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Driscoll Research Group

 

 

Theme 1. Energy efficient ICT

We work on designing and nanoengineering oxide thin films for much improved energy efficient ICT. looking in particular at materials for non-volatile memory and in-memory computing.

We are at the beginning of a Data Age. There is a wide range of rapidly growing dta centric technologies spanning Big Data, IoT, transport, medicine, electric vehicles, security, entertainment, and neuromorphic computing for AI. In most of these areas, memory energy dominates over compute energy and low power non-volatile memory (NVM) is urgently needed. Also, neural network based deep learning embedded in edge computing devices could provide the solution to the high computing efficiencies.

 

Research Theme 1

 

Figure 1. Data centre, with image of film (courtesy of Haiyan Wang and group, Univ. Purdue) used for creating new low power non-volatile memory device and the switching of its resistance states from high resistance state (HRS) and low resistance state (LRS) (plot courtesy of Chao Yun, Driscoll group).

 

Video 1. Laboratory tour by Prof. Judith Driscoll and Dr. Giuliana Di Martino demonstrating their work in the field of nanoplasmonics materials

 

 

Video 2. An introduction to Sustainable Memory Devices by Guliana di Martino, Chiara Ciccarelli and Judith Driscoll

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

 

Arguably oxide memristors represent the most ideal NVM system in terms of simple composition, potential for lowest cost and highest density (Fig. 1). 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. However, currently, there are problems of non-uniformity, difficulty to scale to small dimensions (20 nm and below), and robustness. These are all materials-related problems. We have demonstrated ways to overcome them in model systems (Fig. 2). We are currently working on translating these model systems to industry practical systems.

 

 

Figure 2. Oxide memristor films. (a) As-grown. (b) Schematic illustration of the strain mediated ME effect VAN films. (c) Magnetic hysteresis loops along the OOP direction and (d) magnetic hysteresis loops along the IP direction with and without applying in-situ voltages (plots courtesy of Chao Yun, Driscoll group).

 

 

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). A vertically aligned triple nanocomposite structure in which the strain coupling is independent of the substrate was used and a new, low leakage ferroelectric material was employed. Large converse magnetoelectric coefficients have been achieved of >10-9 s m-1.

 

Research Theme 3

 

Figure 3. Large RT ME effect in composite film. (a) typical AFM image of sample surface. (b) Schematic illustration of the vertical strain mediated effect. (c) Magnetic hysteresis loops along the OOP direction with different voltages applied.

 

Example references:

Rui Wu, Ahmed Kursumovic, Xingyao Gao, Chao Yun, Mary E. Vickers, Haiyan Wang, Seungho Cho, and Judith L. MacManus-Driscoll. Design of a Vertical Composite Thin Film System with Ultralow Leakage To Yield Large Converse Magnetoelectric Effect. ACS Appl. Mater. Interfaces, 2018, 10 (21), pp 18237–18245 (DOI: 10.1021/acsami.8b03837).

Choi EM, Maity T, Kursumovic A, Lu P, Lee OJ, Bi Z, Park Y, Wu R, Gopalan V, Wang H, MacManus-Driscoll JL, Nanoengineering Giant Room Temperature Ferroelectricity into Orthorhombic SmMnO3 Films, Nature Communications. May 2020; 11, 2207.

 

Theme 2. Storage, generation and transmission

A sustainable planet requires not only less use of energy. While our aim in Theme 1 is Energy efficient ICT, i.e. in the use part of energy, we also need to consider greener energy generation, transmission and storage. There are strong links and cross-cutting themes between themes 1 and 2. For example, controlling the electrochemical processes in oxide resistive memory is relevant to thin film batteries and micro-SOFC. Oxide thin film materials are the key enabling platform for all the studies.

 

 

a) Superconductors for lossless power applications

Prof. Driscoll has worked on copper oxide high temperature superconductors (HTS) since their discovery in 1986. She invented nanopinning in YBCO and also low pO2, liquid assisting processing. These methods have been taken up by industry. There is a strong current interest in HTS for fusion power, lossless power transmission, and generators on wind turbines. Both in terms of performance and low cost, successful deployment of these applications requires novel materials science, engineering and processing of HTS systems, not only of YBCO but other less explored cuprates. We are engaged in all these areas (example in Fig. 4). We collaborate with researchers at ENEA in Italy, SuNAM in Korea, the Naval Research Lab in the US, and Tokomak Energy, UK.

 

Research Theme 4

 

Figure 4. Plot of Tc versus c parameter in La2CuO4-d with a parameter as a variable on the plot. For the first time, c and a have been tuned independently in the crystal structure which has produced an increase of the Tc from <30K to 50K.

 

Example references:

Choi EM, Di Bernardo A, Zhu B, Lu P, Alpern H, Zhang KLH, Shapira T, Feighan J, Sun X, Robinson J, Paltiel Y, Millo O, Wang H, Jia Q.X, MacManus-Driscoll JL, 3D strain-induced superconductivity in La2CuO4+δ using a simple vertically aligned nanocomposite approach, Science Advances. April 2019;5,eaav5532.

