Ferroelectric RAM, FeRAM, FRAM

2023: MIPT scientists propose new way to study domain structure of ferroelectric films

Scientists from MIPT have proposed a way to study the domain structure of ferroelectric films. In the future, he will help understand why films lose physical properties when repeatedly exposed to an electric field. Scientists plan to use the method when creating and studying the properties of ferroelectric memory cells. The university announced this on May 31, 2023.

Ferroelectrics are materials that have two stable polarization states. These states are stored in the absence of an electric field, which allows them to be used to create memory elements. computer As a rule, ferroelectrics have a domain structure, that is, they are divided into regions that can have different polarization. When an external electric field is applied, the polarization of the domains changes the sign to the opposite, switches - this is how the memory element is overwritten. However, rewriting domains repeatedly with an external field can destroy the properties of films: some domains lose the ability to switch under given conditions. In order to find the cause of destruction, an effective method of observing domains and switching them is required.

To observe individual domains, as a rule, piezotclick microscopy is used. Physicists from MIPT proposed an alternative way to study the domain structure of thin films - the induced current method - and implemented it using a raster electron microscope.

We once traveled to take measurements on a synchrotron. The sample was connected to a current meter, and we noticed that when an X-ray beam hit the sample, the meter recorded the current flow - the induced current appeared. We decided to try irradiating the sample with the thinnest beam of high-energy electrons instead of X-rays (which illuminate the entire sample at once). We became interested in whether the induced current would occur in this case, as well as whether the magnitude of the current would vary depending on which domain the beam enters. " told the first author of the work Evgeny Korostylev, director of the Center for Collective Use of Scientific Equipment in the Field of Nanotechnology MIPT.

In this work, scientists considered the domain structure of a thin film of mixed hafnium-zirconium oxide Hf0.5Zr0.5O2. An image of the structure of physics was obtained using an electron microscope and a current amplifier. And they switched domains - changed their polarization - supplying external voltage to the sample.

The main idea of ​ ​ the installation, invented and created by scientists, is to use the thinnest electron beam generated in a raster electron microscope as a current exciter in the sample. Due to the different physical characteristics of the domains, the induced current in them will differ, which means that it is possible to restore the structure of the sample. The electron beam of the microscope, hitting the sample, generated electron-hole pairs in the film, which created the current captured by the amplifier (up to pA). Thanks to the small diameter of the electron beam, physicists could study small areas of film that the beam hit. In terms of current strength and direction, the blast-furnace structure of the sample was restored at these sites.

See also

• DRAM Memory (Global Market)
• 3D NAND Flash Memory
• NVRAM Non Volatile Random Access Memory
• ReRAM - Resistive Random Access Memory
• MRAM (magnetoresistive random access memory)