So after three years of silence, I finally have a new scientific publication out - a review paper on my PhD thesis work in Physica Status Solidi (a) with my old postdoc, Kane O'Donnell (who did most of the hard work!)
The paper summarises a lot of the computation and experimental work I did during my PhD, which was up until recently kept secret whilst the patent on the discovery went through.
The main part of our work was the prediction using computational theory that alkali metals (in particular lithium) on the oxygenated diamond surface do some interesting things. Diamond has this ability to display this unusual property called negative electron affinity, where changing the first couple of atoms on the surface can alter the surface electronic states so that the conduction band sits below the vacuum level. That means that any electron given enough energy to be promoted from the occupied valence band into the conduction band will naturally sit above the vacuum level - i.e., it's easier to be ejected from the sample into the vacuum than to fall back to the valence band. This makes it really awesome for electron emission for field emission devices (for super efficient, high resolution displays) or thermionic devices (for converting heat from the sun or waste heat from power stations directly into electrical power).
We predicted that lithium in particular is great for this as lithium is much smaller than other alkali metals (it only has 3 protons/electrons), which means it can sit between surface atoms, rather than on top of them like with bigger alkali metals like cesium or sodium. As they like to be positively charged, these alkali metals form an electric dipole on the surface, where the top surface by the alkali metal is positively charged, and the carbon lattice is negatively charged, essentially making it attractive for the electrons to be emitted from the surface. However, on the bare surface of diamond there is not much to bond to and the alkali metals don't stick very well.
We found that if you oxygenate the surface (easily done by ozone or acid treatment) of the diamond, then add the alkali metal, the alkali metal is much much more strongly bound, and has an even stronger electric dipole. Lithium in particular, but also sodium and magnesium to a certain degree, are awesome for this, because their small size lets them sit between the oxygen atoms, and then the positive charge of the lithium pushes the lone pair electrons in the oxygen atoms into the carbon lattice, creating an even bigger dipole and making the path from valence band to vacuum even stronger.
We took the computational predictions and did experiments using ultraviolet and x-ray photoemission. The first tells you what the valence band structure is (and therefore what the electronic behaviour at the surface is), whilst the second tells you about the core electrons (which tells you which elements are on the surface and how they are bonded.) Luckily for us, the experimental results confirmed the computational predictions, and I got my thesis (and some publications and a patent). It's nice to see that work finally see the light of day, as I'm really pleased with what we achieved.