Professor Shashi Paul

Job: Professor of Nanoscience and Nanotechnology and working for Emerging Technologies Research Centre

Faculty: Computing, Engineering and Media

School/department: School of Engineering and Sustainable Development

Research group(s): Emerging Technologies Research Centre (EMTERC)

Address: De Montfort University, The Gateway, Leicester, LE1 9BH, United Kingdom

T: +44 (0)116 207 8548

E: spaul@dmu.ac.uk

W: https://www.dmu.ac.uk/emterc

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Personal profile

I graduated from Indian Institute of Science, Bangalore, India and have previously worked in Cambridge University., Durham University, and Rutgers University. My research interests include manufacturing and analysis of nano-materials and their applications into energy (e.g. photovoltaic solar cells), electronics (emerging electronic memory devices including neuromorphic) and biological sensors. My particular focus is on the development of materials manufacturing processes to reduce the carbon footprint and next generation electronic devices.

Research group affiliations

Institute of Engineering Sciences (IES)

Publications and outputs

Schottky barrier formation on r.f.-plasma enhanced chemical vapour deposited hydrogenated amorphous carbon
dc.title: Schottky barrier formation on r.f.-plasma enhanced chemical vapour deposited hydrogenated amorphous carbon dc.contributor.author: Paul, Shashi; Clough, F. J. dc.description.abstract: This paper reports the fabrication and electrical characterization of sub-micron metal contacts to thin films of hydrogenated amorphous carbon deposited by the r.f.-plasma enhanced chemical vapour deposition technique. The I–V characteristics of “large” area (diameter 0.5 mm) top metal contacts to amorphous carbon are consistent with bulk limited conduction by the Poole–Frenkel mechanism. The I–V characteristics of sub-micron metal contacts, formed at different locations on the same amorphous carbon film, range from symmetrical to highly asymmetrical with forward-to-reverse rectification ratios up to three orders of magnitude. Asymmetrical I–V characteristics and a linear C−2–V response confirm, for the first time, Schottky barrier formation at the metal/amorphous carbon interface. Spatial non-uniformity in the composition of the hydrogenated amorphous carbon surface is indicated, which mirrors bulk inhomogeneity.
Investigation on the Mist intensity to deposit Gallium Oxide thin films by Mist Chemical Vapour Deposition (M‐CVD)
dc.title: Investigation on the Mist intensity to deposit Gallium Oxide thin films by Mist Chemical Vapour Deposition (M‐CVD) dc.contributor.author: Ganguly, Swapnodoot; Manjunatha, Krishna Nama; Paul, Shashi dc.description.abstract: This study demonstrates a novel, simple and robust Mist‐CVD (M‐CVD) compatible with existing industrial practices to deposit gallium oxide thin films and influence of mist intensity on the properties of gallium oxide. The intensity of the mist generation has been optimized to obtain smooth and uniform thin films. The thin film deposited in this work is mixed phase polycrystalline gallium oxide. UV‐Vis NIR spectroscopy and photo response of thin film unveils that gallium oxide thin film is responsive to ultra‐violet wavelengths including deep UVC and UVB bands and the mist generation intensity has negligible influence on the bandgap of the thin film. Thickness of thin film can be altered by varying the mist intensity. It has been observed that there is no appreciable impact on refractive index of varying mist intensity. Morphological studies prove the formation of ultra‐smooth thin film with rms value of 0.628nm; which is closer and/or better than conventional semiconductor thin film deposition processes used for depositing Ga dc.description: open access article
Electrical Bistability by Creating an Internal Electrical Field and Its Application in Emerging Two-terminal Electronic Memory Devices
dc.title: Electrical Bistability by Creating an Internal Electrical Field and Its Application in Emerging Two-terminal Electronic Memory Devices dc.contributor.author: Paul, Febin; Paul, Shashi dc.description.abstract: This chapter focusses on the electrical bistability observed in nanocomposite memory devices that have been studied over two decades. Bistability, in the context of memory devices, has been discussed and visual tools have been employed for its examination as a general mathematical function. The bistability observed in memory devices, in terms of electrical hysteresis, has been focussed and typical curves observed in several studies over the last fifty years have been consolidated and systematically examined. The development of the field has led to much confusion in terms of understanding of the device switching mechanism, which has been investigated in detail. The discrepancies in the proposed device behaviour and the observations have over time led to the rise of many opinions/models to explain the physics of the device conduction switching. In this chapter, the charge-trap models have been examined and solutions to some open questions have been proposed in terms of analysing at the system from the perspective of field generation, instead of the material interaction.
