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A universal memory that never runs out of steam
Published in Rajesh Singh, Anita Gehlot, Intelligent Circuits and Systems, 2021
Urvashi Sharma, Sachin Mishra, Gulshan Kumar, Reji Thomas
Some of the dielectric materials, ferroelectric materials are also used in non-volatile memories. The perovskite materials, PbTiXZr1xO3 (PZT) and layered strontium-bismuth-tantalite alloy (SBT) are the ferroelectric choice for this so far [5]. This non-volatile memory is termed as ferroelectric RAM (Fe-RAM). The cell construction is the same as DRAM (1T-1C) with a non-linear ferroelectric capacitor instead of a linear dielectric capacitor [9]. Fe-RAMs are based on remnant polarization at zero applied electric field in ferroelectric crystal. These have the ability to switch polarization (±Pr) with an external electric field [5]. It has the non-volatility of Flash, but having demerits of lower density (< DRAM) and high manufacturing cost (~SRAM). Fe-RAM is used in local area network (LAN) bypass, advanced metering, automotive shift-by-wire, process control in industries, navigation, solid-state drive (SSD), gaming, motion control etc. The widely investigated ferroelectric-memories possess low voltage to 0.9 V, endurance more than 1013 write/read cycles, write speed of 100 ns at low voltage with retention of about 10 years [19]. However, the low density is the hindrance in replacing Flash, EEPROM, DRAM and SRAM to realize a “Universal Memory” with ferroelectric and this aspect is discussed in the following section.
Bipolar resistive switching characteristics of amorphous SrTiO3 thin films prepared by the sol-gel process
Published in Journal of Asian Ceramic Societies, 2019
Hui Tang, Xin-Gui Tang, Yan-Ping Jiang, Qiu-Xiang Liu, Wen-Hua Li, Li Luo
In recent decades, continuous optimization of computer technologies marking the rapid development of modern information technology has progressively changed people’s lifestyles. Memory is an indispensable carrier of information technology and is regarded as one of the most important technologies in the field of integrated circuits [1]. Semiconductor memory has been widely applied in various fields, such as information technology, social security, aerospace, defense and military [2]. Compared with volatile memory, however, non-volatile memory has great superiority in the field of mobile storage media owing to its ability, to maintain its internal storage properties even after a power failure. With the burgeoning of technologies, various types of new electronic products have emerged in an endless stream. These electronic products also have more stringent requirements for memory performance, such as high reading and writing speeds, high storage density, low power consumption, long life, greater thinness and smaller size [3,4]. The flash memory devices that play significant roles in the current electronic market still suffer from many disadvantages, such as the low operation speed, poor endurance and high write voltage problems. Eventually, miniaturization limits will be a critical issue for flash memory in future application [5]. As a result, most of today’s electronic technology research is focussing on new types of memory devices nowadays. There are many kinds of memory devices based on different mechanisms and materials that are highly likely to replace non-volatile memory, such as resistive random access memory (ReRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), and phase change memory (PCM) [1–6]. Among these new types of memory, resistive switching (RS) memory has been widely studied due to such advantages as its simple preparation process, low energy consumption, predominant memory density, small size, and good compatibility with the conventional CMOS process [7,8]. The ReRAM memory device is a novel non-volatile memory based on the principle of resistance change of thin film materials [9,10]. The ReRAM’s metal/insulator/metal (MIM) structure is composed of a thin film functioning as an insulating layer, with conductive materials as bottom and top electrodes [11,12]. This development has attracted widespread attention in the industry and academia, and many new investigations of resistive memory have been initiated by researchers [13,14]. The RS effect of the insulator layer has been discovered in various kinds of amorphous metal oxides, such as ZnO, HfO2, TiO2, MgO, Al2O3, and Y2O3 [15–19]; and in amorphous perovskite and layered perovskite oxides such as YCrO3, Pr0.67Sr0.33MnO3, Bi3.15Bd0.85Ti3O12, SrTiO3 and Nb-doped SrTiO3 [20–26], etc. Among these, the amorphous strontium titanate-based memory structure uses the following electrodes: Pt, Ti, and indium tin oxide (ITO) [23–26]. These form Pt/amorphous-SrTiO3 (a-STO)/Pt [23], Pt/Ti/a-STO/Pt [24], Pt/Ti/a-Nb:STOx/Pt [25] and ITO/Ti/Ti2O3/a-STO/ITO [26] memory cells, respectively.