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Century Old Material Key to Next-gen Computer Chips

Silicon -based computer chips power our modern devices requires a lot of energy to operate. Despite continued advances in computer efficiency, information technology is planned to consume nearly 25% of all primary energy produced by 2030. Researchers in the microelectronics and materials science community are looking for ways to continue to manage the global demand for computing power.

Scientists have turned a century -old material into a thin film for next -generation memory and logic devices.

Electron microscope images show the precise atom-by-atom structure of a barium titanate (BaTiO3) thin film inserted between layers of strontium ruthenate (SrRuO3) metal to form a small capacitor. (Credit: Lane Martin/Berkeley Lab)

The holy grail for reducing this digital demand is to make microelectronics operate at much shorter voltages, requiring less energy and a primary purpose in efforts to operate beyond the current state-of -the-art CMOS (complementary metal-oxide semiconductor) devices.

Non-silicon materials with attractive properties for memory and logic devices are available; but their typical bulk form still requires large voltages to maneuver, which is incompatible with modern electronics. Designing thin film alternatives that not only perform well at short operating voltages but can also be packed with microelectronic devices remains a challenge.

Today, a team of researchers at Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley have identified an energy-efficient route-by synthesizing a thin-layer version of a famous material whose properties are exactly what is needed for next generation devices. .

First discovered more than 80 years ago, barium titanate (BaTiO3) have been found to be used in a variety of capacitors for electronic circuits, ultrasonic generators, transducers, and even sonar.

The crystals of the material quickly respond to a small electric field, flop-flopping the orientation of the charged atoms that make up the material in a flexible but permanent manner even if the applied field taken. It provides a way to switch between the proverbial “0” and “1” states in logic and memory storage devices – but still requires voltages greater than 1,000 millivolts (mV) for it to do so.

Aiming to make these properties available to microchips, the Berkeley Lab -led group has created a platform for making BaTiO films.3 Only 25 nanometers thin – less than a thousand the width of a human hair – whose orientation to charged atoms, or polarization, moves as quickly and efficiently as most versions.

“We know about BaTiO3 in the better part of a century and we have known how to make thin films of this material for over 40 years. But so far, no one has been able to make a film that can come close to the structure or performance that is accessible to most, ”said Lane Martin, a faculty scientist in the Materials Sciences Division (MSD) at Berkeley Lab and professor in materials science and engineering at UC Berkeley leading the work.

Historically, synthesis tests have resulted in films with higher concentrations of “defects” – points where the structure differs from an ideal version of the material – compared to most versions. Such a high concentration of defects negatively affects the production of thin films. Martin and colleagues have developed a method of growing films that limits such defects. The findings were published in the journal Natural Materials.

To understand what it takes to produce the best, low -defect BaTiO3 thin films, the researchers turned to a process called pulsed-laser deposition. Firing a powerful beam of an ultraviolet laser light on a ceramic target of BaTiO3 causes the material to transform into a plasma, which then sends atoms from the target to a surface to grow the film. “It’s a multi-purpose tool where we can change a lot of the film’s growth knobs and see what’s most important in controlling the properties,” Martin said.

Martin and his colleagues have shown that their method can achieve precise control of structure, chemistry, thickness, and interfaces with metal electrodes. By cutting each deposited sample in half and looking at the atomic structure by atom using the tools of the National Center for Electron Microscopy at the Molecular Foundry of the Berkeley Lab, the researchers revealed a version that accurately mimics a much thinner slice for the most part.

“It’s fun to think that we can take these classic materials that we think we all know, and flip them over in their heads using new ways of making and recognizing them,” he said. Martin.

Finally, by putting on a BaTiO film3 Between the two metal layers, Martin and his team made small capacitors-electronic components that rapidly store and release energy in a circuit. Applying voltages of 100 mV or less and measuring the current that emerges shows that the polarization of the film shifts within two billion parts of a second and can be much faster – competing with the requirement for today’s computers. to access memory or perform calculations.

The work follows the larger objective of making materials with small transfer voltages, and examines how the interfaces of the metal components required for the devices affect the materials. “This is a good early win in our search for low-power electronics that are beyond the capabilities of today’s silicon-based electronics,” Martin said.

“Unlike our newer devices, the capacitors used in today’s chips won’t hold their data unless you keep applying voltage,” Martin said. And current technologies typically operate at 500 to 600 mV, while a thin film version can operate at 50 to 100 mV or less. Together, these measurements show a successful optimization of voltage and polarization stability-which is likely a trade-off, especially in thinner materials.

Next, the team plans to reduce the material much thinner so that it can be compatible with real computer devices and study how it operates on small dimensions. At the same time, they will collaborate with collaborators at companies such as Intel Corp. “If you could make every logical operation of a computer a million times more efficient, think about how much energy you would save. That’s why we do this, ”said Martin.

This research was supported by the U.S. Department of Energy (DOE) Office of Science. The Molecular Foundry is a DOE Office of Science user facility at Berkeley Lab.

The Berkeley Lab’s “Beyond Moore’s Law” initiative aims to identify ultralow power logic pathways in memory elements. “We need to get to operation at low voltage, because that’s what measures energy,” said co-author Ramamoorthy Ramesh, a senior faculty scientist at Berkeley Lab and professor of physics and materials science and engineering. at UC Berkeley. “This work demonstrates, for the first time, the switching field of the material model, BaTiO3 with voltages below 100 mV, on a relevant platform.

Article courtesy of Lawrence Berkeley National Laboratory (Berkeley Lab).

Related: Global Supply Shortage: No Time, No Chip – No Problem For NREL

Selected photo: A macro on a silicon wafer, by Laura Ockel of Unsplash


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