A new ultra-thin capacitor can enable energy-efficient microchips

A new ultra-thin capacitor can enable energy-efficient microchips

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

Silicon-based computer chips that power our modern devices require huge amounts of energy to operate. Despite ever-improving computing efficiency, information technology is projected to consume about 25% of all primary energy produced by 2030. Researchers in the microelectronics and materials sciences communities are looking for ways to sustainably manage the global computing power demand.

IN The Holy Grail to reduce this digital demand is to develop microelectronics that operate at much lower voltages, which would require less energy and is a major goal of efforts to go beyond modern CMOS (additional metal oxide semiconductor) devices.

There are non-silicon materials with attractive memory properties and logic devices; but their general shape still requires high voltages to manipulate, making them incompatible with modern electronics. Designing thin-film alternatives that not only perform well at low operating voltages but can also be packaged in microelectronic devices remains a challenge.

Now a team of researchers at the Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley have identified an energy-efficient pathway – by synthesizing a thin film version of a well-known material whose properties are exactly what is needed for next-generation devices.

First discovered more than 80 years ago, barium titanate (BaTiO3) is used in various capacitors for electronic circuits, ultrasonic generators, transducers and even sonar.

The crystals of the material react quickly to a small electric field, changing the orientation of the charged atoms that make up the material in a reversible but permanent way, even if the applied field is removed. This provides a way to switch between the proverbial states “0” and “1” in logic and memory storage devices – but still requires voltages higher than 1000 millivolts (mV) to do so.

In an effort to use these properties for use in microchips, the team at Berkeley Laboratory has developed a way to create BaTiO films.3 only 25 nanometers thin – less than a thousandth of the width of a human hair – whose charged atomic orientation or polarization switches as quickly and efficiently as in the bulk version.

“We know about BaTiO3 for most of the century and we know how to make thin films from this material for more than 40 years. But so far no one has been able to make a film that is close to the structure or productivity that can be achieved in bulk, “said Lane Martin, a scientist at the Department of Materials Science (MSD) at Berkeley Laboratory. and a professor of materials science and engineer at UC Berkeley who leads the work.

Historically, fusion attempts have resulted in films that contain higher concentrations of “defects” – points where the structure differs from the idealized version of the material – compared to bulk versions. Such a high concentration of defects adversely affects the performance of thin films. Martin and colleagues have developed an approach to growing films that limits these defects. The findings are published in the journal Natural materials.

To find out what it takes to produce the best low-defect BaTiO3 thin films, researchers turned to a process called pulsed laser deposition. Launch of a powerful beam of ultraviolet laser light on a ceramic target by BaTiO3 causes the material to transform into plasma, which then transmits target atoms to a surface to develop the film. “It’s a universal tool with which we can adjust many buttons in the growth of the film and see which ones are most important for controlling the properties,” said Martin.

Martin and his colleagues showed that their method could achieve precise control on the structure, chemistry, thickness and interfaces of the deposited film with metal electrodes. By cutting each sample in half and examining its structure atom by atom using tools from the National Center for Electron Microscopy at the Berkeley Laboratory Molecular Foundry, the researchers uncovered a version that accurately mimics an extremely thin piece of mass.

“It’s funny to think that we can take these classic materials that we thought we knew everything about and turn them upside down with new approaches to making and characterizing them,” Martin said.

Finally, by putting a movie from BaTiO3 between two layers of metal, Martin and his team created small capacitors – electronic components that quickly store and release energy in a circuit. Applying a voltage of 100 mV or less and measuring the current that appeared showed that the polarization of the film switches within two billionths of a second and could potentially be faster – competing with what is needed on today’s computers to access memory or perform calculations.

The work follows the larger goal of creating materials with low switching voltages and investigating how the interfaces with the metal components required for the devices affect such materials. “It’s a good early victory in our pursuit of low-power electronics that goes beyond what is possible with silicon electronics today,” Martin said.

“Unlike our new devices, the capacitors used in chips today do not store their data unless you continue to apply voltage,” Martin said. And current technologies typically run at 500 to 600 mV, while the thin film version can run at 50 to 100 mV or less. Together, these measurements demonstrate successful optimization of stress resistance and polarization – which tends to be a trade-off, especially for thin materials.

The team then plans to shrink the material even thinner to make it compatible with real devices in computers and to study how it behaves at these small sizes. At the same time, they will work with associates at companies such as Intel Corp. to test feasibility in first generation electronic devices. “If you can make every logical operation on your computer a million times more efficient, think about how much energy you save. That’s why we do it,” Martin said.

Researchers are solving the mystery surrounding the dielectric properties of the unique metal oxide

More info:
Y. Jiang et al, Enabling ultra-low voltage switching in BaTiO3, Natural materials (2022). DOI: 10.1038 / s41563-022-01266-6

Quote: New ultra-thin capacitor can enable energy-efficient microchips (2022, June 22), extracted on June 22, 2022 from https://phys.org/news/2022-06-ultrathin-capacitor-enable-energy -efficient-microchips.html

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