Researchers at the University of Dublin are claiming a major breakthrough in the manufacturing of graphene that could clear the way for mass industrial production of the material. Graphene has a vast number of potential uses — it’s an incredible conductor of electricity, strong, nearly transparent, and extremely thin — but manufacturing it in volume has proven extremely difficult.
The Irish team’s approach focused on mechanical exfoliation of graphene. Graphene was originally discovered through mechanical exfoliation through the repeated application of scotch tape to layers of graphite (yes, Scotch tape). In this new method, graphite is mixed into stabilizing liquids and fed into a high shear mixer, like the one shown below. The mixer cleaves off graphene sheets of sufficient size and quantity to qualify as industrial production; the team claims that “exfoliation can be achieved in liquid volumes from hundreds of milliliters up to hundreds of liters and beyond.”
That’s a huge step forward for graphene and could open the field up to applications in composite materials or conductive coatings. Making graphene cheaper will also spur further research into the material, as it lowers the cost of incorporating graphene into modern products.
Semiconductors, however, are still quite far away. The International Technology Roadmap for Semiconductors (ITRS) recently released its new roadmaps (dated 2013, as the work was completed in that year), so I took a look at what the updated graphene predictions look like.
From 2011 to 2013: a few steps forward, a few steps back
The charts below represent the ITRS’ current thinking on various future materials and whether or not those materials are currently performing better, worse, or equivalently to conventional silicon. I’ve reprinted the charts from both the 2011 and the 2013 reports to give a better indication of how thinking has evolved on multiple materials. Graphene is the focus of our conversation today, but the data on III-V semiconductors, nanowires, and carbon nanotubes is also relevant, given that graphene competes with those materials as the possible future of semiconductor manufacturing.
First, here’s the chart from 2011. Pink boxes indicate that a given technology is performing worse than silicon, green boxes indicate equivalent performance to silicon, white boxes (none shown) would indicate clear advances compared to silicon.
Next, here’s the chart from 2013. The data in these charts is based on surveys of ITRS members and represent the current thinking on how challenging it will be to integrate various materials into CMOS manufacturing.
Flip between the two and you’ll notice that we’ve taken two steps forward and one step back in multiple cases. Several aspects of III-V design are proving more difficult to implement in 2013 than they looked in 2011, while other areas have improved. Graphene has made huge strides forward in gate dielectric compatibility (from 1.3 to 1.9) but fallen sharply backwards in terms of defect density (from 1.8 to 1.3).
There are many facets to this problem, which is why industrial-scale production of graphene remains just one step in a complicated manufacturing process. Integrating exfoliated graphene into semiconductor manufacturing is challenging — it’s extremely difficult to ensure uniform distribution of the material. Epitaxially (depositing a crystalline overlayer on a crystalline substrate) deposited graphene is a preferred solution for managing defects, but scientists are still searching for an effective, low-cost, and easily integrated method of depositing graphene via CVD (chemical vapor deposition). It’s possible, therefore, that this new exfoliation method will still be used in semiconductor applications if it scales effectively enough.
For now, however, graphene still remains a long-term investment not a short-term game-changer. IBM has pioneered building analog processors using graphene, but its integration into conventional CMOS and digital processors remains a difficult problem.
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