Using ferroelectric domain walls for active control of heat flow at the nanoscale
Lead Research Organisation:
Queen's University Belfast
Department Name: Sch of Mathematics and Physics
Abstract
In order to satisfy societal demand for continual improvements in microelectronic device performance, there is an ongoing drive for transistor miniaturisation so that spatial packing densities can be maximised. However, the associated increases in operational power density leads to increased heat generation and rises in on-chip temperature that can prevent reliable device performance. This represents a tremendous technological challenge and there is a clear need to identify and characterise materials with novel thermal properties that will enable superior thermal energy management at the nanoscale. In particular, the ability to actively control heat flow with an external stimulus (e.g. voltage) could have dramatic implications for the thermal management demands and lifetimes of next generation microelectronics. In this regard, oxide ferroelectric materials present an exciting opportunity.
In ferroelectric materials, there exist atomically sharp structural interfaces called 'domain walls' (DWs) that are known to impede heat-flow by disrupting thermal vibrations. What is unique about DWs is their remarkable ability to be created, erased or repositioned inside the material in a fully reversible way by using applied voltages or pressure. This property provides an unprecedented means to actively control heat flow by being able to alter the number of DWs present in the material at a given time and the way in which they are arranged. However, to realise heat flow control using DWs, definitive estimates for the thermal interfacial resistance presented by DWs in different materials must first be determined. Therefore, one of the main goals of this project is to quantify DW thermal resistances through direct thermal conductivity measurements. Ferroelectric material systems having DWs that effectively inhibit heat flow will then be identified. Following this, prototype thermal devices will be fabricated where the relative ease of heat flow through the material will be changed by using applied voltages to reversibly alter the DW pattern. This will also provide the foundation for a longer-term research vision to create a more exotic nanostructured 'thermal mirror' device. In this case, it is envisaged that DWs can be engineered to behave as periodic reflectors of thermal waves in order to maximise the rejection of thermal energy, much like how light is reflected with high efficiency by the multiple layers in a dielectric mirror.
Over the last decade, it has become clear that DWs can be considered as a new type of sheet-like functional material with properties that can be remarkably different than bulk. For example, electrical conduction within DWs can be metallic, or even superconducting, when the bulk is comparatively insulating. Prototype active devices have been fabricated where functionality is derived entirely from deployment of electrically conducting DWs. However, the complementary idea that the narrow DW region may have thermal properties entirely of its own is completely new and unexplored. Within conducting DWs, it is likely that heat flow will be enhanced, due to the availability of extra heat carriers (e.g. mobile electrons), and thermal conductivity measurements will be carried out to confirm this. Conducting DWs will also be explored for conversion of waste heat into electricity since recent predictions indicate that the thermoelectric power can be enhanced by up to 100% within DWs, compared to bulk.
Overall, ferroelectric DWs are exciting candidates for use as the active elements in thermal devices since the DWs may behave functionally to either enhance or restrict heat-flow. However, neither case is currently well characterised nor understood. The innate reconfigurability of these DWs means there is real potential to design and build new types of active thermal devices based on ferroelectric materials that has yet to be capitalised upon.
In ferroelectric materials, there exist atomically sharp structural interfaces called 'domain walls' (DWs) that are known to impede heat-flow by disrupting thermal vibrations. What is unique about DWs is their remarkable ability to be created, erased or repositioned inside the material in a fully reversible way by using applied voltages or pressure. This property provides an unprecedented means to actively control heat flow by being able to alter the number of DWs present in the material at a given time and the way in which they are arranged. However, to realise heat flow control using DWs, definitive estimates for the thermal interfacial resistance presented by DWs in different materials must first be determined. Therefore, one of the main goals of this project is to quantify DW thermal resistances through direct thermal conductivity measurements. Ferroelectric material systems having DWs that effectively inhibit heat flow will then be identified. Following this, prototype thermal devices will be fabricated where the relative ease of heat flow through the material will be changed by using applied voltages to reversibly alter the DW pattern. This will also provide the foundation for a longer-term research vision to create a more exotic nanostructured 'thermal mirror' device. In this case, it is envisaged that DWs can be engineered to behave as periodic reflectors of thermal waves in order to maximise the rejection of thermal energy, much like how light is reflected with high efficiency by the multiple layers in a dielectric mirror.