Non‐Zero and Open‐Loop Current–Voltage Characteristics in Electronic Memory Devices
dc.title: Non‐Zero and Open‐Loop Current–Voltage Characteristics in Electronic Memory Devices dc.contributor.author: Paul, Febin; Nama Manjunatha, Krishna; Paul, Shashi dc.description.abstract: This work focuses on the non-zero-crossing and open-loop current–voltage (I–V) characteristics of electronic memory devices that are studied and focused on primarily for non-volatile memory storage applications. Gold nanoparticles-based devices are fabricated to understand possible non-crossing zero and open-loop current–voltage behavior, where a non-zero current and open loop I–V characteristics are observed at zero voltage. While other studies have attributed this behavior as a “battery effect”, this study presents an alternate perspective for non-redox-based charge storage memory devices. The electrical measurements clearly demonstrate that the non-zero current and open-loop characteristics are due to the charge trapping of the gold nanoparticles. The charge accumulation within the nanoparticle is observed to create a non-zero potential within the device and thereby encouraging such behavior, even though the applied external voltage is zero. The longstanding mystery in deciphering if electrical measurements or the charge storage device contributes toward non-zero property is unfurled in this article. A possible charge storage model is proposed and further verified using liquid crystals-based two terminal devices. The presence of internal potential leads to an offset within the devices, a non-zero current and open-loop I–V even when the external applied voltage is zero. dc.description: open access article
Materials and challenges of 3D printing of emerging memory devices
dc.title: Materials and challenges of 3D printing of emerging memory devices dc.contributor.author: Salaoru, Iulia; Ganguly, Swapnodoot; Morris, Dave; Paul, Shashi dc.description.abstract: The continuous development of the semiconductor industry to meet the increasing demand of modern electronic devices which can enhance computing capabilities is attributed to the exploration of efficient, simple, high-speed operation and multistate information storage capacity of electronic devices called memory devices. Nowadays, one of the main challenges the industry faces is limitations in manufacturing as the current fabrication pathway is complex and relies on the use of rigid substrates that do not match with the needs of industry for flexible, bendable electronics. 3D printing has a huge potential to address this challenge and to completely replace the current fabrication pathways and protocols. In this paper, the materials and the 3D printing technologies that have been explored to fabricate an emerging flexible, bendable memory device will be presented. dc.description: open access article
Organic and Macromolecular Memory – Nanocomposite Bistable Memory Devices
dc.title: Organic and Macromolecular Memory – Nanocomposite Bistable Memory Devices dc.contributor.author: Paul, Shashi dc.description.abstract: The primary aim in the memory devices is to produce structures that exhibit two distinct states when a certain type of stimulus (e.g. electric field or magnetic field) is applied. These two states can be viewed as the realization of memory devices. It is to be noted that the class of memory devices that is discussed in this chapter is based on the admixture of small molecules, nanoparticles, and polymers; such devices are referred to as polymer electronic memory devices. This chapter captured the key developments that have happened in the field of organic memory devices for the last two decades. This chapters include discussions on the progress in this field and address challenges that scholars are currently faced with, such as questions about the mechanism(s) of bistability, the conundrum of the experimental data, and the contradictions prevalent among the different groups and future directions. The chapter also introduces reader some basic terms, concepts and terminology often used in this field.
Storing Electronic information on Semi-Metal Nanoparticles
dc.title: Storing Electronic information on Semi-Metal Nanoparticles dc.contributor.author: Paul, Febin; Nama Manjunatha, Krishna; Paul, Shashi dc.description.abstract: This paper presents the use of selenium nanoparticles for the application of information storage in two terminal electronic memory devices. Selenium is a semi-metal with interesting electronic and optical properties that have seldom been studied in terms of electronic memory. In this study selenium nanoparticles have been demonstrated as an embedded charge storage layer between silicon oxide tunnel layer and silicon nitride blocking layer. The electrical characterisation demonstrates clear evidence that charge storage is taking place, and that it is indispensable without the presence of nanoparticles. AFM images show that selenium nanoparticles are almost uniformly distributed on Silicon substrate having a thin silicon dioxide tunnelling layer, and the electrical retention measurement shows potential for long term data storage dc.description: The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.
