Putting next-gen smart devices to the test

The demand for miniaturisation of electronics, such as smart devices, wearables and the Internet of Things (IoT) devices, is continuing to grow, but the industry is now reaching the scaling limit for traditional silicon materials.

Two-dimensional (2D) materials have attracted significant interest in recent years due to their unique electrical and mechanical properties, alongside atomically-thin dimensions.

While graphene was the first 2D material to be studied in detail, there is now also a focus on other 2D materials with diverse properties and new applications.

Among these is single-layer Molybdenum Disulphide (MoS₂), a semiconducting 2D material which is generating a lot of interest due to its technologically exploitable electronic and optical properties that could pave the way for the next generation of electronics and optoelectronics devices.

Its inherently thin atomic structure not only offers several advantages in scaling down traditional electronics, but also opens up the possibility of adding further functional elements on a chip for applications such as sensors.

In addition, its semiconducting electronic structure renders it very interesting for optical applications such as photovoltaics and light emission.  As such, upscaling the production of MoS₂ and assessing its quality using non-destructive approaches offers vast benefits not only to manufacturers, but also to the industry as a whole.

The challenge

In order to commercialise electronic devices made of 2D materials, industry faces a challenge to carry out quality control checks without destroying or damaging the material.

As a single-layer of a 2D material is only a single atom or molecule thick, assessing their quality so far has only been possible using destructive techniques.

Defects are expected to critically impact the performance of MoS₂-based electronic devices, so the ability to investigate and quantify the number of defects without causing damage is crucial for enabling large-scale manufacture of the material, device fabrication and material functionalisation.

The solution

Oxford Instruments, a leading provider of high technology systems and tools for industry and research, looked to develop a new deposition system and process that could produce MoS₂ in a more industrially-scalable manner to help further its commercialisation.

The team of researchers were in need of a suitable quality control approach, and turned to the research from the National Graphene Metrology Centre (NGMC), a world leader in the characterisation and advanced measurement of 2D materials, at the National Physical Laboratory (NPL).

Senior research scientist at NPL, Dr Andrew Pollard explained: “We were investigating the use of Raman spectroscopy for characterising MoS₂ and found that it is a viable high-throughput and non-destructive technique for quantifying defects in this exciting 2D material.

“Importantly for this study was that we could controllably introduce known defects into MoS₂ as a first step, using a technique from our previous work in graphene.”

Due to this, commented Dr Ravi Sundaram, senior scientist at Oxford Instruments, “We were able to use NPL’s industrially-focused research as a framework for developing our own quality control measure that uses Raman spectroscopy to quantify defects in MoS₂ produced using chemical vapour deposition.

“While such techniques are widely used for graphene, there was no established way of checking the quality of MoS₂ in a non-destructive manner before NPL’s work was published.”

The impact

NPL’s work on MoS₂ provided Oxford Instruments with the methodology it needed to develop its own quality control process, which characterises the 2D MoS₂ layers without having a destructive impact on the material’s structure.

This enables the team to efficiently characterise the MoS₂ produced via an industrially scalable technology, helping to accelerate the commercialisation of 2D materials.