Date:

2012-

Themes:

Nanoelectronics, Nanophotonics and Biomimetics, Quantum Electronics and Spintronics

The emerging field of helium ion microscopy (HIM) is rapidly establishing itself as a valuable surface imaging technique, capable of generating images exhibiting sub-nm resolution and a high depth of field, surpassing that possible with scanning electron microscopy (SEM). This is enabled by the atomically sharp helium ion source and the larger momentum (and so shorter de Broglie wavelength) of helium ions compared to electrons, which together result in a sub-nm probe focused on the sample and a low beam divergence angle. The combination of a small probe size and the low energy of the secondary electrons (SE) generated through the interaction of the helium beam with the sample leads to a small interaction volume and hence enables high resolution imaging of the sample surface. Our Orion at Southampton is capable of an edge resolution of 0.35 nm (a good field emission gun SEM achieves approximately 1 nm). A microchannel plate can be inserted to collect the back-scattered helium ions, forming images that compliment those created by the SE detector, and provide more materials contrast. The system is also fitted with an integrated electron flood gun for charge neutralization which allows insulating samples to be imaged without the application of a conductive coating. Furthermore, the large depth of field can be exploited with stereo imaging techniques to extract 3D information from a sample.

In addition to its imaging capabilities, the focused beam of helium ions generated by the HIM can also used be used for nanofabrication through the direct modification and patterning of material, analogous to the way in which the gallium ion beam is used in focused ion beam (FIB) systems. The smaller probe size in the HIM enables the definition of finer patterns and more controlled milling than with a Ga FIB, with less damage to the surrounding material. A gas injection system also provides the capability for beam induced deposition of metals in well-defined patterns.

Here at Southampton, we are developing both imaging and nanofabrication applications for the helium ion microscope. Examples of these include:

- The imaging of biological micro and nano structures such as those found on the wing scales of lepidoptera (butterflies and moths), which are responsible for the vivid colouration and remarkable optical effects observed in these creatures. Charge neutralization with the flood-gun together with the high resolution and large depth of field provided by the HIM is allowing the fine details on these structures to be imaged clearly for the first time [1].

- Ion induced luminescence spectroscopy with the Gatan MonoCL system, including tests on materials known to exhibit cathodoluminescence in the visible- near IR range, e.g. quantum dots, fluorescent dyes, and rare-earth doped nanocrystals. The aim is to image biological samples tagged with luminenscent species to a resolution beyond that which is possible with cathodoluminescence in an SEM [2].

- The fabrication by direct milling of nanoelectronic devices in materials such as extremely thin silicon-on-insulator and graphene. The technique enables the rapid prototyping of structures such as quantum point contacts, nanowires, side-gated transistors and quantum dot devices in novel thin materials for next-generation computing [3].

- The characterization of the nanoscale chemical variations in polymeric semiconductor thin-film blends being developed for organic solar cells [4].

[1] S. A. Boden, A. Asadollahbaik, H. N. Rutt, and D. M. Bagnall, “Helium ion microscopy of Lepidoptera scales.,� Scanning, vol. 33, pp. 1-14, Jul. 2011.

[2] S. A. Boden, T. M. W. Franklin, L. Scipioni, D. M. Bagnall, and H. N. Rutt, “Ionoluminescence in the helium ion microscope,� Microscopy and Microanalysis 18, 1253-1262 (2012).

[3] S. A. Boden, Z. Moktadir, D. M. Bagnall, H. Mizuta, and H. N. Rutt, “Focused helium ion beam milling and deposition,� Microelectronic Engineering, vol. 88, pp. 2452-2455, Nov. 2011.

[4] A. J. Pearson, S. A. Boden, D. M. Bagnall, D. G. Lidzey, and C. Rodenburg, “Imaging the bulk nanoscale morphology of organic solar cell blends using helium ion microscopy.,� Nano letters, vol. 11, no. 10, pp. 4275-81, Oct. 2011.

