Gilbert Hausmann Award 2018 - Dmitry Ovchinnikov

"For his exceptional contributions to the understanding of electrical conduction in two-dimensional semiconductors and the discovery of a unique switching behavior in electrolytically gated transistors using the two-dimensional semiconductor rhenium disulfide."

Two-dimensional materials (2D materials) are under intensive investigation recently due to the variety of electronic properties and surprising enrichment of condensed matter physics field which they offer. They could in principle outperform commercially available materials and fill several emerging technological niches, for instance flexible electronics and optoelectronics devices, where their combination of high crystallinity, mechanical flexibility and strong light-matter interactions could enable new levels of performance. One unexpected challenge is the ultrathin body of those materials, where transistor or light-emitting diode consists only of one atom thick material and any lattice defect or external perturbation could lead to large variability of performance.

This thesis explores monolayers of semiconducting 2D materials and establishes connection between structural or electrostatic disorder and transport properties of those materials. First, we study grain boundaries, which are well known sources of scattering and show that certain types of engineered grain boundaries would lead to no degradation of carrier mobility. Next, we build a model system, where one could in situ vary electrostatic disorder and measure transport properties simultaneously. This model system based on rhenium disulfide (ReS₂) demonstrates how conductivity and mobility of charge carriers would be affected by different levels of electrostatic disorder. Simple model explains those findings from the perspective of two-dimensional localization and provides “rule of thumb” for materials choice and device design.