Kobus Cilliers | On 08, Dec 2019

Darrell Mann

We head to the University of Manchester for our patent of the month this month. US10,345,490 was granted on July 9 to a trio of inventors, two of whom are Nobel-Prize winners. Andre Geim and Konstantin Novos won the prestigious award for their pioneering work on graphene. Their latest invention shifts the focus to plasmonics…

Plasmonics has established itself as a branch of physics which, among other applications, has the potential to revolutionize data processing, improve photovoltaics, and increase sensitivity of bio-detection. Plasmonics generally relates to the interaction between light and electron plasma oscillations in metals. Surface plasmons are coherent oscillations of free electrons that exist at an interface between two materials where the real part of the dielectric function changes sign across the interface (e.g. a metal-dielectric interface).

Gold is the current metal of choice for plasmonic applications due to its strong plasmonic response. However, gold is not compatible with standard silicon manufacturing processes (e.g. complementary metal oxide semiconductor (CMOS) technology) due to an efficient diffusion of gold into silicon. This incompatibility, together with the relatively high cost of gold, has hindered the widespread use and adoption of plasmonic devices.

There is an on-going search for inexpensive alternative materials that may replace gold for plasmonic applications and make plasmonic devices more economically attractive.

In one numerical (i.e. theoretical) study (Choi et al; Graphene-on-silver substrates for sensitive surface plasmon resonance imaging biosensors. Optics Express, 17 Jan. 2011, Vol. 19, No. 2, 458) it is hypothesized that a silver film coated in graphene may improve the sensing performance of a silver-based surface plasmon resonance (SPR) imaging biosensor beyond that of an equivalent gold-based SPR imaging biosensor. However, experimental attempts to date have not resulted in a device that possesses the desired plasmonic response required to make a functional plasmonic device. As an example, Salihoglu et al. (Plasmon-polaritons on graphene-metal surface and their use in biosensors. Applied Physics Letters, 23 May 2012, vol. 100, 213110) reports an experimental attempt to use graphene coated silver for use in a plasmonic device. However, it was found that the addition of the graphene to the silver significantly degraded the plasmonic response of the material.

There still exists a need, therefore, for alternative plasmonic structures that will enable commercially viable plasmonic devices.

It is an aim of certain embodiments of the present invention to provide a plasmonic structure that is resistant to oxidation.

Another aim of certain embodiments of the present invention is to provide a plasmonic structure that may function in a wet environment.

A further aim of certain embodiments of the present invention is to provide a plasmonic structure that is compatible with complementary metal oxide semiconductors (CMOS) and CMOS fabrication methods.

Here’s how the main compatibility and expensive material aspects of the conflict are best mapped to what the invention is all about:

And here’s how the inventors have overcome the problems:

…there is provided a plasmonic structure comprising: a layer of metal in which the metal is selected from: a Group 8 to Group 11 transition metal, aluminium, germanium, antimony or bismuth; and a barrier layer formed from a 2-D material disposed on a surface of the layer of metal; wherein the metal layer has a roughness that permits the propagation of running plasmons along the interface of the metal layer and the barrier layer.

Which sounds an awful lot like a Principle 35, Principle 3 one-two combination. Change the material and add some Local Quality roughness. Easy when you know how. Nobel-prizing easy.