This week …

2 05 2012

More good news from Omid, his paper entitled ‘Design and Performance Evaluation of SiC MOSFET/JFET Based DC-DC Converters for PV Applications’ has been accepted at the upcoming 2012 IEEE Energy Conversion Congress and Exposition to be held in Raleigh, North Carolina, USA. The reviewers have been very complimentary about the work and hopefully this will result in an oral presentation! As one of the most prestigious conferences in the field, the papers are linked to IEEE Transactions on Power Electronics, which is arguably the place to publish research results in power electronics.

Monday saw the extended abstract deadline for the European Conference on Silicon Carbide and Related Materials (ECSCRM) 2012. We managed to get eight abstracts in for the deadline, which is no mean feat, covering almost the entire breadth of what we do, from graphene growth to the characterisation of oxide layers on SiC CMOS! Without time to catch our breath, the next deadline is Friday, the IEEE Sensors 2012 abstract deadline. This time, we are looking to submit three, graphene sensors, our SiC sensor array and recent work on self starting boost converters for powering sensor nodes.

Tomorrow sees me in Derby to give a presentation at the Electronics, Sensors and Photonics Knowledge Transfer Network meeting. Containing our results and vision for wireless sensor nodes, the slides can be downloaded from here KTN Talk – 3rd May 2012. I am also showing a poster outlining our work, which will hopefully attract lots of attention.


IEEE Sensors – Day 2

30 10 2011

Another packed day here in Limerick. The plenary looked at the developments in sensing technology applied to the mobile phone market and how this will enable ‘The Internet of Everything’. Current research in this field include the use of ultrasonic transducers to communicate with your smart phone (they can hear it even if we can’t), chemical sensors in smart phones for first responders and MEMs based particulate monitors. However, despite the increase in processing power now common in phones (1GHz processors are in our pockets now – that’ the equivalent of 25 Pentium PCs) it’s still the LCD display which drains the battery. There’s a good summary relating to the application of energy harvesting to this problem, which is Vullers, et al, Solid State Electronics, Vol 53 (2008) pp684.

From there, it was off to listen to the application of emergent behaviour to groups of sensors. This showed that it is possible to realise the optimisation of a group of sensors by enabling them to sense their local environment and communicate only with their immediate neighbour. Whilst the application described the minimisation of noise levels in aircraft engines, this has the potential to offer a complete paradigm shift in how we make decisions from a large sensor installation. The next talk, focussed on the development of MEMs based logic structures for hostile environments, mostly targeting ionising radiation and high temperatures. Based on tungsten contacts, this does ask the question about neutron activation, especially as it becomes a gamma emitter with a 24 hour half life! The results though were very encouraging, demonstrating 2V activation and a 100MHz limit, with a 1uW leakage power and a lifetime of 10^9 operations.

A talk on SiC based detectors showed a significant piece of work on understanding H2S detection, through the use of Density Functional Theory (DFT) simulations. This showed that Ir based devices are more stable at high temperatures and have a higher sensitivity than Pt and this is related to the higher oxygen coverage of the surface. However, these results are taken in a 5% oxygen background.

IEEE Sensors poster extreme gas

Waiting for questions at the poster

This afternoon it was the poster session and so I spent the afternoon fielding questions about our work on high temperature HfO2 dielectric sensors. This seems to have attracted a good level of interest and two hours flew by talking to a wide array of people. Hopefully some of this interest will be followed up with some interesting collaborations for the future. As for now, it’s the end of this part of the day and it’s off to Thomond Park, the home of Munster rugby club for the gala dinner, once we get ours glad rags on.

IEEE Sensors Day 1

29 10 2011

A great start to the conference. The opening plenary by Prof Julian Jones from Heriott Watt University was a good introduction to the development and application of fibre interferometry, including work he has undertaken in photonics crystal fibres. This includes the use of photonics crystal fibres, which allow the transmission of longer wavelength light, even though the core is still fabricated from silica. These have also been used to sense hydrogen, by use of a palladium coating.

Then it was a full session looking at gas sensors. This year, there is interest in non contact techniques, such as the one demonstrated by Martin Eickhoff, which used GaN and InGaN nano wires to investigate the concentration of explosive gases, with a sensitivity to hydrogen of around 50ppm at 80C. This was followed by our paper on DNA templates Pd nano wires, which is available in one of the previous posts.

DNA templated Pd nanowires sensor

Alton in the middle of the presentation at IEEE Sensors

This was followed by another talk on hydrogen sensing using WO3 nano particles and carbon nanotubes, before I went off to watch a couple of talks on energy harvesting, following on from the work Simon completed for his thesis.

After a coffee break, the gas sensor talks continued, with the first two concentrating on the use of graphene to form sensor arrays, with the intention of realising electronic noses. The graphene in these two presentations comes from the chemical reduction of graphite oxide and is then dispersed in water, prior to application to the electrodes. The sensitivity of this type of graphene is high, because of the functionalisation of the surface and the high defect density. One interesting fact from these talks is the use of CuO to detect acetone, something which is not possible using a graphene alone. After this, two talks on the development of silicon carbide sensors, which were interesting and showed an improvement on previous work in this field. This was achieved in the main with significant signal processing of the results, and as a result it is possible to identify the concentration of gas species. This has the potential to be a critical enabling step in the quest for commercial applications of SiC gas sensors.

The last talk prior to lunch, was reporting on the 1/f noise of gas sensors, something which we may well consider for our SiC devices in the future. The trend shows a different shape, as well as magnitude, with different gas species and concentration. This is thought to be linked to the adsorption / desorption of gas from the surface of the sensor.

After lunch, the posters. The majority were not related to our interest in gas sensors, so it was a chance to catch our breath in time for the final talks of the day. An interesting session, which discussed the suitability of langasite as a suitable material for acoustic sensors in high temperature environments. Apparently this is available commercially and it appears that it might make an interesting piezomaterial for high temperature energy harvesting.

Not bad for the first day, and there’s still two more to go!

Sensors presentations

25 10 2011

Two presentations finished for this weekend. The first is the oral presentation on the development of Pd nanowires on a DNA template. The sensitivity of these is higher than those grown using alternative techniques and is substantially easier, as it is a self assembled bottom up technique. A pdf of the presentation can be found at IEEE Sensors 2011 – Paper 1457. The other presentation is Ben’s work looking at the mechanism behind gas sensing in high-K/SiC (IEEE Sensors – Poster 1421 – Ben), where we show that HfO2 dielectrics are insensitive to oxygen. This is a key step in us understanding the basic physics behind our target of building an array structure in SiC. The poster has been printed by the reprographics team here in the University, who have recently added the capability to print onto canvas, which means I can fit it into my suitcase and avoid the excess charges for a poster tube on the plane. It’s also cheaper than buying a ‘normal’ A0 paper version and having it laminated!