Phase Change Memory Materials via Non-Aqueous Electrodeposition into Nano-structured Templates
Lead Research Organisation:
University of Southampton
Department Name: Sch of Chemistry
Abstract
This project is concerned with developing non-aqueous electrochemical methods and suitably tailored reagents to facilitate spatially selective electrodeposition of binary (e.g. In2(Se,Te)3, Sb2(Se,Te)3, Ge(Se,Te)) and the ternary chalcogenide materials (e.g. Ge2Sb2Te5, doped Sb2Te3) for applications in solid-state phase change memory (PCM). The key objectives are to demonstrate successful deposition of the target materials inside nano-scale (down to 2 nm) confined cell structures and to establish the effect of down-scaling pore size on the deposition process. Successful electrodeposition of well-defined compound semiconductor alloy compositions of these types will provide a significant new enabling technology which could also have a major impact on the other applications requiring semiconductor alloy deposition on a nano-scale. Using non-aqueous solvents (such as MeCN, propylene carbonate or chlorofluorocarbons) will bring several advantages over aqueous processes:(i) the use of a much wider range of reagents which can be tailored to the application;(ii) access to more reactive alloy compositions;(iii) a wider range of deposition potentials,while these solvents are more readily available, less expensive, much more easy to purify and less viscous (important for penetrating narrow. high aspect-ratio pores) than for example ionic liquids.These chalcogenide alloys are of major interest for phase change memory (PCM) materials - an emerging technology for non-volatile memory which is expected to compete with (and even replace) FLASH memory in specialist and everyday consumer electronics. Production of these alloys by electrodeposition could bring several advantages over current methods of production (mainly PVD), since it allows spatially selective deposition (since the materials are only deposited on the electrode surface), filling the pores of the templates from the bottom, hence enabling complete filling even of very narrow nanopores - leading to a very significant reduction of the dimensions of each individual cell, and hence potentially much higher cell density. In turn this will lead to faster switching between the crystalline and non-crystalline phases, leading to smaller devices and greater energy efficiency. To achieve these targets requires a multidisciplinary approach involving several key contributions: (i) to develop (and refine) new tailored molecular compounds (electrochemical reagents) with elements from the p-block (gallium, indium, germanium, antimony) in combination with groups containing the chalcogens i.e. the elements selenium and tellurium; (ii) to use these as reagents for the growth of the binary & ternary alloy materials by electrochemical deposition into nano-structured silica or alumina templates comprised of very narrow parallel pores with well-defined diameters between 1000 nm and 2 nm; (iii) characterisation of the deposited materials to determine the element ratios present (composition), their crystal structures, and phase change properties;(iv) deposition of the 'best' compositions into well-defined pores on a chip array to allow switching of the arrays memory cells in an actual device, hence demonstrating the true potential of this new approach.The team of investigators brings together a complementary and internationally unique set of skills and expertise to achieve these targets, while the input from our Project Partners, Ilika Technologies Ltd will add considerable value to the project.
Planned Impact
The research described in this proposal will develop non-aqueous electrodeposition as an enabling technology for the controlled growth of binary and ternary semiconductor alloys inside nano-structured templates. The target application is solid-state phase change memory. The work has potential in the short to medium term to have very considerable impact in the field and is likely to attract much interest to companies engaged in materials discovery for a wide range of applications, in addition to those semiconductor companies in the private sector working on PCM manufacture, as indicated in the attached Letter of Support from Ilika Technology Ltd. PCM is a very timely and topical area of research since it is an emerging technology that has the capacity to compete with FLASH memory in specialist and consumer electronic devices. One of the key stumbling blocks at present is the difficulty in down-scaling the memory cell size to the targets set out in the Semiconductor Roadmap - our method has a really good chance of achieving this, since the deposition can only occur at the electrode surface - i.e. at the bottom of the nano-pores. Furthermore, electrodeposition allows control over the thickness of the deposit, simply by switching off the potential. Thus, growing the alloys to a specific (regular) depth inside very narrow pores using our approach is entirely feasible. Key targets are to develop reagents which can be used to demonstrate successful deposition of the target compositions via the non-aqueous electrochemical method, and to demonstrate that these materials can be grown inside the pores of nano-structures of diameter 1000 to 2 nm. Phase change media feature strongly in the new EPSRC-supported Centre for Nanostructured Photonic Metamaterials in the University of Southampton. Discussions with colleagues there have already indicated considerable interest in the electrodeposition of PCMs as an enabling technology and we will be active in exploiting new opportunities arising in this area too. In addition to the IP arising from this work (which we intend to protect through patent applications and exploit with advice and expertise from staff in the Research & Innovation Services in the University of Southampton), the project has the potential to deliver very high impact publications - internationally leading journals such as Nature Materials, Advanced Materials, JACS and Angewandte Chemie will be targeted. The relevance of the topic of this research project and their end applications mean that it lends itself extremely well to public (consumer) dissemination. The investigators have established track records in outreach and the 'promotion of science' to non-specialist audiences and will be active in pursuing these dissemination pathways e.g. through talks and workshops for schools, science fairs etc., articles in newsletters, Education in Chemistry, Chem. & Eng. News etc. Support in the preparation of suitable news items and flyers will be provided by our marketing expert in the Faculty (C. Mills).