Over the last decade, it has become clear that DWs can be considered as a new type of sheet-like functional material with properties that can be remarkably different than bulk. For example, electrical conduction within DWs can be metallic, or even superconducting, when the bulk is comparatively insulating. Prototype active devices have been fabricated where functionality is derived entirely from deployment of electrically conducting DWs. However, the complementary idea that the narrow DW region may have thermal properties entirely of its own is completely new and unexplored. Within conducting DWs, it is likely that heat flow will be enhanced, due to the availability of extra heat carriers (e.g. mobile electrons), and thermal conductivity measurements will be carried out to confirm this. Conducting DWs will also be explored for conversion of waste heat into electricity since recent predictions indicate that the thermoelectric power can be enhanced by up to 100% within DWs, compared to bulk.
Overall, ferroelectric DWs are exciting candidates for use as the active elements in thermal devices since the DWs may behave functionally to either enhance or restrict heat-flow. However, neither case is currently well characterised nor understood. The innate reconfigurability of these DWs means there is real potential to design and build new types of active thermal devices based on ferroelectric materials that has yet to be capitalised upon.
Planned Impact
Knowledge Impact: This is a cutting-edge research programme investigating how reconfigurable structural elements, called domain walls (DWs), can be leveraged to manipulate the flow of heat in nanostructured ferroelectric materials. In recent years, computational modelling capabilities have come of age and started to reveal the potential for DWs to influence nanoscale thermal transport. However, definitive experimental testing of these predictions is lacking and will be directly addressed by the planned research. This will be of high interest to the ferroelectrics community, where there is already substantial activity surrounding the functional properties of DWs in recognition of their potential for use in fundamentally new types of active device. Benchmarking the fundamental thermal properties of DWs will be a short-term impact and demonstration of working prototype devices, where the effective thermal response is tuned according to DW type, orientation, and density, will deliver impact in the medium-term. In the longer-term, attempts to create an artificial phonon band gap using a fundamentally new approach involving DWs is expected to be of tremendous impact to the broader phononics community. Throughout the fellowship, new and existing methods for investigating nanoscale thermal properties will also be developed (e.g. Scanning Thermal Microscopy) and this is expected to be of substantial value to both the functional materials academic community and industry for applications well beyond those described in this proposal.
Economy Impact: The EPSRC strategy document "Materially better: Ensuring the UK is at the forefront of material science" states that there is an "urgent need to deliver a portfolio of research that will underpin and accelerate the development of new, advanced materials" in order to help secure the UK's economic growth and prosperity. While the proposed research is largely fundamental in nature, the potential for new disruptive technologies will be assessed through fabrication of prototype active thermal devices. There is also potential for economic impact though development of new nanoscale thermal characterisation techniques; the PI is supported by an EPSRC grant to develop scanning probe microscopy instrumentation in conjunction with Asylum Research and these close ties could potentially be explored for routes to commercialisation, if necessary. In general, every effort will made to identify and protect any research findings with commercial potential and we will also work closely with QUB's dedicated support team, which specialises in IP protection and mechanisms for commercialisation.
People Impact: The PDRAs and PhD students associated with this activity will benefit from a rigorous programme of training in nanoscale functional materials that includes advanced fabrication methods, scanning probe microscopy techniques and use of low-temperature systems. This will be enabled through access to the combined knowledge base and facilities of the Centre for Nanostructured Media and the industry focused ANSIN advanced materials hub. Following this training, the PDRAs/PhDs will be well positioned to take up research posts in internationally competitive materials laboratories. They will also be attractive candidates to regional high-tech employers such as Seagate, Andor and Intel Ireland.
Society Impact: The scientific insights generated from this programme could lead to fundamentally new ways to actively manipulate heat-flow in device applications and could therefore improve quality of life for end-users and also benefit the environment. This is particularly relevant for the microelectronics industry, where innovative ideas for thermal design of components at the nanoscale have become highly important. There is also the possibility of applications for active temperature regulation at a more blue-skies level e.g., in smart-buildings and in human survival suits.
Economy Impact: The EPSRC strategy document "Materially better: Ensuring the UK is at the forefront of material science" states that there is an "urgent need to deliver a portfolio of research that will underpin and accelerate the development of new, advanced materials" in order to help secure the UK's economic growth and prosperity. While the proposed research is largely fundamental in nature, the potential for new disruptive technologies will be assessed through fabrication of prototype active thermal devices. There is also potential for economic impact though development of new nanoscale thermal characterisation techniques; the PI is supported by an EPSRC grant to develop scanning probe microscopy instrumentation in conjunction with Asylum Research and these close ties could potentially be explored for routes to commercialisation, if necessary. In general, every effort will made to identify and protect any research findings with commercial potential and we will also work closely with QUB's dedicated support team, which specialises in IP protection and mechanisms for commercialisation.
