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Driscoll Research Group

 

Energy Efficient Oxide Materials for ICT

Our three main projects in the field of low-power non-volatile memory (NVM) and neuromorphic computing are funded though Prof. Driscoll's Royal Academy of Engineering Research Chair, her ERC Advanced Grant, and an ECCS-EPSRC grant in collaboration with researchers from the USA. Here, we provide a general overview over our research in this field.

Conventional computer memory is either fast, but volatile (Randem Access Memory - RAM) or non-volatile, but slow (Hard Disk Drives (HDDs) or Magnetic Tape). The closest technology in between these two extremes is NAND Flash such as in Solid State Drives, which is non-volatile and achieves higher speed than HDDs through parallelisation of read and write operations. However, Flash requires much higher programming voltages than the other technologies, so that it is not suitable for low-power applications either.

In non-volatile memory such as HDDs and Magnetic Tape, information is stored in the magnetic polarisation of a storage material, whereas in RAM devices, information is stored in the form of charge on a dedicated capcitor (RRAM) or the charge on the gate terminals of two cross-coupled inverters (SRAM). Charge is prone to leaking out of such terminals, which makes the fast charge-based memores volatile. Our approach to designing new and energy-efficient computer memory relies on the nanoengineering of oxide thin films, where information can be stored in different materials properties other than charge. Such properties can be a stable electrical resistance, the direction of ferroelectric rather than ferromagnetic polarisation, or the arrangement of oxygen vacancies within an oxide. The video below provides more information.

 Example Recent papers

Roy P, Kunwar S, Zhang D, Corey Z, Rutherford B, Wang H, MacManus-Driscoll JL,  Jia QX, Chen A, Role of Defects and Power Dispassion on Ferroelectric Memristive Switching,  accepted Advanced Electronic Materials, https://doi.org/10.1002/aelm.202101392, Feb. 2022.

 

Antoniou G, Halcovitch NR, Mucientes M. Milne WI, Nathan A, MacManus-Driscoll JL, Kolosov OV,  Adamopoulos G, Solution-processed thin film transistors incorporating YSZ gate dielectrics processed at 400°C, APL Materials, https://doi.org/10.1063/5.0079195, Feb. 2022.

 

Silva JPB, Sekhar KC, Negrea RF, MacManus-Driscoll JL, Pintilie L, Progress and perspectives on the different strategies to achieve wake-up free ferroelectric hafnia and zirconia-based thin films, Applied Materials Today, https://doi.org/10.1016/j.apmt.2022.101394: Mar. 2022: 26, 101394.

 

Wu R and MacManus-Driscoll JL, Recent Developments and the Future Perspectives in Magnetoelectric Nanocomposites for Memory Applications, APL Materials, https://doi.org/10.1063/5.0076106: Jan. 2022; 010901.

 

Video 1. An introduction to Sustainable Memory Devices by Dr. Guliana di Martino, Dr. Chiara Ciccarelli,
and Prof. Judith Driscoll, narrated by Sunny Howard.

 

Two Example Studies:

a) Resistive memory (and neuromorphic computing for AI): Scaleable, uniform and robust resistive switching.

 

a) Resistive memory (and neuromorphic computing for AI): Scaleable, uniform and robust resistive switching.

Arguably, oxide memristors represent the most ideal NVM (and possible neuromorphic) system in terms of simple composition, potential for lowest cost and highest density. However, problems still remain in terms of scaling, uniformity and robustness. Memristors could offer the required, low power, technology for both non-volatile memory and neuromorphic computing. We have demonstrated ways to overcome all these problems in model systems. We are currently working on translating these model systems to industry practical systems.

Figure 1. Oxide memristor films. (a) As-grown without defect and interface engineering showing only a small memory window. (b) Precision engineering film showing a large memory window.

 

b) Magnetoelectric memory: Magnetoeletricity above room temperature in simply- grown, self-assembled composite thin film systems.

Electric field control of magnetism (magnetoelectricity) could provide for ultra-high density non-volatile memory. No currents are passed during switching and so these systems have potential for ultra-low power. However, despite intensive research efforts, no practical materials systems have emerged. Interface-coupled, composite systems containing ferroelectric and ferri-/ferromagnetic elements have been the most promising, but they have many problems, e.g. substrate clamping, large unwanted currents (leakage), and they cannot be miniaturized to give high density recording. Through careful materials selection, design, and nanoengineering, we have demonstrated a high-performance room temperature magnetoelectric system (Fig. 3). Large converse magnetoelectric coefficients have been achieved of >10e-9 s/m.

Figure 3. Self-assembled, triple nanocomposite thin film structure designed and fabricated in the Driscoll lab, composed of a ferroelectric (NBT), a ferrimagnet (CFO) and an antiferromagnet (NiO). The three materials ‘interact’ with one another in a new way.  Their interaction enables the first one-shot, simply grown thin film material to enable, for the first, time, electric field control of the magnetic signal at room temperature. This system paves the way for a new form of  highly energy efficient magnetoelectric memory. Images from our papers: https://doi.org/10.1038/s41928-021-00584-y and https://doi.org/10.1063/5.0076106

 

Video 2. Laboratory tour by Prof. Judith Driscoll and Dr. Giuliana Di Martino demonstrating their work in
the field of nanoplasmonics.

 

Prof. Driscoll warmly welcomes enquiries from prospective students, post-docs or visitors who are interested in working with us or learning more about what we do.

For a full list of MacManus-Driscoll publications, please see: https://scholar.google.co.uk/citations?user=-lYrze0AAAAJ&hl=en