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A NEW class of nanoporous thin films could yield improved batteries, gas sensors and more powerful electronics.
CSIRO researchers worked with peers from the University of Leuven in Belgium and the National University of Singapore to develop a way to produce metal organic framework crystals in thin film form, using the chemical vapour deposition process.
Metal organic framework (MOF) crystals are known as the most porous material in the world. A grid of metal ions are pushed aside by organic molecules to create a pattern of nanopores.
Such is the porosity of this material that they can be up to 80 percent empty — nearly every atom is exposed to empty space in the structure, and just one gram of the material can have a surface area from 1000 to 5000 square metres.
This porosity means MOF crystals can be used to trap other molecules. The trapped molecules change the properties of the material, allowing a variety of use cases.
In electronics and semiconductor applications, for example, MOF crystals would allow increased miniaturisation: by fitting more transistors onto a microchip, performance can be multiplied.
Prior to the current breakthrough, MOF crystals were grown and applied using wet chemistry. The resulting powder form of MOF crystals could not be easily integrated into nanoscale applications. Additionally, the solvent used was incompatible with electronics.
The researchers drew on specialist X-ray analysis techniques from CSIRO and the Australian Synchrotron to understand how the vapour-phase deposition process works.
They then deposited layers of zinc, and let them react with the vapour of the organic material. The organic material permeated the metal, expanding the volume and thus converting it into a thin film of MOF.
As CVD is a common technique in the semiconductor fabrication industry, this MOF thin film production process can be adapted and integrated with current processes to rapidly develop new applications.