Choi EM, Zhu B, Lu P, Feighan J, Sun X, Wang H, and MacManus-Driscoll JL, Magnetic signatures of 120 K superconductivity at interfaces in La2CuO4+δ, Nanoscale. Jan 2020; 12, 3157

Celentano G, Rizzo F, Augieri A, Mancini A, Rufoloni A, Vannozzi A, MacManus-Driscoll JL, Feighan J, Kursumovic A, Meledin A, Van Tendeloo, G, YBa2Cu3O7-x films with Ba2Y(Nb,Ta)O6 nanoinclusions for high field application, Supercond. Sci. Tech. Feb 2020; 33, 044010

 

 

b) Ionics for Energy Storage and Conversion

Interfaces in ionic systems, whether they be solid state batteries or fuel cells, are limiting to performance. Using our perfect superlattice and nanocomposite film systems (Fig. 5), and by doing wide ranging characterisation (including NMR of films removed from substrates) we are understanding these limitations, and then devising new film compositions and structures to overcome them.

 

Research Theme 5

 

Figure 5. Self-assembled ionic nanocomposite films used for probing ionic motion along and across interfaces. (courtesy of B. Zhu, Driscoll group.

 

Example references:

Acosta M, Baiutti F, Tarancon A, MacManus-Driscoll JL, Nanostructured Materials and Interfaces for Advanced Ionic Electronic Conducting Oxides, Advanced Materials Interfaces. May 2019; 6, 1900462.

Zhu B, Schusteritsch G, Lu P, MacManus-Driscoll JL, Pickard CJ, Determining Interface Structures in Vertically Aligned Nanocomposite Films, APL Materials. May 2019; 7, 061105.

 

c) Ferroelectrics for energy storage and conversion

High performance energy storage devices are in very high demand in electric vehicles (EVs), where it is critical to store and deliver energy quickly. Ferroelectric materials have high capacitance and can deliver energy more quickly than conventional batteries, while batteries have higher energy density. Oxide thin films have an important role to play in both capacitors and solid state battery components. We have used new thin film processing approaches to demonstrate very high performance ferroelectric material (Fig. 6).

 

The material has a high dielectric breakdown strength, a flat capacitance from 100°C to 300°C, and high energy density, all of which are required for EVs.

 

Research Theme 6

 

Figure 6. High Energy Storage in Precision Engineered Thin films of BaTiO3+BiFeO3

In collaboration with Prof. Khare in IIT Delhi, we’ve showed the benefits of ferroelectricity for photoelectrochemical generation of H2. We used nanoporous ferroelectric Ag,Nb-codoped to achieve a ∼3-fold enhancement in photocurrent by decreasing the flat-band potential (giant ferroelectric tuning of the band alignment at the semiconductor surface) which gave rise to enhanced charge transfer.

 

Example references:

Kursumovic A, Cho S, The DHL, and MacManus-Driscoll JL, Lead-Free Relaxor Ferroelectric Thin Films with Huge Energy Storage Density and Low Dielectric Loss for High Temperature applications, Nano Energy. May 2020; 71,104536.

Singh S, Sangle AL, Khare N, MacManus-Driscoll JL, Growth of Doped SrTiO3, Ferroelectric Nanoporous Thin Films and Tuning of Photoelectrochemical Properties with Switchable Ferroelectric Polarization, ACS Applied Materials and Interfaces, Nov 2019, 11, 49.

 

d) Oxides in solar cells

We have been using oxides in solar cells either as hole or electron transport layers, or for new defect tolerant absorber, e.g. BiOI, or both. Oxides are excellent materials as transport layers as they can be doped to enable good band matching across interfaces (Fig. 7).

 

 Research Theme 7 v2

 

Figure 7. Band positions of electron transport layers (yellow), bismuth-based absorbers (red) and hole transport layers (green).

 

Example references:

Jagt R, Huq TN, Hill SA, Thway M, Liu T, Napari M, Roose B, Galkowsk K, Li W, Lin SF, Stranks SD, MacManus-Driscoll JL, Hoye RLZ, Printed high-mobility p-type buffer layers on perovskite photovoltaics for efficient semi-transparent devices, 2020.

Li Y Hoye RLZ, Gao H-H, Yan L, Zhang X, Zhou Y, MacManus-Driscoll JL, Gan J, Over 20% Efficiency in Methylammonium Lead Iodide Perovskite Solar Cells with Enhanced Stability via “In-Situ Solidification” of the TiO2 Compact Layer, ACS Applied Materials and Interfaces. Jan 2020; 12, 7135.

Huq TN, Lee Eyre L, Li W. Jagt RA, Kim C, Fearn S, Pecunia V, Deschler F, MacManus-Driscoll JL, Hoye RLZ, Electronic Structure and Optoelectronic Properties of Bismuth Oxyiodide Robust Against Percent-Level Iodine, Oxygen- and Bismuth-Related Surface Defects, Advanced Functional Materials. Feb 2020; 30, 1909983

Lee LC, Hug, TH, MacManus-Driscoll, JL, Hoye, RLZ, Bismuth-based perovskite-inspired photovoltaic materials. APL Materials. Aug 2018;6:084502.

 

 

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