Under the support of the Ministry of Science and Technology, the research team led by Professors Jan-Chi Yang and Yi-Chun Chen from Department of Physics of National Cheng Kung University (NCKU) has made a significant leap in manipulation of new generation memory material, Bismuth ferrite (BiFeO3). BiFeO3 is a multi-digit memory material that can simultaneously record eight logic states (0-7) in a single memory unit. Compared to the traditional 1 bit memory system (with two operation states, 0 and 1), utilization of multi-digit memory can greatly increase the density of stored information. The NCKU research team successfully develops a novel technology for non-contact optical control of the multiple memory states. With the multi-digit materials and light control technology, the volume of existing memory can be significantly reduced and the energy consumption/dissipation will be further decreased. Upon the application of light controllable multi-digit memory to artificial intelligence development and cloud computing, it not only can reduce the delay time of data reading, but also further the calculation efficiency. This technology is expected to bring revolutionary breakthrough in the trend of miniaturizing multifunctional nano-devices in the near future. This work is published on May 6th in prestigious international peer-review journal “Nature Materials”.
Breakthrough: New alternative for the future information technology
With the increasing demand of modern society, smart and automated technologies such as Internet of Things, cloud computing, artificial intelligence and big data analytics are booming. When it comes to information processing, data storage is one of the primary parts. If the large-capacity, miniaturized, high-speed, energy-saving and reliable storage technology can be mastered, the ultra-high-performance computing platform can be achieved. The basic unit of the traditional memory is composed of two logic states, 0 and 1. Under similar framework, the memory density can only be increased by continuously reducing the size of the component, and the development limit will be finally reached. Therefore, exploring new materials with more multiple logic states, as well as new access technologies, is the central key towards future information technology.
In the work accomplished by the research group in NCKU, the multi-digit material under investigation provides a new solution to aforementioned requirements. Take the traditional hard disk based on magnetic films as an example: it utilizes ferromagnetic order to record two logic states, 0 and 1. In contrast, the memory element of the multiferroic material BiFeO3 includes the spontaneous electric dipole moment and the electron spin arrangements, offering the possibility for multi-digit operation. Professor Chen mentioned that BiFeO3 contains electrical, magnetic and antiferromagnetic orders, which can record eight logic states in a single storage unit, and the memory size can be theoretically trimmed down to the sub-nano scale without losing its information. Moreover, current non-volatile memory devices generally have the disadvantage of losing data after a long period of power failure, while the memory devices based on the multiferroic material is much more stable.
The most important breakthrough in this research is to provide the light tunability to such multi-digit materials. Generally speaking, light is an alternating electromagnetic wave, thus in traditional experience, it cannot induce specific non-valotile configuration change. Professor Yang pointed out that the key optical approach proposed by the team is to adopt the ight-induced local deformation, i.e. the light induced flexoelectric effect. The optically controllable memory does not require any metal electrode and related complicated fabrication process, which nicely fulfilles the concept of “the material is the device”. The multi-digit memory that is light controllable essentialy brings new thought to the development of new generation memory. Taking advantages of this discovery, the material can be directly integrated with related advanced optical technologies such as quantum storage, quantum communication, etc.
The Ministry of Science and Technology (MOST) has constantly encouraged young scholars to devote innovate ideas, to produce breakthrough results, and to gain a leading position worldwide. Prof. Shieh, Dar-Bin, the deputy minister of MOST, said that Prof, Yang and Prof. Chen are talented and excellent young scholars. The outstanding achievements of this study are not only a demonstration of young scholars' creativity, but also the best example evidencing fundamental researches could respond to forward-looking applications. MOST will unceasingly support the development of fundamental science and look forward to more breakthroughs in innovative technologies.
Professor Jan-Chi Yang
Department of Physics, National Cheng Kung University
Dr. Chin-Wei Chen
Program Manager/Assistant Research Fellow,
Department of Natural Sciences and Sustainable Development,
Ministry of Science and Technology
 "Deterministic optical control of room temperature multiferroicity in BiFeO3 thin films" (https://www.nature.com/articles/s41563-019-0348-x)