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In this work, we study ultra-low energy implantation into MoS₂ monolayers to evaluate the potential of the technique in two-dimensional materials technology. We use 80 Se⁺ ions at the energy of 20 eV and with fluences up to 5.0 · 10¹⁴ cm⁻². Raman spectra of the implanted films show that the implanted ions are predominantly incorporated at the sulfur sites and MoS₂₋₂ₓ Se₂ₓ alloys are formed, indicating high ion retention rates, in agreement with the predictions of molecular dynamics simulations of Se ion irradiation on MoS₂ monolayers. We found that the ion retention rate is improved when implantation is performed at an elevated temperature of the target monolayers. Photoluminescence spectra reveal the presence of defects, which are mostly removed by post-implantation annealing at 200 ˚C, suggesting that, in addition to the Se atoms in the substitutional positions, weakly bound Se adatoms are the most common defects introduced by implantation at this ion energy.

We find that an InAs/GaSb based electron-hole system exhibits insulating behaviour when the numbers of occupied electron and hole Landau levels are equal. In this insulating state, the Hall resistance becomes symmetric under field reversal, and both the Hall and longitudinal resistances display reproducible fluctuations. A comparison with measurements made on a Corbino disc reveals that these features occur due to conduction at the mesa edge. We propose a simple model based on edge states.

InAs/GaSb heterojunctions form bipolar 2-D layers due to the overlapping conduction and valence bands. Such systems have generated considerable interest recently due to the possibilities of gap formation by both excitonic and single particle interactions. The quantum Hall effect in this system shows a digital sequence oscillating from 0-1-0 conductance quanta and the diagonal resistivity, p. shows re-entrant insulating behaviour due to the formation of a total gap in the energy spectrum. The origin of the insulating behaviour is thought to be due to the formation of unusual counter propagating edge states where the electron and hole system interact to form closed loops which generate localised states. Cyclotron resonance on this system is found to show an increased effective mass when the electron and hole states approach each other physically and at high magnetic fields the resonances show large splittings which can be strongly temperature dependent.

During this talk we will present various fabrication approaches to improve the performance of photovoltaic (PV) cells by using metallic nanoparticles in order to generate photocurrent below the bandgap. This effect is possible due to the generation of surface plasmon polaritons (SPPs) in optimized nanoparticles.

InAs/GaSb heterojunctions form bipolar 2-D layers due to the overlapping conduction and valence bands. Such systems have generated considerable interest recently due to the possibilities of gap formation by both excitonic and single particle interactions. The quantum Hall effect in this system shows a digital sequence oscillating from 0-1-0 conductance quanta and the diagonal resistivity, p. shows re-entrant insulating behaviour due to the formation of a total gap in the energy spectrum. The origin of the insulating behaviour is thought to be due to the formation of unusual counter propagating edge states where the electron and hole system interact to form closed loops which generate localised states. Cyclotron resonance on this system is found to show an increased effective mass when the electron and hole states approach each other physically and at high magnetic fields the resonances show large splittings which can be strongly temperature dependent.