Electronics drive our world, from the smart devices we rely on each day to the integral components within everything from vehicles and satellites to robotics and data centers. All demand a consistent source of power, generating energy and heat.
A simple effect such as temperature change can lead to malfunctions in electronics, severely affecting their efficiency or disabling them altogether.
Professor Parag Banerjee and his team have developed a novel material that solves this widespread issue. By meticulously combining atoms of silicon to a thin film of titanium nitride, he and his team have produced an ideal platform for electronics. Their work was recently published in Advanced Materials.
“Electrical resistivity is one of the most fundamental properties of a material that we are all familiar with,” Banerjee says. “We flip a switch to turn on a light. In this simple process, electric current in the form of electrons move inside a metal, usually copper, powering up a light bulb which these days is made up of semiconductor materials. How electrons behave inside a metal versus inside a semiconductor is very different.”
Banerjee explains that in metals, electrons acquire higher speed when temperatures increase. However, the constant collisions of the electrons with each other slow them down, which leads to decreased conductivity when temperatures rise. On the other hand, semiconductors need a boost of thermal energy to get things moving, so conductivity increases with temperature.
Neither situation is optimal for electronics, which require components that operate most efficiently with consistent temperatures.
“Since these films are conductors inside microelectronic chips and they carry electrical signals, stability in electrical conductivity is important,” Banerjee says. “One would not like the electrical conductivity to change with temperature as that can lead to the malfunctioning of the microelectronic chip.”
Banerjee’s group has developed an optimal material for electronic devices — one that conducts electricity while remaining stable across temperature changes. Two former doctoral students in the Banerjee Lab led the work, S. Novia Berriel ’21MS ’24PhD and Corbin Feit ’19MS ’22PhD, now research staff members at Lam Research® and Air Liquide®, respectively.
In collaboration with industry partner Eugenus Inc., the team precisely engineered titanium nitride films incorporating just 2 atomic percent silicon. They demonstrated materials that maintain consistent electrical properties across a range of temperatures using atomic layer deposition, an exacting process that uses films just a few nanometers thick.
“By adding silicon to titanium nitride in tiny amounts, one can increase their ability to further resist heat and temperature while not compromising electrical conductivity,” Banerjee says.
Though such a miniscule amount is added to the films, they create a tremendous impact. The atoms are precisely inserted within titanium nitride grain boundaries, or areas where the atoms aren’t perfectly aligned. Placed in these specific regions, silicon atomic particles eliminate any oxygen in the titanium nitride grain to improve conductivity. The silicon placement also allows electrons to maintain a consistent distance during scattering events, or as the electrons collide with one another and move as they’re carrying current.
“This length scale is temperature independent and amazingly, the conductivity becomes temperature independent as well,” he says. “This arrangement of silicon atoms also allows electrons to maintain a relatively consistent distance between scattering events as they move inside titanium nitride.”
His team’s research has far-reaching impacts. Semiconductors are fundamental to all modern instruments, and having reliable components immune to temperature changes is crucial to maintaining their consistent performance. For systems exposed to extreme environments, such as quantum devices and those found in spacecraft, Banerjee’s development could make a transformative difference.
“While our discovery is fundamental, we are excited that our findings have direct and immediate engineering applications.”
- Written by Bel Huston