"First ever" large-scale 2D surface deposition of piezoelectric material

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A method to 'print' large-scale sheets of 2D piezoelectric material has been developed by FLEET researchers at RMIT University in Melbourne, opening new opportunities for piezo-sensors and energy harvesting.

The process is said to allow the integration of piezoelectric components directly onto silicon chips. Until now, no 2D piezoelectric material has been manufactured in large sheets, making it impossible to integrate into silicon chips or use in large-scale surface manufacturing, the researchers say.

This limitation meant that piezo accelerometer devices have required separate, expensive components to be embedded onto silicon substrates, adding significant manufacturing costs.

Now, the researchers have demonstrated a method to produce large-scale 2D gallium phosphate (GaPO4) sheets, allowing this material to be formed at large scales in low-cost, low-temperature manufacturing processes onto silicon substrates, or any other surface.

"As so often in science, this work builds on past successes," lead researcher Professor Kourosh Kalantar-zadeh explains. "We adopted the liquid-metal material deposition technique we developed recently to create 2D films of GaPO4 through an easy, two-step process."

The process

  1. Exfoliate self-limiting gallium oxide from the surface of liquid gallium made possible by the lack of affinity between oxide and the bulk of the liquid metal
  2. 'Print' that film onto a substrate and transform it into 2D GaPO4 via exposure to phosphate vapour.

The method allows easy, inexpensive growth of large-area (several centimetres), wide-bandgap, 2D GaPO4 nanosheets of unit cell thickness, according to the researchers.