Silicon is the kingpin when it comes to semiconductor technology that’s used in smartphones, computers, electric vehicles, and more. However, the material could soon lose its claim as the most important material for this technology in the coming years.
A team of researchers at the Penn State have used 2D materials in producing a computer capable of simple operations. These 2D materials are thicker compared to silicon and also have the ability to maintain their properties at scale.
This development represents a major shift towards the use of faster, thinner, and more efficient materials.
How did they create the computer?
The researchers have created a complementary CMOS computer without using silicon in the process. Instead, they’ve used two different 2D materials based to develop two types of transistors: molybdenum disulfide for n-type transistors and tungsten diselenide for p-type transistors.
“Silicon has driven remarkable advances in electronics for decades by enabling continuous miniaturization of field-effect transistors (FETs),” said Saptarshi Das, the Ackley Professor of Engineering.
FETs control current flow that is produced on the application of voltage using an electric field.
“However, as silicon devices shrink, their performance begins to degrade. Two-dimensional materials, by contrast, maintain their exceptional electronic properties at atomic thickness, offering a promising path forward.”
Decoding the CMOS technology
The CMOS technology required both n-type and p-type semiconductors to work toegher for achieving high performance while consuming low power. This is a major challenge for researchers in their bid to swap silicon for a different material.
Prior to this, 2D materials were used in small circuits efficiently, however, scaling to complex and functional computers remained a distant dream.
“That’s the key advancement of our work,” Das said. “We have demonstrated, for the first time, a CMOS computer built entirely from 2D materials, combining large area grown molybdenum disulfide and tungsten diselenide transistors.”
The innovation that made it possible
The team used metal-organic chemical vapor deposition (MOCVD) — a fabrication process that involves vaporizing ingredients, forcing a chemical reaction and depositing the products onto a substrate — to grow large sheets of molybdenum disulfide and tungsten diselenide and fabricate over 1,000 of each type of transistor.
They were able to adjust the threshold voltages of both transistor types by carefully tuning the device fabrication and post-processing steps. This enabled the construction of fully functional CMOS logic circuits.
“Our 2D CMOS computer operates at low-supply voltages with minimal power consumption and can perform simple logic operations at frequencies up to 25 kilohertz,” said first author Subir Ghosh, a doctoral student pursuing a degree in engineering science and mechanics under Das’s mentorship.
Ghosh also observed that the computer runs slower than normal silicon CMOS circuits, but it can still do basic logic operations using just one type of instruction.
“We also developed a computational model, calibrated using experimental data and incorporating variations between devices, to project the performance of our 2D CMOS computer and benchmark it against state-of-the-art silicon technology,” Ghosh said.
“Although there remains scope for further optimization, this work marks a significant milestone in harnessing 2D materials to advance the field of electronics.”
Das also explained that more work is needed on developing the 2D CMOS computer for broad usage.
“Silicon technology has been under development for about 80 years, but research into 2D materials is relatively recent, only really arising around 2010,” Das stated. “We expect that the development of 2D material computers is going to be a gradual process, too, but this is a leap forward compared to the trajectory of silicon.”
Ghosh and Das credited the 2D Crystal Consortium Materials Innovation Platform (2DCC-MIP) at Penn State with providing the facilities and tools needed to demonstrate their approach.
The research was published in the journal Nature.