Primary investigators

• Stuart Boden
• Darren Bagnall
• Harvey Nicholas Rutt
• hm2

Secondary investigators

• Asa Asadollahbaik
• nk1d09
• zm
• sh13g08
• jdr2g08

Associated research group

• Nano Research Group

Date:

2013-2014

Themes:

Quantum Electronics and Spintronics, Nanoelectronics

Funding:

EPSRC (EP/K503770/1), Industrial

Single electron transistors (SET) are indispensible devices for quantum information processing and our Si based SETs have several advantages like high integration densities, low cost, and long spin decoherence time. We will further develop the technologies towards the practical implementation to the industry by optimising the fabrication process technologies in Southampton Nanofabrication Centre and examining them in the world leading low temperature measurement facilities. Especially, we will develop Si based SETs defined by the atomically flat interfaces to achieve the robust design capabilities against the interfacial defects and surface roughness, which are important for scalabilities and mass production.

Primary investigator

• Shinichi Saito

Secondary investigator

• mkh

Partner

• Hitachi Cambridge Laboratory

Associated research group

• Nano Research Group

Date:

2010-2014

Theme:

MEMs and NEMs

Funding:

DOST Philippines

Thermoelectric generators (TEGs) are devices that convert heat into electricity. They are very attractive energy harvesters because they are highly reliable and environment-friendly. The efficiency of thermoelectric generators depends on the temperature gradient across the device, the average temperature of operation, and on the thermoelectric properties of the material. Most work on improving the TEG efficiency deals with improving the thermoelectric properties of the material. In this work, we propose a method of improving the efficiency of the TEG by increasing the temperature gradient across the device. To accomplish this, a lens can be used to concentrate solar radiation on the membrane of the TEG. By focusing solar radiation, the input heat flux increases; the temperature gradient across the device also increases; and the efficiency of the TEG improves as well.

Associated research group

• Nano Research Group

Date:

2011-2018

Theme:

Nanoelectronics

Funding:

EPSRC Case Scheme

Many industries heavily rely upon advances in electronic devices. As development of electronics continues, new structures and new materials are being utilised. The reliability of these new technologies therefore need to meet the same high levels as the traditional technologies that they are replacing.

Industries such as space and nuclear in particular, face an additional challenge affecting the reliability of their electrical devices; radiation. Ionizing radiation in particular can damage dielectric layers in devices such as metal-oxide-semiconductor (MOS) transistors and resistive memories. In either case, controlling the radiation effects of dielectrics is essential for the reliability of these devices.

High-k MOS capacitors have been fabricated, analysed and irradiated. TiN/HfOx/Si structures in particular showed superior properties in comparison with silicon dioxide stacks, including high capacitance with low leakage. The ionizing radiation results indicate the high-k metal gate structures are just as radiation hard as the silicon dioxide structures. This verifies the high-k metal gate structures can be used as a replacement for silicon dioxide gate oxides, enabling the scaling limit in CMOS industry to be overcome.

A variety of resistive memory cells are fabricated whereby the effects of the interfacial layers, electrodes and insulator are investigated. Electrochemical metallization memory cells switching kinetics are investigated whereby the switching mechanism is analysed. VCM and ECM radiation responses are also investigated.

Primary investigators

• Kees De Groot
• Liudi Jiang (Engineering)
• Katrina Morgan
• Junqing Fan
• Ruomeng Huang

Secondary investigator

• Fully funded PhD scholarship (2017-2021) available for UK nationals !

Associated research groups

• Nano Research Group
• Southampton Nanofabrication Centre

Date:

2013-2016

Themes:

Channel coding, Wireless Sensing and Sensor Networks, Communication and Networking

Funding:

