[nanoPost] Sensors based in silicon carbide (SiC) for harsh environments

Sensors based in silicon carbide (SiC) for harsh environments
The first strand of my research related to nanotechnology involves the development of fabrication technologies for the construction of resonators and sensor devices based in silicon carbide (SiC) for applications in harsh (high temperature and high vibration) environments.

During the project, we have studied the effect of etch–induced surface modification and damage in SiC. Of particular relevance is the potential application of the significant optimised one–step dry etch process for the etch and release of the SiC microelectromechanical (MEM) structure. The optimised technology has attracted much
industrial interest and is currently the subject of a patent application.
In addition, we have been successful in demonstrating our capability for manufacturing straight resonating cantilevers and bridge structures and using the resonators as electrostatic actuators – fundamental building blocks of MEMS.

Recently, we also discovered a novel
electrothermal actuation mechanism in SiC cantilever resonators that has much implication for future applications in SiC actuators and sensors.

More recently, we have been working on extending the optimised technology to the fabrication of more complex microelectromechanical systems (MEMS) including accelerometers and pressure sensors in SiC as well as their integration with SiC electronics.

Carbon Nanotube Electronics
The second strand of my research related to nanotechnology involves the synthesis, functionalisation, self–assembly and molecular stamping of carbon nanotubes (CNTs) as well as the characterisation of carbon nanotube devices. In this project, we
a) have developed optimised conditions for the growth of carbon nanotubes onto selective
sites;
b) have developed novel techniques for the reliable and time–saving functionalisation of
single–wall carbon nanotubes;
c) have studied the mechanisms associated with the functionalisation process;
d) have demonstrated the construction of CNT transistors with high yield, via self–assembly
and molecular stamping techniques;
e) have demonstrated CNT alignment using dielectrophoresis techniques; and
f) have demonstrated the synthesis of n-doped CNTs via plasma fluorination followed by
amino–functionalisation.
These are absolutely essential steps towards the large–scale integration of nanoelectronics
based in carbon nanotubes.

Microelectromechanical (MEMS) and sensors in SiC potentially could be used in a wide range of applications including the oil, aerospace and communications industries due to SiC's unique chemical inertness, mechanical stability and large acoustic velocity. The overall market for MEMS is now huge, and is forecasted to grow from $5.6b in 2005 to $8.5b in 2008.

Potential application areas of SiC sensors include, pressure sensors for down well oil drilling, accelerometers for jet engines, fire sensors, chemical and gas sensors for harsh environments in general, biomedical sensors; rf resonators and mixer/filters for communications.

Carbon Nanotube Electronics
On the topic of carbon nanotubes, potential application areas in the next 3-10 years include memory, CMOS and sensor devices. Carbon nanotube electronics and sensors research is still in its infancy, despite many groups around the world working in this area. For example, viable solutions are still needed for the controllable nanotube placement and alignment with uniformity over large areas – we think we have developed such a process.

Moreover, there are still many open questions on the influence of the existence of scatterers, defects, doping in the tubes as well as the role of contacts on device performance – issues that we have been
working on and gaining more understanding of.

Currently, we are engaged in specific research into the functionalisation, self–assembly,
nanotube alignment, doping and device characterisation aspects of this topic in order to
devise new solutions to advance the progress of carbon nanoelectronics. Furthermore, in
addition to nanoelectronics, it is envisaged that carbon nanotubes will have a major role to
play in their application in sensor devices.

Scotland