Supporting the development of novel electronic products through advanced nanoscale measurements
The development of nanoelectronics has been driven by both ongoing miniaturisation of components, below the 10 nm scale, and the emergence of new electronic materials exhibiting nanoscale features. In each case the performance of such electronic devices is critically dependent on the nanoscale structure.
Characterising structures on this scale presents a measurement challenge and is a key obstacle to the development of novel electronic products. We are addressing this challenge by developing new measurement techniques, with a particular focus on ensuring reliable and quantitative characterisation.
Our work focuses on:
Scanning probe microscopy
Nanoscale structures cannot be resolved using traditional optical microscopy due to optical diffraction. However, scanning probe microscopy (SPM) is able to resolve features with nanometre dimensions by using a very sharp probe to mechanically characterise a surface. Simple dimensional characterisation with SPM is well-established. However the use of different types of probe enables a wide range of different measurements such as: conductivity, photoconductivity, surface potential, magnetic and piezoelectric properties. A particular area of interest for characterising nanoelectronics is the combination of structural and electrical modes of SPM, and providing a way to relate the device structure to its functional performance and the nanoscale. We are expert in all of these techniques, as can provide consultancy and advice to researchers in nanomaterials.
Tip enhanced optical spectroscopy
Nanoscale chemical measurements are important for emerging material, such as organic electronics, 2D materials, organic-inorganic perovksites and nanostructured inorganic semiconductors. Optical spectroscopy provides a powerful means of probing chemical structures, but does not offer nanoscale spatial resolution.
An attractive solution to this is the combination of optical spectroscopy with SPM, where a plasmonically active probe can be used to achieve a near-field enhancement at the tip apex, enabling optical spectroscopy with ~20 nm resolution. This technique, known as 'Tip Enhanced Optical Spectroscopy' (TEOS), remains experimentally challenging and our ongoing work seeks to improve the reliability with which it can be achieved, and also to develop the fundamental understanding required to extract meaningfully quantitative characterisation.
Through the acquisition of photoluminescence and Raman signals with TEOS, it is possible to identify specific chemical groups, and to undertake in situ measurements of chemical changes occurring during the operation of nanoelectronic devices.
Measurements of nanoscale electronic properties using SPM-based techniques are particularly challenging to interpret. Typically a multi-physical modelling approach is required to understand the relationships between material properties of the sample and the measurement signal acquired.
In particular, the interaction between the SPM probe and the sample surface is complex and is often sensitive to the sub-surface and bulk properties of the sample. In order to distinguish these effects we have developed various simulations, which enable the reliable interpretation of complex nanoelectronic measurement data.