Indium
Indium is a key material in lead-free solder applications for microelectronics due to its excellent wetting properties, extended ductility, and high electrical conductivity.
Researchers from the University of Waterloo, California Institute of Technology, and Los Alamos National Laboratory have studied the small-scale mechanics of indium nanostructures. Studies indicate that the indium microstructure is typical of a well-annealed metal, containing very few initial dislocations and showing close-to-theoretical strength.
Indium structure
Researchers investigated the small-scale plastic deformation of indium nanopillars, a previously unstudied material and crystal structure. This material has a tetragonal crystalline structure and a low melting temperature of about 156 °C (313 °F). The low melting temperature of indium allows it to undergo room-temperature annealing, which helps to reduce or eliminate fabrication-induced stresses, defects, and dislocations. In addition, the small as-deposited indium grains grow into large crystals at ambient conditions.
Applications
Indium and its compounds have many important applications in the field of nanotechnology. For example, it has been demonstrated that indium phosphide (InP) and indium arsenide-phosphide (InAsP) nanowires can be used as highly polarized photoluminescence and infrared photo detection devices. Vertical field-effect transistors have also been constructed with indium oxide (In2O3) nanowires. Indium wire is ideal for many sealing applications, especially cryogenic sealing.
Indium nanopillar
Low-melting-temperature approach is advantageous for materials such as indium, since conventional pillar fabrication by focused ion-beam milling techniques ultimately leads to melting or structural degradation.
When indium nanopillar samples annealed at room temperature for about a month were subjected to uniaxial compression tests, two distinct indexations of the Laue diffraction patterns were collected for a particular indium nanopillar revealing that it consisted of two grains with out-of-plane orientations. The diffraction spots from each grain had similar intensities, suggesting the grains were comparable in size and nonuniform plastic deformation induced by the fabrication process.
Metallic nanopillars were fabricated by lithographic patterning of a polymethylmethacrylate (PMMA) resist with electron-beam lithography, followed by selective metal electroplating into the resist template.