Publications
Bartlett P
(2015)
Non-aqueous electrodeposition of functional semiconducting metal chalcogenides: Ge 2 Sb 2 Te 5 phase change memory
in Materials Horizons
Bartlett P
(2013)
Non-aqueous electrodeposition of p-block metals and metalloids from halometallate salts
in RSC Advances
Bartlett P
(2016)
Haloplumbate salts as reagents for the non-aqueous electrodeposition of lead
in RSC Advances
Benjamin S
(2015)
Chemical vapour deposition of antimony chalcogenides with positional and orientational control: precursor design and substrate selectivity
in Journal of Materials Chemistry C
Benjamin S
(2014)
Controlling the nanostructure of bismuth telluride by selective chemical vapour deposition from a single source precursor
in Journal of Materials Chemistry A
Benjamin SL
(2013)
Area Selective Growth of Titanium Diselenide Thin Films into Micropatterned Substrates by Low-Pressure Chemical Vapor Deposition.
in Chemistry of materials : a publication of the American Chemical Society
De Groot C
(2012)
Highly Selective Chemical Vapor Deposition of Tin Diselenide Thin Films onto Patterned Substrates via Single Source Diselenoether Precursors
in Chemistry of Materials
Everett M
(2015)
Cationic aza-macrocyclic complexes of germanium(II) and silicon(IV).
in Dalton transactions (Cambridge, England : 2003)
Everett M
(2014)
Unexpected neutral aza-macrocycle complexes of sodium.
in Chemical communications (Cambridge, England)
Description | This work has developed a highly versatile non-aqueous electrolyte system that can be used electrodeposit a wide range of technologically important semiconducting materials. This has been demonstrated specifically for one of the most challenging targets, the ternary alloy Ge2Sb2Te5. We have also shown that by varying the relative concentrations of the 3 custom-made precursor compounds (to supply the individual elements in the alloy) and by varying the deposition potential, it is possible to adjust the stoichiometry in a very controlled manner across the whole phase diagram and to create individual memory cells on the 50-100 nm scale. Device structures based upon these cells can be repeatedly switched between the amorphous and crystalline phases with good endurance and resistance ratio - key demonstrators of device quality material. |
Exploitation Route | This work could be taken forward in a number of different ways - e.g. to develop multi-level memory devices, or by further scaling down the dimensions of the individual memory cells to sub 10 nm, to the point at which new memory architectures could be realised. The generality of our (patented) process also opens this approach to other application areas based upon other semiconducting materials, such as thermoelectrics. |
Sectors | Electronics,Energy |
URL | http://www.southampton.ac.uk/chemistry/research/projects/electrodeposition-of-semiconducting-chalcogenides-from-unusual-meida.page? |
Description | EPSRC Programme Grant |
Amount | £6,330,000 (GBP) |
Funding ID | EP/N035437/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 07/2016 |
End | 07/2021 |
Title | A PROCESS FOR THE ELECTROCHEMICAL DEPOSITION OF A SEMICONDUCTOR MATERIAL |
Description | A process for the electrochemical deposition of a semiconductor material, which process comprises: (i) providing a non-aqueous solvent; (ii) providing at least one precursor salt which forms a source of the constituent elements within the semiconductor material to be deposited; and (iii) electrodepositing the semiconductor material onto an electrode substrate using the precursor salt in the non-aqueous solvent, characterised in that: (iv) the semiconductor material is a p-block or a post-transition metal semiconductor material containing at least one p-block element or post-transition metal; and (v) the non-aqueous solvent is a halocarbon non-aqueous solvent. |
IP Reference | WO2014016544 |
Protection | Patent granted |
Year Protection Granted | 2014 |
Licensed | No |
Impact | n/a |
Description | Atoms Crystals & Diffraction |
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 | Public/other audiences |
Results and Impact | Activities sparked discussion with members of the public and school students Invited to present at school science clubs |
Year(s) Of Engagement Activity |
Description | Electrochemical Preparation of Nanostructured Phase Change Random Access Memory Devices |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | sparked discussions with other academic experts and with industry representatives prompted requests for further information and invited lecture at international conference |
Year(s) Of Engagement Activity | 2014 |
Description | Electrodeposition of Alloys for Phase Change Random Access Memory Applications |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | Prompted discussion re potential applications of the work Increased interest from colleagues & peers |
Year(s) Of Engagement Activity | 2014 |
Description | Electrodeposition of Phase Change Materials |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | Increased interest in the research in this project and its potential application. Increased discussion with other researchers and companies. |
Year(s) Of Engagement Activity | 2012 |
Description | Electrodeposition of Ternary Alloys for Phase Change Random Access Memory Applications |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | prompted detailed discussions - |
Year(s) Of Engagement Activity | 2014 |
Description | Electrodeposition of Ternary Alloys for Phase Change Random Access Memory Applications |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | prompted discussion and questions - |
Year(s) Of Engagement Activity | 2014 |
Description | GST in Nanostructures through Electrodeposition - a New Approach to the Preparation of Phase Change Materials |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | prompted requests for further information - |
Year(s) Of Engagement Activity |
Description | Miniaturisation of electronics components using electrodeposition |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | sparked focussed discussion on application of electrochemistry in electronics - |
Year(s) Of Engagement Activity | 2014 |
Description | Preparation of Phase Change Materials through the Electrodeposition of Individual and Alloyed p-Block compounds |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other academic audiences (collaborators, peers etc.) |
Results and Impact | Awarded prize for oral presentation Increased interest in research topic |
Year(s) Of Engagement Activity | 2012 |
Description | Supercritical Fluid Electrodeposition |
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 | Public/other audiences |
Results and Impact | Stimulated discussion with members of the public; prompted application to exhibit at Royal Society Summer Exhibition (pending) enthusiastic engagement and discussions |
Year(s) Of Engagement Activity |
Description | UK Thermoelectrics Network Meeting |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | Invited talk at the EPSRC Thermoelectric Meeting, Manchester, February 2017 |
Year(s) Of Engagement Activity | 2017 |
Description | school visit (Winchester) |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | activities stimulated enthusiastic discussion and engagement from pupils invited back |
Year(s) Of Engagement Activity |