People Impact: The PDRAs and PhD students associated with this activity will benefit from a rigorous programme of training in nanoscale functional materials that includes advanced fabrication methods, scanning probe microscopy techniques and use of low-temperature systems. This will be enabled through access to the combined knowledge base and facilities of the Centre for Nanostructured Media and the industry focused ANSIN advanced materials hub. Following this training, the PDRAs/PhDs will be well positioned to take up research posts in internationally competitive materials laboratories. They will also be attractive candidates to regional high-tech employers such as Seagate, Andor and Intel Ireland.
Society Impact: The scientific insights generated from this programme could lead to fundamentally new ways to actively manipulate heat-flow in device applications and could therefore improve quality of life for end-users and also benefit the environment. This is particularly relevant for the microelectronics industry, where innovative ideas for thermal design of components at the nanoscale have become highly important. There is also the possibility of applications for active temperature regulation at a more blue-skies level e.g., in smart-buildings and in human survival suits.
Organisations
Publications
Baxter O
(2023)
High resolution spatial mapping of the electrocaloric effect in a multilayer ceramic capacitor using scanning thermal microscopy
in Journal of Physics: Energy
Maguire J
(2023)
Ferroelectric Domain Wall p-n Junctions
in Nano Letters
Suna A
(2023)
Tuning Local Conductance to Enable Demonstrator Ferroelectric Domain Wall Diodes and Logic Gates
in Advanced Physics Research
Suna A
(2022)
Conducting ferroelectric domain walls emulating aspects of neurological behavior
in Applied Physics Letters
McCluskey CJ
(2022)
Ultrahigh Carrier Mobilities in Ferroelectric Domain Wall Corbino Cones at Room Temperature.
in Advanced materials (Deerfield Beach, Fla.)
Maguire J
(2022)
Imaging Ferroelectrics: Reinterpreting Charge Gradient Microscopy as Potential Gradient Microscopy
in Advanced Electronic Materials
Zhigulin Bogdan
(2022)
Regulation of thermal transport via ferroic interfaces
Guy JGM
(2021)
Anomalous Motion of Charged Domain Walls and Associated Negative Capacitance in Copper-Chlorine Boracite.
in Advanced materials (Deerfield Beach, Fla.)
Cochard C
(2021)
Influence of charged walls and defects on DC resistivity and dielectric relaxations in Cu-Cl boracite
in Applied Physics Letters
Black N
(2021)
Deterministic Dual Control of Phase Competition in Strained BiFeO3: A Multiparametric Structural Lithography Approach
in Nanomanufacturing and Metrology
Description | Independent review of UK Research and Innovation (UKRI) |
Geographic Reach | National |
Policy Influence Type | Participation in a guidance/advisory committee |
Title | Development of High-Voltage Kelvin Probe Force Microscopy |
Description | In commercially available Kelvin Probe Microscopy systems (KPFM), voltages can typically only be sensed in the range of up to a maximum 10V which restricts the applicability of the technique for investigating circuits or samples involving applied voltages larger than 10V. In conjunction with Oxford Instruments, we have developed a measurement protocol for measuring surface potential with magnitudes larger than 10V using their high-voltage KPFM holder that enables KPFM measurements up to several hundred volts. Discussions with Oxford Instruments are ongoing regarding opportunities for patent/commercialisation if needed. |
Type Of Material | Improvements to research infrastructure |
Year Produced | 2022 |
Provided To Others? | No |
Impact | Impacts are envisioned to be forthcoming once the technique is disseminated via a peer reviewed research article |
Title | Mapping spatial variation in thermal properties using Scanning Thermal Microscopy |
Description | Scanning Thermal Microscopy is a promising technique for mapping the thermal properties of a sample with nanoscale spatial resolution by using a very sharp tip as a temperature sensor. However, in order to measure key thermal transport properties of interest, such as thermal conductivity, a microscopic heat source is also required in addition to the temperature probe. In our approach, the heater comprises of a thin gold bar deposited on the surface of the sample of interest which is periodically Joule heated. The temperature distribution across the surface of the gold bar is mapped locally using the scanning probe to detect temperature oscillations resulting from the periodic Joule heating. Spatial heterogeneity in thermal properties is inferred through variations in the amplitude of the temperature oscillations and assessed through finite element modelling of the system under study. |
Type Of Material | Improvements to research infrastructure |
Year Produced | 2021 |
Provided To Others? | No |
Impact | The technique has not yet been reported to the wider community. The technique will be reported in a peer-reviewed journal once the exploratory investigations are complete and it is anticipated that it can be implemented by any user who has access to an Atomic Force Microscope (a relatively common instrument in materials science laboratories). |
