Materials manufacturing with micro-explosions

Scientists from The Australian National University (ANU) have utilised laser-induced micro-explosions in silicon to create exotic new materials. According to the leader of the research, Professor Andrei Rode, the technique could lead to the simple creation and manufacture of superconductors or high-efficiency solar cells and light sensors.

By focusing lasers onto silicon buried under a clear layer of silicon dioxide, the group perfected a way to reliably blast tiny cavities in the solid silicon. This creates extremely high pressure around the explosion site — many times higher than the strength of diamond crystal can produce — and forms new crystal arrangements, or phases.

“The recently developed method of ultrashort laser-induced confined micro-explosions initiates a non-equilibrium disordered plasma state,” the team explained in the journal Nature Communications. “Ultrahigh quenching rates overcome kinetic barriers to the formation of new metastable phases, which are preserved in the surrounding pristine crystal for subsequent exploitation.”

Professor Rode said the team has created two entirely new phases in silicon and seen indications of potentially four more. He said, “Theory predicts these materials could have very interesting electronic properties, such as an altered band gap, and possibly superconductivity if properly doped.”

Using a combination of electron diffraction patterns and structure predictions, the team discovered the new materials have crystal structures that repeat every 12, 16 or 32 atoms respectively, said co-author Professor Jim Williams. “The micro-explosions change silicon’s simplicity to much more complex structures, which opens up possibility for unusual and unexpected properties,” he said.

Co-author Dr Jodie Bradby said the new method promises a cheap and industrially friendly method for large-scale manufacturing of these exotic materials, noting, “We reliably create thousands of micron-size modified zones in normal silicon within a second.

“The semiconductor industry is a multibillion-dollar operation — even a small change in the position of a few silicon atoms has the potential to have a major impact,” she said.

Image caption: Professor Jim Williams, Professor Andrei Rode and Associate Professor Jodie Bradbury with the complex electron diffraction patterns. Image credit: Stuart Hay, ANU.

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