Epitaxial Cu-Sn bulk crystals grown by electric current

Epitaxial Cu₃Sn and Cu₆Sn₅ grown by liquid-phase electroepitaxy (LPEE) have been demonstrated in this work. X-ray diffraction analysis reveals that LPEE-grown Cu₃Sn and Cu ₆Sn₅ grew in particular directions (planes) with respect to the electron flow. LPEE-grown Cu₃Sn grew in the 〈0 2 0〉 and 〈4 0 0〉 directions, and LPEE-grown Cu₆Sn₅ grew in the 〈2 0 4〉 and 〈623̄〉 directions. With the aid of a molecular simulation software tool, we conclude that the particular growth directions represent the low-resistance paths for electron flow. This means that, along those particular directions in the LPEE-grown Cu-Sn compounds, the traveling electrons would be scattered least by the lattice. Thus, as the electromigrating Cu atoms form Cu-Sn compound, the newly forming Cu-Sn unit cells would orientate themselves in those particular growth directions to facilitate electron flow. Then, the well-oriented newly formed Cu-Sn compound unit cells can incorporate the growth of the highly orientated LPEE-grown Cu-Sn compounds. In addition, the anisotropy of a number of properties of LPEE-grown Cu₃Sn and Cu₆Sn₅, i.e. coefficient of thermal expansion, Vickers microhardness and electrical properties (resistivity, carrier mobility and carrier concentration), along the particular orientations were measured and reported.