Thin films are everywhere in modern technology. But when scientists want to squeeze them to see how they change, they face a surprising problem: the thinner the film, the harder it is to press.
Researchers from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, together with Changzhou University and South China University of Technology, have developed a method to study electrical changes in freestanding thin films under high pressure.
Using this approach, they discovered that the thickness of a material can dramatically change how it responds to pressure. In SrIrO₃ films, three-dimensional structures transformed from semimetals to insulators and then metals as pressure increased, while two-dimensional films remained insulating even under high pressure.
Thin films are usually grown on substrates that act like a support. But this support creates a problem: when pressure is applied, much of the force is absorbed or affected by the much larger substrate rather than the nanoscale film itself.
Removing the substrate would allow pressure to act more directly on the film. The catch? Freestanding thin films are extremely fragile and difficult to connect with electrodes for electrical measurements.
The research team solved this challenge by developing techniques to protect and release thin films, build nanoscale electrodes, and perform electrical measurements under high pressure.
They tested the method on SrIrO₃, a quantum material whose electronic properties are highly sensitive to changes in structure.
The experiments revealed a surprising difference. Three-dimensional SrIrO₃ films changed their electronic state under pressure, while two-dimensional films showed a much stronger resistance to pressure-induced changes.
Sometimes, the biggest challenge in science is not finding a new material — it is finding a way to gently push it and see what happens.
