Marko Kralj: Chemical doping of atomically thin materials

M. Kralj, M. Petrović, I. Delač Marion, D. Čapeta, D. Novko, N. Vujičić Center of Excellence for Advanced Materials and Sensing Devices, Institute of Physics, Croatia In analogy to intercalation of bulk layered materials, the concept of chemical doping of their atomically thin building blocks presents a powerful tool to tailor physical and chemical properties and applications of two-dimensional (2D) materials. First, we present examples of epitaxial graphene and hBN subjected to adsorption and intercalation of cesium atoms with high degree of structural ordering [1]. In particular, we observed significant n-doping for semimetal graphene and band shifts for insulating hBN and related effects in electron scattering and in particular modification of optical reflectivity. Next, we investigate the effects of doping in CVD grown 2D semiconductor MoS2. We analyzed a concentration and homogeneity of point defects related to intrinsic n-doping [2]. In addition, by deposition of lithium atoms and increasing of n-doping we measured a degradation of valley polarization and activation of non-zone-center Raman modes [3]. In this case, the lack of structural order in alkali metal atoms overlayer was responsible for disorder-activated scattering.  [1] J. Cai, et al., Phys. Rev. B 98 (2018) 195443. [2] I. Delač Marion, et al., Nanotechnology 29 (2018) 305703. [3] N. Saigal, et al., Appl. Phys. Lett. 112 (2018) 121902. Marko Kralj received PhD in Physics in 2003 from University of Zagreb studying quantum well effects in atomically thin metal films by ARPES and STM. He was a postdoctoral researcher at University of Bonn for 3 years studying ultrathin oxides as templates by variable temperature STM. He joined Institute of Physics in Zagreb in 2006 where currently he is a Senior Scientist and a Director. He investigates 2D materials for more than 10 years, in particular their electronic properties and more recently their optical response. He was awarded by Humboldt Fellowship (2005), Croatian State Award for Science (2013) and Award for Highest Scientific Accomplishments (2016) awarded by Croatian Academy of Sciences and Arts.