SiC Movie Stars!

30 01 2013

Tomorrow sees the official launch of the UK’s first silicon carbide foundry. Raytheon Uk have been busy updating their facilities to offer a complete foundry service for 4″ SiC wafers. This is running alongside their development of SiC CMOS, a project leading the realisation of 400C CMOS strcutures, from amplifiers to digital circuits.
As part of this big launch, two of our colleagues from Raytheon have found themselves on YouTube explaining the benefits from the use of SiC in high temperature electronics. The video of Robin and Ewan can be found here.





Chemical Sensors

20 04 2011

Following the gas sensor findings from a few weeks ago, where we showed that we can make an array that can discriminate between species in a mixture, rather than just the overall level, our first graphene results have landed. Whilst we wait for the gas rig to be fixed (the BOC fairy dropped off a new cylinder and we took the opportunity to install the closed loop pressure system) our graphene sensors have been tested for their sensitivity to solvents.

Graphene solvent sensitivity sensor

Room temperature sensitivity to solvents

As expected this shows a difference between polar and non polar solvents and the next step is to try this with more realistic gas conditions to understand how it can function as something like an air quality monitor. Then we need to work out how we can make an array, so it might well be back to the idea behind the SiC arrays!





Graphene bonds!

3 03 2011

Having identified in a previous post that wire bonding to contacts on a graphene device is tricky if the underlying metals have a low binding energy, we have now solved the problem!

Wire bond graphene solution

Gold wedge bonds on a dummy graphene gas sensor

Whilst this chip doesn’t have the full etch steps required to produce our intended gas sensor structures, this is a substantial step forward in our research.





Curious conductance

13 02 2011

The conductance data from the aged capacitors is throwing up a number of interesting surprises. It’s strange, but it is often considered to be the poor cousin of the capacitance – voltage characteristic, however it would appear that there’s plenty to discover in here and not all of it appears to be described in the literature. The first observation is that the amplitude of the peak can be used to describe the interface trap density, Dit, using the HIll – Coleman technique. (although this generally underestimates Dit, this is the technique everyone uses in SiC) That for most people is the end of the story …

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JFETs and Circuits …

18 11 2010

The JFETs are back from being diced and so it’s time to move up a gear. The first challenge is to simulate the behaviour of our eventual circuits, so having spent hours and hours testing the devices, we’ve dropped the parameters into SPICE. We’re pretty happy with the results, as can be seen below…

Silicon Carbide JFET data SPICE

SPICE model for SiC JFET

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Graphene just doesn’t bond …

12 11 2010

From what we have been told, people putting contacts down onto graphene samples are having issues with wire bonding. This is a serious problem, as without the ability to put wires on, it’s difficult to connect it up to the rest of the circuit and do something interesting with it. Testing in the lab is not going to be affected, as everybody makes contacts with probes, but this is only useful for short term tests! Longer term, the ability to connect the devices up with wires is an absolute necessity…

Recently, we’ve had this problem as well and we’ve made a discovery.

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Why Silicon Carbide ?

15 10 2010

One of the first electronic materials, silicon carbide (SiC) is actually best known as an abrasive and the the majority of the worlds production is used as the black sandpaper you can buy in B&Q (or Home Depot for people in the states). Originally discovered in Sweden in 1824 by Berzelius (who was trying to make diamonds), it was Acheson who found the first production method for the manufacture of carborundum abrasives in 1893. Around this time Henri Moissan found grains of silicon carbide in the Diablo Canyon meteorite and hence the geological name for SiC is still Moissanite.

Moissanite Grain Silicon Carbide

Scanning Electron Micrograph of Moissanite (www.ciw.edu/lrn/psgtypes.html)

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