Matthew Hamer is a post-doctoral research associate in The University of Manchester’s Department of Physics and Astronomy, based in the National Graphene Institute. In November 2020, he received the Elsevier\/Scopus Early Career Research UK award for his work with graphene and other 2D materials. We sat down to discuss his research in more detail and find out what it meant to him to be honoured in this way.<\/p>\n
I make stacks of 2D materials called heterostructures, where different layers have different properties, so you can tailor the properties of the device you\u2019re making. These devices can be simple things such as field-effect transistors or LEDs, or more complicated structures such as quantum dots.<\/p>\n
One thing that sets my work apart is that we work with materials that are sensitive to the air and that degrade in ambient conditions. So they lose the properties that we\u2019re interested in looking at – for example, superconductivity or magnetism. Many of the materials that show the most interesting properties happen to be the ones that are most sensitive.<\/p>\n
The traditional way of working with these materials is inside a glovebox, where you have an inert atmosphere – usually argon or nitrogen – and this means you can work with the materials in this environment and they don\u2019t break down. That\u2019s what a lot of my early PhD was on.<\/p>\n
More recently, we\u2019ve managed to develop some technology which uses ultra-high vacuums and this piece of equipment allows us to suck all the air out of the system. We can then exfoliate these materials and have pristine interfaces. This leads to a significant improvement in the interface quality and therefore the device quality compared to glovebox encapsulated samples that we\u2019ve worked with in the past.<\/p>\n
Good question! Essentially we make a sandwich of the air-sensitive materials so it\u2019s encapsulated on all sides by a more stable material. This encapsulation layer is impermeable to the things in the air that might degrade the central layer and then you can do all the processing that you would normally associate with these devices.<\/p>\n
Usually, we use hexagonal boron nitride (h-BN), which is a very wide-band-gap insulator. So if, say, we\u2019re concerned with conductive properties, because h-BN is an insulator, it doesn\u2019t matter. If you were looking at optical properties, h-BN is going to change the dielectric environment a little \u2013 it may absorb a bit of the light coming in \u2013 so you may get a reduced intensity. But generally, by engineering the encapsulation layers, you can negate any adverse effects. Generally it\u2019s better than no encapsulation at all.<\/p>\n
That\u2019s a more difficult question because the type of work we do doesn\u2019t lend itself so easily to that kind of categorisation. Because of the nature of these air-sensitive materials, using gloveboxes and ultra-high vacuum systems is a necessity which leads to very low throughput. You can only make a couple of devices and it\u2019s difficult.<\/p>\n
One thing we can do is to see physical properties that we might not otherwise be able to observe \u2013 for example, unconventional superconductivity or electron-electron interactions. With these very pristine interfaces, the layers have fewer impurities and defects so the crystal structure can be of higher quality, and we can see effects that might otherwise be \u2018blurred out\u2019, so to speak, because of background interference.<\/p>\n
If I had to name an application, quantum computing would probably stand out, because in theory we could make qubits<\/a> with the UHV system and reduce one of the problems with them \u2013\u00a0 that of decoherence. Even if we could make just a couple of qubits, that might be enough to revolutionise quantum computing.<\/p>\n