Altera

Low Density Parity Check (LDPC) error correction codes have found application in numerous standards for both wired and wireless communication, including those for home networking, Local Area Networking (LAN), cellular systems, wireless LAN and Digital Video Broadcasting (DVB). LDPC codes enjoy near-optimal error correction performance, which facilitates communication throughputs that approach the capacity of the channel and meet the ever-increasing consumer demand for high-speed data. However, in order to realise these high communication throughputs, the LDPC encoder and decoder must have correspondingly-high processing throughputs. In order to facilitate the rapid prototyping of high-speed communication systems, there is a need for Field Programmable Gate Array (FPGA) realisations of LDPC decoders having high processing throughputs. While a throughput of 16.2 Gbps has already been achieved by the current state-of-the-art design, this is achieved by employing a fully-parallel architecture, which supports only a single LDPC matrix. Indeed, many more high-throughput FPGA LDPC architectures have been proposed in the literature, but each has its own drawbacks. These drawbacks may be manifested as relatively poor error correction performance, resource usage, energy consumption, latency, reconfigurability or LDPC matrix dimensions, for example. Hence, there is a need for generalised high-throughput FPGA architectures that can be configured to support not only various different LDPC matrices, but also various different trade-offs between the contradictory system characteristics listed above. Furthermore, there is a need for methodologies that allow the configuration of these architectures to be holistically designed, in order to readily achieve an appropriate trade-off between the characteristics. In this way, the resultant general purpose architectures would have significantly more applicability and commercial viability than existing high-throughput architectures.

Primary investigator

• Robert Maunder

Secondary investigators

• Bashir Al-Hashimi
• Lajos Hanzo

Partner

• Altera

Associated research groups

• Communications, Signal Processing and Control
• Pervasive Systems Centre
• Electronic and Software Systems

Date:

2014-2017

Themes:

Channel coding, Communication and Networking, Wireless Sensing and Sensor Networks

Funding:

EPSRC (EP/L010550/1)

During the past two decades, reliable wireless communication at near-theoretical-limit transmission throughputs has been facilitated by receivers that operate on the basis of the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm. Most famously, this algorithm is employed for turbo error correction in the Long Term Evolution (LTE) standard for cellular telephony, as well as in its previous-generation predecessors. However, the transmission throughput of these standards is limited by the processing throughput of the turbo decoder. This limit may be attributed to the data dependencies of the BCJR algorithm, resulting in an inherently serial nature that cannot be readily mapped to processing architectures having a high degree of parallelism. Against this background, this project will redesign turbo decoder implementations at an algorithmic level, rather than only at the architectural level, which is the State-Of-the-Art (SOA) approach. More specifically, we have devised an alternative to the BCJR algorithm, which has the same error correction capability, but does not have any data dependencies. Owing to this, our algorithm can be mapped to highly-parallel many-core processing architectures, facilitating an LTE turbo decoder processing throughput that is several times higher than the SOA, satisfying future demands for gigabit throughputs. In collaboration with ARM, Altera and BT, this research addresses key EPSRC priorities in the Information and Communication Technologies theme, including 'Many-core architectures and concurrency in distributed and embedded systems' and 'Towards an intelligent information infrastructure'.

Primary investigator

• Robert Maunder

Secondary investigators

• Lajos Hanzo
• Bashir Al-Hashimi

Partners

• Altera
• ARM
• BT

Associated research groups

• Pervasive Systems Centre
• Communications, Signal Processing and Control
• Electronic and Software Systems

Date:

2008-2012

Theme:

Novel Sensors

Funding:

European Commission

Primary investigators

• Steve Beeby
• John Tudor

Secondary investigators

• Russel Neil Torah
• Kai Yang

Partners

• IFTH
• DITF
• Klopman International Srl

Associated research group

• Electronics and Electrical Engineering

Date:

2012-2013

Themes:

Nanoelectronics, Biomimetics, Biologically Inspired Computing and Robotics

Funding:

EPSRC

This project aspires to investigate memory mechanisms in emerging non-CMOS devices and to correlate these with the short-term dynamics of biological synapses. Nanoionic devices are nowadays regarded a promising solution for establishing next-generation’s memory elements, yet most of their impact is anticipated through the realization of bio-inspired systems and applications. While brain-inspired computing typically focuses on the long-term dynamics of the synapses, it was recently shown that short-term dynamics play an important role in enhancing neural information processing. To this end, we seek to realistically emulate dynamical synapses behaviour with volatile memory elements, towards developing fundamental blocks for establishing unconventional computational formalisms.

