The development of silicon-based computers is approaching its limits. To achieve further miniaturization and reduce power consumption, a variety of materials and architectures are important. Tamalika Banerjee, professor of spintronics of functional materials at the Zernike Institute for Advanced Materials at the University of Groningen, is studying many quantum elements to create these (Complex oxides may make the computers of the future) new devices. “Our approach is to study these things in their visual environment, but always look at the application, such as memory or a combination of memory and logic.”
Works well
Banerjee’s team has previously demonstrated how doped strontium titanate can be used to create memristors, which combine memory and logic. They recently published two papers on “beyond CMOS” devices, the additive metal-oxide semiconductor that is the cornerstone of today’s computer chips.
The successor to CMOS is the magneto-electric spin-orbit (MESO) device, which can be 10 to 30 times more efficient. Much has been studied about their ability to create such devices. Job van Rijn, a PhD student in Banerjee’s group, is the first author of an article in Physical Review B published in December 2022, explaining how strontium manganate (SrMnO3 or SMO for short) can be a good candidate for MESO device. Van Rijn says, “It is a multiferroic material that couples spintronics with charge-based effects.” Spintronics is based on the spin (magnetic moment) of electrons. Banerjee: “Magnetic laws and charges are combined in this material, so we can change the magnetism and polarization in the magnetic field with electricity. And, above all, these effects are at temperatures close to room temperature .Van Rijn studies the strong connection between the two effects. “We know that ferromagnetism and ferroelectricity are manipulated by breaking the thin SMO film. This filter was made by growing the film on different substrates.
String
Van Rijn studies how pressure creates heat in matter and its effects on magnetic systems. He examined the domains in the disordered films and found that the magnetic interaction strongly depends on the crystal structure and, in particular, on the oxygen availability, which changes the preferred direction of the magnetic system. “Tourist experiments lead us to the conclusion that magnetic fields play an important role in devices made of this material. Therefore, this study is the first step in creating the possibility of using strontium manganate for the design of new computers.
On February 14, Banerjee’s team published a second article on “beyond CMOS” devices, in the journal Advanced Electronic Materials. Doctoral student Anouk Goossens is the first author of this article on the miniaturization of memristors based on niobium-doped strontium titanate (SrTiO3 or STO). “The number of devices per area is important,” Goossens said. “But some types of memristors are difficult to scale.”
Goossens has previously shown that it is possible to create “in-memory logic” devices using STO. His latest report shows that it is possible to reduce the number of these devices. A common problem with memristors is that their performance is greatly affected by miniaturization. Surprisingly, making memristors smaller with STO increases the difference between high resistance and low resistance. Goossens explains, “We studied the material using electron transmission electron microscopy and found a large number of oxygen vacancies at the interface between the substrate and the device electrode.” “After we applied an electrical voltage, we saw oxygen availability, which is the key to controlling the resistive states.”
New design
The conclusion is that the better performance comes from the effects, which can be bad for normal memory. But in STO, the electric current increases at the edge supporting the operation of the memristor. “In our case, price is a tool,” Goossens concluded. “Also, the specific materials depend on the amount of niobium doping, so the material is flexible for different purposes.”
Finally, the two articles published by the group show
“That’s exactly what we’re working on,” Banerjee says. “We want to understand the physics of matter and how our devices work, and develop applications.” Goosens: “We are considering many applications and the one we are looking at is a numerical code that works without an algorithm and therefore it is impossible to predict.’
Source: University of Groningen.