Flexible Silicon Photovoltaic Solar Cells
dc.title: Flexible Silicon Photovoltaic Solar Cells dc.contributor.author: Shende, Pratik Deorao; Nama Manjunatha, Krishna; Salaoru, Iulia; Paul, Shashi dc.description.abstract: This chapter discusses research and development of emerging silicon-based flexible solar cells. More emphasis is shown on the technology, underlying principles, device architecture, fabrication process, strengths, and challenges of the flexible solar cells fabricated using silicon. This chapter considers all the counterparts of silicon, from bulk to nanostructures that are used to fabricate photovoltaic devices. Change in the structure (low-dimensional and bulk materials), morphology (surface texturing and pyramid structures), and crystallinity (amorphous, poly-crystalline, and crystalline) of silicon as an absorber layer has shown enhanced efficiencies and reliabilities in flexible silicon solar cells. Flexibility and stretchability in solar cells are achieved mainly due to the adoption of novel structures, fabrication techniques, and, most importantly, the adoption of various flexible substrates (metal foils, polymers, and thin glass). The advantages and disadvantages of solar cells are discussed in terms of achieved efficiency, fabrication method, flexibility, and chosen substrate.
To Be or Not to Be – Review of Electrical Bistability Mechanisms in Polymer Memory Devices
dc.title: To Be or Not to Be – Review of Electrical Bistability Mechanisms in Polymer Memory Devices dc.contributor.author: Paul, Febin; Paul, Shashi dc.description.abstract: Organic memory devices are a rapidly evolving field with much improvement in device performance, fabrication, and application. But the reports have been disparate in terms of the material behavior and the switching mechanisms in the devices. And, despite the advantages, the lack of agreement in regards to the switching behavior of the memory devices is the biggest challenge that the field must overcome to mature as a commercial competitor. This lack of consensus has been the motivation of this work wherein various works are compiled together to understand influencing factors in the memory devices. Different works are compared together to discover some clues about the nature of the switching occurring in the devices, along with some missing links that would require further investigation. The charge storage mechanism is critically analyzed alongside the various resistive switching mechanisms such as filamentary conduction, redox-based switching, metal oxide switching, and other proposed mechanisms. The factors that affect the switching process are also analyzed including the effect of nanoparticles, the effect of the choice of polymer, or even the effect of electrodes on the switching behavior and the performance parameters of the memory device. dc.description: open access article
Rational design on materials for developing next generation Lithium-ion secondary battery
dc.title: Rational design on materials for developing next generation Lithium-ion secondary battery dc.contributor.author: Mambazhasseri Divakaran, Arun; Minakshi, Manickam; Arabzadeh Bahri, Parisa; Paul, Shashi; Kumari, Pooja; Mambazhasseri Divakaran, Anoop; Nama Manjunatha, Krishna dc.description.abstract: Lithium-ion batteries (LIBs) gained global attention as the most promising energy storing technology for the mobile and stationary applications due to its high energy density, low self-discharge property, long life span, high open-circuit voltage and nearly zero memory effects. However, to meet the growing energy demand, this energy storage technology must be further explored and developed for high power applications. The conventional lithium-ion batteries mainly based on Li-ion intercalation mechanism cannot offer high-charge capacities. To transcend this situation, alloy-type anode and conversion-type anode materials are gaining popularity. This review article focuses on the historical and recent advancements in cathode and anode materials including the future scope of the lithium nickel manganese cobalt oxide (NMC) cathode. Equal emphasis is dedicated in this review to discuss about lithium based and beyond lithium-based anode materials. This review additionally focuses on the role of technological advancements in nanomaterials as a performance improvement technique for new novel anode and cathode materials. Also, this review offers rational cell and material design, perspectives and future challenges to promote the application of these materials in practical lithium-ion batteries. dc.description: research groups involved: 1. Emerging Technologies Research Centre, De Montfort University, Leicester, United Kingdom 2. Engineering and Energy, Murdoch University, Murdoch, Australia 3. Malaviya National Institute of Technology, Jaipur, India 4.School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.