Primary investigator

• Themistoklis Prodromakis

Associated research groups

• Nano Research Group
• Southampton Nanofabrication Centre

Date:

2013-2016

Themes:

Nanoelectronics, Bionanotechnology and Biosensors, Biologically Inspired Computing and Robotics

Funding:

European Commission

Information processing in classical ‘von Neumann’ architectures is less efficient compared to biological counterparts when dealing with ill-posed problems and noisy data. The reason is that the biological brain is configured differently and the key is its evolving structure, where connectivity elements between individual neurons, the synapses, undergo ‘birth’ and ‘death’ as well as strengthening and weakening through a selection process, reconfiguring neuronal connectivity in a self-organizing manner and allowing the networked population of neuronal processors to adapt motor and behavioural responses to the ever changing environment. Artificial neural networks in the form of software run on conventional ‘von Neumann’ computers appear incomparable to the biological systems in terms of speed, energy efficiency, adaptability and robustness. The challenge is to propose a ‘physical’ neural network where elements overcome this deficiency by merging data storage and processing into single electronic devices and by self-organizing and reconfiguring connectivity. Along this route, we aim to create a new biohybrid architecture of natural and artificial neurons endowed with plasticity properties. Communication between artificial and natural worlds will be established through new nano- and microtransducers allowing direct electrical interfacing of a network of neurons in culture to an artificial CMOS-based counterpart. Adaptation properties of the artificial network will rely on memristive nanoelectronic devices with synaptic-like plasticity and on activity-dependent rearrangement of neuronal connectivity. As such, the biohybrid system will provide new and unique adaptive, self-organizing and evolving properties deriving from the fusion of natural and artificial neuronal elements into a new plastic entity and will represent a fundamental step towards the development of novel brain-inspired computing architectures as well as ‘intelligent’ autonomous systems and prostheses.

Primary investigator

• Themistoklis Prodromakis

Associated research groups

• Nano Research Group
• Southampton Nanofabrication Centre

Date:

2013-2018

Themes:

Nanoelectronics, Biomimetics, Biologically Inspired Computing and Robotics

Funding:

EPSRC (EP/K017829/1)

Nanoscale resistive switching (RS) elements, also known as memristors, are nowadays regarded as a promising solution for establishing next-generation memory, due to their infinitesimal dimensions, their capacity to store multiple bits of information per element and the miniscule energy required to write distinct states. Currently, the microelectronics community aspires exploiting these attributes in a deterministic fashion where information encoding and processing is realised via static representations. In consequence, research efforts are focused on optimising memristor technology in a "More Moore" approach to comply with existing CMOS devices attributes, i.e. high-yield, supreme reproducibility, very long retention characteristics and conventional circuit design formalisms. The functional properties of such elements are however associated with irreversible rate-limiting electro/thermo-dynamic changes that often bring them in "far from equilibrium" conditions, manifesting opportunities for unconventional computing within a probabilistic framework.

This fellowship aims exploiting the strong emergence of ultra-thin functional oxides, nanoscale resistive switching elements and large-scale systems of the same. We will first investigate the effect of quantum phase transitions and the mechanisms leading into thermodynamically stable/unstable long-range order/disorder of distinct materials. These mechanisms will then be exploited in nanoscale solid-state devices for establishing the state-of-the-art in non-volatile multi-state memory but also volatile elements that could potentially be employed as dynamic computational elements. The rich-dynamics of the later will be compared against reaction-diffusion mechanisms of naturally occurring nano-systems to facilitate novel design paradigms and emerging ICT applications for substantiating unconventional computation formalisms. A successful outcome will demonstrate a mature memristive device manufacturing technology that will be supported by the necessary design tools, for taking CMOS technology far beyond its current state-of-art.

Primary investigator

• Themistoklis Prodromakis

Secondary investigators

• ak1a12
• Spyridon Stathopoulos
• dc1e13

Associated research groups

• Nano Research Group
• Southampton Nanofabrication Centre