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MOSCOW, April 7. /TASS /.Russian scientists from the Moscow Institute of Physics and Technology (MIPT) have succeeded in growing ultra-thin (2.5-nanometre) ferroelectric films based on hafnium oxide that could potentially be used to develop non-volatile memory elements, the MIPT press service said.
"Since the structures of this material are compatible with silicon technology, we can expect that new non-volatile memory devices with ferroelectric polycrystalline layers of hafnium oxide will be able to be built directly onto silicon in the near future," said the corresponding author of the study and head of the Laboratory of Functional Materials and Devices for Nanoelectronics, Andrei Zenkevich.
Humans are constantly expanding the volume of stored and processed information, which according to statistics is doubling every 1.5 years. To store this information, we need increasing amounts of computer memory, especially non-volatile memory, which stores information even in the event of a power outage. The ideal would be a "universal" memory device with the speed of RAM, the capacity of a hard drive, and the non-volatility of a flash drive. Non-volatile memory based on ferroelectric tunnel junctions is a promising development that has not yet been fully implemented.
The schematic representation of silicon-based ferroelectric tunnel junctionImage courtesy of the authors of the study
Ferroelectrics are generally insulators and do not conduct electricity. However, if the ferroelectric layer is very thin, electrons can "slip" through with a certain probability, thanks to the quantum tunneling effect. The probability of tunneling depends on the size and shape of the potential barrier (the energy characteristics of the structure), and the electrons that "pass through" create a tunnel current. So, information in ferroelectrics memory elements is written by applying a voltage to the electrodes next to the ultra-thin ferroelectric, and it is read by measuring the tunneling current.
In theory, this type of memory may have an extremely high density, fast reading and writing speeds, and a low level of power consumption. It could become a non-volatile alternative to modern DRAM (dynamic random-access memory), that has a short retention time (approximately 0.1 seconds), after which the data is either lost or overwritten. However, until now, all prototypes of devices based on conventional ferroelectrics have not been compatible with silicon technology, which is used in the production of most modern chips.
The team of researchers from MIPT’s Laboratory of Functional Materials and Devices for Nanoelectronics, with the participation of their colleagues from the University of Nebraska (USA) and the University of Lausanne (Switzerland), have for the first time experimentally demonstrated that polycrystalline alloyed-fused films of hafnium and zirconium oxides with a thickness of just 2.5 nm retain their ferroelectric properties.
While Hhafnium oxide is already used in the production of modern silicon logic chips, and a few years ago ferroelectric properties were discovered in one of its modifications. In their study, the scientists from MIPT succeeded in growing an ultra-thin, tunnel-transparent film of this material on a silicon substrate, while maintaining the ferroelectric properties. It is important to note that the film was grown by method of Aatomic Llayer Ddeposition (ALD), which is used today in the production of microprocessors.
The results of the study have been published in the journal ACS Appl. Mater. Interfaces.
Cross section of the structure developed: a polycrystalline alloyedfused film of hafnium -and zirconium oxides grown directly on a highly doped Si substrateImage courtesy of the authors of the study