Abstract
Abstract : In the last decade, a new class of solids known as “2D Dirac materials” has led to an outburst of research activity in condensed matter physics and materials science. The quasiparticles in these materials are described by the relativistic (2+1) Dirac equation rather than Schrödinger’s equation. The relativistic effect in these systems confers on them some unusual properties not observed in normal condensed matter systems. This makes them very attractive for fundamental research as well for practical applications in technology. Recently, germanene has been predicted to be a 2D Dirac material and to show behaviour beyond that of existing 2D Dirac materials (graphene, silicene), such as a detectable quantum spin Hall effect. That makes it more applicable in the semiconductor and spintronics industries. Although germanene has been predicted from first principles calculation to exist and claimed to have been synthesized on various substrates, convincing experimental evidence of its Dirac cone structure has not yet been presented. This lack of evidence has led to controversy about germanene’s existence on one hand and about the existence of any Dirac cones in this material on the other hand, especially on metallic substrates. In this project, we explored the possible growth of germanene on Pt(111) by thermally depositing Ge onto clean Pt(111). Three structures were identified with low energy electron diffraction, depending on the growth conditions. Their chemical environment was characterized by x-ray photoemission spectroscopy. Finally, the electronic band structure of all three was determined by the use of angle-resolved photoemission spectroscopy. Our findings point towards the formation Ge-Pt alloys instead of germanene in all cases. There is therefore a need to revisit recent results alleging the synthesis of germanene on Pt(111) and other metallic substrates.
M.Sc. (Physics)