The next generation of computer chips is on the horizon, and that’s good news for the next generation of smaller, faster computers, high efficiency solar cells and other clean tech gear. In the latest development, a research team at Lawrence Berkeley National Laboratory has broken a longstanding, presumed limit to the size of a transistor, and they did it with a common lubricant widely used in the auto industry.
So far the lab’s research is in the proof of concept stage, so don’t hold your breath for the new transistor to make it into your life. However, since LBNL is a publicly funded facility (group hug for US taxpayers!), this foundational research can keep chugging along to the next stage.
What’s Standing Between You And Next-Gen Clean Tech
Two competing factors are behind the new Berkeley Lab discovery. One is Moore’s Law, named after the founder of Intel Gordon Moore. As far back as 1965 he observed that technological progress was running at such a rapid pace that the size of computer chips was shrinking practically before your eyes.
By 1975 the observation was refined into “Moore’s Law,” which holds that the number of transistors that can fit on a chip doubles every two years.
That’s great news in terms of sustaining the electronic age. Smaller transistors translate into smaller and potentially more efficient devices, to the benefit of solar technology, smart grids, and other clean tech fields.
The problem is that sooner or later, Moore’s Law is going to bump up against physical laws. That’s where the second factor comes in. According to the Berkeley team the standard assumption has been that five nanometers is the floor for gate length in a transistor. In other words, anything below five nanometers will not function, so there is no way to fabricate a transistor smaller than five nanometers.
If you’re new to the topic of transistors, the team at Berkeley offers this 101:
Transistors consist of three terminals: a source, a drain, and a gate. Current flows from the source to the drain, and that flow is controlled by the gate, which switches on and off in response to the voltage applied.
The silicon-based transistors currently on the high end of the market have a gate length of 20 nanometers, so the industry still has a way to go before it hits the 5-nanometer wall.
The Road To A 1-Nanometer Transistor
The Berkeley team seems to have bought the industry even more time. They have demonstrated that, at least in concept, a gate length of just one nanometer is within the realm of possibility.
Silicon has been deemed a superior material for computer chips because its distinct crystal lattice structure outperforms other materials when it comes to enabling the flow of electrons.
However, when you shrink the size of the transistor past five nanometers, that advantage disappears. That means other materials — in this case, molybdenum disulfide (MoS2) — have a chance to show their stuff.
Here’s the explainer from the Berkeley team:
Both silicon and MoS2 have a crystalline lattice structure, but electrons flowing through silicon are lighter and encounter less resistance compared with MoS2. That is a boon when the gate is 5 nanometers or longer. But below that length, a quantum mechanical phenomenon called tunneling kicks in, and the gate barrier is no longer able to keep the electrons from barging through from the source to the drain terminals.
In addition to ditching silicon, the team also dispensed with the lithography-based fabrication method used for conventional transistors. Instead, they used carbon nanotubes.
Here’s what the transistor looks like via electron microscopy:
You can pick up a tube of MoS2 lube for a couple of bucks on Amazon, but the convenience of online shopping was not the reason why the Berkeley team settled on that material for their new nanoscale transistor.
In 2-D form it belongs to a class of graphene-ish materials called transition metal dichalcogenides (TMDCs).
Here’s an explainer from a study published last year in the Journal of Materiomics:
…Molybdenum disulfide (MoS2) is one of the most typical TMDCs. Its particular direct band gap of 1.8 eV in monolayer and layer dependence of band structure tackle the gapless problems of graphene, thus making it scientific and industrial importance.
The next steps for the Berkeley team include fabricating a chip with the new transistors, so stay tuned for that — however long it takes.
Images: via Lawrence Berkeley National Laboratory.