Click here to view a full listing of Shashi Paul's publications and outputs

Key research outputs

Memory effect in thin films of insulating polymer and C60 nanocomposites, Paul, S., Chhowalla, M. and Kanwal, A., Nanotechnology (2006), 17(1), pp. 145-151.

Langmuir-Blodgett film deposition of metallic nanoparticles and their application to electronic memory structures, Paul, S et al, Nano letters (2003), 3, 191-195.

Realisation of Non-volatile Memory Devices using Small Organic Molecules and Polymer”, S. Paul, IEEE Transaction on Nanotechnology, 2007, 6 , 191-195.

Ferroelectric nanoparticles in polyvinyl acetate (PVAc) matrix-A method to enhance the dielectric constant of polymers. D Black, I Salaoru, S Paul, Nanoscience and Nanotechnology Letters (2010), Volume 2, Issue 1, March 2010, Pages 41-45.

Prime, D. and Paul, S. (2010) First contact-charging of gold nanoparticles by electrostatic force, Applied Physics Letters, 96 (4) 043120.

Research interests/expertise

Organic and inorganic materials for plastic electronics (including printing techniques for their deposition)
Emerging Electronic Memory Devices (including neuromorphic)
New Growth Processes/Methods for Nano-structures/materials
Photovoltaic Solar Cells (organic and inorganic)
Energy Storage (Electrical and Heat)

Areas of teaching

Electrical & Electronic Principles 1 (ENGD1103)
Emerging Materials and Processes (ENGD3114)
Energy Conversion & Storage Systems (ENGD3121)
Physics of Semiconductor Devices (ENGT5128)
Study Skills and Research Methods (ENGT5214)

Qualifications

MSc, PhD

Courses taught

MSc(Electronics Engineering)- Programme Leader, B.Engg (Mechanical Engineering), BSc(Energy Engineering) and a common module to all engineering disciplines in the school of engineering and sustainable development

Membership of external committees

The 4th International Conference “Smart Materials, Structures and Systems”- a part of CIMTEC2012 conference organising programme committee

Dr S Paul is member of international programme committee for the forthcoming Conference on Renewable Energies and Power Quality (ICREPQ) by the European Association for the Development of Renewable Energies, Environment and Power Quality (EA4EPQ)", (http://www.icrepq.com/), 28-30 March, 2012, Santiago de Compostela, Spain.

The 3rd International Conference “Smart Materials, Structures and Systems” held in Acireale Catania District), Sicily, Italy, on June 8 to 13, 2008. Organised a special session on “Recent Development in Electrical Writable Organic Memory Devices”.

The 4th International Conference “Smart Materials, Structures and Systems” will be held in Acireale Catania District), Sicily, Italy, on June 8 to 13, 2008. Dr S Paul is organising a special session on “Emerging Non-volatile Memory Devices”.

Visiting Professor in the Physics department of Alexandru Ioan Cuza University of Iasi, Romania. From 24/12/2011 to 24/12/2013.