Title | Nanoscale mapping of the electrocaloric effect in oxide ferroelectrics |
Description | The electrocaloric effect involves changes in temperature (heating or cooling) of a solid body under adiabatic application of an electric field. The physical mechanism underpinning the effect is deemed to be entropy changes arising from changes in the relative alignment of microscopic dipoles. However, there is little direct evidence of the correlation between heating/cooling and the associated microstructural changes that are responsible. Hence, we have been developing a technique that allows us to measure electrocaloric temperature changes with sub-micron resolution using an Atomic Force Microscopy technique known as Scanning Thermal Microscopy (SThM). SThM enables local mapping of temperature distributions by using a very sharp temperature probe which enables sub-micron spatial resolution and order of 10mK temperature resolution. The tip monitors induced temperature changes at a given point on the surface while an electric field is cycled on and off. Once the measurement is complete, the tip moves to a neighbouring location and the field cycling and temperature recording process is repeated. Iterating this process across the surface allows 2D maps of electrocaloric heating and cooling to be extracted with sub-micron spatial resolution. |
Type Of Material | Improvements to research infrastructure |
Year Produced | 2022 |
Provided To Others? | No |
Impact | The technique has not yet been reported to the wider community. The technique will be reported in a peer-reviewed journal once the exploratory investigations are complete and it is anticipated that it can be implemented by any user who has access to an Atomic Force Microscope (a relatively common instrument in materials science laboratories). |
Description | Hosting roundtable discussion between researchers at online workshop |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | This was a roundhouse discussion between presenting academics at the online QUOROM conference (recurs quarterly) where I was one of the hosts for the discussion. The audience was mainly postgraduate research students and was a chance for the students to engage directly with the speakers in an informal way during the pandemic, when opportunities for free flow interaction have been limited. |
Year(s) Of Engagement Activity | 2022 |
URL | https://quoromvirtualconference.wordpress.com/ |
Description | Invited presentation on use of Atomic Force Microscopy for functional measurements to electron microscopists |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | This was a talk to practicing electron microscopists (academics and industry) at the joint conference of the Microscopy Society of Ireland and Scottish Microscopy Society (IMS-SMS 2022) introducing them to ways in which functional variants of Atomic Force Microscopy could be used in their research. |
Year(s) Of Engagement Activity | 2022 |
Description | Open day talk for Ewald Microscopy Facility at QUB |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Industry/Business |
Results and Impact | I delivered a presentation about some aspects of our electron and ion beam microscopy capabilities to an audience of potential academic and industry users, as part of an open day event for our microscopy facility. The event led to a doubling of the facility income from users compared to the previous financial year, with work undertaken by companies such as IceMos, Seagate, Stryker and Andor. |
Year(s) Of Engagement Activity | 2022 |
Description | Presentation to A-level students on my pathway to a career as university lecturer |
Form Of Engagement Activity | Participation in an open day or visit at my research institution |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Schools |
Results and Impact | This was a presentation on my career path to lecturer at QUB delivered to A-level students that are prospective physics degree applicants. |
Year(s) Of Engagement Activity | 2022 |
Description | Training session on how to deliver a research talk |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Undergraduate students |
Results and Impact | I delivered a 1.5hr training session on how to deliver effective research talks to a non-expert audience, using my own research as the example for how to do this. |
Year(s) Of Engagement Activity | 2022 |
Description | UKRI senior team delegation visit to NI |
Form Of Engagement Activity | Participation in an open day or visit at my research institution |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Policymakers/politicians |
Results and Impact | This was an opportunity to meet the senior UKRI delegation (CEO Professor Dame Ottoline Leyser, Chair Sir Andrew MacKenzie and teams) on their visit to NI. The visit saw UKRI chair a meeting of the Science and Innovation Strategy Forum, bringing together senior Research, Development and Innovation representatives from UKRI, BEIS and DA Governments and Funding Bodies. I had an opportunity to meet members or the delegation during evening dinner to discuss my experience so far with the Future Leaders Fellows scheme as well as help showcase the strength of Queen's research community and to discuss alignment of the university's 2030 goals to UKRI strategy. |
Year(s) Of Engagement Activity | 2022 |