Characterization of the microstructure and phase formation in the Au-In system using transmission electron microscopy

The Au-In system is of both fundamental and technical importance for engine ering applications such as microelectronic packaging. The growth mechanism and crystal orientation of the Au and In thin films produced by thermal eva poration on NaCl substrates are studied by transmission electron microscopy (TEM). Like most metals, the growth of both Au and In thin films on single crystals of NaCl follows the Volmer-Weber mode, i.e. formation of metal nu clei first, and then grain growth and coalescence of the particles to form a continuous thin film. In contrast, the growth of In on the An-coated NaCl substrates follows the Frank-van der Merwe mode, i.e. layer by layer, as a result of strong interactions between Au and In. The formation of AuIn2 ph ase occurs instantly upon In deposition, and the intermetallic exhibits an epitaxial orientation to the underlayer Au single crystals. In addition, cr oss-section TEM observation of the Au/In/Au thin sections by ultramicrotomy shows that the AuIn2 intermetallic is brittle. (C) 2001 Elsevier Science B .V. All rights reserved.