Membership of professional associations and societies

Association Name, period start, period end, description

Member IEEE (January, 2012 to December 2012)

Member Materials Research Society

Forthcoming events

Organising a special symposium on Emerging Memory Devices in CIMTEC2012

Conference attendance

Attended a number of international conferences (e.g.: IEEE, MRS, CIMTEC)

Current research students

1. Febin Paul (1st supervisor)
2. Swapnodoot Ganguly (2nd supervisor)
3. Chris Yang (1st supervisor)
4. Abdulrahaman Ogunji (1st supervisor)
5. Pratik Deorao Shende (1st supervisor)
6. Shashikala Madaiah (1st supervisor)
7. Maher Nahhas(1st supervisor)

Externally funded research grants information

Awarded an ICURe (Innovation & Commercialisation of University Research - funded by UKRI) £27k (from 1/1/2021 to 31/1/2021) for ‘Storing Electrical Energy in Silicon-Tin’ to explore commercialisation of his research. The CURe Programme offers university research teams with commercially-promising ideas funding and support to ‘get out of the lab’ and validate their ideas in the marketplace.
Energy Catalyst-3 - Creating electricity by reducing cost, payback time and Carbon footprint - An exploitation of a novel method into manufacturing Crystalline Silicon Photovoltaic solar Cells. (£70k) with 3 industrial partners.
EPSRC High Value Manufacturing (HVM) Catapult fellowship to work on the project “Manufacturing Silicon Nano-structure at low temperature – route to increase charge capacity and lower the cost of Li-Ion batteries” (£36,070)- February-2016 to February-2018.
EPSRC funding (#EP/E047785/1) on “Nano-Scale Rewritable Non-Volatile Polymer Memory Arrays”, principal investigator (£207k) – July-2007- November-2009.
National Physical Lab funding “Electrical Charging Mechanism in C60”, principal investigator (£20k)- October-2005 – September-2010.
EPSRC CASE Studentship (£57k) – October-2005 – March 2009.
“Low-temperature Si Nonvolatile memory”, principle investigator, European Integrated Activity of Excellence and Networking for Nano and Micro- Electronics Analysis (FP6), December-2010
Hosting visitor from Iraq (6k) – 2013
Consultancy (AFM analysis) – 1k -2008.
EPSRC-DTA studentship (~40k) – 2008 for 3 years.

Internally funded research project information

RIF project: A Cleaner, Greener, Low Carbon Fabrication Process for Photovoltaic (PV) Solar Cells (PI). Start date: 01/04/10; End date: 01/07/10.

DMU PhD Bursary on Plastic compatiable Electronic Memory Devices, October-2011 to September 2014.

Published patents

GB2482915 - A low temperature method for the production of polycrystalline silicon, aligned silicon columns and silicon nanowires (Date Lodged: 20 August 2010, Granted on 5/2/2013).
GB2484743 - Organic photoconductive material (Filing date: 23 October 2010, Publication Date 25 April 2012, Granted in October, 2014).
2 patent applications submitted in 2020.

Professional esteem indicators

Guest editor of the issue of the Philosophical Transaction of the Royal Society A, on the theme of “Making Nano-Bits Remember: A Recent Development in Organic Electronic Memory Devices”. Volume 367, Issue 1905, 28 October 2009.

Reviewer for a number of journals in the field of electronic materials and devices.

Visiting Professor, Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Romania.

Case studies

Nano-bits Enabled Application in storing electronic information and creating electrical energy:

Ribbon award – MRS Fall Meeting 2004, Boston, USA

News in Science -2004: http://www.sciencenews.org/view/generic/id/5717/title/Buckyballs_store_1s_and_0s_in_new_memory_device

Gold nanoparticles for memory storage: http://www.theengineer.co.uk/news/gold-nanoparticles-for-memory-storage/1001480.article

Organic electronic memory chip to be demonstrated in the UK

Huge breakthrough in tiny technology by DMU: http://www.findaphd.com/custadverts/dmu/2010.asp

De Montfort University Shows the Benefits of Gold Nanoparticles for Organic Electronics: http://nanopatentsandinnovations.blogspot.com/2010/03/de-montfort-university-shows-benefits.html

Flexible memory has wide ranging application

ORCID number

0000-0002-7077-8235