si-concentration Si–Ge crystalline phase.