Tungsten and Molybdenum New Material Memory is 10,000 Times Faster Than U Disk

Recently, Professors Zhang Wei and Zhou Peng of Microelectronics College of Fudan University have realized a disruptive two-dimensional semiconductor quasi-nonvolatile storage prototype device, and initiated a third type of storage technology. The writing speed is 10,000 times faster than the current U disk, and the storage time of data can also be determined by themselves, which will automatically disappear after the expiry date. This also solves the difficult problem of "writing speed" and "non-volatility" in the international semiconductor charge storage technology. This new type of memory transistor uses three kinds of single-layer two-dimensional nano-transition metal materials: molybdenum disulfide, tungsten disulfide and hafnium disulfide.

The new charge storage technology not only meets the requirement of 10 nanoseconds data writing speed, but also realizes the quasi-non-volatile characteristics of customized (10 seconds-10 years) adjustable data. This new feature can not only greatly reduce the storage power consumption in high-speed memory, but also realize the natural disappearance of data after the expiration date. It solves the contradiction between confidentiality and transmission in special application scenarios.

"This research innovatively chooses multiple two-dimensional stacks to construct semi-floating gate transistors: molybdenum disulfide, tungsten disulfide and hafnium disulfide for switching charge transport and storage respectively, and boron nitride as tunneling layer to fabricate Van der Waals heterojunctions with step-valley structure." Choosing these two-dimensional materials will give full play to the rich band characteristics of the two-dimensional materials, according to Zhou Peng, a researcher. "One part is like a door that can be switched on and off at will, and the other part is like a wall with a closed surface, which makes it difficult for electrons to enter and exit. The regulation of'write speed'and'non-volatility' lies in the proportion of these two parts.

Writing speed is 10,000 times faster than the current U disk, data refresh time is 156 times faster than memory technology, and has excellent controllability, can achieve the design of memory structure according to the data valid time requirements... After testing, the researchers found that this new type of heterojunction based on two-dimensional materials can achieve a new third type of storage characteristics.

In the future, due to quantum phenomena, traditional circuits based on field effect transistors are approaching their physical limits, so semi-floating gate transistors have become an alternative to ultra-fast and silicon compatible technologies. The quasi-nonvolatile memory presented by the research team has a half-band floating gate structure and an engineering Van der Waals heterostructure. The dynamic random access memory refresh time of this two-dimensional Half-Floating gate memory is 156 times higher than that of the nanosecond time scale. Semi-floating gate structure greatly improves the performance of write operation, about 106 memory is faster than other memory based on two-dimensional materials. The characteristics show that quasi-nonvolatile memory may bridge the gap between volatile and nonvolatile memory technologies and reduce the power consumption required for frequent refresh operations, thus achieving high-speed and low-power random access memory.

Quasi-nonvolatile memory based on two-dimensional semiconductor can realize high-density integration on the basis of large-scale synthesis technology. It will play an important role in many fields, such as very low power consumption, high-speed storage, utilization of data validity freedom and so on. In 2017, the team reported in Smalll that using the rich band structure of two-dimensional semiconductors to solve the "over-erasure" phenomenon in charge storage technology. In subsequent memory studies, the team found that when two-dimensional semiconductors were used to achieve new structural storage, there would be more "strange new features".

From technical definition, structural model to performance analysis, this scientific breakthrough was independently completed by the scientific research team of Fudan University. The team is based in China and takes root in China. It has made an important scientific breakthrough in the field of storage technology in the future. It is published in the form of a long article in Natural Nanotechnology.